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rfc:rfc2828

Network Working Group R. Shirey Request for Comments: 2828 GTE / BBN Technologies FYI: 36 May 2000 Category: Informational

                     Internet Security Glossary

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

 This Glossary (191 pages of definitions and 13 pages of references)
 provides abbreviations, explanations, and recommendations for use of
 information system security terminology. The intent is to improve the
 comprehensibility of writing that deals with Internet security,
 particularly Internet Standards documents (ISDs). To avoid confusion,
 ISDs should use the same term or definition whenever the same concept
 is mentioned. To improve international understanding, ISDs should use
 terms in their plainest, dictionary sense. ISDs should use terms
 established in standards documents and other well-founded
 publications and should avoid substituting private or newly made-up
 terms. ISDs should avoid terms that are proprietary or otherwise
 favor a particular vendor, or that create a bias toward a particular
 security technology or mechanism versus other, competing techniques
 that already exist or might be developed in the future.

Shirey Informational [Page 1] RFC 2828 Internet Security Glossary May 2000

Table of Contents

 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   2
 2. Explanation of Paragraph Markings  . . . . . . . . . . . . . .   4
    2.1 Recommended Terms with an Internet Basis ("I") . . . . . .   4
    2.2 Recommended Terms with a Non-Internet Basis ("N")  . . . .   5
    2.3 Other Definitions ("O")  . . . . . . . . . . . . . . . . .   5
    2.4 Deprecated Terms, Definitions, and Uses ("D")  . . . . . .   6
    2.5 Commentary and Additional Guidance ("C") . . . . . . . . .   6
 3. Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .   6
 4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 197
 5. Security Considerations  . . . . . . . . . . . . . . . . . . . 211
 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 211
 7. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 211
 8. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 212

1. Introduction

 This Glossary provides an internally consistent, complementary set of
 abbreviations, definitions, explanations, and recommendations for use
 of terminology related to information system security. The intent of
 this Glossary is to improve the comprehensibility of Internet
 Standards documents (ISDs)--i.e., RFCs, Internet-Drafts, and other
 material produced as part of the Internet Standards Process [R2026]--
 and of all other Internet material, too. Some non-security terms are
 included to make the Glossary self-contained, but more complete lists
 of networking terms are available elsewhere [R1208, R1983].
 Some glossaries (e.g., [Raym]) list terms that are not listed here
 but could be applied to Internet security. However, those terms have
 not been included in this Glossary because they are not appropriate
 for ISDs.
 This Glossary marks terms and definitions as being either endorsed or
 deprecated for use in ISDs, but this Glossary is not an Internet
 standard. The key words "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
 and "OPTIONAL" are intended to be interpreted the same way as in an
 Internet Standard [R2119], but this guidance represents only the
 recommendations of this author. However, this Glossary includes
 reasons for the recommendations--particularly for the SHOULD NOTs--so
 that readers can judge for themselves whether to follow the
 recommendations.

Shirey Informational [Page 2] RFC 2828 Internet Security Glossary May 2000

 This Glossary supports the goals of the Internet Standards Process:
 o Clear, Concise, and Easily Understood Documentation
    This Glossary seeks to improve comprehensibility of security-
    related content of ISDs. That requires wording to be clear and
    understandable, and requires the set of security-related terms and
    definitions to be consistent and self-supporting. Also, the
    terminology needs to be uniform across all ISDs; i.e., the same
    term or definition needs to be used whenever and wherever the same
    concept is mentioned. Harmonization of existing ISDs need not be
    done immediately, but it is desirable to correct and standardize
    the terminology when new versions are issued in the normal course
    of standards development and evolution.
 o Technical Excellence
    Just as Internet Standard (STD) protocols should operate
    effectively, ISDs should use terminology accurately, precisely,
    and unambiguously to enable Internet Standards to be implemented
    correctly.
 o Prior Implementation and Testing
    Just as STD protocols require demonstrated experience and
    stability before adoption, ISDs need to use well-established
    language. Using terms in their plainest, dictionary sense (when
    appropriate) helps to ensure international understanding. ISDs
    need to avoid using private, made-up terms in place of generally-
    accepted terms from standards and other publications. ISDs need to
    avoid substituting new definitions that conflict with established
    ones. ISDs need to avoid using "cute" synonyms (e.g., see: Green
    Book); no matter how popular a nickname may be in one community,
    it is likely to cause confusion in another.
 o Openness, Fairness, and Timeliness
    ISDs need to avoid terms that are proprietary or otherwise favor a
    particular vendor, or that create a bias toward a particular
    security technology or mechanism over other, competing techniques
    that already exist or might be developed in the future. The set of
    terminology used across the set of ISDs needs to be flexible and
    adaptable as the state of Internet security art evolves.

Shirey Informational [Page 3] RFC 2828 Internet Security Glossary May 2000

2. Explanation of Paragraph Markings

 Section 3 marks terms and definitions as follows:
 o Capitalization: Only terms that are proper nouns are capitalized.
 o Paragraph Marking: Definitions and explanations are stated in
    paragraphs that are marked as follows:
  1. "I" identifies a RECOMMENDED Internet definition.
  2. "N" identifies a RECOMMENDED non-Internet definition.
  3. "O" identifies a definition that is not recommended as the first

choice for Internet documents but is something that authors of

      Internet documents need to know.
    - "D" identifies a term or definition that SHOULD NOT be used in
      Internet documents.
    - "C" identifies commentary or additional usage guidance.
 The rest of Section 2 further explains these five markings.

2.1 Recommended Terms with an Internet Basis ("I")

 The paragraph marking "I" (as opposed to "O") indicates a definition
 that SHOULD be the first choice for use in ISDs. Most terms and
 definitions of this type MAY be used in ISDs; however, some "I"
 definitions are accompanied by a "D" paragraph that recommends
 against using the term. Also, some "I" definitions are preceded by an
 indication of a contextual usage limitation (e.g., see:
 certification), and ISDs should not the term and definition outside
 that context
 An "I" (as opposed to an "N") also indicates that the definition has
 an Internet basis. That is, either the Internet Standards Process is
 authoritative for the term, or the term is sufficiently generic that
 this Glossary can freely state a definition without contradicting a
 non-Internet authority (e.g., see: attack).
 Many terms with "I" definitions are proper nouns (e.g., see:
 Internet Protocol). For such terms, the "I" definition is intended
 only to provide basic information; the authoritative definition is
 found elsewhere.
 For a proper noun identified as an "Internet protocol", please refer
 to the current edition of "Internet Official Protocol Standards" (STD
 1) for the standardization state and status of the protocol.

Shirey Informational [Page 4] RFC 2828 Internet Security Glossary May 2000

2.2 Recommended Terms with a Non-Internet Basis ("N")

 The paragraph marking "N" (as opposed to "O") indicates a definition
 that SHOULD be the first choice for the term, if the term is used at
 all in Internet documents. Terms and definitions of this type MAY be
 used in Internet documents (e.g., see: X.509 public-key certificate).
 However, an "N" (as opposed to an "I") also indicates a definition
 that has a non-Internet basis or origin. Many such definitions are
 preceded by an indication of a contextual usage limitation, and this
 Glossary's endorsement does not apply outside that context.  Also,
 some contexts are rarely if ever expected to occur in a Internet
 document (e.g., see: baggage). In those cases, the listing exists to
 make Internet authors aware of the non-Internet usage so that they
 can avoid conflicts with non-Internet documents.
 Many terms with "N" definitions are proper nouns (e.g., see:
 Computer Security Objects Register). For such terms, the "N"
 definition is intended only to provide basic information; the
 authoritative definition is found elsewhere.

2.3 Other Definitions ("O")

 The paragraph marking "O" indicates a definition that has a non-
 Internet basis, but indicates that the definition SHOULD NOT be used
 in ISDs *except* in cases where the term is specifically identified
 as non-Internet.
 For example, an ISD might mention "BCA" (see: brand certification
 authority) or "baggage" as an example to illustrate some concept; in
 that case, the document should specifically say "SET(trademark) BCA"
 or "SET(trademark) baggage" and include the definition of the term.
 For some terms that have a definition published by a non-Internet
 authority--government (see: object reuse), industry (see: Secure Data
 Exchange), national (see: Data Encryption Standard), or international
 (see: data confidentiality)--this Glossary marks the definition "N",
 recommending its use in Internet documents. In other cases, the non-
 Internet definition of a term is inadequate or inappropriate for
 ISDs. For example, it may be narrow or outdated, or it may need
 clarification by substituting more careful or more explanatory
 wording using other terms that are defined in this Glossary. In those
 cases, this Glossary marks the tern "O" and provides an "I"
 definition (or sometimes a different "N" definition), which precedes
 and supersedes the definition marked "O".

Shirey Informational [Page 5] RFC 2828 Internet Security Glossary May 2000

 In most of the cases where this Glossary provides a definition to
 supersede one from a non-Internet standard, the substitute is
 intended to subsume the meaning of the superseded "O" definition and
 not conflict with it. For the term "security service", for example,
 the "O" definition deals narrowly with only communication services
 provided by layers in the OSI model and is inadequate for the full
 range of ISD usage; the "I" definition can be used in more situations
 and for more kinds of service. However, the "O" definition is also
 provided here so that ISD authors will be aware of the context in
 which the term is used more narrowly.
 When making substitutions, this Glossary attempts to use
 understandable English that does not contradict any non-Internet
 authority. Still, terminology differs between the standards of the
 American Bar Association, OSI, SET, the U.S. Department of Defense,
 and other authorities, and this Glossary probably is not exactly
 aligned with all of them.

2.4 Deprecated Terms, Definitions, and Uses ("D")

 If this Glossary recommends that a term or definition SHOULD NOT be
 used in ISDs, then either the definition has the paragraph marking
 "D", or the restriction is stated in a "D" paragraph that immediately
 follows the term or definition.

2.5 Commentary and Additional Guidance ("C")

 The paragraph marking "C" identifies text that is advisory or
 tutorial. This text MAY be reused in other Internet documents.  This
 text is not intended to be authoritative, but is provided to clarify
 the definitions and to enhance this Glossary so that Internet
 security novices can use it as a tutorial.

3. Definitions

 Note: Each acronym or other abbreviation (except items of common
 English usage, such as "e.g.", "etc.", "i.e.", "vol.", "pp.", "U.S.")
 that is used in this Glossary, either in a definition or as a subpart
 of a defined term, is also defined in this Glossary.
 $ 3DES
    See: triple DES.
 $ *-property
    (N) (Pronounced "star property".) See: "confinement property"
    under Bell-LaPadula Model.

Shirey Informational [Page 6] RFC 2828 Internet Security Glossary May 2000

 $ ABA Guidelines
    (N) "American Bar Association (ABA) Digital Signature Guidelines"
    [ABA], a framework of legal principles for using digital
    signatures and digital certificates in electronic commerce.
 $ Abstract Syntax Notation One (ASN.1)
    (N) A standard for describing data objects. [X680]
    (C) OSI standards use ASN.1 to specify data formats for protocols.
    OSI defines functionality in layers. Information objects at higher
    layers are abstractly defined to be implemented with objects at
    lower layers. A higher layer may define transfers of abstract
    objects between computers, and a lower layer may define transfers
    concretely as strings of bits. Syntax is needed to define abstract
    objects, and encoding rules are needed to transform between
    abstract objects and bit strings. (See: Basic Encoding Rules.)
    (C) In ASN.1, formal names are written without spaces, and
    separate words in a name are indicated by capitalizing the first
    letter of each word except the first word. For example, the name
    of a CRL is "certificateRevocationList".
 $ ACC
    See: access control center.
 $ access
    (I) The ability and means to communicate with or otherwise
    interact with a system in order to use system resources to either
    handle information or gain knowledge of the information the system
    contains.
    (O) "A specific type of interaction between a subject and an
    object that results in the flow of information from one to the
    other." [NCS04]
    (C) In this Glossary, "access" is intended to cover any ability to
    communicate with a system, including one-way communication in
    either direction. In actual practice, however, entities outside a
    security perimeter that can receive output from the system but
    cannot provide input or otherwise directly interact with the
    system, might be treated as not having "access" and, therefore, be
    exempt from security policy requirements, such as the need for a
    security clearance.
 $ access control
    (I) Protection of system resources against unauthorized access; a
    process by which use of system resources is regulated according to
    a security policy and is permitted by only authorized entities

Shirey Informational [Page 7] RFC 2828 Internet Security Glossary May 2000

    (users, programs, processes, or other systems) according to that
    policy. (See: access, access control service.)
    (O) "The prevention of unauthorized use of a resource, including
    the prevention of use of a resource in an unauthorized manner."
    [I7498 Part 2]
 $ access control center (ACC)
    (I) A computer containing a database with entries that define a
    security policy for an access control service.
    (C) An ACC is sometimes used in conjunction with a key center to
    implement access control in a key distribution system for
    symmetric cryptography.
 $ access control list (ACL)
    (I) A mechanism that implements access control for a system
    resource by enumerating the identities of the system entities that
    are permitted to access the resource. (See: capability.)
 $ access control service
    (I) A security service that protects against a system entity using
    a system resource in a way not authorized by the system's security
    policy; in short, protection of system resources against
    unauthorized access. (See: access control, discretionary access
    control, identity-based security policy, mandatory access control,
    rule-based security policy.)
    (C) This service includes protecting against use of a resource in
    an unauthorized manner by an entity that is authorized to use the
    resource in some other manner. The two basic mechanisms for
    implementing this service are ACLs and tickets.
 $ access mode
    (I) A distinct type of data processing operation--e.g., read,
    write, append, or execute--that a subject can potentially perform
    on an object in a computer system.
 $ accountability
    (I) The property of a system (including all of its system
    resources) that ensures that the actions of a system entity may be
    traced uniquely to that entity, which can be held responsible for
    its actions. (See: audit service.)
    (C) Accountability permits detection and subsequent investigation
    of security breaches.

Shirey Informational [Page 8] RFC 2828 Internet Security Glossary May 2000

 $ accredit
 $ accreditation
    (I) An administrative declaration by a designated authority that
    an information system is approved to operate in a particular
    security configuration with a prescribed set of safeguards.
    [FP102] (See: certification.)
    (C) An accreditation is usually based on a technical certification
    of the system's security mechanisms. The terms "certification" and
    "accreditation" are used more in the U.S. Department of Defense
    and other government agencies than in commercial organizations.
    However, the concepts apply any place where managers are required
    to deal with and accept responsibility for security risks. The
    American Bar Association is developing accreditation criteria for
    CAs.
 $ ACL
    See: access control list.
 $ acquirer
    (N) SET usage: "The financial institution that establishes an
    account with a merchant and processes payment card authorizations
    and payments." [SET1]
    (O) "The institution (or its agent) that acquires from the card
    acceptor the financial data relating to the transaction and
    initiates that data into an interchange system." [SET2]
 $ active attack
    See: (secondary definition under) attack.
 $ active wiretapping
    See: (secondary definition under) wiretapping.
 $ add-on security
    (I) "The retrofitting of protection mechanisms, implemented by
    hardware or software, after the [automatic data processing] system
    has become operational." [FP039]
 $ administrative security
    (I) Management procedures and constraints to prevent unauthorized
    access to a system. (See: security architecture.)
    (O) "The management constraints, operational procedures,
    accountability procedures, and supplemental controls established
    to provide an acceptable level of protection for sensitive data."
    [FP039]

Shirey Informational [Page 9] RFC 2828 Internet Security Glossary May 2000

    (C) Examples include clear delineation and separation of duties,
    and configuration control.
 $ Advanced Encryption Standard (AES)
    (N) A future FIPS publication being developed by NIST to succeed
    DES. Intended to specify an unclassified, publicly-disclosed,
    symmetric encryption algorithm, available royalty-free worldwide.
 $ adversary
    (I) An entity that attacks, or is a threat to, a system.
 $ aggregation
    (I) A circumstance in which a collection of information items is
    required to be classified at a higher security level than any of
    the individual items that comprise it.
 $ AH
    See: Authentication Header
 $ algorithm
    (I) A finite set of step-by-step instructions for a problem-
    solving or computation procedure, especially one that can be
    implemented by a computer. (See: cryptographic algorithm.)
 $ alias
    (I) A name that an entity uses in place of its real name, usually
    for the purpose of either anonymity or deception.
 $ American National Standards Institute (ANSI)
    (N) A private, not-for-profit association of users, manufacturers,
    and other organizations, that administers U.S. private sector
    voluntary standards.
    (C) ANSI is the sole U.S. representative to the two major non-
    treaty international standards organizations, ISO and, via the
    U.S. National Committee (USNC), the International Electrotechnical
    Commission (IEC).
 $ anonymous
    (I) The condition of having a name that is unknown or concealed.
    (See: anonymous login.)
    (C) An application may require security services that maintain
    anonymity of users or other system entities, perhaps to preserve
    their privacy or hide them from attack. To hide an entity's real
    name, an alias may be used. For example, a financial institution
    may assign an account number. Parties to a transaction can thus
    remain relatively anonymous, but can also accept the transaction

Shirey Informational [Page 10] RFC 2828 Internet Security Glossary May 2000

    as legitimate. Real names of the parties cannot be easily
    determined by observers of the transaction, but an authorized
    third party may be able to map an alias to a real name, such as by
    presenting the institution with a court order. In other
    applications, anonymous entities may be completely untraceable.
 $ anonymous login
    (I) An access control feature (or, rather, an access control
    weakness) in many Internet hosts that enables users to gain access
    to general-purpose or public services and resources on a host
    (such as allowing any user to transfer data using File Transfer
    Protocol) without having a pre-established, user-specific account
    (i.e., user name and secret password).
    (C) This feature exposes a system to more threats than when all
    the users are known, pre-registered entities that are individually
    accountable for their actions. A user logs in using a special,
    publicly known user name (e.g., "anonymous", "guest", or "ftp").
    To use the public login name, the user is not required to know a
    secret password and may not be required to input anything at all
    except the name. In other cases, to complete the normal sequence
    of steps in a login protocol, the system may require the user to
    input a matching, publicly known password (such as "anonymous") or
    may ask the user for an e-mail address or some other arbitrary
    character string.
 $ APOP
    See: POP3 APOP.
 $ archive
     (I) (1.) Noun: A collection of data that is stored for a
    relatively long period of time for historical and other purposes,
    such as to support audit service, availability service, or system
    integrity service. (See: backup.) (2.) Verb: To store data in such
    a way. (See: back up.)
    (C) A digital signature may need to be verified many years after
    the signing occurs. The CA--the one that issued the certificate
    containing the public key needed to verify that signature--may not
    stay in operation that long. So every CA needs to provide for
    long-term storage of the information needed to verify the
    signatures of those to whom it issues certificates.
 $ ARPANET
    (N) Advanced Research Projects Agency Network, a pioneer packet-
    switched network that was built in the early 1970s under contract
    to the U.S. Government, led to the development of today's
    Internet, and was decommissioned in June 1990.

Shirey Informational [Page 11] RFC 2828 Internet Security Glossary May 2000

 $ ASN.1
    See: Abstract Syntax Notation One.
 $ association
    (I) A cooperative relationship between system entities, usually
    for the purpose of transferring information between them. (See:
    security association.)
 $ assurance
    (I) (1.) An attribute of an information system that provides
    grounds for having confidence that the system operates such that
    the system security policy is enforced. (2.) A procedure that
    ensures a system is developed and operated as intended by the
    system's security policy.
 $ assurance level
    (I) Evaluation usage: A specific level on a hierarchical scale
    representing successively increased confidence that a target of
    evaluation adequately fulfills the requirements. (E.g., see:
    TCSEC.)
 $ asymmetric cryptography
    (I) A modern branch of cryptography (popularly known as "public-
    key cryptography") in which the algorithms employ a pair of keys
    (a public key and a private key) and use a different component of
    the pair for different steps of the algorithm. (See: key pair.)
    (C) Asymmetric algorithms have key management advantages over
    equivalently strong symmetric ones. First, one key of the pair
    does not need to be known by anyone but its owner; so it can more
    easily be kept secret. Second, although the other key of the pair
    is shared by all entities that use the algorithm, that key does
    not need to be kept secret from other, non-using entities; so the
    key distribution part of key management can be done more easily.
    (C) For encryption: In an asymmetric encryption algorithm (e.g.,
    see: RSA), when Alice wants to ensure confidentiality for data she
    sends to Bob, she encrypts the data with a public key provided by
    Bob. Only Bob has the matching private key that is needed to
    decrypt the data.
    (C) For signature: In an asymmetric digital signature algorithm
    (e.g., see: DSA), when Alice wants to ensure data integrity or
    provide authentication for data she sends to Bob, she uses her
    private key to sign the data (i.e., create a digital signature
    based on the data). To verify the signature, Bob uses the matching
    public key that Alice has provided.

Shirey Informational [Page 12] RFC 2828 Internet Security Glossary May 2000

    (C) For key agreement: In an asymmetric key agreement algorithm
    (e.g., see: Diffie-Hellman), Alice and Bob each send their own
    public key to the other person. Then each uses their own private
    key and the other's public key to compute the new key value.
 $ attack
    (I) An assault on system security that derives from an intelligent
    threat, i.e., an intelligent act that is a deliberate attempt
    (especially in the sense of a method or technique) to evade
    security services and violate the security policy of a system.
    (See: penetration, violation, vulnerability.)
  1. Active vs. passive: An "active attack" attempts to alter system

resources or affect their operation. A "passive attack"

       attempts to learn or make use of information from the system
       but does not affect system resources. (E.g., see: wiretapping.)
  1. Insider vs. outsider: An "inside attack" is an attack initiated

by an entity inside the security perimeter (an "insider"),

       i.e., an entity that is authorized to access system resources
       but uses them in a way not approved by those who granted the
       authorization. An "outside attack" is initiated from outside
       the perimeter, by an unauthorized or illegitimate user of the
       system (an "outsider"). In the Internet, potential outside
       attackers range from amateur pranksters to organized criminals,
       international terrorists, and hostile governments.
    (C) The term "attack" relates to some other basic security terms
    as shown in the following diagram:
    + - - - - - - - - - - - - +  + - - - - +  + - - - - - - - - - - -+
    | An Attack:              |  |Counter- |  | A System Resource:   |
    | i.e., A Threat Action   |  | measure |  | Target of the Attack |
    | +----------+            |  |         |  | +-----------------+  |
    | | Attacker |<==================||<=========                 |  |
    | |   i.e.,  |   Passive  |  |         |  | |  Vulnerability  |  |
    | | A Threat |<=================>||<========>                 |  |
    | |  Agent   |  or Active |  |         |  | +-------|||-------+  |
    | +----------+   Attack   |  |         |  |         VVV          |
    |                         |  |         |  | Threat Consequences  |
    + - - - - - - - - - - - - +  + - - - - +  + - - - - - - - - - - -+
 $ attribute authority
    (I) A CA that issues attribute certificates.
    (O) "An authority, trusted by the verifier to delegate privilege,
    which issues attribute certificates." [FPDAM]

Shirey Informational [Page 13] RFC 2828 Internet Security Glossary May 2000

 $ attribute certificate
    (I) A digital certificate that binds a set of descriptive data
    items, other than a public key, either directly to a subject name
    or to the identifier of another certificate that is a public-key
    certificate. [X509]
    (O) "A set of attributes of a user together with some other
    information, rendered unforgeable by the digital signature created
    using the private key of the CA which issued it." [X509]
    (O) "A data structure that includes some attribute values and
    identification information about the owner of the attribute
    certificate, all digitally signed by an Attribute Authority. This
    authority's signature serves as the guarantee of the binding
    between the attributes and their owner." [FPDAM]
    (C) A public-key certificate binds a subject name to a public key
    value, along with information needed to perform certain
    cryptographic functions. Other attributes of a subject, such as a
    security clearance, may be certified in a separate kind of digital
    certificate, called an attribute certificate. A subject may have
    multiple attribute certificates associated with its name or with
    each of its public-key certificates.
    (C) An attribute certificate might be issued to a subject in the
    following situations:
  1. Different lifetimes: When the lifetime of an attribute binding

is shorter than that of the related public-key certificate, or

       when it is desirable not to need to revoke a subject's public
       key just to revoke an attribute.
  1. Different authorities: When the authority responsible for the

attributes is different than the one that issues the public-key

       certificate for the subject. (There is no requirement that an
       attribute certificate be issued by the same CA that issued the
       associated public-key certificate.)
 $ audit service
    (I) A security service that records information needed to
    establish accountability for system events and for the actions of
    system entities that cause them. (See: security audit.)
 $ audit trail
    See: security audit trail.

Shirey Informational [Page 14] RFC 2828 Internet Security Glossary May 2000

 $ AUTH
    See: POP3 AUTH.
 $ authentic signature
    (I) A signature (particularly a digital signature) that can be
    trusted because it can be verified. (See: validate vs. verify.)
 $ authenticate
    (I) Verify (i.e., establish the truth of) an identity claimed by
    or for a system entity. (See: authentication.)
    (D) In general English usage, this term usually means "to prove
    genuine" (e.g., an art expert authenticates a Michelangelo
    painting). But the recommended definition carries a much narrower
    meaning. For example, to be precise, an ISD SHOULD NOT say "the
    host authenticates each received datagram". Instead, the ISD
    SHOULD say "the host authenticates the origin of each received
    datagram". In most cases, we also can say "and verifies the
    datagram's integrity", because that is usually implied. (See:
    ("relationship between data integrity service and authentication
    services" under) data integrity service.)
    (D) ISDs SHOULD NOT talk about authenticating a digital signature
    or digital certificate. Instead, we "sign" and then "verify"
    digital signatures, and we "issue" and then "validate" digital
    certificates. (See: validate vs. verify.)
 $ authentication
    (I) The process of verifying an identity claimed by or for a
    system entity. (See: authenticate, authentication exchange,
    authentication information, credential, data origin
    authentication, peer entity authentication.)
    (C) An authentication process consists of two steps:
    1. Identification step: Presenting an identifier to the security
       system. (Identifiers should be assigned carefully, because
       authenticated identities are the basis for other security
       services, such as access control service.)
    2. Verification step: Presenting or generating authentication
       information that corroborates the binding between the entity
       and the identifier. (See: verification.)
    (C) See: ("relationship between data integrity service and
    authentication services" under) data integrity service.

Shirey Informational [Page 15] RFC 2828 Internet Security Glossary May 2000

 $ authentication code
    (D) ISDs SHOULD NOT use this term as a synonym for any form of
    checksum, whether cryptographic or not. The word "authentication"
    is misleading because the mechanism involved usually serves a data
    integrity function rather than an authentication function, and the
    word "code" is misleading because it implies that either encoding
    or encryption is involved or that the term refers to computer
    software. (See: message authentication code.)
 $ authentication exchange
    (I) A mechanism to verify the identity of an entity by means of
    information exchange.
    (O) "A mechanism intended to ensure the identity of an entity by
    means of information exchange." [I7498 Part 2]
 $ Authentication Header (AH)
    (I) An Internet IPsec protocol [R2402] designed to provide
    connectionless data integrity service and data origin
    authentication service for IP datagrams, and (optionally) to
    provide protection against replay attacks.
    (C) Replay protection may be selected by the receiver when a
    security association is established. AH authenticates upper-layer
    protocol data units and as much of the IP header as possible.
    However, some IP header fields may change in transit, and the
    value of these fields, when the packet arrives at the receiver,
    may not be predictable by the sender. Thus, the values of such
    fields cannot be protected end-to-end by AH; protection of the IP
    header by AH is only partial when such fields are present.
    (C) AH may be used alone, or in combination with the IPsec ESP
    protocol, or in a nested fashion with tunneling. Security services
    can be provided between a pair of communicating hosts, between a
    pair of communicating security gateways, or between a host and a
    gateway. ESP can provide the same security services as AH, and ESP
    can also provide data confidentiality service. The main difference
    between authentication services provided by ESP and AH is the
    extent of the coverage; ESP does not protect IP header fields
    unless they are encapsulated by AH.
 $ authentication information
    (I) Information used to verify an identity claimed by or for an
    entity. (See: authentication, credential.)
    (C) Authentication information may exist as, or be derived from,
    one of the following:

Shirey Informational [Page 16] RFC 2828 Internet Security Glossary May 2000

  1. Something the entity knows. (See: password).
  2. Something the entity possesses. (See: token.)
  3. Something the entity is. (See: biometric authentication.)
 $ authentication service
    (I) A security service that verifies an identity claimed by or for
    an entity. (See: authentication.)
    (C) In a network, there are two general forms of authentication
    service: data origin authentication service and peer entity
    authentication service.
 $ authenticity
    (I) The property of being genuine and able to be verified and be
    trusted. (See: authenticate, authentication, validate vs. verify)
 $ authority
    (D) "An entity, responsible for the issuance of certificates."
    [FPDAM]
    (C) ISDs SHOULD NOT use this term as a synonym for AA, CA, RA,
    ORA, or similar terms, because it may cause confusion. Instead,
    use the full term at the first instance of usage and then, if it
    is necessary to shorten text, use the style of abbreviation
    defined in this Glossary.
    (C) ISDs SHOULD NOT use this definition for any PKI entity,
    because the definition is ambiguous with regard to whether the
    entity actually issues certificates (e.g., attribute authority or
    certification authority) or just has accountability for processes
    that precede or follow signing (e.g., registration authority).
    (See: issue.)
 $ authority certificate
    (D) "A certificate issued to an authority (e.g. either to a
    certification authority or to an attribute authority)." [FPDAM]
    (See: authority.)
    (C) ISDs SHOULD NOT use this term or definition because they are
    ambiguous with regard to which specific types of PKI entities they
    address.
 $ authority revocation list (ARL)
    (I) A data structure that enumerates digital certificates that
    were issued to CAs but have been invalidated by their issuer prior
    to when they were scheduled to expire. (See: certificate
    expiration, X.509 authority revocation list.)

Shirey Informational [Page 17] RFC 2828 Internet Security Glossary May 2000

    (O) "A revocation list containing a list of public-key
    certificates issued to authorities, which are no longer considered
    valid by the certificate issuer." [FPDAM]
 $ authorization
 $ authorize
    (I) (1.) An "authorization" is a right or a permission that is
    granted to a system entity to access a system resource. (2.) An
    "authorization process" is a procedure for granting such rights.
    (3.) To "authorize" means to grant such a right or permission.
    (See: privilege.)
    (O) SET usage: "The process by which a properly appointed person
    or persons grants permission to perform some action on behalf of
    an organization. This process assesses transaction risk, confirms
    that a given transaction does not raise the account holder's debt
    above the account's credit limit, and reserves the specified
    amount of credit. (When a merchant obtains authorization, payment
    for the authorized amount is guaranteed--provided, of course, that
    the merchant followed the rules associated with the authorization
    process.)" [SET2]
 $ automated information system
    (I) An organized assembly of resources and procedures--i.e.,
    computing and communications equipment and services, with their
    supporting facilities and personnel--that collect, record,
    process, store, transport, retrieve, or display information to
    accomplish a specified set of functions.
 $ availability
    (I) The property of a system or a system resource being accessible
    and usable upon demand by an authorized system entity, according
    to performance specifications for the system; i.e., a system is
    available if it provides services according to the system design
    whenever users request them. (See: critical, denial of service,
    reliability, survivability.)
    (O) "The property of being accessible and usable upon demand by an
    authorized entity." [I7498 Part 2]
 $ availability service
    (I) A security service that protects a system to ensure its
    availability.
    (C) This service addresses the security concerns raised by denial-
    of-service attacks. It depends on proper management and control of
    system resources, and thus depends on access control service and
    other security services.

Shirey Informational [Page 18] RFC 2828 Internet Security Glossary May 2000

 $ back door
    (I) A hardware or software mechanism that (a) provides access to a
    system and its resources by other than the usual procedure, (b)
    was deliberately left in place by the system's designers or
    maintainers, and (c) usually is not publicly known. (See: trap
    door.)
    (C) For example, a way to access a computer other than through a
    normal login. Such access paths do not necessarily have malicious
    intent; e.g., operating systems sometimes are shipped by the
    manufacturer with privileged accounts intended for use by field
    service technicians or the vendor's maintenance programmers. (See:
    trap door.)
 $ back up vs. backup
    (I) Verb "back up": To store data for the purpose of creating a
    backup copy. (See: archive.)
    (I) Noun/adjective "backup": (1.) A reserve copy of data that is
    stored separately from the original, for use if the original
    becomes lost or damaged. (See: archive.) (2.) Alternate means to
    permit performance of system functions despite a disaster to
    system resources. (See: contingency plan.)
 $ baggage
    (D) ISDs SHOULD NOT use this term to describe a data element
    except when stated as "SET(trademark) baggage" with the following
    meaning:
    (O) SET usage: An "opaque encrypted tuple, which is included in a
    SET message but appended as external data to the PKCS encapsulated
    data. This avoids superencryption of the previously encrypted
    tuple, but guarantees linkage with the PKCS portion of the
    message." [SET2]
 $ bandwidth
    (I) Commonly used to mean the capacity of a communication channel
    to pass data through the channel in a given amount of time.
    Usually expressed in bits per second.
 $ bank identification number (BIN)
    (N) The digits of a credit card number that identify the issuing
    bank. (See: primary account number.)
    (O) SET usage: The first six digits of a primary account number.

Shirey Informational [Page 19] RFC 2828 Internet Security Glossary May 2000

 $ Basic Encoding Rules (BER)
    (I) A standard for representing ASN.1 data types as strings of
    octets. [X690] (See: Distinguished Encoding Rules.)
 $ bastion host
    (I) A strongly protected computer that is in a network protected
    by a firewall (or is part of a firewall) and is the only host (or
    one of only a few hosts) in the network that can be directly
    accessed from networks on the other side of the firewall.
    (C) Filtering routers in a firewall typically restrict traffic
    from the outside network to reaching just one host, the bastion
    host, which usually is part of the firewall. Since only this one
    host can be directly attacked, only this one host needs to be very
    strongly protected, so security can be maintained more easily and
    less expensively. However, to allow legitimate internal and
    external users to access application resources through the
    firewall, higher layer protocols and services need to be relayed
    and forwarded by the bastion host. Some services (e.g., DNS and
    SMTP) have forwarding built in; other services (e.g., TELNET and
    FTP) require a proxy server on the bastion host.
 $ BCA
    See: brand certification authority.
 $ BCI
    See: brand CRL identifier.
 $ Bell-LaPadula Model
    (N) A formal, mathematical, state-transition model of security
    policy for multilevel-secure computer systems. [Bell]
    (C) The model separates computer system elements into a set of
    subjects and a set of objects. To determine whether or not a
    subject is authorized for a particular access mode on an object,
    the clearance of the subject is compared to the classification of
    the object. The model defines the notion of a "secure state", in
    which the only permitted access modes of subjects to objects are
    in accordance with a specified security policy. It is proven that
    each state transition preserves security by moving from secure
    state to secure state, thereby proving that the system is secure.
    (C) In this model, a multilevel-secure system satisfies several
    rules, including the following:

Shirey Informational [Page 20] RFC 2828 Internet Security Glossary May 2000

  1. "Confinement property" (also called "*-property", pronounced

"star property"): A subject has write access to an object only

       if classification of the object dominates the clearance of the
       subject.
  1. "Simple security property": A subject has read access to an

object only if the clearance of the subject dominates the

       classification of the object.
  1. "Tranquillity property": The classification of an object does

not change while the object is being processed by the system.

 $ BER
    See: Basic Encoding Rules.
 $ beyond A1
    (O) (1.) Formally, a level of security assurance that is beyond
    the highest level of criteria specified by the TCSEC. (2.)
    Informally, a level of trust so high that it cannot be provided or
    verified by currently available assurance methods, and
    particularly not by currently available formal methods.
 $ BIN
    See: bank identification number.
 $ bind
    (I) To inseparably associate by applying some mechanism, such as
    when a CA uses a digital signature to bind together a subject and
    a public key in a public-key certificate.
 $ biometric authentication
    (I) A method of generating authentication information for a person
    by digitizing measurements of a physical characteristic, such as a
    fingerprint, a hand shape, a retina pattern, a speech pattern
    (voiceprint), or handwriting.
 $ bit
    (I) The smallest unit of information storage; a contraction of the
    term "binary digit"; one of two symbols--"0" (zero) and "1" (one)
    --that are used to represent binary numbers.
 $ BLACK
    (I) Designation for information system equipment or facilities
    that handle (and for data that contains) only ciphertext (or,
    depending on the context, only unclassified information), and for
    such data itself. This term derives from U.S. Government COMSEC
    terminology. (See: RED, RED/BLACK separation.)

Shirey Informational [Page 21] RFC 2828 Internet Security Glossary May 2000

 $ block cipher
    (I) An encryption algorithm that breaks plaintext into fixed-size
    segments and uses the same key to transform each plaintext segment
    into a fixed-size segment of ciphertext. (See: mode, stream
    cipher.)
    (C) For example, Blowfish, DEA, IDEA, RC2, and SKIPJACK. However,
    a block cipher can be adapted to have a different external
    interface, such as that of a stream cipher, by using a mode of
    operation to "package" the basic algorithm.
 $ Blowfish
    (N) A symmetric block cipher with variable-length key (32 to 448
    bits) designed in 1993 by Bruce Schneier as an unpatented,
    license-free, royalty-free replacement for DES or IDEA. [Schn]
 $ brand
    (I) A distinctive mark or name that identifies a product or
    business entity.
    (O) SET usage: The name of a payment card. Financial institutions
    and other companies have founded payment card brands, protect and
    advertise the brands, establish and enforce rules for use and
    acceptance of their payment cards, and provide networks to
    interconnect the financial institutions. These brands combine the
    roles of issuer and acquirer in interactions with cardholders and
    merchants. [SET1]
 $ brand certification authority (BCA)
    (O) SET usage: A CA owned by a payment card brand, such as
    MasterCard, Visa, or American Express. [SET2] (See: certification
    hierarchy, SET.)
 $ brand CRL identifier (BCI)
    (O) SET usage: A digitally signed list, issued by a BCA, of the
    names of CAs for which CRLs need to be processed when verifying
    signatures in SET messages. [SET2]
 $ break
    (I) Cryptographic usage: To successfully perform cryptanalysis and
    thus succeed in decrypting data or performing some other
    cryptographic function, without initially having knowledge of the
    key that the function requires. (This term applies to encrypted
    data or, more generally, to a cryptographic algorithm or
    cryptographic system.)

Shirey Informational [Page 22] RFC 2828 Internet Security Glossary May 2000

 $ bridge
    (I) A computer that is a gateway between two networks (usually two
    LANs) at OSI layer 2. (See: router.)
 $ British Standard 7799
    (N) Part 1 is a standard code of practice and provides guidance on
    how to secure an information system. Part 2 specifies the
    management framework, objectives, and control requirements for
    information security management systems [B7799]. The certification
    scheme works like ISO 9000. It is in use in the UK, the
    Netherlands, Australia, and New Zealand and might be proposed as
    an ISO standard or adapted to be part of the Common Criteria.
 $ browser
    (I) An client computer program that can retrieve and display
    information from servers on the World Wide Web.
    (C) For example, Netscape's Navigator and Communicator, and
    Microsoft's Explorer.
 $ brute force
    (I) A cryptanalysis technique or other kind of attack method
    involving an exhaustive procedure that tries all possibilities,
    one-by-one.
    (C) For example, for ciphertext where the analyst already knows
    the decryption algorithm, a brute force technique to finding the
    original plaintext is to decrypt the message with every possible
    key.
 $ BS7799
    See: British Standard 7799.
 $ byte
    (I) A fundamental unit of computer storage; the smallest
    addressable unit in a computer's architecture. Usually holds one
    character of information and, today, usually means eight bits.
    (See: octet.)
    (C) Larger than a "bit", but smaller than a "word". Although
    "byte" almost always means "octet" today, bytes had other sizes
    (e.g., six bits, nine bits) in earlier computer architectures.
 $ CA
    See: certification authority.

Shirey Informational [Page 23] RFC 2828 Internet Security Glossary May 2000

 $ CA certificate
    (I) "A [digital] certificate for one CA issued by another CA."
    [X509]
    (C) That is, a digital certificate whose holder is able to issue
    digital certificates. A v3 X.509 public-key certificate may have a
    "basicConstraints" extension containing a "cA" value that
    specifically "indicates whether or not the public key may be used
    to verify certificate signatures."
 $ call back
    (I) An authentication technique for terminals that remotely access
    a computer via telephone lines. The host system disconnects the
    caller and then calls back on a telephone number that was
    previously authorized for that terminal.
 $ capability
    (I) A token, usually an unforgeable data value (sometimes called a
    "ticket") that gives the bearer or holder the right to access a
    system resource. Possession of the token is accepted by a system
    as proof that the holder has been authorized to access the
    resource named or indicated by the token. (See: access control
    list, credential, digital certificate.)
    (C) This concept can be implemented as a digital certificate.
    (See: attribute certificate.)
 $ CAPI
    See: cryptographic application programming interface.
 $ CAPSTONE chip
    (N) An integrated circuit (the Mykotronx, Inc. MYK-82) with a Type
    II cryptographic processor that implements SKIPJACK, KEA, DSA,
    SHA, and basic mathematical functions to support asymmetric
    cryptography, and includes the key escrow feature of the CLIPPER
    chip. (See: FORTEZZA card.)
 $ card
    See: cryptographic card, FORTEZZA card, payment card, PC card,
    smart card, token.
 $ card backup
    See: token backup.
 $ card copy
    See: token copy.

Shirey Informational [Page 24] RFC 2828 Internet Security Glossary May 2000

 $ card restore
    See: token restore.
 $ cardholder
    (I) An entity that has been issued a card.
    (O) SET usage: "The holder of a valid payment card account and
    user of software supporting electronic commerce." [SET2] A
    cardholder is issued a payment card by an issuer. SET ensures that
    in the cardholder's interactions with merchants, the payment card
    account information remains confidential. [SET1]
 $ cardholder certificate
    (O) SET usage: A digital certificate that is issued to a
    cardholder upon approval of the cardholder's issuing financial
    institution and that is transmitted to merchants with purchase
    requests and encrypted payment instructions, carrying assurance
    that the account number has been validated by the issuing
    financial institution and cannot be altered by a third party.
    [SET1]
 $ cardholder certification authority (CCA)
    (O) SET usage: A CA responsible for issuing digital certificates
    to cardholders and operated on behalf of a payment card brand, an
    issuer, or another party according to brand rules. A CCA maintains
    relationships with card issuers to allow for the verification of
    cardholder accounts. A CCA does not issue a CRL but does
    distribute CRLs issued by root CAs, brand CAs, geopolitical CAs,
    and payment gateway CAs. [SET2]
 $ CAST
    (N) A design procedure for symmetric encryption algorithms, and a
    resulting family of algorithms, invented by C.A. (Carlisle Adams)
    and S.T. (Stafford Tavares). [R2144, R2612]
 $ category
    (I) A grouping of sensitive information items to which a non-
    hierarchical restrictive security label is applied to increase
    protection of the data. (See: compartment.)
 $ CAW
    See: certification authority workstation.
 $ CBC
    See: cipher block chaining.
 $ CCA
    See: cardholder certification authority.

Shirey Informational [Page 25] RFC 2828 Internet Security Glossary May 2000

 $ CCITT
    (N) Acronym for French translation of International Telephone and
    Telegraph Consultative Committee. Now renamed ITU-T.
 $ CERT
    See: computer emergency response team.
 $ certificate
    (I) General English usage: A document that attests to the truth of
    something or the ownership of something.
    (C) Security usage: See: capability, digital certificate.
    (C) PKI usage: See: attribute certificate, public-key certificate.
 $ certificate authority
    (D) ISDs SHOULD NOT use this term because it looks like sloppy use
    of "certification authority", which is the term standardized by
    X.509.
 $ certificate chain
    (D) ISDs SHOULD NOT use this term because it duplicates the
    meaning of a standardized term. Instead, use "certification path".
 $ certificate chain validation
    (D) ISDs SHOULD NOT use this term because it duplicates the
    meaning of standardized terms and mixes concepts in a potentially
    misleading way. Instead, use "certificate validation" or "path
    validation", depending on what is meant. (See: validate vs.
    verify.)
 $ certificate creation
    (I) The act or process by which a CA sets the values of a digital
    certificate's data fields and signs it. (See: issue.)
 $ certificate expiration
    (I) The event that occurs when a certificate ceases to be valid
    because its assigned lifetime has been exceeded. (See: certificate
    revocation, validity period.)
 $ certificate extension
    See: extension.

Shirey Informational [Page 26] RFC 2828 Internet Security Glossary May 2000

 $ certificate holder
    (D) ISDs SHOULD NOT use this term as a synonym for the subject of
    a digital certificate because the term is potentially ambiguous.
    For example, the term could also refer to a system entity, such as
    a repository, that simply has possession of a copy of the
    certificate. (See: certificate owner.)
 $ certificate management
    (I) The functions that a CA may perform during the life cycle of a
    digital certificate, including the following:
  1. Acquire and verify data items to bind into the certificate.
  2. Encode and sign the certificate.
  3. Store the certificate in a directory or repository.
  4. Renew, rekey, and update the certificate.
  5. Revoke the certificate and issue a CRL.
    (See: archive management, certificate management, key management,
    security architecture, token management.)
 $ certificate owner
    (D) ISDs SHOULD NOT use this term as a synonym for the subject of
    a digital certificate because the term is potentially ambiguous.
    For example, the term could also refer to a system entity, such as
    a corporation, that has acquired a certificate to operate some
    other entity, such as a Web server. (See: certificate holder.)
 $ certificate policy
    (I) "A named set of rules that indicates the applicability of a
    certificate to a particular community and/or class of application
    with common security requirements." [X509] (See: certification
    practice statement.)
    (C) A certificate policy can help a certificate user decide
    whether a certificate should be trusted in a particular
    application. "For example, a particular certificate policy might
    indicate applicability of a type of certificate for the
    authentication of electronic data interchange transactions for the
    trading goods within a given price range." [R2527]
    (C) A v3 X.509 public-key certificate may have a
    "certificatePolicies" extension that lists certificate policies,
    recognized by the issuing CA, that apply to the certificate and
    govern its use. Each policy is denoted by an object identifier and
    may optionally have certificate policy qualifiers.

Shirey Informational [Page 27] RFC 2828 Internet Security Glossary May 2000

    (C) SET usage: Every SET certificate specifies at least one
    certificate policy, that of the SET root CA. SET uses certificate
    policy qualifiers to point to the actual policy statement and to
    add qualifying policies to the root policy. (See: SET qualifier.)
 $ certificate policy qualifier
    (I) Information that pertains to a certificate policy and is
    included in a "certificatePolicies" extension in a v3 X.509
    public-key certificate.
 $ certificate reactivation
    (I) The act or process by which a digital certificate, which a CA
    has designated for revocation but not yet listed on a CRL, is
    returned to the valid state.
 $ certificate rekey
    (I) The act or process by which an existing public-key certificate
    has its public key value changed by issuing a new certificate with
    a different (usually new) public key. (See: certificate renewal,
    certificate update, rekey.)
    (C) For an X.509 public-key certificate, the essence of rekey is
    that the subject stays the same and a new public key is bound to
    that subject. Other changes are made, and the old certificate is
    revoked, only as required by the PKI and CPS in support of the
    rekey. If changes go beyond that, the process is a "certificate
    update".
    (O) MISSI usage: To rekey a MISSI X.509 public-key certificate
    means that the issuing authority creates a new certificate that is
    identical to the old one, except the new one has a new, different
    KEA key; or a new, different DSS key; or new, different KEA and
    DSS keys. The new certificate also has a different serial number
    and may have a different validity period. A new key creation date
    and maximum key lifetime period are assigned to each newly
    generated key. If a new KEA key is generated, that key is assigned
    a new KMID. The old certificate remains valid until it expires,
    but may not be further renewed, rekeyed, or updated.
 $ certificate renewal
    (I) The act or process by which the validity of the data binding
    asserted by an existing public-key certificate is extended in time
    by issuing a new certificate. (See: certificate rekey, certificate
    update.)
    (C) For an X.509 public-key certificate, this term means that the
    validity period is extended (and, of course, a new serial number
    is assigned) but the binding of the public key to the subject and

Shirey Informational [Page 28] RFC 2828 Internet Security Glossary May 2000

    to other data items stays the same. The other data items are
    changed, and the old certificate is revoked, only as required by
    the PKI and CPS to support the renewal. If changes go beyond that,
    the process is a "certificate rekey" or "certificate update".
 $ certificate request
    (D) ISDs SHOULD NOT use this term because it looks like imprecise
    use of a term standardized by PKCS #10 and used in PKIX. Instead,
    use the standard term, "certification request".
 $ certificate revocation
    (I) The event that occurs when a CA declares that a previously
    valid digital certificate issued by that CA has become invalid;
    usually stated with a revocation date.
    (C) In X.509, a revocation is announced to potential certificate
    users by issuing a CRL that mentions the certificate. Revocation
    and listing on a CRL is only necessary before certificate
    expiration.
 $ certificate revocation list (CRL)
    (I) A data structure that enumerates digital certificates that
    have been invalidated by their issuer prior to when they were
    scheduled to expire. (See: certificate expiration, X.509
    certificate revocation list.)
    (O) "A signed list indicating a set of certificates that are no
    longer considered valid by the certificate issuer. After a
    certificate appears on a CRL, it is deleted from a subsequent CRL
    after the certificate's expiry. CRLs may be used to identify
    revoked public-key certificates or attribute certificates and may
    represent revocation of certificates issued to authorities or to
    users. The term CRL is also commonly used as a generic term
    applying to all the different types of revocation lists, including
    CRLs, ARLs, ACRLs, etc." [FPDAM]
 $ certificate revocation tree
    (I) A mechanism for distributing notice of certificate
    revocations; uses a tree of hash results that is signed by the
    tree's issuer. Offers an alternative to issuing a CRL, but is not
    supported in X.509. (See: certificate status responder.)
 $ certificate serial number
    (I) An integer value that (a) is associated with, and may be
    carried in, a digital certificate; (b) is assigned to the
    certificate by the certificate's issuer; and (c) is unique among
    all the certificates produced by that issuer.

Shirey Informational [Page 29] RFC 2828 Internet Security Glossary May 2000

    (O) "An integer value, unique within the issuing CA, which is
    unambiguously associated with a certificate issued by that CA."
    [X509]
 $ certificate status responder
    (N) FPKI usage: A trusted on-line server that acts for a CA to
    provide authenticated certificate status information to
    certificate users. [FPKI] Offers an alternative to issuing a CRL,
    but is not supported in X.509. (See: certificate revocation tree.)
 $ certificate update
    (I) The act or process by which non-key data items bound in an
    existing public-key certificate, especially authorizations granted
    to the subject, are changed by issuing a new certificate. (See:
    certificate rekey, certificate renewal.)
    (C) For an X.509 public-key certificate, the essence of this
    process is that fundamental changes are made in the data that is
    bound to the public key, such that it is necessary to revoke the
    old certificate. (Otherwise, the process is only a "certificate
    rekey" or "certificate renewal".)
 $ certificate user
    (I) A system entity that depends on the validity of information
    (such as another entity's public key value) provided by a digital
    certificate. (See: relying party.)
    (O) "An entity that needs to know, with certainty, the public key
    of another entity." [X509]
    (C) The system entity may be a human being or an organization, or
    a device or process under the control of a human or an
    organization.
    (D) ISDs SHOULD NOT use this term as a synonym for the "subject"
    of a certificate.
 $ certificate validation
    (I) An act or process by which a certificate user establishes that
    the assertions made by a digital certificate can be trusted. (See:
    valid certificate, validate vs. verify.)
    (O) "The process of ensuring that a certificate is valid including
    possibly the construction and processing of a certification path,
    and ensuring that all certificates in that path have not expired
    or been revoked." [FPDAM]

Shirey Informational [Page 30] RFC 2828 Internet Security Glossary May 2000

    (C) To validate a certificate, a certificate user checks that the
    certificate is properly formed and signed and currently in force:
  1. Checks the signature: Employs the issuer's public key to verify

the digital signature of the CA who issued the certificate in

       question. If the verifier obtains the issuer's public key from
       the issuer's own public-key certificate, that certificate
       should be validated, too. That validation may lead to yet
       another certificate to be validated, and so on. Thus, in
       general, certificate validation involves discovering and
       validating a certification path.
  1. Checks the syntax and semantics: Parses the certificate's

syntax and interprets its semantics, applying rules specified

       for and by its data fields, such as for critical extensions in
       an X.509 certificate.
  1. Checks currency and revocation: Verifies that the certificate

is currently in force by checking that the current date and

       time are within the validity period (if that is specified in
       the certificate) and that the certificate is not listed on a
       CRL or otherwise announced as invalid. (CRLs themselves require
       a similar validation process.)
 $ certification
    (I) Information system usage: Technical evaluation (usually made
    in support of an accreditation action) of an information system's
    security features and other safeguards to establish the extent to
    which the system's design and implementation meet specified
    security requirements. [FP102] (See: accreditation.)
    (I) Digital certificate usage: The act or process of vouching for
    the truth and accuracy of the binding between data items in a
    certificate. (See: certify.)
    (I) Public key usage: The act or process of vouching for the
    ownership of a public key by issuing a public-key certificate that
    binds the key to the name of the entity that possesses the
    matching private key. In addition to binding a key to a name, a
    public-key certificate may bind those items to other restrictive
    or explanatory data items. (See: X.509 public-key certificate.)
    (O) SET usage: "The process of ascertaining that a set of
    requirements or criteria has been fulfilled and attesting to that
    fact to others, usually with some written instrument. A system
    that has been inspected and evaluated as fully compliant with the
    SET protocol by duly authorized parties and process would be said
    to have been certified compliant." [SET2]

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 $ certification authority (CA)
    (I) An entity that issues digital certificates (especially X.509
    certificates) and vouches for the binding between the data items
    in a certificate.
    (O) "An authority trusted by one or more users to create and
    assign certificates. Optionally, the certification authority may
    create the user's keys." [X509]
    (C) Certificate users depend on the validity of information
    provided by a certificate. Thus, a CA should be someone that
    certificate users trust, and usually holds an official position
    created and granted power by a government, a corporation, or some
    other organization. A CA is responsible for managing the life
    cycle of certificates (see: certificate management) and, depending
    on the type of certificate and the CPS that applies, may be
    responsible for the life cycle of key pairs associated with the
    certificates (see: key management).
 $ certification authority workstation (CAW)
    (I) A computer system that enables a CA to issue digital
    certificates and supports other certificate management functions
    as required.
 $ certification hierarchy
    (I) A tree-structured (loop-free) topology of relationships among
    CAs and the entities to whom the CAs issue public-key
    certificates. (See: hierarchical PKI.)
    (C) In this structure, one CA is the top CA, the highest level of
    the hierarchy. (See: root, top CA.) The top CA may issue public-
    key certificates to one or more additional CAs that form the
    second highest level. Each of these CAs may issue certificates to
    more CAs at the third highest level, and so on. The CAs at the
    second-lowest of the hierarchy issue certificates only to non-CA
    entities, called "end entities" that form the lowest level. (See:
    end entity.) Thus, all certification paths begin at the top CA and
    descend through zero or more levels of other CAs. All certificate
    users base path validations on the top CA's public key.
    (O) MISSI usage: A MISSI certification hierarchy has three or four
    levels of CAs:
  1. A CA at the highest level, the top CA, is a "policy approving

authority".

  1. A CA at the second-highest level is a "policy creation

authority".

Shirey Informational [Page 32] RFC 2828 Internet Security Glossary May 2000

  1. A CA at the third-highest level is a local authority called a

"certification authority".

  1. A CA at the fourth-highest (optional) level is a "subordinate

certification authority".

    (O) PEM usage: A PEM certification hierarchy has three levels of
    CAs [R1422]:
  1. The highest level is the "Internet Policy Registration

Authority".

  1. A CA at the second-highest level is a "policy certification

authority".

  1. A CA at the third-highest level is a "certification authority".
    (O) SET usage: A SET certification hierarchy has three or four
    levels of CAs:
  1. The highest level is a "SET root CA".
  2. A CA at the second-highest level is a "brand certification

authority".

  1. A CA at the third-highest (optional) level is a "geopolitical

certification authority".

  1. A CA at the fourth-highest level is a "cardholder CA", a

"merchant CA", or a "payment gateway CA".

 $ certification path
    (I) An ordered sequence of public-key certificates (or a sequence
    of public-key certificates followed by one attribute certificate)
    that enables a certificate user to verify the signature on the
    last certificate in the path, and thus enables the user to obtain
    a certified public key (or certified attributes) of the entity
    that is the subject of that last certificate. (See: certificate
    validation, valid certificate.)
    (O) "An ordered sequence of certificates of objects in the [X.500
    Directory Information Tree] which, together with the public key of
    the initial object in the path, can be processed to obtain that of
    the final object in the path." [X509, R2527]
    (C) The path is the "list of certificates needed to allow a
    particular user to obtain the public key of another." [X509] The
    list is "linked" in the sense that the digital signature of each
    certificate (except the first) is verified by the public key
    contained in the preceding certificate; i.e., the private key used
    to sign a certificate and the public key contained in the
    preceding certificate form a key pair owned by the entity that
    signed.

Shirey Informational [Page 33] RFC 2828 Internet Security Glossary May 2000

    (C) In the X.509 quotation in the previous "C" paragraph, the word
    "particular" points out that a certification path that can be
    validated by one certificate user might not be able to be
    validated by another. That is because either the first certificate
    should be a trusted certificate (it might be a root certificate)
    or the signature on the first certificate should be verified by a
    trusted key (it might be a root key), but such trust is defined
    relative to each user, not absolutely for all users.
 $ certification policy
    (D) ISDs SHOULD NOT use this term. Instead, use either
    "certificate policy" or "certification practice statement",
    depending on what is meant.
 $ certification practice statement (CPS)
    (I) "A statement of the practices which a certification authority
    employs in issuing certificates." [ABA96, R2527] (See: certificate
    policy.)
    (C) A CPS is a published security policy that can help a
    certificate user to decide whether a certificate issued by a
    particular CA can be trusted enough to use in a particular
    application. A CPS may be (a) a declaration by a CA of the details
    of the system and practices it employs in its certificate
    management operations, (b) part of a contract between the CA and
    an entity to whom a certificate is issued, (c) a statute or
    regulation applicable to the CA, or (d) a combination of these
    types involving multiple documents. [ABA]
    (C) A CPS is usually more detailed and procedurally oriented than
    a certificate policy. A CPS applies to a particular CA or CA
    community, while a certificate policy applies across CAs or
    communities. A CA with a single CPS may support multiple
    certificate policies, which may be used for different application
    purposes or by different user communities. Multiple CAs, each with
    a different CPS, may support the same certificate policy. [R2527]
 $ certification request
    (I) A algorithm-independent transaction format, defined by PCKS
    #10 and used in PKIX, that contains a DN, a public key, and
    optionally a set of attributes, collectively signed by the entity
    requesting certification, and sent to a CA, which transforms the
    request to an X.509 public-key certificate or another type of
    certificate.

Shirey Informational [Page 34] RFC 2828 Internet Security Glossary May 2000

 $ certify
    1. (I) Issue a digital certificate and thus vouch for the truth,
    accuracy, and binding between data items in the certificate (e.g.,
    see: X.509 public key certificate), such as the identity of the
    certificate's subject and the ownership of a public key. (See:
    certification.)
    (C) To "certify a public key" means to issue a public-key
    certificate that vouches for the binding between the certificate's
    subject and the key.
    2. (I) The act by which a CA employs measures to verify the truth,
    accuracy, and binding between data items in a digital certificate.
    (C) A description of the measures used for verification should be
    included in the CA's CPS.
 $ CFB
    See: cipher feedback.
 $ Challenge Handshake Authentication Protocol (CHAP)
    (I) A peer entity authentication method for PPP, using a randomly-
    generated challenge and requiring a matching response that depends
    on a cryptographic hash of the challenge and a secret key. [R1994]
    (See: challenge-response, PAP.)
 $ challenge-response
    (I) An authentication process that verifies an identity by
    requiring correct authentication information to be provided in
    response to a challenge. In a computer system, the authentication
    information is usually a value that is required to be computed in
    response to an unpredictable challenge value.
 $ Challenge-Response Authentication Mechanism (CRAM)
    (I) IMAP4 usage: A mechanism [R2195], intended for use with IMAP4
    AUTHENTICATE, by which an IMAP4 client uses a keyed hash [R2104]
    to authenticate itself to an IMAP4 server. (See: POP3 APOP.)
    (C) The server includes a unique timestamp in its ready response
    to the client. The client replies with the client's name and the
    hash result of applying MD5 to a string formed from concatenating
    the timestamp with a shared secret that is known only to the
    client and the server.
 $ channel
    (I) An information transfer path within a system. (See: covert
    channel.)

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 $ CHAP
    See: Challenge Handshake Authentication Protocol.
 $ checksum
    (I) A value that (a) is computed by a function that is dependent
    on the contents of a data object and (b) is stored or transmitted
    together with the object, for the purpose of detecting changes in
    the data. (See: cyclic redundancy check, data integrity service,
    error detection code, hash, keyed hash, protected checksum.)
    (C) To gain confidence that a data object has not been changed, an
    entity that later uses the data can compute a checksum and compare
    it with the checksum that was stored or transmitted with the
    object.
    (C) Computer systems and networks employ checksums (and other
    mechanisms) to detect accidental changes in data. However, active
    wiretapping that changes data could also change an accompanying
    checksum to match the changed data. Thus, some checksum functions
    by themselves are not good countermeasures for active attacks. To
    protect against active attacks, the checksum function needs to be
    well-chosen (see: cryptographic hash), and the checksum result
    needs to be cryptographically protected (see: digital signature,
    keyed hash).
 $ chosen-ciphertext attack
    (I) A cryptanalysis technique in which the analyst tries to
    determine the key from knowledge of plaintext that corresponds to
    ciphertext selected (i.e., dictated) by the analyst.
 $ chosen-plaintext attack
    (I) A cryptanalysis technique in which the analyst tries to
    determine the key from knowledge of ciphertext that corresponds to
    plaintext selected (i.e., dictated) by the analyst.
 $ CIAC
    See: Computer Incident Advisory Capability.
 $ CIK
    See: cryptographic ignition key.
 $ cipher
    (I) A cryptographic algorithm for encryption and decryption.
 $ cipher block chaining (CBC)
    (I) An block cipher mode that enhances electronic codebook mode by
    chaining together blocks of ciphertext it produces. [FP081] (See:
    [R1829], [R2451].)

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    (C) This mode operates by combining (exclusive OR-ing) the
    algorithm's ciphertext output block with the next plaintext block
    to form the next input block for the algorithm.
 $ cipher feedback (CFB)
    (I) An block cipher mode that enhances electronic code book mode
    by chaining together the blocks of ciphertext it produces and
    operating on plaintext segments of variable length less than or
    equal to the block length. [FP081]
    (C) This mode operates by using the previously generated
    ciphertext segment as the algorithm's input (i.e., by "feeding
    back" the ciphertext) to generate an output block, and then
    combining (exclusive OR-ing) that output block with the next
    plaintext segment (block length or less) to form the next
    ciphertext segment.
 $ ciphertext
    (I) Data that has been transformed by encryption so that its
    semantic information content (i.e., its meaning) is no longer
    intelligible or directly available. (See: cleartext, plaintext.)
    (O) "Data produced through the use of encipherment. The semantic
    content of the resulting data is not available." [I7498 Part 2]
 $ ciphertext-only attack
    (I) A cryptanalysis technique in which the analyst tries to
    determine the key solely from knowledge of intercepted ciphertext
    (although the analyst may also know other clues, such as the
    cryptographic algorithm, the language in which the plaintext was
    written, the subject matter of the plaintext, and some probable
    plaintext words.)
 $ CIPSO
    See: Common IP Security Option.
 $ CKL
    See: compromised key list.
 $ class 2, 3, 4, or 5
    (O) U.S. Department of Defense usage: Levels of PKI assurance
    based on risk and value of information to be protected [DOD3]:
  1. Class 2: For handling low-value information (unclassified, not

mission-critical, or low monetary value) or protection of

       system-high information in low- to medium-risk environment.

Shirey Informational [Page 37] RFC 2828 Internet Security Glossary May 2000

  1. Class 3: For handling medium-value information in low- to

medium-risk environment. Typically requires identification of a

       system entity as a legal person, rather than merely a member of
       an organization.
  1. Class 4: For handling medium- to high-value information in any

environment. Typically requires identification of an entity as

       a legal person, rather than merely a member of an organization,
       and a cryptographic hardware token for protection of keying
       material.
  1. Class 5: For handling high-value information in a high-risk

environment.

 $ classification
 $ classification level
    (I) (1.) A grouping of classified information to which a
    hierarchical, restrictive security label is applied to increase
    protection of the data. (2.) The level of protection that is
    required to be applied to that information. (See: security level.)
 $ classified
    (I) Refers to information (stored or conveyed, in any form) that
    is formally required by a security policy to be given data
    confidentiality service and to be marked with a security label
    (which in some cases might be implicit) to indicate its protected
    status. (See: unclassified.)
    (C) The term is mainly used in government, especially in the
    military, although the concept underlying the term also applies
    outside government. In the U.S. Department of Defense, for
    example, it means information that has been determined pursuant to
    Executive Order 12958 ("Classified National Security Information",
    20 April 1995) or any predecessor order to require protection
    against unauthorized disclosure and is marked to indicate its
    classified status when in documentary form.
 $ clean system
    (I) A computer system in which the operating system and
    application system software and files have just been freshly
    installed from trusted software distribution media.
    (C) A clean system is not necessarily in a secure state.
 $ clearance
    See: security clearance.

Shirey Informational [Page 38] RFC 2828 Internet Security Glossary May 2000

 $ clearance level
    (I) The security level of information to which a security
    clearance authorizes a person to have access.
 $ cleartext
    (I) Data in which the semantic information content (i.e., the
    meaning) is intelligible or is directly available. (See:
    plaintext.)
    (O) "Intelligible data, the semantic content of which is
    available." [I7498 Part 2]
    (D) ISDs SHOULD NOT use this term as a synonym for "plaintext",
    the input to an encryption operation, because the plaintext input
    to encryption may itself be ciphertext that was output from
    another operation. (See: superencryption.)
 $ client
    (I) A system entity that requests and uses a service provided by
    another system entity, called a "server". (See: server.)
    (C) Usually, the requesting entity is a computer process, and it
    makes the request on behalf of a human user. In some cases, the
    server may itself be a client of some other server.
 $ CLIPPER chip
    (N) The Mykotronx, Inc. MYK-82, an integrated microcircuit with a
    cryptographic processor that implements the SKIPJACK encryption
    algorithm and supports key escrow. (See: CAPSTONE, Escrowed
    Encryption Standard.)
    (C) The key escrow scheme for a chip involves a SKIPJACK key
    common to all chips that protects the unique serial number of the
    chip, and a second SKIPJACK key unique to the chip that protects
    all data encrypted by the chip. The second key is escrowed as
    split key components held by NIST and the U.S. Treasury
    Department.
 $ closed security environment
    (O) U.S. Department of Defense usage: A system environment that
    meets both of the following conditions: (a) Application developers
    (including maintainers) have sufficient clearances and
    authorizations to provide an acceptable presumption that they have
    not introduced malicious logic. (b) Configuration control provides
    sufficient assurance that system applications and the equipment
    they run on are protected against the introduction of malicious
    logic prior to and during the operation of applications. [NCS04]
    (See: open security environment.)

Shirey Informational [Page 39] RFC 2828 Internet Security Glossary May 2000

 $ code
    (I) noun: A system of symbols used to represent information, which
    might originally have some other representation. (See: encode.)
    (D) ISDs SHOULD NOT use this term as synonym for the following:
    (a) "cipher", "hash", or other words that mean "a cryptographic
    algorithm"; (b) "ciphertext"; or (c) "encrypt", "hash", or other
    words that refer to applying a cryptographic algorithm.
    (D) ISDs SHOULD NOT this word as an abbreviation for the following
    terms: country code, cyclic redundancy code, Data Authentication
    Code, error detection code, Message Authentication Code, object
    code, or source code. To avoid misunderstanding, use the fully
    qualified term, at least at the point of first usage.
 $ color change
    (I) In a system that is being operated in periods processing mode,
    the act of purging all information from one processing period and
    then changing over to the next processing period.
 $ Common Criteria
 $ Common Criteria for Information Technology Security
    (N) "The Common Criteria" is a standard for evaluating information
    technology products and systems, such as operating systems,
    computer networks, distributed systems, and applications. It
    states requirements for security functions and for assurance
    measures. [CCIB]
    (C) Canada, France, Germany, the Netherlands, the United Kingdom,
    and the United States (NIST and NSA) began developing this
    standard in 1993, based on the European ITSEC, the Canadian
    Trusted Computer Product Evaluation Criteria (CTCPEC), and the
    U.S. "Federal Criteria for Information Technology Security" (FC)
    and its precursor, the TCSEC. Work was done in cooperation with
    ISO/IEC Joint Technical Committee 1 (Information Technology),
    Subcommittee 27 (Security Techniques), Working Group 3 (Security
    Criteria). Version 2.1 of the Criteria is equivalent to ISO's
    International Standard 15408 [I15408]. The U.S. Government intends
    that this standard eventually will supersede both the TCSEC and
    FIPS PUB 140-1. (See: NIAP.)
    (C) The standard addresses data confidentiality, data integrity,
    and availability and may apply to other aspects of security. It
    focuses on threats to information arising from human activities,
    malicious or otherwise, but may apply to non-human threats. It
    applies to security measures implemented in hardware, firmware, or
    software. It does not apply to (a) administrative security not
    related directly to technical security, (b) technical physical

Shirey Informational [Page 40] RFC 2828 Internet Security Glossary May 2000

    aspects of security such as electromagnetic emanation control, (c)
    evaluation methodology or administrative and legal framework under
    which the criteria may be applied, (d) procedures for use of
    evaluation results, or (e) assessment of inherent qualities of
    cryptographic algorithms.
 $ Common IP Security Option (CIPSO)
    See: (secondary definition under) Internet Protocol Security
    Option.
 $ common name
    (I) A character string that (a) may be a part of the X.500 DN of a
    Directory object ("commonName" attribute), (b) is a (possibly
    ambiguous) name by which the object is commonly known in some
    limited scope (such as an organization), and (c) conforms to the
    naming conventions of the country or culture with which it is
    associated. [X520] (See: ("subject" and "issuer" under) X.509
    public-key certificate.)
    (C) For example, "Dr. E. F. Moore", "The United Nations", or
    "12-th Floor Laser Printer".
 $ communication security (COMSEC)
    (I) Measures that implement and assure security services in a
    communication system, particularly those that provide data
    confidentiality and data integrity and that authenticate
    communicating entities.
    (C) Usually understood to include cryptographic algorithms and key
    management methods and processes, devices that implement them, and
    the life cycle management of keying material and devices.
 $ community string
    (I) A community name in the form of an octet string that serves as
    a cleartext password in SNMP version 1. [R1157]
 $ compartment
    (I) A grouping of sensitive information items that require special
    access controls beyond those normally provided for the basic
    classification level of the information. (See: category.)
    (C) The term is usually understood to include the special handling
    procedures to be used for the information.
 $ compromise
    See: data compromise, security compromise.

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 $ compromised key list (CKL)
    (O) MISSI usage: A list that identifies keys for which
    unauthorized disclosure or alteration may have occurred. (See:
    compromise.)
    (C) A CKL is issued by an CA, like a CRL is issued. But a CKL
    lists only KMIDs, not subjects that hold the keys, and not
    certificates in which the keys are bound.
 $ COMPUSEC
    See: computer security.
 $ computer emergency response team (CERT)
    (I) An organization that studies computer and network INFOSEC in
    order to provide incident response services to victims of attacks,
    publish alerts concerning vulnerabilities and threats, and offer
    other information to help improve computer and network security.
    (See: CSIRT, security incident.)
    (C) For example, the CERT Coordination Center at Carnegie-Mellon
    University (sometimes called "the" CERT) and the Computer Incident
    Advisory Capability.
 $ Computer Incident Advisory Capability (CIAC)
    (N) A computer emergency response team in the U.S. Department of
    Energy.
 $ computer network
    (I) A collection of host computers together with the subnetwork or
    internetwork through which they can exchange data.
    (C) This definition is intended to cover systems of all sizes and
    types, ranging from the complex Internet to a simple system
    composed of a personal computer dialing in as a remote terminal of
    another computer.
 $ computer security (COMPUSEC)
    (I) Measures that implement and assure security services in a
    computer system, particularly those that assure access control
    service.
    (C) Usually understood to include functions, features, and
    technical characteristics of computer hardware and software,
    especially operating systems.

Shirey Informational [Page 42] RFC 2828 Internet Security Glossary May 2000

 $ computer security incident response team (CSIRT)
    (I) An organization "that coordinates and supports the response to
    security incidents that involve sites within a defined
    constituency." [R2350] (See: CERT, FIRST, security incident.)
    (C) To be considered a CSIRT, an organization must do as follows:
  1. Provide a (secure) channel for receiving reports about

suspected security incidents.

  1. Provide assistance to members of its constituency in handling

the incidents.

  1. Disseminate incident-related information to its constituency

and other involved parties.

 $ computer security object
    (I) The definition or representation of a resource, tool, or
    mechanism used to maintain a condition of security in computerized
    environments. Includes many elements referred to in standards that
    are either selected or defined by separate user communities.
    [CSOR] (See: object identifier, Computer Security Objects
    Register.)
 $ Computer Security Objects Register (CSOR)
    (N) A service operated by NIST is establishing a catalog for
    computer security objects to provide stable object definitions
    identified by unique names. The use of this register will enable
    the unambiguous specification of security parameters and
    algorithms to be used in secure data exchanges.
    (C) The CSOR follows registration guidelines established by the
    international standards community and ANSI. Those guidelines
    establish minimum responsibilities for registration authorities
    and assign the top branches of an international registration
    hierarchy. Under that international registration hierarchy the
    CSOR is responsible for the allocation of unique identifiers under
    the branch {joint-iso-ccitt(2) country(16) us(840) gov(101)
    csor(3)}.
 $ COMSEC
    See: communication security.
 $ confidentiality
    See: data confidentiality.
 $ configuration control
    (I) The process of regulating changes to hardware, firmware,
    software, and documentation throughout the development and
    operational life of a system. (See: administrative security.)

Shirey Informational [Page 43] RFC 2828 Internet Security Glossary May 2000

    (C) Configuration control helps protect against unauthorized or
    malicious alteration of a system and thus provides assurance of
    system integrity. (See: malicious logic.)
 $ confinement property
    See: (secondary definition under) Bell-LaPadula Model.
 $ connectionless data integrity service
    (I) A security service that provides data integrity service for an
    individual IP datagram, by detecting modification of the datagram,
    without regard to the ordering of the datagram in a stream of
    datagrams.
    (C) A connection-oriented data integrity service would be able to
    detect lost or reordered datagrams within a stream of datagrams.
 $ contingency plan
    (I) A plan for emergency response, backup operations, and post-
    disaster recovery in a system as part of a security program to
    ensure availability of critical system resources and facilitate
    continuity of operations in a crisis. [NCS04] (See: availability.)
 $ controlled security mode
    (D) ISDs SHOULD NOT use this term. It was defined in an earlier
    version of the U.S. Department of Defense policy that regulates
    system accreditation, but was subsumed by "partitioned security
    mode" in the current version. [DOD2]
    (C) The term refers to a mode of operation of an information
    system, wherein at least some users with access to the system have
    neither a security clearance nor a need-to-know for all classified
    material contained in the system. However, separation and control
    of users and classified material on the basis, respectively, of
    clearance and classification level are not essentially under
    operating system control like they are in "multilevel security
    mode".
    (C) Controlled mode was intended to encourage ingenuity in meeting
    the security requirements of Defense policy in ways less
    restrictive than "dedicated security mode" and "system high
    security mode", but at a level of risk lower than that generally
    associated with the true "multilevel security mode". This was to
    be accomplished by implementation of explicit augmenting measures
    to reduce or remove a substantial measure of system software
    vulnerability together with specific limitation of the security
    clearance levels of users permitted concurrent access to the
    system.

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 $ cookie
    (I) access control usage: A synonym for "capability" or "ticket"
    in an access control system.
    (I) IPsec usage: Data exchanged by ISAKMP to prevent certain
    denial-of-service attacks during the establishment of a security
    association.
    (I) HTTP usage: Data exchanged between an HTTP server and a
    browser (a client of the server) to store state information on the
    client side and retrieve it later for server use.
    (C) An HTTP server, when sending data to a client, may send along
    a cookie, which the client retains after the HTTP connection
    closes. A server can use this mechanism to maintain persistent
    client-side state information for HTTP-based applications,
    retrieving the state information in later connections. A cookie
    may include a description of the range of URLs for which the state
    is valid. Future requests made by the client in that range will
    also send the current value of the cookie to the server. Cookies
    can be used to generate profiles of web usage habits, and thus may
    infringe on personal privacy.
 $ Coordinated Universal Time (UTC)
    (N) UTC is derived from International Atomic Time (TAI) by adding
    a number of leap seconds. The International Bureau of Weights and
    Measures computes TAI once each month by averaging data from many
    laboratories. (See: GeneralizedTime, UTCTime.)
 $ copy
    See: card copy.
 $ correctness integrity
    (I) Accuracy and consistency of the information that data values
    represent, rather than of the data itself. Closely related to
    issues of accountability and error handling. (See: data integrity,
    source integrity.)
 $ correctness proof
    (I) A mathematical proof of consistency between a specification
    for system security and the implementation of that specification.
    (See: formal specification.)
 $ countermeasure
    (I) An action, device, procedure, or technique that reduces a
    threat, a vulnerability, or an attack by eliminating or preventing
    it, by minimizing the harm it can cause, or by discovering and
    reporting it so that corrective action can be taken.

Shirey Informational [Page 45] RFC 2828 Internet Security Glossary May 2000

    (C) In an Internet protocol, a countermeasure may take the form of
    a protocol feature, an element function, or a usage constraint.
 $ country code
    (I) An identifier that is defined for a nation by ISO. [I3166]
    (C) For each nation, ISO Standard 3166 defines a unique two-
    character alphabetic code, a unique three-character alphabetic
    code, and a three-digit code. Among many uses of these codes, the
    two-character codes are used as top-level domain names.
 $ covert channel
    (I) A intra-system channel that permits two cooperating entities,
    without exceeding their access authorizations, to transfer
    information in a way that violates the system's security policy.
    (See: channel, out of band.)
    (O) "A communications channel that allows two cooperating
    processes to transfer information in a manner that violates the
    system's security policy." [NCS04]
    (C) The cooperating entities can be either two insiders or an
    insider and an outsider. Of course, an outsider has no access
    authorization at all. A covert channel is a system feature that
    the system architects neither designed nor intended for
    information transfer:
  1. "Timing channel": A system feature that enable one system

entity to signal information to another by modulating its own

       use of a system resource in such a way as to affect system
       response time observed by the second entity.
  1. "Storage channel": A system feature that enables one system

entity to signal information to another entity by directly or

       indirectly writing a storage location that is later directly or
       indirectly read by the second entity.
 $ CPS
    See: certification practice statement.
 $ cracker
    (I) Someone who tries to break the security of, and gain access
    to, someone else's system without being invited to do so. (See:
    hacker and intruder.)
 $ CRAM
    See: Challenge-Response Authentication Mechanism.

Shirey Informational [Page 46] RFC 2828 Internet Security Glossary May 2000

 $ CRC
    See: cyclic redundancy check.
 $ credential(s)
    (I) Data that is transferred or presented to establish either a
    claimed identity or the authorizations of a system entity. (See:
    authentication information, capability, ticket.)
    (O) "Data that is transferred to establish the claimed identity of
    an entity." [I7498 Part 2]
 $ critical
    1. (I) "Critical" system resource: A condition of a service or
    other system resource such that denial of access to (i.e., lack of
    availability of) that resource would jeopardize a system user's
    ability to perform a primary function or would result in other
    serious consequences. (See: availability, sensitive.)
    2. (N) "Critical" extension: Each extension of an X.509
    certificate (or CRL) is marked as being either critical or non-
    critical. If an extension is critical and a certificate user (or
    CRL user) does not recognize the extension type or does not
    implement its semantics, then the user is required to treat the
    certificate (or CRL) as invalid. If an extension is non-critical,
    a user that does not recognize or implement that extension type is
    permitted to ignore the extension and process the rest of the
    certificate (or CRL).
 $ CRL
    See: certificate revocation list.
 $ CRL distribution point
    See: distribution point.
 $ CRL extension
    See: extension.
 $ cross-certificate
    See: cross-certification.
 $ cross-certification
    (I) The act or process by which two CAs each certify a public key
    of the other, issuing a public-key certificate to that other CA.
    (C) Cross-certification enables users to validate each other's
    certificate when the users are certified under different
    certification hierarchies.

Shirey Informational [Page 47] RFC 2828 Internet Security Glossary May 2000

 $ cryptanalysis
    (I) The mathematical science that deals with analysis of a
    cryptographic system in order to gain knowledge needed to break or
    circumvent the protection that the system is designed to provide.
    (See: cryptology.)
    (O) "The analysis of a cryptographic system and/or its inputs and
    outputs to derive confidential variables and/or sensitive data
    including cleartext." [I7498 Part 2]
    (C) The "O" definition states the traditional goal of
    cryptanalysis--convert the ciphertext to plaintext (which usually
    is cleartext) without knowing the key--but that definition applies
    only to encryption systems. Today, the term is used with reference
    to all kinds of cryptographic algorithms and key management, and
    the "I" definition reflects that. In all cases, however, a
    cryptanalyst tries to uncover or reproduce someone else's
    sensitive data, such as cleartext, a key, or an algorithm. The
    basic cryptanalytic attacks on encryption systems are ciphertext-
    only, known-plaintext, chosen-plaintext, and chosen-ciphertext;
    and these generalize to the other kinds of cryptography.
 $ crypto
    (D) Except as part of certain long-established terms listed in
    this Glossary, ISDs SHOULD NOT use this abbreviated term because
    it may be misunderstood. Instead, use "cryptography" or
    "cryptographic".
 $ cryptographic algorithm
    (I) An algorithm that employs the science of cryptography,
    including encryption algorithms, cryptographic hash algorithms,
    digital signature algorithms, and key agreement algorithms.
 $ cryptographic application programming interface (CAPI)
    (I) The source code formats and procedures through which an
    application program accesses cryptographic services, which are
    defined abstractly compared to their actual implementation. For
    example, see: PKCS #11, [R2628].
 $ cryptographic card
    (I) A cryptographic token in the form of a smart card or a PC
    card.
 $ cryptographic component
    (I) A generic term for any system component that involves
    cryptography. (See: cryptographic module.)

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 $ cryptographic hash
    See: (secondary definition under) hash function.
 $ cryptographic ignition key (CIK)
    (I) A physical (usually electronic) token used to store,
    transport, and protect cryptographic keys. (Sometimes abbreviated
    as "crypto ignition key".)
    (C) A typical use is to divide a split key between a CIK and a
    cryptographic module, so that it is necessary to combine the two
    to regenerate a key-encrypting key and thus activate the module
    and other keys it contains.
 $ cryptographic key
    (I) Usually shortened to just "key". An input parameter that
    varies the transformation performed by a cryptographic algorithm.
    (O) "A sequence of symbols that controls the operations of
    encipherment and decipherment." [I7498 Part 2]
    (C) If a key value needs to be kept secret, the sequence of
    symbols (usually bits) that comprise it should be random, or at
    least pseudo-random, because that makes the key hard for an
    adversary to guess. (See: cryptanalysis, brute force attack.)
 $ Cryptographic Message Syntax (CMS)
    (I) A encapsulation syntax for digital signatures, hashes, and
    encryption of arbitrary messages. [R2630]
    (C) CMS was derived from PKCS #7. CMS values are specified with
    ASN.1 and use BER encoding. The syntax permits multiple
    encapsulation with nesting, permits arbitrary attributes to be
    signed along with message content, and supports a variety of
    architectures for digital certificate-based key management.
 $ cryptographic module
    (I) A set of hardware, software, firmware, or some combination
    thereof that implements cryptographic logic or processes,
    including cryptographic algorithms, and is contained within the
    module's cryptographic boundary, which is an explicitly defined
    contiguous perimeter that establishes the physical bounds of the
    module. [FP140]
 $ cryptographic system
    (I) A set of cryptographic algorithms together with the key
    management processes that support use of the algorithms in some
    application context.

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    (C) This "I" definition covers a wider range of algorithms than
    the following "O" definition:
    (O) "A collection of transformations from plaintext into
    ciphertext and vice versa [which would exclude digital signature,
    cryptographic hash, and key agreement algorithms], the particular
    transformation(s) to be used being selected by keys. The
    transformations are normally defined by a mathematical algorithm."
    [X509]
 $ cryptographic token
    (I) A portable, user-controlled, physical device used to store
    cryptographic information and possibly perform cryptographic
    functions. (See: cryptographic card, token.)
    (C) A smart token may implement some set of cryptographic
    algorithms and may implement related algorithms and key management
    functions, such as a random number generator. A smart
    cryptographic token may contain a cryptographic module or may not
    be explicitly designed that way.
 $ cryptography
    (I) The mathematical science that deals with transforming data to
    render its meaning unintelligible (i.e., to hide its semantic
    content), prevent its undetected alteration, or prevent its
    unauthorized use. If the transformation is reversible,
    cryptography also deals with restoring encrypted data to
    intelligible form. (See: cryptology, steganography.)
    (O) "The discipline which embodies principles, means, and methods
    for the transformation of data in order to hide its information
    content, prevent its undetected modification and/or prevent its
    unauthorized use. . . . Cryptography determines the methods used
    in encipherment and decipherment." [I7498 Part 2]
 $ Cryptoki
    See: (secondary definition under) PKCS #11.
 $ cryptology
    (I) The science that includes both cryptography and cryptanalysis,
    and sometimes is said to include steganography.
 $ cryptonet
    (I) A group of system entities that share a secret cryptographic
    key for a symmetric algorithm.

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 $ cryptoperiod
    (I) The time span during which a particular key is authorized to
    be used in a cryptographic system. (See: key management.)
    (C) A cryptoperiod is usually stated in terms of calendar or clock
    time, but sometimes is stated in terms of the maximum amount of
    data permitted to be processed by a cryptographic algorithm using
    the key. Specifying a cryptoperiod involves a tradeoff between the
    cost of rekeying and the risk of successful cryptanalysis.
    (C) Although we deprecate its prefix, this term is long-
    established in COMPUSEC usage. (See: crypto) In the context of
    certificates and public keys, "key lifetime" and "validity period"
    are often used instead.
 $ cryptosystem
    (D) ISDs SHOULD NOT use this term as an abbreviation for
    cryptographic system. (For rationale, see: crypto.)
 $ CSIRT
    See: computer security incident response team.
 $ CSOR
    See: Computer Security Objects Register.
 $ cut-and-paste attack
    (I) An active attack on the data integrity of ciphertext, effected
    by replacing sections of ciphertext with other ciphertext, such
    that the result appears to decrypt correctly but actually decrypts
    to plaintext that is forged to the satisfaction of the attacker.
 $ cyclic redundancy check (CRC)
    (I) Sometimes called "cyclic redundancy code". A type of checksum
    algorithm that is not a cryptographic hash but is used to
    implement data integrity service where accidental changes to data
    are expected.
 $ DAC
    See: Data Authentication Code, discretionary access control.
 $ DASS
    See: Distributed Authentication Security Service.
 $ data
    (I) Information in a specific physical representation, usually a
    sequence of symbols that have meaning; especially a representation
    of information that can be processed or produced by a computer.

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 $ Data Authentication Algorithm
    (N) A keyed hash function equivalent to DES cipher block chaining
    with IV = 0. [A9009]
    (D) ISDs SHOULD NOT use the uncapitalized form of this term as a
    synonym for other kinds of checksums.
 $ data authentication code vs. Data Authentication Code (DAC)
    1. (N) Capitalized: "The Data Authentication Code" refers to a
    U.S. Government standard [FP113] for a checksum that is computed
    by the Data Authentication Algorithm. (Also known as the ANSI
    standard Message Authentication Code [A9009].)
    2. (D) Not capitalized: ISDs SHOULD NOT use "data authentication
    code" as a synonym for another kind of checksum, because this term
    mixes concepts in a potentially misleading way. (See:
    authentication code.) Instead, use "checksum", "error detection
    code", "hash", "keyed hash", "Message Authentication Code", or
    "protected checksum", depending on what is meant.
 $ data compromise
    (I) A security incident in which information is exposed to
    potential unauthorized access, such that unauthorized disclosure,
    alteration, or use of the information may have occurred. (See:
    compromise.)
 $ data confidentiality
    (I) "The property that information is not made available or
    disclosed to unauthorized individuals, entities, or processes
    [i.e., to any unauthorized system entity]." [I7498 Part 2]. (See:
    data confidentiality service.)
    (D) ISDs SHOULD NOT use this term as a synonym for "privacy",
    which is a different concept.
 $ data confidentiality service
    (I) A security service that protects data against unauthorized
    disclosure. (See: data confidentiality.)
    (D) ISDs SHOULD NOT use this term as a synonym for "privacy",
    which is a different concept.
 $ Data Encryption Algorithm (DEA)
    (N) A symmetric block cipher, defined as part of the U.S.
    Government's Data Encryption Standard. DEA uses a 64-bit key, of
    which 56 bits are independently chosen and 8 are parity bits, and
    maps a 64-bit block into another 64-bit block. [FP046] (See: DES,
    symmetric cryptography.)

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    (C) This algorithm is usually referred to as "DES". The algorithm
    has also been adopted in standards outside the Government (e.g.,
    [A3092]).
 $ data encryption key (DEK)
    (I) A cryptographic key that is used to encipher application data.
    (See: key-encrypting key.)
 $ Data Encryption Standard (DES)
    (N) A U.S. Government standard [FP046] that specifies the Data
    Encryption Algorithm and states policy for using the algorithm to
    protect unclassified, sensitive data. (See: AES, DEA.)
 $ data integrity
    (I) The property that data has not been changed, destroyed, or
    lost in an unauthorized or accidental manner. (See: data integrity
    service.)
    (O) "The property that information has not been modified or
    destroyed in an unauthorized manner." [I7498 Part 2]
    (C) Deals with constancy of and confidence in data values, not
    with the information that the values represent (see: correctness
    integrity) or the trustworthiness of the source of the values
    (see: source integrity).
 $ data integrity service
    (I) A security service that protects against unauthorized changes
    to data, including both intentional change or destruction and
    accidental change or loss, by ensuring that changes to data are
    detectable. (See: data integrity.)
    (C) A data integrity service can only detect a change and report
    it to an appropriate system entity; changes cannot be prevented
    unless the system is perfect (error-free) and no malicious user
    has access. However, a system that offers data integrity service
    might also attempt to correct and recover from changes.
    (C) Relationship between data integrity service and authentication
    services: Although data integrity service is defined separately
    from data origin authentication service and peer entity
    authentication service, it is closely related to them.
    Authentication services depend, by definition, on companion data
    integrity services. Data origin authentication service provides
    verification that the identity of the original source of a
    received data unit is as claimed; there can be no such
    verification if the data unit has been altered. Peer entity

Shirey Informational [Page 53] RFC 2828 Internet Security Glossary May 2000

    authentication service provides verification that the identity of
    a peer entity in a current association is as claimed; there can be
    no such verification if the claimed identity has been altered.
 $ data origin authentication
    (I) "The corroboration that the source of data received is as
    claimed." [I7498 Part 2] (See: authentication.)
 $ data origin authentication service
    (I) A security service that verifies the identity of a system
    entity that is claimed to be the original source of received data.
    (See: authentication, authentication service.)
    (C) This service is provided to any system entity that receives or
    holds the data. Unlike peer entity authentication service, this
    service is independent of any association between the originator
    and the recipient, and the data in question may have originated at
    any time in the past.
    (C) A digital signature mechanism can be used to provide this
    service, because someone who does not know the private key cannot
    forge the correct signature. However, by using the signer's public
    key, anyone can verify the origin of correctly signed data.
    (C) This service is usually bundled with connectionless data
    integrity service. (See: (relationship between data integrity
    service and authentication services under) data integrity service.
 $ data privacy
    (D) ISDs SHOULD NOT use this term because it mix concepts in a
    potentially misleading way. Instead, use either "data
    confidentiality" or "privacy", depending on what is meant.
 $ data security
    (I) The protection of data from disclosure, alteration,
    destruction, or loss that either is accidental or is intentional
    but unauthorized.
    (C) Both data confidentiality service and data integrity service
    are needed to achieve data security.
 $ datagram
    (I) "A self-contained, independent entity of data carrying
    sufficient information to be routed from the source to the
    destination." [R1983]
 $ DEA
    See: Data Encryption Algorithm.

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 $ deception
    See: (secondary definition under) threat consequence.
 $ decipher
    (D) ISDs SHOULD NOT use this term as a synonym for "decrypt",
    except in special circumstances. (See: (usage discussion under)
    encryption.)
 $ decipherment
    (D) ISDs SHOULD NOT use this term as a synonym for "decryption",
    except in special circumstances. (See: (usage discussion under)
    encryption.)
 $ decode
    (I) Convert encoded data back to its original form of
    representation. (See: decrypt.)
    (D) ISDs SHOULD NOT use this term as a synonym for "decrypt",
    because that would mix concepts in a potentially misleading way.
 $ decrypt
    (I) Cryptographically restore ciphertext to the plaintext form it
    had before encryption.
 $ decryption
    See: (secondary definition under) encryption.
 $ dedicated security mode
    (I) A mode of operation of an information system, wherein all
    users have the clearance or authorization, and the need-to-know,
    for all data handled by the system. In this mode, the system may
    handle either a single classification level or category of
    information or a range of levels and categories. [DOD2]
    (C) This mode is defined formally in U.S. Department of Defense
    policy regarding system accreditation, but the term is also used
    outside the Defense Department and outside the Government.
 $ default account
    (I) A system login account (usually accessed with a user name and
    password) that has been predefined in a manufactured system to
    permit initial access when the system is first put into service.
    (C) Sometimes, the default user name and password are the same in
    each copy of the system. In any case, when the system is put into
    service, the default password should immediately be changed or the
    default account should be disabled.

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 $ degauss
    (N) Apply a magnetic field to permanently remove, erase, or clear
    data from a magnetic storage medium, such as a tape or disk
    [NCS25]. Reduce magnetic flux density to zero by applying a
    reversing magnetic field.
 $ degausser
    (N) An electrical device that can degauss magnetic storage media.
 $ DEK
    See: data encryption key.
 $ delta CRL
    (I) A partial CRL that only contains entries for X.509
    certificates that have been revoked since the issuance of a prior,
    base CRL. This method can be used to partition CRLs that become
    too large and unwieldy.
 $ denial of service
    (I) The prevention of authorized access to a system resource or
    the delaying of system operations and functions. (See:
    availability, critical (resource of a system), flooding.)
 $ DES
    See: Data Encryption Standard.
 $ dictionary attack
    (I) An attack that uses a brute-force technique of successively
    trying all the words in some large, exhaustive list.
    (C) For example, an attack on an authentication service by trying
    all possible passwords; or an attack on encryption by encrypting
    some known plaintext phrase with all possible keys so that the key
    for any given encrypted message containing that phrase may be
    obtained by lookup.
 $ Diffie-Hellman
    (N) A key agreement algorithm published in 1976 by Whitfield
    Diffie and Martin Hellman [DH76, R2631].
    (C) Diffie-Hellman does key establishment, not encryption.
    However, the key that it produces may be used for encryption, for
    further key management operations, or for any other cryptography.
    (C) The difficulty of breaking Diffie-Hellman is considered to be
    equal to the difficulty of computing discrete logarithms modulo a
    large prime. The algorithm is described in [R2631] and [Schn]. In
    brief, Alice and Bob together pick large integers that satisfy

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    certain mathematical conditions, and then use the integers to each
    separately compute a public-private key pair. They send each other
    their public key. Each person uses their own private key and the
    other person's public key to compute a key, k, that, because of
    the mathematics of the algorithm, is the same for each of them.
    Passive wiretapping cannot learn the shared k, because k is not
    transmitted, and neither are the private keys needed to compute k.
    However, without additional mechanisms to authenticate each party
    to the other, a protocol based on the algorithm may be vulnerable
    to a man-in-the-middle attack.
 $ digest
    See: message digest.
 $ digital certificate
    (I) A certificate document in the form of a digital data object (a
    data object used by a computer) to which is appended a computed
    digital signature value that depends on the data object. (See:
    attribute certificate, capability, public-key certificate.)
    (D) ISDs SHOULD NOT use this term to refer to a signed CRL or CKL.
    Although the recommended definition can be interpreted to include
    those items, the security community does not use the term with
    those meanings.
 $ digital certification
    (D) ISDs SHOULD NOT use this term as a synonym for
    "certification", unless the context is not sufficient to
    distinguish between digital certification and another kind of
    certification, in which case it would be better to use "public-key
    certification" or another phrase that indicates what is being
    certified.
 $ digital document
    (I) An electronic data object that represents information
    originally written in a non-electronic, non-magnetic  medium
    (usually ink on paper) or is an analogue of a document of that
    type.
 $ digital envelope
    (I) A digital envelope for a recipient is a combination of (a)
    encrypted content data (of any kind) and (b) the content
    encryption key in an encrypted form that has been prepared for the
    use of the recipient.
    (C) In ISDs, this term should be defined at the point of first use
    because, although the term is defined in PKCS #7 and used in
    S/MIME, it is not yet widely established.

Shirey Informational [Page 57] RFC 2828 Internet Security Glossary May 2000

    (C) Digital enveloping is not simply a synonym for implementing
    data confidentiality with encryption; digital enveloping is a
    hybrid encryption scheme to "seal" a message or other data, by
    encrypting the data and sending both it and a protected form of
    the key to the intended recipient, so that no one other than the
    intended recipient can "open" the message. In PCKS #7, it means
    first encrypting the data using a symmetric encryption algorithm
    and a secret key, and then encrypting the secret key using an
    asymmetric encryption algorithm and the public key of the intended
    recipient. In S/MIME, additional methods are defined for
    conveying the content encryption key.
 $ Digital ID(service mark)
    (D) ISDs SHOULD NOT use this term as a synonym for "digital
    certificate" because (a) it is the service mark of a commercial
    firm, (b) it unnecessarily duplicates the meaning of other, well-
    established terms, and (c) a certificate is not always used as
    authentication information. In some contexts, however, it may be
    useful to explain that the key conveyed in a public-key
    certificate can be used to verify an identity and, therefore, that
    the certificate can be thought of as digital identification
    information. (See: identification information.)
 $ digital key
    (C) The adjective "digital" need not be used with "key" or
    "cryptographic key", unless the context is insufficient to
    distinguish the digital key from another kind of key, such as a
    metal key for a door lock.
 $ digital notary
    (I) Analogous to a notary public. Provides a trusted date-and-time
    stamp for a document, so that someone can later prove that the
    document existed at a point in time. May also verify the
    signature(s) on a signed document before applying the stamp. (See:
    notarization.)
 $ digital signature
    (I) A value computed with a cryptographic algorithm and appended
    to a data object in such a way that any recipient of the data can
    use the signature to verify the data's origin and integrity. (See:
    data origin authentication service, data integrity service,
    digitized signature, electronic signature, signer.)
    (I) "Data appended to, or a cryptographic transformation of, a
    data unit that allows a recipient of the data unit to prove the
    source and integrity of the data unit and protect against forgery,
    e.g. by the recipient." [I7498 Part 2]

Shirey Informational [Page 58] RFC 2828 Internet Security Glossary May 2000

    (C) Typically, the data object is first input to a hash function,
    and then the hash result is cryptographically transformed using a
    private key of the signer. The final resulting value is called the
    digital signature of the data object. The signature value is a
    protected checksum, because the properties of a cryptographic hash
    ensure that if the data object is changed, the digital signature
    will no longer match it. The digital signature is unforgeable
    because one cannot be certain of correctly creating or changing
    the signature without knowing the private key of the supposed
    signer.
    (C) Some digital signature schemes use a asymmetric encryption
    algorithm (e.g., see: RSA) to transform the hash result. Thus,
    when Alice needs to sign a message to send to Bob, she can use her
    private key to encrypt the hash result. Bob receives both the
    message and the digital signature. Bob can use Alice's public key
    to decrypt the signature, and then compare the plaintext result to
    the hash result that he computes by hashing the message himself.
    If the values are equal, Bob accepts the message because he is
    certain that it is from Alice and has arrived unchanged. If the
    values are not equal, Bob rejects the message because either the
    message or the signature was altered in transit.
    (C) Other digital signature schemes (e.g., see: DSS) transform the
    hash result with an algorithm (e.g., see: DSA, El Gamal) that
    cannot be directly used to encrypt data. Such a scheme creates a
    signature value from the hash and provides a way to verify the
    signature value, but does not provide a way to recover the hash
    result from the signature value. In some countries, such a scheme
    may improve exportability and avoid other legal constraints on
    usage.
 $ Digital Signature Algorithm (DSA)
    (N) An asymmetric cryptographic algorithm that produces a digital
    signature in the form of a pair of large numbers. The signature is
    computed using rules and parameters such that the identity of the
    signer and the integrity of the signed data can be verified. (See:
    Digital Signature Standard.)
 $ Digital Signature Standard (DSS)
    (N) The U.S. Government standard [FP186] that specifies the
    Digital Signature Algorithm (DSA), which involves asymmetric
    cryptography.
 $ digital watermarking
    (I) Computing techniques for inseparably embedding unobtrusive
    marks or labels as bits in digital data--text, graphics, images,
    video, or audio--and for detecting or extracting the marks later.

Shirey Informational [Page 59] RFC 2828 Internet Security Glossary May 2000

    (C) The set of embedded bits (the digital watermark) is sometimes
    hidden, usually imperceptible, and always intended to be
    unobtrusive. Depending on the particular technique that is used,
    digital watermarking can assist in proving ownership, controlling
    duplication, tracing distribution, ensuring data integrity, and
    performing other functions to protect intellectual property
    rights. [ACM]
 $ digitized signature
    (D) ISDs SHOULD NOT use this term because there is no current
    consensus on its definition. Although it appears to be used mainly
    to refer to various forms of digitized images of handwritten
    signatures, the term should be avoided because it might be
    confused with "digital signature".
 $ directory
 $ Directory
    See: directory vs. Directory.
 $ Directory Access Protocol (DAP)
    (N) An OSI protocol [X519] for communication between a Directory
    User Agent (a client) and a Directory System Agent (a server).
    (See: Lightweight Directory Access Protocol.)
 $ directory vs. Directory
    1. (I) Not capitalized: The term "directory" refers generically to
    a database server or other system that provides information--such
    as a digital certificate or CRL--about an entity whose name is
    known.
    2. (I) Capitalized: "Directory" refers specifically to the X.500
    Directory. (See: repository.)
 $ disaster plan
    (D) A synonym for "contingency plan". In the interest of
    consistency, ISDs SHOULD use "contingency plan" instead of
    "disaster plan".
 $ disclosure (i.e., unauthorized disclosure)
    See: (secondary definition under) threat consequence.
 $ discretionary access control (DAC)
    (I) An access control service that enforces a security policy
    based on the identity of system entities and their authorizations
    to access system resources. (See: access control list, identity-
    based security policy, mandatory access control.)

Shirey Informational [Page 60] RFC 2828 Internet Security Glossary May 2000

    (C) This service is termed "discretionary" because an entity might
    have access rights that permit the entity, by its own volition, to
    enable another entity to access some resource.
    (O) "A means of restricting access to objects based on the
    identity of subjects and/or groups to which they belong. The
    controls are discretionary in the sense that a subject with a
    certain access permission is capable of passing that permission
    (perhaps indirectly) on to any other subject." [DOD1]
 $ disruption
    See: (secondary definition under) threat consequence.
 $ Distinguished Encoding Rules (DER)
    (N) A subset of the Basic Encoding Rules, which gives exactly one
    way to represent any ASN.1 value as an octet string [X690].
    (C) Since there is more than one way to encode ASN.1 in BER, DER
    is used in applications in which a unique encoding is needed, such
    as when a digital signature is computed on an ASN.1 value.
 $ distinguished name (DN)
    (I) An identifier that uniquely represents an object in the X.500
    Directory Information Tree (DIT) [X501]. (See: domain name.)
    (C) A DN is a set of attribute values that identify the path
    leading from the base of the DIT to the object that is named. An
    X.509 public-key certificate or CRL contains a DN that identifies
    its issuer, and an X.509 attribute certificate contains a DN or
    other form of name that identifies its subject.
 $ Distributed Authentication Security Service (DASS)
    (I) An experimental Internet protocol [R1507] that uses
    cryptographic mechanisms to provide strong, mutual authentication
    services in a distributed environment.
 $ distribution point
    (I) An X.500 Directory entry or other information source that is
    named in a v3 X.509 public-key certificate extension as a location
    from which to obtain a CRL that might list the certificate.
    (C) A v3 X.509 public-key certificate may have a
    "cRLDistributionPoints" extension that names places to get CRLs on
    which the certificate might be listed. A CRL obtained from a
    distribution point may (a) cover either all reasons for which a
    certificate might be revoked or only some of the reasons, (b) be
    issued by either the authority that signed the certificate or some

Shirey Informational [Page 61] RFC 2828 Internet Security Glossary May 2000

    other authority, and (c) contain revocation entries for only a
    subset of the full set of certificates issued by one CA or (c')
    contain revocation entries for multiple CAs.
 $ DN
    See: distinguished name.
 $ DNS
    See: Domain Name System.
 $ DOI
    See: Domain of Interpretation.
 $ domain
    (I) Security usage: An environment or context that is defined by a
    security policy, security model, or security architecture to
    include a set of system resources and the set of system entities
    that have the right to access the resources. (See: domain of
    interpretation, security perimeter.)
    (I) Internet usage: That part of the Internet domain name space
    tree [R1034] that is at or below the name the specifies the
    domain. A domain is a subdomain of another domain if it is
    contained within that domain. For example, D.C.B.A is a subdomain
    of C.B.A. (See: Domain Name System.)
    (O) MISSI usage: The domain of a MISSI CA is the set of MISSI
    users whose certificates are signed by the CA.
    (O) OSI usage: An administrative partition of a complex
    distributed OSI system.
 $ domain name
    (I) The style of identifier--a sequence of case-insensitive ASCII
    labels separated by dots ("bbn.com.")--defined for subtrees in the
    Internet Domain Name System [R1034] and used in other Internet
    identifiers, such as host names (e.g., "rosslyn.bbn.com."),
    mailbox names (e.g., "rshirey@bbn.com."), and URLs (e.g.,
    "http://www.rosslyn.bbn.com/foo"). (See: distinguished name,
    domain.)
    (C) The domain name space of the DNS is a tree structure in which
    each node and leaf holds records describing a resource. Each node
    has a label. The domain name of a node is the list of labels on
    the path from the node to the root of the tree. The labels in a
    domain name are printed or read left to right, from the most
    specific (lowest, farthest from the root) to the least specific
    (highest, closest to the root). The root's label is the null

Shirey Informational [Page 62] RFC 2828 Internet Security Glossary May 2000

    string, so a complete domain name properly ends in a dot. The top-
    level domains, those immediately below the root, include COM, EDU,
    GOV, INT, MIL, NET, ORG, and two-letter country codes (such as US)
    from ISO-3166. [R1591] (See: country code.)
 $ Domain Name System (DNS)
    (I) The main Internet operations database, which is distributed
    over a collection of servers and used by client software for
    purposes such as translating a domain name-style host name into an
    IP address (e.g., "rosslyn.bbn.com" is "192.1.7.10") and locating
    a host that accepts mail for some mailbox address. [R1034]
    (C) The DNS has three major components:
  1. Domain name space and resource records: Specifications for the

tree-structured domain name space, and data associated with the

       names.
  1. Name servers: Programs that hold information about a subset of

the tree's structure and data holdings, and also hold pointers

       to other name servers that can provide information from any
       part of the tree.
  1. Resolvers: Programs that extract information from name servers

in response to client requests; typically, system routines

       directly accessible to user programs.
    (C) Extensions to the DNS [R2065, R2137, R2536] support (a) key
    distribution for public keys needed for the DNS and for other
    protocols, (b) data origin authentication service and data
    integrity service for resource records, (c) data origin
    authentication service for transactions between resolvers and
    servers, and (d) access control of records.
 $ domain of interpretation (DOI)
    (I) IPsec usage: An ISAKMP/IKE DOI defines payload formats,
    exchange types, and conventions for naming security-relevant
    information such as security policies or cryptographic algorithms
    and modes.
    (C) For example, see [R2407]. The DOI concept is based on work by
    the TSIG's CIPSO Working Group.
 $ dominate
    (I) Security level A is said to "dominate" security level B if the
    hierarchical classification level of A is greater (higher) than or
    equal to that of B and the nonhierarchical categories of A include
    all of those of B.

Shirey Informational [Page 63] RFC 2828 Internet Security Glossary May 2000

 $ dongle
    (I) A portable, physical, electronic device that is required to be
    attached to a computer to enable a particular software program to
    run. (See: token.)
    (C) A dongle is essentially a physical key used for copy
    protection of software, because the program will not run unless
    the matching dongle is attached. When the software runs, it
    periodically queries the dongle and quits if the dongle does not
    reply with the proper authentication information. Dongles were
    originally constructed as an EPROM (erasable programmable read-
    only memory) to be connected to a serial input-output port of a
    personal computer.
 $ downgrade
    (I) Reduce the classification level of information in an
    authorized manner.
 $ draft RFC
    (D) ISDs SHOULD NOT use this term, because the Request for Comment
    series is archival in nature and does not have a "draft" category.
    (Instead, see: Internet Draft, Draft Standard (in Internet
    Standard).)
 $ DSA
    See: Digital Signature Algorithm.
 $ DSS
    See: Digital Signature Standard.
 $ dual control
    (I) A procedure that uses two or more entities (usually persons)
    operating in concert to protect a system resource, such that no
    single entity acting alone can access that resource. (See: no-lone
    zone, separation of duties, split knowledge.)
 $ dual signature
    (D) ISDs SHOULD NOT use this term except when stated as
    "SET(trademark) dual signature" with the following meaning:
    (O) SET usage: A single digital signature that protects two
    separate messages by including the hash results for both sets in a
    single encrypted value. [SET2]

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    (C) Generated by hashing each message separately, concatenating
    the two hash results, and then hashing that value and encrypting
    the result with the signer's private key. Done to reduce the
    number of encryption operations and to enable verification of data
    integrity without complete disclosure of the data.
 $ EAP
    See: Extensible Authentication Protocol
 $ eavesdropping
    (I) Passive wiretapping done secretly, i.e., without the knowledge
    of the originator or the intended recipients of the communication.
 $ ECB
    See: electronic codebook.
 $ ECDSA
    See: Elliptic Curve Digital Signature Algorithm.
 $ economy of mechanism
    (I) The principle that each security mechanism should be designed
    to be as simple as possible, so that the mechanism can be
    correctly implemented and so that it can be verified that the
    operation of the mechanism enforces the containing system's
    security policy. (See: least privilege.)
 $ EDI
    See: electronic data interchange.
 $ EDIFACT
    See: (secondary definition under) electronic data interchange.
 $ EE
    (D) ISDs SHOULD NOT use this abbreviation because of possible
    confusion among "end entity", "end-to-end encryption", "escrowed
    encryption standard", and other terms.
 $ EES
    See: Escrowed Encryption Standard.
 $ El Gamal algorithm
    (N) An algorithm for asymmetric cryptography, invented in 1985 by
    Taher El Gamal, that is based on the difficulty of calculating
    discrete logarithms and can be used for both encryption and
    digital signatures. [ElGa, Schn]

Shirey Informational [Page 65] RFC 2828 Internet Security Glossary May 2000

 $ electronic codebook (ECB)
    (I) An block cipher mode in which a plaintext block is used
    directly as input to the encryption algorithm and the resultant
    output block is used directly as ciphertext [FP081].
 $ electronic commerce
    (I) General usage: Business conducted through paperless exchanges
    of information, using electronic data interchange, electronic
    funds transfer (EFT), electronic mail, computer bulletin boards,
    facsimile, and other paperless technologies.
    (O) SET usage: "The exchange of goods and services for payment
    between the cardholder and merchant when some or all of the
    transaction is performed via electronic communication." [SET2]
 $ electronic data interchange (EDI)
    (I) Computer-to-computer exchange, between trading partners, of
    business data in standardized document formats.
    (C) EDI formats have been standardized primarily by ANSI X12 and
    by EDIFACT (EDI for Administration, Commerce, and Transportation),
    which is an international, UN-sponsored standard primarily used in
    Europe and Asia. X12 and EDIFACT are aligning to create a single,
    global EDI standard.
 $ electronic signature
    (D) ISDs SHOULD NOT use this term because there is no current
    consensus on its definition. (Instead, see: digital signature.)
 $ elliptic curve cryptography (ECC)
    (I) A type of asymmetric cryptography based on mathematics of
    groups that are defined by the points on a curve.
    (C) The most efficient implementation of ECC is claimed to be
    stronger per bit of key (against cryptanalysis that uses a brute
    force attack) than any other known form of asymmetric
    cryptography. ECC is based on mathematics different than the kinds
    originally used to define the Diffie-Hellman algorithm and the
    Digital Signature Algorithm. ECC is based on the mathematics of
    groups defined by the points on a curve, where the curve is
    defined by a quadratic equation in a finite field. ECC can be used
    to define both an algorithm for key agreement that is an analog of
    Diffie-Hellman and an algorithm for digital signature that is an
    analog of DSA. (See: ECDSA.)
 $ Elliptic Curve Digital Signature Algorithm (ECDSA)
    (N) A standard [A9062] that is the elliptic curve cryptography
    analog of the Digital Signature Algorithm.

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 $ emanation
    (I) An signal (electromagnetic, acoustic, or other medium) that is
    emitted by a system (through radiation or conductance) as a
    consequence (i.e., byproduct) of its operation, and that may
    contain information. (See: TEMPEST.)
 $ emanations security (EMSEC)
    (I) Physical constraints to prevent information compromise through
    signals emanated by a system, particular the application of
    TEMPEST technology to block electromagnetic radiation.
 $ emergency plan
    (D) A synonym for "contingency plan". In the interest of
    consistency, ISDs SHOULD use "contingency plan" instead of
    "emergency plan".
 $ EMSEC
    See: emanations security.
 $ EMV
    (I) An abbreviation of "Europay, MasterCard, Visa". Refers to a
    specification for smart cards that are used as payment cards, and
    for related terminals and applications. [EMV1, EMV2, EMV3]
 $ Encapsulating Security Payload (ESP)
    (I) An Internet IPsec protocol [R2406] designed to provide a mix
    of security services--especially data confidentiality service--in
    the Internet Protocol. (See: Authentication Header.)
    (C) ESP may be used alone, or in combination with the IPsec AH
    protocol, or in a nested fashion with tunneling. Security services
    can be provided between a pair of communicating hosts, between a
    pair of communicating security gateways, or between a host and a
    gateway. The ESP header is encapsulated by the IP header, and the
    ESP header encapsulates either the upper layer protocol header
    (transport mode) or an IP header (tunnel mode). ESP can provide
    data confidentiality service, data origin authentication service,
    connectionless data integrity service, an anti-replay service, and
    limited traffic flow confidentiality. The set of services depends
    on the placement of the implementation and on options selected
    when the security association is established.
 $ encipher
    (D) ISDs SHOULD NOT use this term as a synonym for "encrypt".
    However, see the usage note under "encryption".

Shirey Informational [Page 67] RFC 2828 Internet Security Glossary May 2000

 $ encipherment
    (D) ISDs SHOULD NOT use this term as a synonym for "encryption",
    except in special circumstances that are explained in the usage
    discussion under "encryption".
 $ encode
    (I) Use a system of symbols to represent information, which might
    originally have some other representation. (See: decode.)
    (C) Examples include Morse code, ASCII, and BER.
    (D) ISDs SHOULD NOT use this term as a synonym for "encrypt",
    because encoding is not usually intended to conceal meaning.
 $ encrypt
    (I) Cryptographically transform data to produce ciphertext. (See:
    encryption.)
 $ encryption
    (I) Cryptographic transformation of data (called "plaintext") into
    a form (called "ciphertext") that conceals the data's original
    meaning to prevent it from being known or used. If the
    transformation is reversible, the corresponding reversal process
    is called "decryption", which is a transformation that restores
    encrypted data to its original state. (See: cryptography.)
    (C) Usage note: For this concept, ISDs should use the verb "to
    encrypt" (and related variations: encryption, decrypt, and
    decryption). However, because of cultural biases, some
    international usage, particularly ISO and CCITT standards, avoids
    "to encrypt" and instead uses the verb "to encipher" (and related
    variations: encipherment, decipher, decipherment).
    (O) "The cryptographic transformation of data (see: cryptography)
    to produce ciphertext." [I7498 Part 2]
    (C) Usually, the plaintext input to an encryption operation is
    cleartext. But in some cases, the plaintext may be ciphertext that
    was output from another encryption operation. (See:
    superencryption.)
    (C) Encryption and decryption involve a mathematical algorithm for
    transforming data. In addition to the data to be transformed, the
    algorithm has one or more inputs that are control parameters: (a)
    a key value that varies the transformation and, in some cases, (b)
    an initialization value that establishes the starting state of the
    algorithm.

Shirey Informational [Page 68] RFC 2828 Internet Security Glossary May 2000

 $ encryption certificate
    (I) A public-key certificate that contains a public key that is
    intended to be used for encrypting data, rather than for verifying
    digital signatures or performing other cryptographic functions.
    C) A v3 X.509 public-key certificate may have a "keyUsage"
    extension that indicates the purpose for which the certified
    public key is intended.
 $ end entity
    (I) A system entity that is the subject of a public-key
    certificate and that is using, or is permitted and able to use,
    the matching private key only for a purpose or purposes other than
    signing a digital certificate; i.e., an entity that is not a CA.
    (D) "A certificate subject which uses its public [sic] key for
    purposes other than signing certificates." [X509]
    (C) ISDs SHOULD NOT use the X.509 definition, because it is
    misleading and incomplete. First, the X.509 definition should say
    "private key" rather than "public key" because certificates are
    not usefully signed with a public key. Second, the X.509
    definition is weak regarding whether an end entity may or may not
    use the private key to sign a certificate, i.e., whether the
    subject may be a CA. The intent of X.509's authors was that an end
    entity certificate is not valid for use in verifying a signature
    on an X.509 certificate or X.509 CRL. Thus, it would have been
    better for the X.509 definition to have said "only for purposes
    other than signing certificates".
    (C) Despite the problems in the X.509 definition, the term itself
    is useful in describing applications of asymmetric cryptography.
    The way the term is used in X.509 implies that it was meant to be
    defined, as we have done here, relative to roles that an entity
    (which is associated with an OSI end system) is playing or is
    permitted to play in applications of asymmetric cryptography other
    than the PKI that supports applications.
    (C) Whether a subject can play both CA and non-CA roles, with
    either the same or different certificates, is a matter of policy.
    (See: certification practice statement.) A v3 X.509 public-key
    certificate may have a "basicConstraints" extension containing a
    "cA" value that specifically "indicates whether or not the public
    key may be used to verify certificate signatures".

Shirey Informational [Page 69] RFC 2828 Internet Security Glossary May 2000

 $ end system
    (I) An OSI term for a computer that implements all seven layers of
    the OSIRM and may attach to a subnetwork. (In the context of the
    Internet Protocol Suite, usually called a "host".)
 $ end-to-end encryption
    (I) Continuous protection of data that flows between two points in
    a network, provided by encrypting data when it leaves its source,
    leaving it encrypted while it passes through any intermediate
    computers (such as routers), and decrypting only when the data
    arrives at the intended destination. (See: link encryption,
    wiretapping.)
    (C) When two points are separated by multiple communication links
    that are connected by one or more intermediate relays, end-to-end
    encryption enables the source and destination systems to protect
    their communications without depending on the intermediate systems
    to provide the protection.
 $ end user
    (I) General usage: A system entity, usually a human individual,
    that makes use of system resources, primarily for application
    purposes as opposed to system management purposes.
    (I) PKI usage: A synonym for "end entity"; but the term "end
    entity" is preferred.
 $ entity
    See: system entity.
 $ entrapment
    (I) "The deliberate planting of apparent flaws in a system for the
    purpose of detecting attempted penetrations or confusing an
    intruder about which flaws to exploit." [FP039] (See: honey pot.)
 $ ephemeral key
    (I) A public key or a private key that is relatively short-lived.
    (See: session key.)
 $ error detection code
    (I) A checksum designed to detect, but not correct, accidental
    (i.e., unintentional) changes in data.
 $ Escrowed Encryption Standard (EES)
    (N) A U.S. Government standard [FP185] that specifies use of a
    symmetric encryption algorithm (SKIPJACK) and a Law Enforcement

Shirey Informational [Page 70] RFC 2828 Internet Security Glossary May 2000

    Access Field (LEAF) creation method to implement part of a key
    escrow system that provides for decryption of encrypted
    telecommunications when interception is lawfully authorized.
    (C) Both SKIPJACK and the LEAF are to be implemented in equipment
    used to encrypt and decrypt unclassified, sensitive
    telecommunications data.
 $ ESP
    See: Encapsulating Security Payload.
 $ Estelle
    (N) A language (ISO 9074-1989) for formal specification of
    computer network protocols.
 $ evaluated products list
    (O) General usage: A list of information system equipment items
    that have been evaluated against, and found to be compliant with,
    a particular set of criteria.
    (O) U.S. Department of Defense usage: The Evaluated Products List
    (http://www.radium.ncsc.mil/tpep/epl/) contains items that have
    been evaluated against the TCSEC by the NCSC, or against the
    Common Criteria by the NCSC or one of its partner agencies in
    another county. The List forms Chapter 4 of NSA's "Information
    Systems Security Products and Services Catalogue".
 $ evaluated system
    (I) Refers to a system that has been evaluated against security
    criteria such as the TCSEC or the Common Criteria.
 $ expire
    See: certificate expiration.
 $ exposure
    See: (secondary definition under) threat consequence.
 $ Extensible Authentication Protocol
    (I) A framework that supports multiple, optional authentication
    mechanisms for PPP, including cleartext passwords, challenge-
    response, and arbitrary dialog sequences. [R2284]
    (C) This protocol is intended for use primarily by a host or
    router that connects to a PPP network server via switched circuits
    or dial-up lines.

Shirey Informational [Page 71] RFC 2828 Internet Security Glossary May 2000

 $ extension
    (I) A data item defined for optional inclusion in a v3 X.509
    public-key certificate or a v2 X.509 CRL.
    (C) The formats defined in X.509 can be extended to provide
    methods for associating additional attributes with subjects and
    public keys and for managing a certification hierarchy:
  1. "Certificate extension": X.509 defines standard extensions that

may be included in v3 certificates to provide additional key

       and security policy information, subject and issuer attributes,
       and certification path constraints.
  1. "CRL extension": X.509 defines extensions that may be included

in v2 CRLs to provide additional issuer key and name

       information, revocation reasons and constraints, and
       information about distribution points and delta CRLs.
  1. "Private extension": Additional extensions, each named by an

OID, can be locally defined as needed by applications or

       communities. (See: PKIX private extension, SET private
       extensions.)
 $ extranet
    (I) A computer network that an organization uses to carry
    application data traffic between the organization and its business
    partners. (See: intranet.)
    (C) An extranet can be implemented securely, either on the
    Internet or using Internet technology, by constructing the
    extranet as a VPN.
 $ fail safe
    (I) A mode of system termination that automatically leaves system
    processes and components in a secure state when a failure occurs
    or is detected in the system.
 $ fail soft
    (I) Selective termination of affected non-essential system
    functions and processes when a failure occurs or is detected in
    the system.
 $ failure control
    (I) A methodology used to provide fail-safe or fail-soft
    termination and recovery of functions and processes when failures
    are detected or occur in a system. [FP039]

Shirey Informational [Page 72] RFC 2828 Internet Security Glossary May 2000

 $ Federal Information Processing Standards (FIPS)
    (N) The Federal Information Processing Standards Publication (FIPS
    PUB) series issued by the U.S. National Institute of Standards and
    Technology as technical guidelines for U.S. Government
    procurements of information processing system equipment and
    services. [FP031, FP039, FP046, FP081, FP102, FP113, FP140, FP151,
    FP180, FP185, FP186, FP188]
    (C) Issued under the provisions of section 111(d) of the Federal
    Property and Administrative Services Act of 1949 as amended by the
    Computer Security Act of 1987, Public Law 100-235.
 $ Federal Public-key Infrastructure (FPKI)
    (N) A PKI being planned to establish facilities, specifications,
    and policies needed by the U.S. Federal Government to use public-
    key certificates for INFOSEC, COMSEC, and electronic commerce
    involving unclassified but sensitive applications and interactions
    between Federal agencies as well as with entities of other
    branches of the Federal Government, state, and local governments,
    business, and the public. [FPKI]
 $ Federal Standard 1027
    (N) An U.S. Government document defining emanation, anti-tamper,
    security fault analysis, and manual key management criteria for
    DES encryption devices, primary for OSI layer 2. Was renamed "FIPS
    PUB 140" when responsibility for protecting unclassified,
    sensitive information was transferred from NSA to NIST, and then
    was superseded by FIPS PUB 140-1.
 $ File Transfer Protocol (FTP)
    (I) A TCP-based, application-layer, Internet Standard protocol
    [R0959] for moving data files from one computer to another.
 $ filtering router
    (I) An internetwork router that selectively prevents the passage
    of data packets according to a security policy.
    (C) A filtering router may be used as a firewall or part of a
    firewall. A router usually receives a packet from a network and
    decides where to forward it on a second network. A filtering
    router does the same, but first decides whether the packet should
    be forwarded at all, according to some security policy. The policy
    is implemented by rules (packet filters) loaded into the router.
    The rules mostly involve values of data packet control fields
    (especially IP source and destination addresses and TCP port
    numbers). [R2179]

Shirey Informational [Page 73] RFC 2828 Internet Security Glossary May 2000

 $ financial institution
    (N) "An establishment responsible for facilitating customer-
    initiated transactions or transmission of funds for the extension
    of credit or the custody, loan, exchange, or issuance of money."
    [SET2]
 $ fingerprint
    (I) A pattern of curves formed by the ridges on a fingertip. (See:
    biometric authentication, thumbprint.)
    (D) ISDs SHOULD NOT use this term as a synonym for "hash result"
    because it mixes concepts in a potentially misleading way.
    (D) ISDs SHOULD NOT use this term with the following PGP
    definition, because the term and definition mix concepts in a
    potentially misleading way and duplicate the meaning of "hash
    result":
    (O) PGP usage: A hash result used to authenticate a public key
    (key fingerprint) or other data. [PGP]
 $ FIPS
    See: Federal Information Processing Standards.
 $ FIPS PUB 140-1
    (N) The U.S. Government standard [FP140] for security requirements
    to be met by a cryptographic module used to protect unclassified
    information in computer and communication systems. (See: Common
    Criteria, FIPS, Federal Standard 1027.)
    (C) The standard specifies four increasing levels (from "Level 1"
    to "Level 4") of requirements to cover a wide range of potential
    applications and environments. The requirements address basic
    design and documentation, module interfaces, authorized roles and
    services, physical security, software security, operating system
    security, key management, cryptographic algorithms,
    electromagnetic interference and electromagnetic compatibility
    (EMI/EMC), and self-testing. NIST and the Canadian Communication
    Security Establishment jointly certify modules.
 $ firewall
    (I) An internetwork gateway that restricts data communication
    traffic to and from one of the connected networks (the one said to
    be "inside" the firewall) and thus protects that network's system
    resources against threats from the other network (the one that is
    said to be "outside" the firewall). (See: guard, security
    gateway.)

Shirey Informational [Page 74] RFC 2828 Internet Security Glossary May 2000

    (C) A firewall typically protects a smaller, secure network (such
    as a corporate LAN, or even just one host) from a larger network
    (such as the Internet). The firewall is installed at the point
    where the networks connect, and the firewall applies security
    policy rules to control traffic that flows in and out of the
    protected network.
    (C) A firewall is not always a single computer. For example, a
    firewall may consist of a pair of filtering routers and one or
    more proxy servers running on one or more bastion hosts, all
    connected to a small, dedicated LAN between the two routers. The
    external router blocks attacks that use IP to break security (IP
    address spoofing, source routing, packet fragments), while proxy
    servers block attacks that would exploit a vulnerability in a
    higher layer protocol or service. The internal router blocks
    traffic from leaving the protected network except through the
    proxy servers. The difficult part is defining criteria by which
    packets are denied passage through the firewall, because a
    firewall not only needs to keep intruders out, but usually also
    needs to let authorized users in and out.
 $ firmware
    (I) Computer programs and data stored in hardware--typically in
    read-only memory (ROM) or programmable read-only memory (PROM)--
    such that the programs and data cannot be dynamically written or
    modified during execution of the programs. (See: hardware,
    software.)
 $ FIRST
    See: Forum of Incident Response and Security Teams.
 $ flaw hypothesis methodology
    (I) An evaluation or attack technique in which specifications and
    documentation for a system are analyzed to hypothesize flaws in
    the system. The list of hypothetical flaws is prioritized on the
    basis of the estimated probability that a flaw exists and,
    assuming it does, on the ease of exploiting it and the extent of
    control or compromise it would provide. The prioritized list is
    used to direct a penetration test or attack against the system.
    [NCS04]
 $ flooding
    (I) An attack that attempts to cause a failure in (especially, in
    the security of) a computer system or other data processing entity
    by providing more input than the entity can process properly.
    (See: denial of service.)

Shirey Informational [Page 75] RFC 2828 Internet Security Glossary May 2000

 $ flow analysis
    (I) An analysis performed on a nonprocedural formal system
    specification that locates potential flows of information between
    system variables. By assigning security levels to the variables,
    the analysis can find some types of covert channels.
 $ flow control
    (I) A procedure or technique to ensure that information transfers
    within a system are not made from one security level to another
    security level, and especially not from a higher level to a lower
    level. (See: covert channel, simple security property, confinement
    property.)
 $ formal specification
    (I) A specification of hardware or software functionality in a
    computer-readable language; usually a precise mathematical
    description of the behavior of the system with the aim of
    providing a correctness proof.
 $ formulary
    (I) A technique for enabling a decision to grant or deny access to
    be made dynamically at the time the access is attempted, rather
    than earlier when an access control list or ticket is created.
 $ FORTEZZA(trademark)
    (N) A registered trademark of NSA, used for a family of
    interoperable security products that implement a NIST/NSA-approved
    suite of cryptographic algorithms for digital signature, hash,
    encryption, and key exchange. The products include a PC card that
    contains a CAPSTONE chip, serial port modems, server boards, smart
    cards, and software implementations.
 $ Forum of Incident Response and Security Teams (FIRST)
    (N) An international consortium of CSIRTs that work together to
    handle computer security incidents and promote preventive
    activities. (See: CSIRT, security incident.)
    (C) FIRST was founded in 1990 and, as of September 1999, had
    nearly 70 members spanning the globe. Its mission includes:
  1. Provide members with technical information, tools, methods,

assistance, and guidance.

  1. Coordinate proactive liaison activities and analytical support.
  2. Encourage development of quality products and services.
  3. Improve national and international information security for

government, private industry, academia, and the individual.

  1. Enhance the image and status of the CSIRT community.

Shirey Informational [Page 76] RFC 2828 Internet Security Glossary May 2000

 $ forward secrecy
    See: public-key forward secrecy.
 $ FPKI
    See: Federal Public-Key Infrastructure.
 $ FTP
    See: File Transfer Protocol.
 $ gateway
    (I) A relay mechanism that attaches to two (or more) computer
    networks that have similar functions but dissimilar
    implementations and that enables host computers on one network to
    communicate with hosts on the other; an intermediate system that
    is the interface between two computer networks. (See: bridge,
    firewall, guard, internetwork, proxy server, router, and
    subnetwork.)
    (C) In theory, gateways are conceivable at any OSI layer. In
    practice, they operate at OSI layer 3 (see: bridge, router) or
    layer 7 (see: proxy server). When the two networks differ in the
    protocol by which they offer service to hosts, the gateway may
    translate one protocol into another or otherwise facilitate
    interoperation of hosts (see: Internet Protocol).
 $ GCA
    See: geopolitical certificate authority.
 $ GeneralizedTime
    (N) The ASN.1 data type "GeneralizedTime" (specified in ISO 8601)
    contains a calendar date (YYYYMMDD) and a time of day, which is
    either (a) the local time, (b) the Coordinated Universal Time, or
    (c) both the local time and an offset allowing Coordinated
    Universal Time to be calculated. (See: Coordinated Universal Time,
    UTCTime.)
 $ Generic Security Service Application Program Interface (GSS-API)
    (I) An Internet Standard protocol [R2078] that specifies calling
    conventions by which an application (typically another
    communication protocol) can obtain authentication, integrity, and
    confidentiality security services independently of the underlying
    security mechanisms and technologies, thus allowing the
    application source code to be ported to different environments.
    (C) "A GSS-API caller accepts tokens provided to it by its local
    GSS-API implementation and transfers the tokens to a peer on a
    remote system; that peer passes the received tokens to its local

Shirey Informational [Page 77] RFC 2828 Internet Security Glossary May 2000

    GSS-API implementation for processing. The security services
    available through GSS-API in this fashion are implementable (and
    have been implemented) over a range of underlying mechanisms based
    on [symmetric] and [asymmetric cryptography]." [R2078]
 $ geopolitical certificate authority (GCA)
    (O) SET usage: In a SET certification hierarchy, an optional level
    that is certified by a BCA and that may certify cardholder CAs,
    merchant CAs, and payment gateway CAs. Using GCAs enables a brand
    to distribute responsibility for managing certificates to
    geographic or political regions, so that brand policies can vary
    between regions as needed.
 $ Green Book
    (D) Except as an explanatory appositive, ISDs SHOULD NOT use this
    term as a synonym for "Defense Password Management Guideline"
    [CSC2]. Instead, use the full proper name of the document or, in
    subsequent references, a conventional abbreviation. (See: Rainbow
    Series.)
    (D) Usage note: To improve international comprehensibility of
    Internet Standards and the Internet Standards Process, ISDs SHOULD
    NOT use "cute" synonyms for document titles. No matter how popular
    and clearly understood a nickname may be in one community, it is
    likely to cause confusion in others. For example, several other
    information system standards also are called "the Green Book". The
    following are some examples:
  1. Each volume of 1992 ITU-T (at that time, CCITT) standards.
  2. "PostScript Language Program Design", Adobe Systems, Addison-

Wesley, 1988.

  1. IEEE 1003.1 POSIX Operating Systems Interface.
  2. "Smalltalk-80: Bits of History, Words of Advice", Glenn

Krasner, Addison-Wesley, 1983.

  1. "X/Open Compatibility Guide".
  2. A particular CD-ROM format developed by Phillips.
 $ GRIP
    (I) A contraction of "Guidelines and Recommendations for Security
    Incident Processing", the name of the IETF working group that
    seeks to facilitate consistent handling of security incidents in
    the Internet community. (See: security incident.)
    (C) Guidelines to be produced by the WG will address technology
    vendors, network service providers, and response teams in their
    roles assisting organizations in resolving security incidents.
    These relationships are functional and can exist within and across
    organizational boundaries.

Shirey Informational [Page 78] RFC 2828 Internet Security Glossary May 2000

 $ GSS-API
    See: Generic Security Service Application Program Interface.
 $ guard
    (I) A gateway that is interposed between two networks (or
    computers, or other information systems) operating at different
    security levels (one level is usually higher than the other) and
    is trusted to mediate all information transfers between the two
    levels, either to ensure that no sensitive information from the
    first (higher) level is disclosed to the second (lower) level, or
    to protect the integrity of data on the first (higher) level.
    (See: firewall.)
 $ guest login
    See: anonymous login.
 $ GULS
    (I) Generic Upper Layer Security service element (ISO 11586), a
    five-part standard for the exchange of security information and
    security-transformation functions that protect confidentiality and
    integrity of application data.
 $ hacker
    (I) Someone with a strong interest in computers, who enjoys
    learning about them and experimenting with them. (See: cracker.)
    (C) The recommended definition is the original meaning of the term
    (circa 1960), which then had a neutral or positive connotation of
    "someone who figures things out and makes something cool
    happen". Today, the term is frequently misused, especially by
    journalists, to have the pejorative meaning of cracker.
 $ handle
    (I) (1.) Verb: Perform processing operations on data, such as
    receive and transmit, collect and disseminate, create and delete,
    store and retrieve, read and write, and compare. (2.) Noun: An on-
    line pseudonym, particularly one used by a cracker; derived from
    citizens band radio culture.
 $ hardware
    (I) The material physical components of a computer system. (See:
    firmware, software.)
 $ hardware token
    See: token.

Shirey Informational [Page 79] RFC 2828 Internet Security Glossary May 2000

 $ hash code
    (D) ISDs SHOULD NOT use this term (especially not as a synonym for
    "hash result") because it mixes concepts in a potentially
    misleading way. A hash result is not a "code" in any sense defined
    by this glossary. (See: code, hash result, hash value, message
    digest.)
 $ hash function
    (I) An algorithm that computes a value based on a data object
    (such as a message or file; usually variable-length; possibly very
    large), thereby mapping the data object to a smaller data object
    (the "hash result") which is usually a fixed-size value. (See:
    checksum, keyed hash.)
    (O) "A (mathematical) function which maps values from a large
    (possibly very large) domain into a smaller range. A 'good' hash
    function is such that the results of applying the function to a
    (large) set of values in the domain will be evenly distributed
    (and apparently at random) over the range." [X509]
    (C) The kind of hash function needed for security applications is
    called a "cryptographic hash function", an algorithm for which it
    is computationally infeasible (because no attack is significantly
    more efficient than brute force) to find either (a) a data object
    that maps to a pre-specified hash result (the "one-way" property)
    or (b) two data objects that map to the same hash result (the
    "collision-free" property). (See: MD2, MD4, MD5, SHA-1.)
    (C) A cryptographic hash is "good" in the sense stated in the "O"
    definition for hash function. Any change to an input data object
    will, with high probability, result in a different hash result, so
    that the result of a cryptographic hash makes a good checksum for
    a data object.
 $ hash result
    (I) The output of a hash function. (See: hash code, hash value.)
    (O) "The output produced by a hash function upon processing a
    message" (where "message" is broadly defined as "a digital
    representation of data"). [ABA] (The recommended definition is
    compatible with this ABA definition, but we avoid the unusual
    definition of "message".)
 $ hash value
    (D) ISDs SHOULD NOT use this term (especially not as a synonym for
    "hash result", the output of a hash function) because it might be
    confused with "hashed value" (the input to a hash function). (See:
    hash code, hash result, message digest.)

Shirey Informational [Page 80] RFC 2828 Internet Security Glossary May 2000

 $ hierarchical PKI
    (I) A PKI architecture based on a certification hierarchy. (See:
    mesh PKI, trust-file PKI.)
 $ hierarchy management
    (I) The process of generating configuration data and issuing
    public-key certificates to build and operate a certification
    hierarchy.
 $ hierarchy of trust
    (D) ISDs SHOULD NOT use this term with regard to PKI, especially
    not as a synonym for "certification hierarchy", because this term
    mixes concepts in a potentially misleading way. (See:
    certification hierarchy, trust, web of trust.)
 $ hijack attack
    (I) A form of active wiretapping in which the attacker seizes
    control of a previously established communication association.
    (See: man-in-the-middle attack, pagejacking, piggyback attack.)
 $ HMAC
    (I) A keyed hash [R2104] that can be based on any iterated
    cryptographic hash (e.g., MD5 or SHA-1), so that the cryptographic
    strength of HMAC depends on the properties of the selected
    cryptographic hash. (See: [R2202, R2403, R2404].)
    (C) Assume that H is a generic cryptographic hash in which a
    function is iterated on data blocks of length B bytes. L is the
    length of the of hash result of H. K is a secret key of length L
    <= K <= B. The values IPAD and OPAD are fixed strings used as
    inner and outer padding and defined as follows: IPAD = the byte
    0x36 repeated B times, OPAD = the byte 0x5C repeated B times. HMAC
    is computed by H(K XOR OPAD, H(K XOR IPAD, inputdata)).
    (C) The goals of HMAC are as follows:
  1. To use available cryptographic hash functions without

modification, particularly functions that perform well in

       software and for which software is freely and widely available.
     - To preserve the original performance of the selected hash
       without significant degradation.
     - To use and handle keys in a simple way.
     - To have a well-understood cryptographic analysis of the
       strength of the mechanism based on reasonable assumptions about
       the underlying hash function.
     - To enable easy replacement of the hash function in case a
       faster or stronger hash is found or required.

Shirey Informational [Page 81] RFC 2828 Internet Security Glossary May 2000

 $ honey pot
    (I) A system (e.g., a web server) or a system resource (e.g., a
    file on a server), that is designed to be attractive to potential
    crackers and intruders, like honey is attractive to bears. (See:
    entrapment.)
    (D) It is likely that other cultures have different metaphors for
    this concept. To ensure international understanding, ISDs should
    not use this term unless they also provide an explanation like
    this one. (See: (usage note under) Green Book.)
 $ host
    (I) General computer network usage: A computer that is attached to
    a communication subnetwork or internetwork and can use services
    provided by the network to exchange data with other attached
    systems. (See: end system.)
    (I) Specific Internet Protocol Suite usage: A networked computer
    that does not forward Internet Protocol packets that are not
    addressed to the computer itself. (See: router.)
    (C) Derivation: As viewed by its users, a host "entertains"
    guests, providing application layer services or access to other
    computers attached to the network. However, even though some
    traditional peripheral service devices, such as printers, can now
    be independently connected to networks, they are not usually
    called hosts.
 $ HTML
    See: Hypertext Markup Language.
 $ HTTP
    See: Hypertext Transfer Protocol.
 $ https
    (I) When used in the first part of a URL (the part that precedes
    the colon and specifies an access scheme or protocol), this term
    specifies the use of HTTP enhanced by a security mechanism, which
    is usually SSL. (See: S-HTTP.)
 $ hybrid encryption
    (I) An application of cryptography that combines two or more
    encryption algorithms, particularly a combination of symmetric and
    asymmetric encryption. (E.g., see: digital envelope.)
    (C) Asymmetric algorithms require more computation than
    equivalently strong symmetric ones. Thus, asymmetric encryption is
    not normally used for data confidentiality except in distributing

Shirey Informational [Page 82] RFC 2828 Internet Security Glossary May 2000

    symmetric keys in applications where the key data is usually short
    (in terms of bits) compared to the data it protects. (E.g., see:
    MSP, PEM, PGP.)
 $ hyperlink
    (I) In hypertext or hypermedia, an information object (such as a
    word, a phrase, or an image; usually highlighted by color or
    underscoring) that points (indicates how to connect) to related
    information that is located elsewhere and can be retrieved by
    activating the link (e.g., by selecting the object with a mouse
    pointer and then clicking).
 $ hypermedia
    (I) A generalization of hypertext; any media that contain
    hyperlinks that point to material in the same or another data
    object.
 $ hypertext
    (I) A computer document, or part of a document, that contains
    hyperlinks to other documents; i.e., text that contains active
    pointers to other text. Usually written in Hypertext Markup
    Language and accessed using a web browser. (See: hypermedia.)
 $ Hypertext Markup Language (HTML)
    (I) A platform-independent system of syntax and semantics for
    adding characters to data files (particularly text files) to
    represent the data's structure and to point to related data, thus
    creating hypertext for use in the World Wide Web and other
    applications. [R1866]
 $ Hypertext Transfer Protocol (HTTP)
    (I) A TCP-based, application-layer, client-server, Internet
    protocol [R2616] used to carry data requests and responses in the
    World Wide Web. (See: hypertext.)
 $ IAB
    See: Internet Architecture Board.
 $ IANA
    See: Internet Assigned Numbers Authority.
 $ ICANN
    See: Internet Corporation for Assigned Names and Numbers.
 $ ICMP
    See: Internet Control Message Protocol.

Shirey Informational [Page 83] RFC 2828 Internet Security Glossary May 2000

 $ ICMP flood
    (I) A denial of service attack that sends a host more ICMP echo
    request ("ping") packets than the protocol implementation can
    handle. (See: flooding, smurf.)
 $ ICRL
    See: indirect certificate revocation list.
 $ IDEA
    See: International Data Encryption Algorithm.
 $ identification
    (I) An act or process that presents an identifier to a system so
    that the system can recognize a system entity and distinguish it
    from other entities. (See: authentication.)
 $ Identification Protocol
    (I) An client-server Internet protocol [R1413] for learning the
    identity of a user of a particular TCP connection.
    (C) Given a TCP port number pair, the server returns a character
    string that identifies the owner of that connection on the
    server's system. The protocol is not intended for authorization or
    access control. At best, it provides additional auditing
    information with respect to TCP.
 $ identity-based security policy
    (I) "A security policy based on the identities and/or attributes
    of users, a group of users, or entities acting on behalf of the
    users and the resources/objects being accessed." [I7498 Part 2]
    (See: rule-based security policy.)
 $ IEEE
    See: Institute of Electrical and Electronics Engineers, Inc.
 $ IEEE 802.10
    (N) An IEEE committee developing security standards for local area
    networks. (See: SILS.)
 $ IEEE P1363
    (N) An IEEE working group, Standard for Public-Key Cryptography,
    developing a comprehensive reference standard for asymmetric
    cryptography. Covers discrete logarithm (e.g., DSA), elliptic
    curve, and integer factorization (e.g., RSA); and covers key
    agreement, digital signature, and encryption.
 $ IESG
    See: Internet Engineering Steering Group.

Shirey Informational [Page 84] RFC 2828 Internet Security Glossary May 2000

 $ IETF
    See: Internet Engineering Task Force.
 $ IKE
    See: IPsec Key Exchange.
 $ IMAP4
    See: Internet Message Access Protocol, version 4.
 $ IMAP4 AUTHENTICATE
    (I) A IMAP4 "command" (better described as a transaction type, or
    a protocol-within-a-protocol) by which an IMAP4 client optionally
    proposes a mechanism to an IMAP4 server to authenticate the client
    to the server and provide other security services. (See: POP3.)
    (C) If the server accepts the proposal, the command is followed by
    performing a challenge-response authentication protocol and,
    optionally, negotiating a protection mechanism for subsequent POP3
    interactions. The security mechanisms that are used by IMAP4
    AUTHENTICATE--including Kerberos, GSSAPI, and S/Key--are described
    in [R1731].
 $ in the clear
    (I) Not encrypted. (See: cleartext.)
 $ indirect certificate revocation list (ICRL)
    (I) In X.509, a CRL that may contain certificate revocation
    notifications for certificates issued by CAs other than the issuer
    of the ICRL.
 $ indistinguishability
    (I) An attribute of an encryption algorithm that is a
    formalization of the notion that the encryption of some string is
    indistinguishable from the encryption of an equal-length string of
    nonsense.
    (C) Under certain conditions, this notion is equivalent to
    "semantic security".
 $ information
    (I) Facts and ideas, which can be represented (encoded) as various
    forms of data.
 $ Information Technology Security Evaluation Criteria (ITSEC)
    (N) Standard developed for use in the European Union; accommodates
    a wider range of security assurance and functionality combinations
    than the TCSEC. Superseded by the Common Criteria. [ITSEC]

Shirey Informational [Page 85] RFC 2828 Internet Security Glossary May 2000

 $ INFOSEC
    (I) Abbreviation for "information security", referring to security
    measures that implement and assure security services in computer
    systems (i.e., COMPUSEC) and communication systems (i.e., COMSEC).
 $ initialization value (IV)
    (I) An input parameter that sets the starting state of a
    cryptographic algorithm or mode. (Sometimes called "initialization
    vector" or "message indicator".)
    (C) An IV can be used to introduce cryptographic variance in
    addition to that provided by a key (see: salt), and to synchronize
    one cryptographic process with another. For an example of the
    latter, cipher block chaining mode requires an IV. [R2405]
 $ initialization vector
    (D) For consistency, ISDs SHOULD NOT use this term as a synonym
    for "initialization value".
 $ insider attack
    See: (secondary definition under) attack.
 $ Institute of Electrical and Electronics Engineers, Inc. (IEEE)
    (N) The IEEE is a not-for-profit association of more than 330,000
    individual members in 150 countries. The IEEE produces 30 percent
    of the world's published literature in electrical engineering,
    computers, and control technology; holds annually more than 300
    major conferences; and has more than 800 active standards with 700
    under development. (See: Standards for Interoperable LAN/MAN
    Security.)
 $ integrity
    See: data integrity, correctness integrity, source integrity,
    system integrity.
 $ integrity check
    (D) ISDs SHOULD NOT use this term as a synonym for "cryptographic
    hash" or "protected checksum", because this term unnecessarily
    duplicates the meaning of other, well-established terms.
 $ intelligent threat
    (I) A circumstance in which an adversary has the technical and
    operational capability to detect and exploit a vulnerability and
    also has the demonstrated, presumed, or inferred intent to do so.
    (See: threat.)

Shirey Informational [Page 86] RFC 2828 Internet Security Glossary May 2000

 $ International Data Encryption Algorithm (IDEA)
    (N) A patented, symmetric block cipher that uses a 128-bit key and
    operates on 64-bit blocks. [Schn] (See: symmetric cryptography.)
 $ International Standard
    See: (secondary definition under) ISO.
 $ International Traffic in Arms Regulations (ITAR)
    (N) Rules issued by the U.S. State Department, by authority of the
    Arms Export Control Act (22 U.S.C. 2778), to control export and
    import of defense articles and defense services, including
    information security systems, such as cryptographic systems, and
    TEMPEST suppression technology. (See: Wassenaar Arrangement.)
 $ internet
 $ Internet
    See: internet vs. Internet.
 $ Internet Architecture Board (IAB)
    (I) A technical advisory group of the ISOC, chartered by the ISOC
    Trustees to provide oversight of Internet architecture and
    protocols and, in the context of Internet Standards, a body to
    which decisions of the IESG may be appealed. Responsible for
    approving appointments to the IESG from among nominees submitted
    by the IETF nominating committee. [R2026]
 $ Internet Assigned Numbers Authority (IANA)
    (I) From the early days of the Internet, the IANA was chartered by
    the ISOC and the U.S. Government's Federal Network Council to be
    the central coordination, allocation, and registration body for
    parameters for Internet protocols. Superseded by ICANN.
 $ Internet Control Message Protocol (ICMP)
    (I) An Internet Standard protocol [R0792] that is used to report
    error conditions during IP datagram processing and to exchange
    other information concerning the state of the IP network.
 $ Internet Corporation for Assigned Names and Numbers (ICANN)
    (I) The non-profit, private corporation that has assumed
    responsibility for the IP address space allocation, protocol
    parameter assignment, domain name system management, and root
    server system management functions formerly performed under U.S.
    Government contract by IANA and other entities.
    (C) The Internet Protocol Suite, as defined by the IETF and the
    IESG, contains numerous parameters, such as internet addresses,
    domain names, autonomous system numbers, protocol numbers, port
    numbers, management information base object identifiers, including

Shirey Informational [Page 87] RFC 2828 Internet Security Glossary May 2000

    private enterprise numbers, and many others. The Internet
    community requires that the values used in these parameter fields
    be assigned uniquely. ICANN makes those assignments as requested
    and maintains a registry of the current values.
    (C) ICANN was formed in October 1998, by a coalition of the
    Internet's business, technical, and academic communities. The U.S.
    Government designated ICANN to serve as the global consensus
    entity with responsibility for coordinating four key functions for
    the Internet: the allocation of IP address space, the assignment
    of protocol parameters, the management of the DNS, and the
    management of the DNS root server system.
 $ Internet Draft
    (I) A working document of the IETF, its areas, and its working
    groups. (Other groups may also distribute working documents as
    Internet Drafts.) An Internet Draft is not an archival document
    like an RFC is. Instead, an Internet Draft is a preliminary or
    working document that is valid for a maximum of six months and may
    be updated, replaced, or made obsolete by other documents at any
    time. It is inappropriate to use an Internet Draft as reference
    material or to cite it other than as "work in progress."
 $ Internet Engineering Steering Group (IESG)
    (I) The part of the ISOC responsible for technical management of
    IETF activities and administration of the Internet Standards
    Process according to procedures approved by the ISOC Trustees.
    Directly responsible for actions along the "standards track",
    including final approval of specifications as Internet Standards.
    Composed of IETF Area Directors and the IETF chairperson, who also
    chairs the IESG. [R2026]
 $ Internet Engineering Task Force (IETF)
    (I) A self-organized group of people who make contributions to the
    development of Internet technology. The principal body engaged in
    developing Internet Standards, although not itself a part of the
    ISOC. Composed of Working Groups, which are arranged into Areas
    (such as the Security Area), each coordinated by one or more Area
    Directors. Nominations to the IAB and the IESG are made by a
    committee selected at random from regular IETF meeting attendees
    who have volunteered. [R2026, R2323]
 $ Internet Message Access Protocol, version 4 (IMAP4)
    (I) An Internet protocol [R2060] by which a client workstation can
    dynamically access a mailbox on a server host to manipulate and
    retrieve mail messages that the server has received and is holding
    for the client. (See: POP3.)

Shirey Informational [Page 88] RFC 2828 Internet Security Glossary May 2000

    (C) IMAP4 has mechanisms for optionally authenticating a client to
    a server and providing other security services. (See: IMAP4
    AUTHENTICATE.)
 $ Internet Policy Registration Authority (IPRA)
    (I) An X.509-compliant CA that is the top CA of the Internet
    certification hierarchy operated under the auspices of the ISOC
    [R1422]. (See: (PEM usage under) certification hierarchy.)
 $ Internet Protocol (IP)
    (I) A Internet Standard protocol (version 4 [R0791] and version 6
    [R2460]) that moves datagrams (discrete sets of bits) from one
    computer to another across an internetwork but does not provide
    reliable delivery, flow control, sequencing, or other end-to-end
    services that TCP provides. (See: IP address, TCP/IP.)
    (C) In the OSIRM, IP would be located at the top of layer 3.
 $ Internet Protocol security (IPsec)
    (I) (1.) The name of the IETF working group that is specifying a
    security architecture [R2401] and protocols to provide security
    services for Internet Protocol traffic. (2.) A collective name for
    that architecture and set of protocols. (Implementation of IPsec
    protocols is optional for IP version 4, but mandatory for IP
    version 6.) (See: Internet Protocol Security Option.)
    (C) Note that the letters "sec" are lower-case.
    (C) The IPsec architecture specifies (a) security protocols (AH
    and ESP), (b) security associations (what they are, how they work,
    how they are managed, and associated processing), (c) key
    management (IKE), and (d) algorithms for authentication and
    encryption. The set of security services include access control
    service, connectionless data integrity service, data origin
    authentication service, protection against replays (detection of
    the arrival of duplicate datagrams, within a constrained window),
    data confidentiality service, and limited traffic flow
    confidentiality.
 $ Internet Protocol Security Option (IPSO)
    (I) Refers to one of three types of IP security options, which are
    fields that may be added to an IP datagram for the purpose of
    carrying security information about the datagram. (See: IPsec.)
    (D) ISDs SHOULD NOT use this term without a modifier to indicate
    which of the three types is meant.

Shirey Informational [Page 89] RFC 2828 Internet Security Glossary May 2000

    1. "DoD Basic Security Option" (IP option type 130): Defined for
    use on U.S. Department of Defense common user data networks.
    Identifies the Defense classification level at which the
    datagram is to be protected and the protection authorities
    whose rules apply to the datagram. [R1108]
    A "protection authority" is a National Access Program (e.g.,
    GENSER, SIOP-ESI, SCI, NSA, Department of Energy) or Special
    Access Program that specifies protection rules for transmission
    and processing of the information contained in the datagram.
    [R1108]
    2. "DoD Extended Security Option" (IP option type 133): Permits
    additional security labeling information, beyond that present
    in the Basic Security Option, to be supplied in the datagram to
    meet the needs of registered authorities. [R1108]
    3. "Common IP Security Option" (CIPSO) (IP option type 134):
    Designed by TSIG to carry hierarchic and non-hierarchic
    security labels. (Formerly called "Commercial IP Security
    Option".) Was published as Internet-Draft [CIPSO]; not advanced
    to RFC.
 $ Internet Protocol Suite
    See: (secondary definition under) Internet.
 $ Internet Security Association and Key Management Protocol (ISAKMP)
    (I) An Internet IPsec protocol [R2408] to negotiate, establish,
    modify, and delete security associations, and to exchange key
    generation and authentication data, independent of the details of
    any specific key generation technique, key establishment protocol,
    encryption algorithm, or authentication mechanism.
    (C) ISAKMP supports negotiation of security associations for
    protocols at all TCP/IP layers. By centralizing management of
    security associations, ISAKMP reduces duplicated functionality
    within each protocol. ISAKMP can also reduce connection setup
    time, by negotiating a whole stack of services at once. Strong
    authentication is required on ISAKMP exchanges, and a digital
    signature algorithm based on asymmetric cryptography is used
    within ISAKMP's authentication component.
 $ Internet Society (ISOC)
    (I) A professional society concerned with Internet development
    (including technical Internet Standards); with how the Internet is
    and can be used; and with social, political, and technical issues

Shirey Informational [Page 90] RFC 2828 Internet Security Glossary May 2000

    that result. The ISOC Board of Trustees approves appointments to
    the IAB from among nominees submitted by the IETF nominating
    committee. [R2026]
 $ Internet Standard
    (I) A specification, approved by the IESG and published as an RFC,
    that is stable and well-understood, is technically competent, has
    multiple, independent, and interoperable implementations with
    substantial operational experience, enjoys significant public
    support, and is recognizably useful in some or all parts of the
    Internet. [R2026] (See: RFC.)
    (C) The Internet Standards Process is an activity of the ISOC and
    is organized and managed by the IAB and the IESG. The process is
    concerned with all protocols, procedures, and conventions used in
    or by the Internet, whether or not they are part of the Internet
    Protocol Suite. The "Internet Standards Track" has three levels of
    increasing maturity: Proposed Standard, Draft Standard, and
    Standard. (See: (standards levels under) ISO.)
 $ Internet Standards document (ISD)
    (C) In this Glossary, this term refers to an RFC, Internet-Draft,
    or other item that is produced as part of the Internet Standards
    Process [R2026]. However, neither the term nor the abbreviation is
    widely accepted and, therefore, SHOULD NOT be used in an ISD
    unless it is accompanied by an explanation like this. (See:
    Internet Standard.)
 $ internet vs. Internet
    1. (I) Not capitalized: A popular abbreviation for "internetwork".
    2. (I) Capitalized: "The Internet" is the single, interconnected,
    worldwide system of commercial, government, educational, and other
    computer networks that share the set of protocols specified by the
    IAB [R2026] and the name and address spaces managed by the ICANN.
    (C) The protocol set is named the "Internet Protocol Suite". It
    also is popularly known as "TCP/IP", because TCP and IP are two of
    its fundamental components. These protocols enable a user of any
    one of the networks in the Internet to communicate with, or use
    services located on, any of the other networks.
    (C) Although the Internet does have architectural principles
    [R1958], no Internet Standard formally defines a layered reference
    model for the IPS that is similar to the OSIRM. However, Internet
    community documents do refer (inconsistently) to layers:
    application, socket, transport, internetwork, network, data link,

Shirey Informational [Page 91] RFC 2828 Internet Security Glossary May 2000

    and physical. In this Glossary, Internet layers are referred to by
    name to avoid confusing them with OSIRM layers, which are referred
    to by number.
 $ internetwork
    (I) A system of interconnected networks; a network of networks.
    Usually shortened to "internet". (See: internet vs. Internet.)
    (C) An internet is usually built using OSI layer 3 gateways to
    connect a set of subnetworks. When the subnetworks differ in the
    OSI layer 3 protocol service they provide, the gateways sometimes
    implement a uniform internetwork protocol (e.g., IP) that operates
    at the top of layer 3 and hides the underlying heterogeneity from
    hosts that use communication services provided by the internet.
    (See: router.)
 $ intranet
    (I) A computer network, especially one based on Internet
    technology, that an organization uses for its own internal, and
    usually private, purposes and that is closed to outsiders. (See:
    extranet, virtual private network.)
 $ intruder
    (I) An entity that gains or attempts to gain access to a system or
    system resource without having authorization to do so. (See:
    cracker.)
 $ intrusion
    See: security intrusion.
 $ intrusion detection
    (I) A security service that monitors and analyzes system events
    for the purpose of finding, and providing real-time or near real-
    time warning of, attempts to access system resources in an
    unauthorized manner.
 $ invalidity date
    (N) An X.509 CRL entry extension that "indicates the date at which
    it is known or suspected that the [revoked certificate's private
    key] was compromised or that the certificate should otherwise be
    considered invalid" [X509].
    (C) This date may be earlier than the revocation date in the CRL
    entry, and may even be earlier than the date of issue of earlier
    CRLs. However, the invalidity date is not, by itself, sufficient
    for purposes of non-repudiation service. For example, to

Shirey Informational [Page 92] RFC 2828 Internet Security Glossary May 2000

    fraudulently repudiate a validly-generated signature, a private
    key holder may falsely claim that the key was compromised at some
    time in the past.
 $ IP
    See: Internet Protocol.
 $ IP address
    (I) A computer's internetwork address that is assigned for use by
    the Internet Protocol and other protocols.
    (C) An IP version 4 [R0791] address is written as a series of four
    8-bit numbers separated by periods. For example, the address of
    the host named "rosslyn.bbn.com" is 192.1.7.10.
    (C) An IP version 6 [R2373] address is written as x:x:x:x:x:x:x:x,
    where each "x" is the hexadecimal value of one of the eight 16-bit
    parts of the address. For example, 1080:0:0:0:8:800:200C:417A and
    FEDC:BA98:7654:3210:FEDC:BA98:7654:3210.
 $ IP Security Option
    See: Internet Protocol Security Option.
 $ IPRA
    See: Internet Policy Registration Authority.
 $ IPsec
    See: Internet Protocol security.
 $ IPsec Key Exchange (IKE)
    (I) An Internet, IPsec, key-establishment protocol [R2409] (partly
    based on OAKLEY) that is intended for putting in place
    authenticated keying material for use with ISAKMP and for other
    security associations, such as in AH and ESP.
 $ IPSO
    See: Internet Protocol Security Option.
 $ ISAKMP
    See: Internet Security Association and Key Management Protocol.
 $ ISD
    See: Internet Standards document.
 $ ISO
    (I) International Organization for Standardization, a voluntary,
    non-treaty, non-government organization, established in 1947, with
    voting members that are designated standards bodies of

Shirey Informational [Page 93] RFC 2828 Internet Security Glossary May 2000

    participating nations and non-voting observer organizations. (See:
    ANSI, ITU-T.)
    (C) Legally, ISO is a Swiss, non-profit, private organization. ISO
    and the IEC (the International Electrotechnical Commission) form
    the specialized system for worldwide standardization. National
    bodies that are members of ISO or IEC participate in developing
    international standards through ISO and IEC technical committees
    that deal with particular fields of activity. Other international
    governmental and non-governmental organizations, in liaison with
    ISO and IEC, also take part. (ANSI is the U.S. voting member of
    ISO. ISO is a class D member of ITU-T.)
    (C) The ISO standards development process has four levels of
    increasing maturity: Working Draft (WD), Committee Draft (CD),
    Draft International Standard (DIS), and International Standard
    (IS). (See: (standards track levels under) Internet Standard.) In
    information technology, ISO and IEC have a joint technical
    committee, ISO/IEC JTC 1. DISs adopted by JTC 1 are circulated to
    national bodies for voting, and publication as an IS requires
    approval by at least 75% of the national bodies casting a vote.
 $ ISOC
    See: Internet Society.
 $ issue (a digital certificate or CRL)
    (I) Generate and sign a digital certificate (or CRL) and, usually,
    distribute it and make it available to potential certificate users
    (or CRL users). (See: certificate creation.)
    (C) The ABA Guidelines [ABA] explicitly limit this term to
    certificate creation, and exclude the act of publishing. In
    general usage, however, "issuing" a digital certificate (or CRL)
    includes not only certificate creation but also making it
    available to potential users, such as by storing it in a
    repository or other directory or otherwise publishing it.
 $ issuer
    1. (I) "Issuer" of a certificate or CRL: The CA that signs the
    digital certificate or CRL.
    (C) An X.509 certificate always includes the issuer's name. The
    name may include a common name value.
    2. (N) "Issuer" of a payment card: SET usage: "The financial
    institution or its agent that issues the unique primary account
    number to the cardholder for the payment card brand." [SET2]

Shirey Informational [Page 94] RFC 2828 Internet Security Glossary May 2000

    (C) The institution that establishes the account for a cardholder
    and issues the payment card also guarantees payment for authorized
    transactions that use the card in accordance with card brand
    regulations and local legislation. [SET1]
 $ ITAR
    See: International Traffic in Arms Regulations.
 $ ITSEC
    See: Information Technology System Evaluation Criteria.
 $ ITU-T
    (N) International Telecommunications Union, Telecommunication
    Standardization Sector (formerly "CCITT"), a United Nations treaty
    organization that is composed mainly of postal, telephone, and
    telegraph authorities of the member countries and that publishes
    standards called "Recommendations". (See: X.400, X.500.)
    (C) The Department of State represents the United States. ITU-T
    works on many kinds of communication systems. ITU-T cooperates
    with ISO on communication protocol standards, and many
    Recommendations in that area are also published as an ISO standard
    with an ISO name and number.
 $ IV
    See: initialization value.
 $ KDC
    See: Key Distribution Center.
 $ KEA
    See: Key Exchange Algorithm.
 $ KEK
    See: key-encrypting key.
 $ Kerberos
    (N) A system developed at the Massachusetts Institute of
    Technology that depends on passwords and symmetric cryptography
    (DES) to implement ticket-based, peer entity authentication
    service and access control service distributed in a client-server
    network environment. [R1510, Stei]
    (C) Kerberos was developed by Project Athena and is named for the
    three-headed dog guarding Hades.
 $ key
    See: cryptographic key.

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 $ key agreement (algorithm or protocol)
    (I) A key establishment method (especially one involving
    asymmetric cryptography) by which two or more entities, without
    prior arrangement except a public exchange of data (such as public
    keys), each computes the same key value. I.e., each can
    independently generate the same key value, but that key cannot be
    computed by other entities. (See: Diffie-Hellman, key
    establishment, Key Exchange Algorithm, key transport.)
    (O) "A method for negotiating a key value on line without
    transferring the key, even in an encrypted form, e.g., the Diffie-
    Hellman technique." [X509]
    (O) "The procedure whereby two different parties generate shared
    symmetric keys such that any of the shared symmetric keys is a
    function of the information contributed by all legitimate
    participants, so that no party [alone] can predetermine the value
    of the key." [A9042]
    (C) For example, a message originator and the intended recipient
    can each use their own private key and the other's public key with
    the Diffie-Hellman algorithm to first compute a shared secret
    value and, from that value, derive a session key to encrypt the
    message.
 $ key authentication
    (N) "The assurance of the legitimate participants in a key
    agreement that no non-legitimate party possesses the shared
    symmetric key." [A9042]
 $ key center
    (I) A centralized key distribution process (used in symmetric
    cryptography), usually a separate computer system, that uses key-
    encrypting keys (master keys) to encrypt and distribute session
    keys needed in a community of users.
    (C) An ANSI standard [A9017] defines two types of key center: key
    distribution center and key translation center.
 $ key confirmation
    (N) "The assurance of the legitimate participants in a key
    establishment protocol that the intended parties sharing the
    symmetric key actually possess the shared symmetric key." [A9042]
 $ key distribution
    (I) A process that delivers a cryptographic key from the location
    where it is generated to the locations where it is used in a
    cryptographic algorithm. (See: key management.)

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 $ key distribution center (KDC)
    (I) A type of key center (used in symmetric cryptography) that
    implements a key distribution protocol to provide keys (usually,
    session keys) to two (or more) entities that wish to communicate
    securely. (See: key translation center.)
    (C) A KDC distributes keys to Alice and Bob, who (a) wish to
    communicate with each other but do not currently share keys, (b)
    each share a KEK with the KDC, and (c) may not be able to generate
    or acquire keys by themselves. Alice requests the keys from the
    KDC. The KDC generates or acquires the keys and makes two
    identical sets. The KDC encrypts one set in the KEK it shares with
    Alice, and sends that encrypted set to Alice. The KDC encrypts the
    second set in the KEK it shares with Bob, and either sends that
    encrypted set to Alice for her to forward to Bob, or sends it
    directly to Bob (although the latter option is not supported in
    the ANSI standard [A9017]).
 $ key encapsulation
    See: (secondary definition under) key recovery.
 $ key-encrypting key (KEK)
    (I) A cryptographic key that is used to encrypt other keys, either
    DEKs or other KEKs, but usually is not used to encrypt application
    data.
 $ key escrow
    See: (secondary definition under) key recovery.
 $ key establishment (algorithm or protocol)
    (I) A process that combines the key generation and key
    distribution steps needed to set up or install a secure
    communication association. (See: key agreement, key transport.)
    (O) "The procedure to share a symmetric key among different
    parties by either key agreement or key transport." [A9042]
    (C) Key establishment involves either key agreement or key
    transport:
  1. Key transport: One entity generates a secret key and securely

sends it to the other entity. (Or each entity generates a

       secret value and securely sends it to the other entity, where
       the two values are combined to form a secret key.)
  1. Key agreement: No secret is sent from one entity to another.

Instead, both entities, without prior arrangement except a

       public exchange of data, compute the same secret value. I.e.,

Shirey Informational [Page 97] RFC 2828 Internet Security Glossary May 2000

       each can independently generate the same value, but that value
       cannot be computed by other entities.
 $ Key Exchange Algorithm (KEA)
    (N) A key agreement algorithm [NIST] that is similar to the
    Diffie-Hellman algorithm, uses 1024-bit asymmetric keys, and was
    developed and formerly classified at the "Secret" level by NSA.
    (See: CAPSTONE, CLIPPER, FORTEZZA, SKIPJACK.)
    (C) On 23 June 1998, the NSA announced that KEA had been
    declassified.
 $ key generation
    (I) A process that creates the sequence of symbols that comprise a
    cryptographic key. (See: key management.)
 $ key generator
    1. (I) An algorithm that uses mathematical rules to
    deterministically produce a pseudo-random sequence of
    cryptographic key values.
    2. (I) An encryption device that incorporates a key generation
    mechanism and applies the key to plaintext (e.g., by exclusive OR-
    ing the key bit string with the plaintext bit string) to produce
    ciphertext.
 $ key length
    (I) The number of symbols (usually bits) needed to be able to
    represent any of the possible values of a cryptographic key. (See:
    key space.)
 $ key lifetime
    (N) MISSI usage: An attribute of a MISSI key pair that specifies a
    time span that bounds the validity period of any MISSI X.509
    public-key certificate that contains the public component of the
    pair. (See: cryptoperiod.)
 $ key management
    (I) The process of handling and controlling cryptographic keys and
    related material (such as initialization values) during their life
    cycle in a cryptographic system, including ordering, generating,
    distributing, storing, loading, escrowing, archiving, auditing,
    and destroying the material. (See: key distribution, key escrow,
    keying material, public-key infrastructure.)
    (O) "The generation, storage, distribution, deletion, archiving
    and application of keys in accordance with a security policy."
    [I7498 Part 2]

Shirey Informational [Page 98] RFC 2828 Internet Security Glossary May 2000

    (O) "The activities involving the handling of cryptographic keys
    and other related security parameters (e.g., IVs, counters) during
    the entire life cycle of the keys, including their generation,
    storage, distribution, entry and use, deletion or destruction, and
    archiving." [FP140]
 $ Key Management Protocol (KMP)
    (N) A protocol to establish a shared symmetric key between a pair
    (or a group) of users. (One version of KMP was developed by SDNS,
    and another by SILS.)
 $ key material identifier (KMID)
    (N) MISSI usage: A 64-bit identifier that is assigned to a key
    pair when the public key is bound in a MISSI X.509 public-key
    certificate.
 $ key pair
    (I) A set of mathematically related keys--a public key and a
    private key--that are used for asymmetric cryptography and are
    generated in a way that makes it computationally infeasible to
    derive the private key from knowledge of the public key (e.g.,
    see: Diffie-Hellman, Rivest-Shamir-Adleman).
    (C) A key pair's owner discloses the public key to other system
    entities so they can use the key to encrypt data, verify a digital
    signature, compute a protected checksum, or generate a key in a
    key agreement algorithm. The matching private key is kept secret
    by the owner, who uses it to decrypt data, generate a digital
    signature, verify a protected checksum, or generate a key in a key
    agreement algorithm.
 $ key recovery
    1. (I) A process for learning the value of a cryptographic key
    that was previously used to perform some cryptographic operation.
    (See: cryptanalysis.)
    2. (I) Techniques that provide an intentional, alternate (i.e.,
    secondary) means to access the key used for data confidentiality
    service in an encrypted association. [DOD4]
    (C) We assume that the encryption mechanism has a primary means of
    obtaining the key through a key establishment algorithm or
    protocol. For the secondary means, there are two classes of key
    recovery techniques--key escrow and key encapsulation:

Shirey Informational [Page 99] RFC 2828 Internet Security Glossary May 2000

  1. "Key escrow": A key recovery technique for storing knowledge of

a cryptographic key or parts thereof in the custody of one or

       more third parties called "escrow agents", so that the key can
       be recovered and used in specified circumstances.
       Key escrow is typically implemented with split knowledge
       techniques. For example, the Escrowed Encryption Standard
       [FP185] entrusts two components of a device-unique split key to
       separate escrow agents. The agents provide the components only
       to someone legally authorized to conduct electronic
       surveillance of telecommunications encrypted by that specific
       device. The components are used to reconstruct the device-
       unique key, and it is used to obtain the session key needed to
       decrypt communications.
  1. "Key encapsulation": A key recovery technique for storing

knowledge of a cryptographic key by encrypting it with another

       key and ensuring that that only certain third parties called
       "recovery agents" can perform the decryption operation to
       retrieve the stored key.
       Key encapsulation typically allows direct retrieval of the
       secret key used to provide data confidentiality.
 $ key space
    (I) The range of possible values of a cryptographic key; or the
    number of distinct transformations supported by a particular
    cryptographic algorithm. (See: key length.)
 $ key translation center
    (I) A type of key center (used in a symmetric cryptography) that
    implements a key distribution protocol to convey keys between two
    (or more) parties who wish to communicate securely. (See: key
    distribution center.)
    (C) A key translation center translates keys for future
    communication between Bob and Alice, who (a) wish to communicate
    with each other but do not currently share keys, (b) each share a
    KEK with the center, and (c) have the ability to generate or
    acquire keys by themselves. Alice generates or acquires a set of
    keys for communication with Bob. Alice encrypts the set in the KEK
    she shares with the center and sends the encrypted set to the
    center. The center decrypts the set, reencrypts the set in the KEK
    it shares with Bob, and either sends that encrypted set to Alice
    for her to forward to Bob, or sends it directly to Bob (although
    direct distribution is not supported in the ANSI standard
    [A9017]).

Shirey Informational [Page 100] RFC 2828 Internet Security Glossary May 2000

 $ key transport (algorithm or protocol)
    (I) A key establishment method by which a secret key is generated
    by one entity in a communication association and securely sent to
    another entity in the association. (See: key agreement.)
    (O) "The procedure to send a symmetric key from one party to other
    parties. As a result, all legitimate participants share a common
    symmetric key in such a way that the symmetric key is determined
    entirely by one party." [A9042]
    (C) For example, a message originator can generate a random
    session key and then use the Rivest-Shamir-Adleman algorithm to
    encrypt that key with the public key of the intended recipient.
 $ key update
    (I) Derive a new key from an existing key. (See: certificate
    rekey.)
 $ key validation
    (N) "The procedure for the receiver of a public key to check that
    the key conforms to the arithmetic requirements for such a key in
    order to thwart certain types of attacks." [A9042]
 $ keyed hash
    (I) A cryptographic hash (e.g., [R1828]) in which the mapping to a
    hash result is varied by a second input parameter that is a
    cryptographic key. (See: checksum.)
    (C) If the input data object is changed, a new hash result cannot
    be correctly computed without knowledge of the secret key. Thus,
    the secret key protects the hash result so it can be used as a
    checksum even when there is a threat of an active attack on the
    data. There are least two forms of keyed hash:
  1. A function based on a keyed encryption algorithm. (E.g., see:

Data Authentication Code.)

  1. A function based on a keyless hash that is enhanced by

combining (e.g., by concatenating) the input data object

       parameter with a key parameter before mapping to the hash
       result. (E.g., see: HMAC.)
 $ keying material
    (I) Data (such as keys, key pairs, and initialization values)
    needed to establish and maintain a cryptographic security
    association.

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 $ KMID
    See: key material identifier.
 $ known-plaintext attack
    (I) A cryptanalysis technique in which the analyst tries to
    determine the key from knowledge of some plaintext-ciphertext
    pairs (although the analyst may also have other clues, such as the
    knowing the cryptographic algorithm).
 $ L2F
    See: Layer 2 Forwarding Protocol.
 $ L2TP
    See: Layer 2 Tunneling Protocol.
 $ label
    See: security label.
 $ Language of Temporal Ordering Specification (LOTOS)
    (N) A language (ISO 8807-1990) for formal specification of
    computer network protocols; describes the order in which events
    occur.
 $ lattice model
    (I) A security model for flow control in a system, based on the
    lattice that is formed by the finite security levels in a system
    and their partial ordering. [Denn] (See: flow control, security
    level, security model.)
    (C) The model describes the semantic structure formed by a finite
    set of security levels, such as those used in military
    organizations.
    (C) A lattice is a finite set together with a partial ordering on
    its elements such that for every pair of elements there is a least
    upper bound and a greatest lower bound. For example, a lattice is
    formed by a finite set S of security levels -- i.e., a set S of all
    ordered pairs (x, c), where x is one of a finite set X of
    hierarchically ordered classification levels (X1, ..., Xm), and c
    is a (possibly empty) subset of a finite set C of non-hierarchical
    categories (C1, ..., Cn) -- together with the "dominate" relation.
    (See: dominate.)
 $ Law Enforcement Access Field (LEAF)
    (N) A data item that is automatically embedded in data encrypted
    by devices (e.g., see: CLIPPER chip) that implement the Escrowed
    Encryption Standard.

Shirey Informational [Page 102] RFC 2828 Internet Security Glossary May 2000

 $ Layer 2 Forwarding Protocol (L2F)
    (N) An Internet protocol (originally developed by Cisco
    Corporation) that uses tunneling of PPP over IP to create a
    virtual extension of a dial-up link across a network, initiated by
    the dial-up server and transparent to the dial-up user. (See:
    L2TP.)
 $ Layer 2 Tunneling Protocol (L2TP)
    (N) An Internet client-server protocol that combines aspects of
    PPTP and L2F and supports tunneling of PPP over an IP network or
    over frame relay or other switched network. (See: virtual private
    network.)
    (C) PPP can in turn encapsulate any OSI layer 3 protocol. Thus,
    L2TP does not specify security services; it depends on protocols
    layered above and below it to provide any needed security.
 $ LDAP
    See: Lightweight Directory Access Protocol.
 $ least privilege
    (I) The principle that a security architecture should be designed
    so that each system entity is granted the minimum system resources
    and authorizations that the entity needs to do its work. (See:
    economy of mechanism.)
    (C) This principle tends to limit damage that can be caused by an
    accident, error, or unauthorized act.
 $ Lightweight Directory Access Protocol (LDAP)
    (N) A client-server protocol that supports basic use of the X.500
    Directory (or other directory servers) without incurring the
    resource requirements of the full Directory Access Protocol (DAP).
    [R1777]
    (C) Designed for simple management and browser applications that
    provide simple read/write interactive directory service. Supports
    both simple authentication and strong authentication of the client
    to the directory server.
 $ link
    (I) World Wide Web usage: See: hyperlink.
    (I) Subnetwork usage: A point-to-point communication channel
    connecting two subnetwork relays (especially one between two
    packet switches) that is implemented at OSI layer 2. (See: link
    encryption.)

Shirey Informational [Page 103] RFC 2828 Internet Security Glossary May 2000

    (C) The relay computers assume that links are logically passive.
    If a computer at one end of a link sends a sequence of bits, the
    sequence simply arrives at the other end after a finite time,
    although some bits may have been changed either accidentally
    (errors) or by active wiretapping.
 $ link-by-link encryption
 $ link encryption
    (I) Stepwise protection of data that flows between two points in a
    network, provided by encrypting data separately on each network
    link, i.e., by encrypting data when it leaves a host or subnetwork
    relay and decrypting when it arrives at the next host or relay.
    Each link may use a different key or even a different algorithm.
    [R1455] (See: end-to-end encryption.)
 $ logic bomb
    (I) Malicious logic that activates when specified conditions are
    met. Usually intended to cause denial of service or otherwise
    damage system resources. (See: Trojan horse, virus, worm.)
 $ login
    (I) The act of a system entity gaining access to a session in
    which the entity can use system resources; usually accomplished by
    providing a user name and password to an access control system
    that authenticates the user.
    (C) Derives from "log" file", a security audit trail that records
    security events, such as the beginning of sessions, and who
    initiates them.
 $ LOTOS
    See: Language of Temporal Ordering Specification.
 $ MAC
    See: mandatory access control, Message Authentication Code.
 $ malicious logic
    (I) Hardware, software, or firmware that is intentionally included
    or inserted in a system for a harmful purpose. (See: logic bomb,
    Trojan horse, virus, worm.)
 $ malware
    (I) A contraction of "malicious software". (See: malicious logic.)
    (D) ISDs SHOULD NOT use this term because it is not listed in most
    dictionaries and could confuse international readers.

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 $ man-in-the-middle
    (I) A form of active wiretapping attack in which the attacker
    intercepts and selectively modifies communicated data in order to
    masquerade as one or more of the entities involved in a
    communication association. (See: hijack attack, piggyback attack.)
    (C) For example, suppose Alice and Bob try to establish a session
    key by using the Diffie-Hellman algorithm without data origin
    authentication service. A "man in the middle" could (a) block
    direct communication between Alice and Bob and then (b) masquerade
    as Alice sending data to Bob, (c) masquerade as Bob sending data
    to Alice, (d) establish separate session keys with each of them,
    and (e) function as a clandestine proxy server between them in
    order to capture or modify sensitive information that Alice and
    Bob think they are sending only to each other.
 $ mandatory access control (MAC)
    (I) An access control service that enforces a security policy
    based on comparing (a) security labels (which indicate how
    sensitive or critical system resources are) with (b) security
    clearances (which indicate system entities are eligible to access
    certain resources). (See: discretionary access control, rule-based
    security policy.)
    (C) This kind of access control is called "mandatory" because an
    entity that has clearance to access a resource may not, just by
    its own volition, enable another entity to access that resource.
    (O) "A means of restricting access to objects based on the
    sensitivity (as represented by a label) of the information
    contained in the objects and the formal authorization (i.e.,
    clearance) of subjects to access information of such sensitivity."
    [DOD1]
 $ manipulation detection code
    (D) ISDs SHOULD NOT use this term as a synonym for "checksum"
    because the word "manipulation" implies protection against active
    attacks, which an ordinary checksum might not provide. Instead, if
    such protection is intended, use "protected checksum" or some
    particular type thereof, depending on which is meant. If such
    protection is not intended, use "error detection code" or some
    specific type of checksum that is not protected.
 $ masquerade attack
    (I) A type of attack in which one system entity illegitimately
    poses as (assumes the identity of) another entity. (See: spoofing
    attack.)

Shirey Informational [Page 105] RFC 2828 Internet Security Glossary May 2000

 $ MCA
    See: merchant certificate authority.
 $ MD2
    (N) A cryptographic hash [R1319] that produces a 128-bit hash
    result, was designed by Ron Rivest, and is similar to MD4 and MD5
    but slower. (See: message digest.)
 $ MD4
    (N) A cryptographic hash [R1320] that produces a 128-bit hash
    result and was designed by Ron Rivest. (See: message digest and
    SHA-1.)
 $ MD5
    (N) A cryptographic hash [R1321] that produces a 128-bit hash
    result and was designed by Ron Rivest to be an improved version of
    MD4.
 $ merchant
    (O) SET usage: "A seller of goods, services, and/or other
    information who accepts payment for these items electronically."
    [SET2] A merchant may also provide electronic selling services
    and/or electronic delivery of items for sale. With SET, the
    merchant can offer its cardholders secure electronic interactions,
    but a merchant that accepts payment cards is required to have a
    relationship with an acquirer. [SET1, SET2]
 $ merchant certificate
    (O) SET usage: A public-key certificate issued to a merchant.
    Sometimes used to refer to a pair of such certificates where one
    is for digital signature use and the other is for encryption.
 $ merchant certification authority (MCA)
    (O) SET usage: A CA that issues digital certificates to merchants
    and is operated on behalf of a payment card brand, an acquirer, or
    another party according to brand rules. Acquirers verify and
    approve requests for merchant certificates prior to issuance by
    the MCA. An MCA does not issue a CRL, but does distribute CRLs
    issued by root CAs, brand CAs, geopolitical CAs, and payment
    gateway CAs. [SET2]
 $ mesh PKI
    (I) A non-hierarchical PKI architecture in which there are several
    trusted CAs rather than a single root. Each certificate user bases
    path validations on the public key of one of the trusted CAs,
    usually the one that issued that user's own public-key
    certificate. Rather than having superior-to-subordinate

Shirey Informational [Page 106] RFC 2828 Internet Security Glossary May 2000

    relationships between CAs, the relationships are peer-to-peer, and
    CAs issue cross-certificates to each other. (See: hierarchical
    PKI, trust-file PKI.)
 $ message authentication code vs. Message Authentication Code (MAC)
    1. (N) Capitalized: "(The) Message Authentication Code" refers to
    an ANSI standard for a checksum that is computed with a keyed hash
    that is based on DES. [A9009] (Also known as the U.S. Government
    standard Data Authentication Code. [FP113])
    (C) The ANSI standard MAC algorithm is equivalent to cipher block
    chaining with IV = 0.
    2. (D) Not capitalized: ISDs SHOULD NOT use the uncapitalized form
    "message authentication code", because this term mixes concepts in
    a potentially misleading way. Instead, use "checksum", "error
    detection code", "hash", "keyed hash", "Message Authentication
    Code", or "protected checksum", depending on what is meant. (See:
    authentication code.)
    (C) In the uncapitalized form, the word "message" is misleading
    because it implies that the mechanism is particularly suitable for
    or limited to electronic mail (see: Message Handling Systems), the
    word "authentication" is misleading because the mechanism
    primarily serves a data integrity function rather than an
    authentication function, and the word "code" is misleading because
    it implies that either encoding or encryption is involved or that
    the term refers to computer software.
 $ message digest
    (D) ISDs SHOULD NOT use this term as a synonym for "hash result"
    because it unnecessarily duplicates the meaning of the other, more
    general term and mixes concepts in a potentially misleading way.
    (See: cryptographic hash, Message Handling System.)
 $ Message Handling Systems
    (I) A ITU-T/ISO system concept, which encompasses the notion of
    electronic mail but defines more comprehensive OSI systems and
    services that enable users to exchange messages on a store-and-
    forward basis. (The ISO equivalent is "Message Oriented Text
    Interchange System".) (See: X.400.)
 $ message indicator
    (D) ISDs SHOULD NOT use this term as a synonym for "initialization
    value" because it mixes concepts in a potentially misleading way.

Shirey Informational [Page 107] RFC 2828 Internet Security Glossary May 2000

 $ message integrity check
 $ message integrity code
    (D) ISDs SHOULD NOT use these terms because they mix concepts in a
    potentially misleading way. (The word "message" is misleading
    because it suggests that the mechanism is particularly suitable
    for or limited to electronic mail. The word "code" is misleading
    because it suggests that either encoding or encryption is
    involved, or that the term refers to computer software.) Instead,
    use "checksum", "error detection code", "hash", "keyed hash",
    "Message Authentication Code", or "protected checksum", depending
    on what is meant.
 $ Message Security Protocol (MSP)
    (N) A secure message handling protocol [SDNS7] for use with X.400
    and Internet mail protocols. Developed by NSA's SDNS program and
    used in the U.S. Defense Message System.
 $ MHS
    See: message handling system.
 $ MIME
    See: Multipurpose Internet Mail Extensions.
 $ MIME Object Security Services (MOSS)
    (I) An Internet protocol [R1848] that applies end-to-end
    encryption and digital signature to MIME message content, using
    symmetric cryptography for encryption and asymmetric cryptography
    for key distribution and signature. MOSS is based on features and
    specifications of PEM. (See: S/MIME.)
 $ Minimum Interoperability Specification for PKI Components (MISPC)
    (N) A technical description to provide a basis for interoperation
    between PKI components from different vendors; consists primarily
    of a profile of certificate and CRL extensions and a set of
    transactions for PKI operation. [MISPC]
 $ MISPC
    See: Minimum Interoperability Specification for PKI Components.
 $ MISSI
    (N) Multilevel Information System Security Initiative, an NSA
    program to encourage development of interoperable, modular
    products for constructing secure network information systems in
    support of a wide variety of Government missions. (See: MSP.)

Shirey Informational [Page 108] RFC 2828 Internet Security Glossary May 2000

 $ MISSI user
    (O) MISSI usage: A system entity that is the subject of one or
    more MISSI X.509 public-key certificates issued under a MISSI
    certification hierarchy. (See: personality.)
    (C) MISSI users include both end users and the authorities that
    issue certificates. A MISSI user is usually a person but may be a
    machine or other automated process. Some machines are required to
    operate non-stop. To avoid downtime needed to exchange the
    FORTEZZA cards of machine operators at shift changes, the machines
    may be issued their own cards, as if they were persons.
 $ mode
 $ mode of operation
    (I) Encryption usage: A technique for enhancing the effect of a
    cryptographic algorithm or adapting the algorithm for an
    application, such as applying a block cipher to a sequence of data
    blocks or a data stream. (See: electronic codebook, cipher block
    chaining, cipher feedback, output feedback.)
    (I) System operation usage: A type of security policy that states
    the range of classification levels of information that a system is
    permitted to handle and the range of clearances and authorizations
    of users who are permitted to access the system. (See: dedicated
    security mode, multilevel security mode, partitioned security
    mode, system high security mode.)
 $ modulus
    (I) The defining constant in modular arithmetic, and usually a
    part of the public key in asymmetric cryptography that is based on
    modular arithmetic. (See: Diffie-Hellman, Rivest-Shamir-Adleman.)
 $ Morris Worm
    (I) A worm program written by Robert T. Morris, Jr. that flooded
    the ARPANET in November, 1988, causing problems for thousands of
    hosts. (See: worm.)
 $ MOSS
    See: MIME Object Security Services.
 $ MSP
    See: Message Security Protocol.
 $ multilevel secure (MLS)
    (I) A class of system that has system resources (particularly
    stored information) at more than one security level (i.e., has
    different types of sensitive resources) and that permits

Shirey Informational [Page 109] RFC 2828 Internet Security Glossary May 2000

    concurrent access by users who differ in security clearance and
    need-to-know, but is able to prevent each user from accessing
    resources for which the user lacks authorization.
 $ multilevel security mode
    (I) A mode of operation of an information system, that allows two
    or more classification levels of information to be processed
    concurrently within the same system when not all users have a
    clearance or formal access authorization for all data handled by
    the system.
    (C) This mode is defined formally in U.S. Department of Defense
    policy regarding system accreditation [DOD2], but the term is also
    used outside the Defense Department and outside the Government.
 $ Multipurpose Internet Mail Extensions (MIME)
    (I) An Internet protocol [R2045] that enhances the basic format of
    Internet electronic mail messages [R0822] to be able to use
    character sets other than US-ASCII for textual headers and text
    content, and to carry non-textual and multi-part content. (See:
    S/MIME.)
 $ mutual suspicion
    (I) The state that exists between two interacting system entities
    in which neither entity can trust the other to function correctly
    with regard to some security requirement.
 $ National Computer Security Center (NCSC)
    (N) A U.S. Department of Defense organization, housed in NSA, that
    has responsibility for encouraging widespread availability of
    trusted computer systems throughout the Federal Government. It has
    established criteria for, and performs evaluations of, computer
    and network systems that have a trusted computing base. (See:
    Evaluated Products List, Rainbow Series, TCSEC.)
 $ National Information Assurance Partnership (NIAP)
    (N) An organization created by NIST and NSA to enhance the quality
    of commercial products for information security and increase
    consumer confidence in those products through objective evaluation
    and testing methods.
    (C) NIAP is registered, through the U.S. Department of Defense, as
    a National Performance Review Reinvention Laboratory. NIAP
    functions include the following:
  1. Developing tests, test methods, and other tools that developers

and testing laboratories may use to improve and evaluate

       security products.

Shirey Informational [Page 110] RFC 2828 Internet Security Glossary May 2000

  1. Collaborating with industry and others on research and testing

programs.

  1. Using the Common Criteria to develop protection profiles and

associated test sets for security products and systems.

  1. Cooperating with the NIST National Voluntary Laboratory

Accreditation Program to develop a program to accredit private-

       sector laboratories for the testing of information security
       products using the Common Criteria.
     - Working to establish a formal, international mutual recognition
       scheme for a Common Criteria-based evaluation.
 $ National Institute of Standards and Technology (NIST)
    (N) A U.S. Department of Commerce agency that promotes U.S.
    economic growth by working with industry to develop and apply
    technology, measurements, and standards. Has primary Government
    responsibility for INFOSEC standards for unclassified but
    sensitive information. (See: ANSI, DES, DSA, DSS, FIPS, NIAP,
    NSA.)
 $ National Security Agency (NSA)
    (N) A U.S. Department of Defense intelligence agency that has
    primary Government responsibility for INFOSEC for classified
    information and for unclassified but sensitive information handled
    by national security systems. (See: FORTEZZA, KEA, MISSI, NIAP,
    NIST, SKIPJACK.)
 $ need-to-know
    (I) The necessity for access to, knowledge of, or possession of
    specific information required to carry out official duties.
    (C) This criterion is used in security procedures that require a
    custodian of sensitive information, prior to disclosing the
    information to someone else, to establish that the intended
    recipient has proper authorization to access the information.
 $ network
    See: computer network.
 $ NIAP
    See: National Information Assurance Partnership.
 $ NIST
    See: National Institute of Standards and Technology.
 $ NLSP
    Network Layer Security Protocol. An OSI protocol (IS0 11577) for
    end-to-end encryption services at the top of OSI layer 3. NLSP is
    derived from an SDNS protocol, SP3, but is much more complex.

Shirey Informational [Page 111] RFC 2828 Internet Security Glossary May 2000

 $ no-lone zone
    (I) A room or other space to which no person may have
    unaccompanied access and that, when occupied, is required to be
    occupied by two or more appropriately authorized persons. (See:
    dual control.)
 $ nonce
    (I) A random or non-repeating value that is included in data
    exchanged by a protocol, usually for the purpose of guaranteeing
    liveness and thus detecting and protecting against replay attacks.
 $ non-critical
    See: critical (extension of certificate).
 $ non-repudiation service
    (I) A security service that provide protection against false
    denial of involvement in a communication. (See: repudiation.)
    (C) Non-repudiation service does not and cannot prevent an entity
    from repudiating a communication. Instead, the service provides
    evidence that can be stored and later presented to a third party
    to resolve disputes that arise if and when a communication is
    repudiated by one of the entities involved. There are two basic
    kinds of non-repudiation service:
  1. "Non-repudiation with proof of origin" provides the recipient

of data with evidence that proves the origin of the data, and

       thus protects the recipient against an attempt by the
       originator to falsely deny sending the data. This service can
       be viewed as a stronger version of an data origin
       authentication service, in that it proves authenticity to a
       third party.
  1. "Non-repudiation with proof of receipt" provides the originator

of data with evidence that proves the data was received as

       addressed, and thus protects the originator against an attempt
       by the recipient to falsely deny receiving the data.
    (C) Phases of a Non-Repudiation Service: Ford [For94, For97] uses
    the term "critical action" to refer to the act of communication
    that is the subject of the service:

Shirey Informational [Page 112] RFC 2828 Internet Security Glossary May 2000

  1. ——- ——– ——– ——– ——– . ——–

Phase 1: Phase 2: Phase 3: Phase 4: Phase 5: . Phase 6:

    Request    Generate   Transfer   Verify     Retain     . Resolve
    Service    Evidence   Evidence   Evidence   Evidence   . Dispute
    --------   --------   --------   --------   --------   . --------
    Service    Critical   Evidence   Evidence   Archive    . Evidence
    Request => Action  => Stored  => Is      => Evidence   . Is
    Is Made    Occurs     For Later  Tested     In Case    . Verified
               and        Use |          ^      Critical   .     ^
               Evidence       v          |      Action Is  .     |
               Is         +-------------------+ Repudiated .     |
               Generated  |Verifiable Evidence|------> ... . ----+
                          +-------------------+
    Phase / Explanation
    -------------------
    1. Before the critical action, the service requester asks, either
       implicitly or explicitly, to have evidence of the action be
       generated.
    2. When the critical action occurs, evidence is generated by a
       process involving the potential repudiator and possibly also a
       trusted third party.
    3. The evidence is transferred to the requester, or stored by a
       third party, for later use if needed.
    4. The entity that holds the evidence tests to be sure that it
       will suffice if a dispute arises.
    5. The evidence is retained for possible future retrieval and use.
    6. In this phase, which occurs only if the critical action is
       repudiated, the evidence is retrieved from storage, presented,
       and verified to resolve the dispute.
 $ no-PIN ORA (NORA)
    (O) MISSI usage: An organizational RA that operates in a mode in
    which the ORA performs no card management functions and,
    therefore, does not require knowledge of either the SSO PIN or
    user PIN for an end user's FORTEZZA PC card.
 $ NORA
    See: no-PIN ORA.
 $ notarization
    (I) Registration of data under the authority or in the care of a
    trusted third party, thus making it possible to provide subsequent
    assurance of the accuracy of characteristics claimed for the data,
    such as content, origin, time, and delivery. [I7498 Part 2] (See:
    digital notary.)

Shirey Informational [Page 113] RFC 2828 Internet Security Glossary May 2000

 $ NULL encryption algorithm
    (I) An algorithm [R2410] that does nothing to transform plaintext
    data; i.e., a no-op. It originated because of IPsec ESP, which
    always specifies the use of an encryption algorithm to provide
    confidentiality. The NULL encryption algorithm is a convenient way
    to represent the option of not applying encryption in ESP (or in
    any other context where this is needed).
 $ OAKLEY
    (I) A key establishment protocol (proposed for IPsec but
    superseded by IKE) based on the Diffie-Hellman algorithm and
    designed to be a compatible component of ISAKMP. [R2412]
    (C) OAKLEY establishes a shared key with an assigned identifier
    and associated authenticated identities for parties. I.e., OAKLEY
    provides authentication service to ensure the entities of each
    other's identity, even if the Diffie-Hellman exchange is
    threatened by active wiretapping. Also, provides public-key
    forward secrecy for the shared key and supports key updates,
    incorporation of keys distributed by out-of-band mechanisms, and
    user-defined abstract group structures for use with Diffie-
    Hellman.
 $ object
    (I) Trusted computer system modeling usage: A system element that
    contains or receives information. (See: Bell-LaPadula Model,
    trusted computer system.)
 $ object identifier (OID)
    (I) An official, globally unique name for a thing, written as a
    sequence of integers (which are formed and assigned as defined in
    the ASN.1 standard) and used to reference the thing in abstract
    specifications and during negotiation of security services in a
    protocol.
    (O) "A value (distinguishable from all other such values) which is
    associated with an object." [X680]
    (C) Objects named by OIDs are leaves of the object identifier tree
    (which is similar to but different from the X.500 Directory
    Information Tree). Each arc (i.e., each branch of the tree) is
    labeled with a non-negative integer. An OID is the sequence of
    integers on the path leading from the root of the tree to a named
    object.
    (C) The OID tree has three arcs immediately below the root: {0}
    for use by ITU-T, {1} for use by ISO, and {2} for use by both
    jointly. Below ITU-T are four arcs, where {0 0} is for ITU-T

Shirey Informational [Page 114] RFC 2828 Internet Security Glossary May 2000

    recommendations. Below {0 0} are 26 arcs, one for each series of
    recommendations starting with the letters A to Z, and below these
    are arcs for each recommendation. Thus, the OID for ITU-T
    Recommendation X.509 is {0 0 24 509}. Below ISO are four arcs,
    where {1 0 }is for ISO standards, and below these are arcs for
    each ISO standard. Thus, the OID for ISO/IEC 9594-8 (the ISO
    number for X.509) is {1 0 9594 8}.
    (C) The following are additional examples: ANSI registers
    organization names below the branch {joint-iso-ccitt(2)
    country(16) US(840) organization(1)}. The NIST CSOR records PKI
    objects below the branch {joint-iso-ccitt(2) country(16) us(840)
    gov(101) csor(3) pki(4)}. The U.S. Department of Defense registers
    INFOSEC objects below the branch {joint-iso-ccitt(2) country(16)
    us(840) organization(1) gov(101) dod(2) infosec(1)}. The OID for
    the PKIX private extension is defined in an arc below the arc for
    the PKIX name space, as {iso(1) identified-organization(3) dod(6)
    internet(1) security(5) mechanisms(5) pkix(7) 1 1}.
 $ object reuse
    (N) "The reassignment and reuse of a storage medium (e.g., page
    frame, disk sector, magnetic tape) that once contained one or more
    [information] objects. To be securely reused and assigned to a new
    subject, storage media must contain no residual data (magnetic
    remanence) from the object(s) previously contained in the media."
    [NCS04]
 $ OCSP
    See: On-line Certificate Status Protocol.
 $ octet
    (I) A data unit of eight bits. (See: byte.)
    (c) This term is used in networking (especially in OSI standards)
    in preference to "byte", because some systems use "byte" for data
    storage units of a size other than eight.
 $ OFB
    See: output feedback.
 $ ohnosecond
    (C) That minuscule fraction of time in which you realize that your
    private key has been compromised.
 $ OID
    See: object identifier.

Shirey Informational [Page 115] RFC 2828 Internet Security Glossary May 2000

 $ On-line Certificate Status Protocol (OCSP)
    (I) An Internet protocol used by a client to obtain from a server
    the validity status and other information concerning a digital
    certificate.
    (C) In some applications, such as those involving high-value
    commercial transactions, it may be necessary to obtain certificate
    revocation status that is more timely than is possible with CRLs
    or to obtain other kinds of status information. OCSP may be used
    to determine the current revocation status of a digital
    certificate, in lieu of or as a supplement to checking against a
    periodic CRL. An OCSP client issues a status request to an OCSP
    server and suspends acceptance of the certificate in question
    until the server provides a response.
 $ one-time pad
    (I) An encryption algorithm in which the key is a random sequence
    of symbols and each symbol is used for encryption only one time--
    to encrypt only one plaintext symbol to produce only one
    ciphertext symbol--and a copy of the key is used similarly for
    decryption.
    (C) To ensure one-time use, the copy of the key used for
    encryption is destroyed after use, as is the copy used for
    decryption. This is the only encryption algorithm that is truly
    unbreakable, even given unlimited resources for cryptanalysis
    [Schn], but key management costs and synchronization problems make
    it impractical except in special situations.
 $ one-time password
 $ One-Time Password (OTP)
    1. Not capitalized: A "one-time password" is a simple
    authentication technique in which each password is used only once
    as authentication information that verifies an identity. This
    technique counters the threat of a replay attack that uses
    passwords captured by wiretapping.
    2. Capitalized: "One-Time Password" is an Internet protocol
    [R1938] that is based on S/KEY and uses a cryptographic hash
    function to generate one-time passwords for use as authentication
    information in system login and in other processes that need
    protection against replay attacks.
 $ one-way encryption
    (I) Irreversible transformation of plaintext to ciphertext, such
    that the plaintext cannot be recovered from the ciphertext by
    other than exhaustive procedures even if the cryptographic key is
    known. (See: encryption.)

Shirey Informational [Page 116] RFC 2828 Internet Security Glossary May 2000

 $ one-way function
    (I) "A (mathematical) function, f, which is easy to compute, but
    which for a general value y in the range, it is computationally
    difficult to find a value x in the domain such that f(x) = y.
    There may be a few values of y for which finding x is not
    computationally difficult." [X509]
    (D) ISDs SHOULD NOT use this term as a synonym for "cryptographic
    hash".
 $ open security environment
    (O) U.S. Department of Defense usage: A system environment that
    meets at least one of the following conditions: (a) Application
    developers (including maintainers) do not have sufficient
    clearance or authorization to provide an acceptable presumption
    that they have not introduced malicious logic. (b) Configuration
    control does not provide sufficient assurance that applications
    and the equipment are protected against the introduction of
    malicious logic prior to and during the operation of system
    applications. [NCS04] (See: closed security environment.)
 $ Open Systems Interconnection (OSI) Reference Model (OSIRM)
    (N) A joint ISO/ITU-T standard [I7498 Part 1] for a seven-layer,
    architectural communication framework for interconnection of
    computers in networks.
    (C) OSI-based standards include communication protocols that are
    mostly incompatible with the Internet Protocol Suite, but also
    include security models, such as X.509, that are used in the
    Internet.
    (C) The OSIRM layers, from highest to lowest, are (7) Application,
    (6) Presentation, (5) Session, (4) Transport, (3) Network, (2)
    Data Link, and (1) Physical. In this Glossary, these layers are
    referred to by number to avoid confusing them with Internet
    Protocol Suite layers, which are referred to by name.
    (C) Some unknown person described how the OSI layers correspond to
    the seven deadly sins:
    7. Wrath: Application is always angry at the mess it sees below
       itself. (Hey! Who is it to be pointing fingers?)
    6. Sloth: Presentation is too lazy to do anything productive by
       itself.
    5. Lust: Session is always craving and demanding what truly
       belongs to Application's functionality.
    4. Avarice: Transport wants all of the end-to-end functionality.
       (Of course, it deserves it, but life isn't fair.)

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    3. Gluttony: (Connection-Oriented) Network is overweight and
       overbearing after trying too often to eat Transport's lunch.
    2. Envy: Poor Data Link is always starved for attention. (With
       Asynchronous Transfer Mode, maybe now it is feeling less
       neglected.)
    1. Pride: Physical has managed to avoid much of the controversy,
       and nearly all of the embarrassment, suffered by the others.
    (C) John G. Fletcher described how the OSI layers also correspond
    to Snow White's dwarf friends:
    7. Doc: Application acts as if it is in charge, but sometimes
       muddles its syntax.
    6. Sleepy: Presentation is indolent, being guilty of the sin of
       Sloth.
    5. Dopey: Session is confused because its charter is not very
       clear.
    4. Grumpy: Transport is irritated because Network has encroached
       on Transport's turf.
    3. Happy: Network smiles for the same reason that Transport is
       irritated.
    2. Sneezy: Data Link makes loud noises in the hope of attracting
       attention.
    1. Bashful: Physical quietly does its work, unnoticed by the
       others.
 $ operational integrity
    (I) A synonym for "system integrity"; emphasizes the actual
    performance of system functions rather than just the ability to
    perform them.
 $ operations security (OPSEC)
    (I) A process to identify, control, and protect evidence of the
    planning and execution of sensitive activities and operations, and
    thereby prevent potential adversaries from gaining knowledge of
    capabilities and intentions.
 $ OPSEC
    See: operations security.
 $ ORA
    See: organizational registration authority.
 $ Orange Book
    (D) ISDs SHOULD NOT use this term as a synonym for "Trusted
    Computer System Evaluation Criteria" [CSC001, DOD1]. Instead, use

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    the full, proper name of the document or, in subsequent
    references, the abbreviation "TCSEC". (See: (usage note under)
    Green Book.)
 $ organizational certificate
    (O) MISSI usage: A type of MISSI X.509 public-key certificate that
    is issued to support organizational message handling for the U.S.
    Government's Defense Message System.
 $ organizational registration authority (ORA)
    (I) General usage: An RA for an organization.
    (O) MISSI usage: The MISSI implementation of RA. A MISSI end
    entity that (a) assists a PCA, CA, or SCA to register other end
    entities, by gathering, verifying, and entering data and
    forwarding it to the signing authority and (b) may also assist
    with card management functions. An ORA is a local administrative
    authority, and the term refers both to the office or role, and to
    the person who fills that office. An ORA does not sign
    certificates, CRLs, or CKLs. (See: no-PIN ORA, SSO-PIN ORA, user-
    PIN ORA.)
 $ origin authentication
 $ origin authenticity
    (D) ISDs SHOULD NOT use these terms because they look like
    careless use of an internationally standardized term. Instead, use
    "data origin authentication" or "peer entity authentication",
    depending which is meant.
 $ OSI
 $ OSIRM
    See: Open Systems Interconnection Reference Model.
 $ OTP
    See: One-Time Password.
 $ out of band
    (I) Transfer of information using a channel that is outside (i.e.,
    separate from) the channel that is normally used. (See: covert
    channel.)
    (C) Out-of-band mechanisms are often used to distribute shared
    secrets (e.g., a symmetric key) or other sensitive information
    items (e.g., a root key) that are needed to initialize or
    otherwise enable the operation of cryptography or other security
    mechanisms. (See: key distribution.)

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 $ output feedback (OFB)
    (N) A block cipher mode [FP081] that modifies electronic codebook
    mode to operate on plaintext segments of variable length less than
    or equal to the block length.
    (C) This mode operates by directly using the algorithm's
    previously generated output block as the algorithm's next input
    block (i.e., by "feeding back" the output block) and combining
    (exclusive OR-ing) the output block with the next plaintext
    segment (of block length or less) to form the next ciphertext
    segment.
 $ outside attack
 $ outsider attack
    See: (secondary definition under) attack.
 $ P1363
    See: IEEE P1363.
 $ PAA
    See: policy approving authority.
 $ packet filter
    See: (secondary definition under) filtering router.
 $ pagejacking
    (I) A contraction of "Web page hijacking". A masquerade attack in
    which the attacker copies (steals) a home page or other material
    from the target server, rehosts the page on a server the attacker
    controls, and causes the rehosted page to be indexed by the major
    Web search services, thereby diverting browsers from the target
    server to the attacker's server.
    (D) ISDs SHOULD NOT use this term without including a definition,
    because the term is not listed in most dictionaries and could
    confuse international readers. (See: (usage note under) Green
    Book.)
 $ PAN
    See: primary account number.
 $ PAP
    See: Password Authentication Protocol.

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 $ partitioned security mode
    (N) A mode of operation of an information system, wherein all
    users have the clearance, but not necessarily formal access
    authorization and need-to-know, for all information handled by the
    system. This mode is defined in U.S. Department of Defense policy
    regarding system accreditation. [DoD2]
 $ passive attack
    See: (secondary definition under) attack.
 $ passive wiretapping
    See: (secondary definition under) wiretapping.
 $ password
    (I) A secret data value, usually a character string, that is used
    as authentication information. (See: challenge-response.)
    (C) A password is usually matched with a user identifier that is
    explicitly presented in the authentication process, but in some
    cases the identity may be implicit.
    (C) Using a password as authentication information assumes that
    the password is known only by the system entity whose identity is
    being authenticated. Therefore, in a network environment where
    wiretapping is possible, simple authentication that relies on
    transmission of static (i.e., repetitively used) passwords as
    cleartext is inadequate. (See: one-time password, strong
    authentication.)
 $ Password Authentication Protocol (PAP)
    (I) A simple authentication mechanism in PPP. In PAP, a user
    identifier and password are transmitted in cleartext. [R1334]
    (See: CHAP.)
 $ password sniffing
    (I) Passive wiretapping, usually on a local area network, to gain
    knowledge of passwords. (See: (usage note under) sniffing.)
 $ path discovery
    (I) For a digital certificate, the process of finding a set of
    public-key certificates that comprise a certification path from a
    trusted key to that specific certificate.
 $ path validation
    (I) The process of validating (a) all of the digital certificates
    in a certification path and (b) the required relationships between
    those certificates, thus validating the contents of the last
    certificate on the path. (See: certificate validation.)

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 $ payment card
    (N) SET usage: Collectively refers "to credit cards, debit cards,
    charge cards, and bank cards issued by a financial institution and
    which reflects a relationship between the cardholder and the
    financial institution." [SET2]
 $ payment gateway
    (O) SET usage: A system operated by an acquirer, or a third party
    designated by an acquirer, for the purpose of providing electronic
    commerce services to the merchants in support of the acquirer, and
    which interfaces to the acquirer to support the authorization,
    capture, and processing of merchant payment messages, including
    payment instructions from cardholders. [SET1, SET2]
 $ payment gateway certification authority (SET PCA)
    (O) SET usage: A CA that issues digital certificates to payment
    gateways and is operated on behalf of a payment card brand, an
    acquirer, or another party according to brand rules. A SET PCA
    issues a CRL for compromised payment gateway certificates. [SET2]
    (See: PCA.)
 $ PC card
    (N) A type of credit card-sized, plug-in peripheral device that
    was originally developed to provide memory expansion for portable
    computers, but is also used for other kinds of functional
    expansion. (See: FORTEZZA, PCMCIA.)
    (C) The international PC Card Standard defines a non-proprietary
    form factor in three standard sizes--Types I, II and III--each of
    which have a 68-pin interface between the card and the socket into
    which it plugs.  All three types have the same length and width,
    roughly the size of a credit card, but differ in their thickness
    from 3.3 to 10.5 mm. Examples include storage modules, modems,
    device interface adapters, and cryptographic modules.
 $ PCA
    (D) ISDs SHOULD NOT use this acronym without a qualifying
    adjective because that would be ambiguous. (See: Internet policy
    certification authority, (MISSI) policy creation authority, (SET)
    payment gateway certification authority.)
 $ PCMCIA
    (N) Personal Computer Memory Card International Association, a
    group of manufacturers, developers, and vendors, founded in 1989
    to standardize plug-in peripheral memory cards for personal
    computers and now extended to deal with any technology that works
    in the PC card form factor. (See: PC card.)

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 $ peer entity authentication
    (I) "The corroboration that a peer entity in an association is the
    one claimed." [I7498 Part 2] (See: authentication.)
 $ peer entity authentication service
    (I) A security service that verifies an identity claimed by or for
    a system entity in an association. (See: authentication,
    authentication service.)
    (C) This service is used at the establishment of, or at times
    during, an association to confirm the identity of one entity to
    another, thus protecting against a masquerade by the first entity.
    However, unlike data origin authentication service, this service
    requires an association to exist between the two entities, and the
    corroboration provided by the service is valid only at the current
    time that the service is provided.
    (C) See: "relationship between data integrity service and
    authentication services" under data integrity service.
 $ PEM
    See: Privacy Enhanced Mail.
 $ penetration
    (I) Successful, repeatable, unauthorized access to a protected
    system resource. (See: attack, violation.)
 $ penetration test
    (I) A system test, often part of system certification, in which
    evaluators attempt to circumvent the security features of the
    system. [NCS04]
    (C) Penetration testing may be performed under various constraints
    and conditions. However, for a TCSEC evaluation, testers are
    assumed to have all system design and implementation
    documentation, including source code, manuals, and circuit
    diagrams, and to work under no greater constraints than those
    applied to ordinary users.
 $ perfect forward secrecy
    See: (discussion under) public-key forward secrecy.
 $ perimeter
    See: security perimeter.

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 $ periods processing
    (I) A mode of system operation in which information of different
    sensitivities is processed at distinctly different times by the
    same system, with the system being properly purged or sanitized
    between periods. (See: color change.)
 $ permission
    (I) A synonym for "authorization", but "authorization" is
    preferred in the PKI context. (See: privilege.)
 $ personal identification number (PIN)
    (I) A character string used as a password to gain access to a
    system resource. (See: authentication information.)
    (C) Despite the words "identification" and "number", a PIN seldom
    serves as a user identifier, and a PIN's characters are not
    necessarily all numeric. A better name for this concept would have
    been "personal authentication system string (PASS)".
    (C) Retail banking applications commonly use 4-digit PINs.
    FORTEZZA PC card's use up to 12 characters for user or SSO PINs.
 $ personality
 $ personality label
    (O) MISSI usage: A set of MISSI X.509 public-key certificates that
    have the same subject DN, together with their associated private
    keys and usage specifications, that is stored on a FORTEZZA PC
    card to support a role played by the card's user.
    (C) When a card's user selects a personality to use in a FORTEZZA-
    aware application, the data determines behavior traits (the
    personality) of the application. A card's user may have multiple
    personalities on the card. Each has a "personality label", a user-
    friendly character string that applications can display to the
    user for selecting or changing the personality to be used. For
    example, a military user's card might contain three personalities:
    GENERAL HALFTRACK, COMMANDER FORT SWAMPY, and NEW YEAR'S EVE PARTY
    CHAIRMAN. Each personality includes one or more certificates of
    different types (such as DSA versus RSA), for different purposes
    (such as digital signature versus encryption), or with different
    authorizations.
 $ personnel security
    (I) Procedures to ensure that persons who access a system have
    proper clearance, authorization, and need-to-know as required by
    the system's security policy.

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 $ PGP(trademark)
    See: Pretty Good Privacy.
 $ Photuris
    (I) A UDP-based, key establishment protocol for session keys,
    designed for use with the IPsec protocols AH and ESP. Superseded
    by IKE.
 $ phreaking
    (I) A contraction of "telephone breaking". An attack on or
    penetration of a telephone system or, by extension, any other
    communication or information system. [Raym]
    (D) ISDs SHOULD NOT use this term because it is not listed in most
    dictionaries and could confuse international readers.
 $ physical security
    (I) Tangible means of preventing unauthorized physical access to a
    system. E.g., fences, walls, and other barriers; locks, safes, and
    vaults; dogs and armed guards; sensors and alarm bells. [FP031,
    R1455]
 $ piggyback attack
    (I) A form of active wiretapping in which the attacker gains
    access to a system via intervals of inactivity in another user's
    legitimate communication connection. Sometimes called a "between-
    the-lines" attack. (See: hijack attack, man-in-the-middle attack.)
 $ PIN
    See: personal identification number.
 $ ping of death
    (I) An attack that sends an improperly large ICMP [R0792] echo
    request packet (a "ping") with the intent of overflowing the input
    buffers of the destination machine and causing it to crash.
 $ ping sweep
    (I) An attack that sends ICMP [R0792] echo requests ("pings") to a
    range of IP addresses, with the goal of finding hosts that can be
    probed for vulnerabilities.
 $ PKCS
    See: Public-Key Cryptography Standards.
 $ PKCS #7
    (N) A standard [PKC07, R2315] from the PKCS series; defines a
    syntax for data that may have cryptography applied to it, such as
    for digital signatures and digital envelopes.

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 $ PKCS #10
    (N) A standard [PKC10] from the PKCS series; defines a syntax for
    requests for public-key certificates. (See: certification
    request.)
    (C) A PKCS #10 request contains a DN and a public key, and may
    contain other attributes, and is signed by the entity making the
    request. The request is sent to a CA, who converts it to an X.509
    public-key certificate (or some other form) and returns it,
    possibly in PKCS #7 format.
 $ PKCS #11
    (N) A standard [PKC11] from the PKCS series; defines a software
    CAPI called Cryptoki (pronounced "crypto-key"; short for
    "cryptographic token interface") for devices that hold
    cryptographic information and perform cryptographic functions.
 $ PKI
    See: public-key infrastructure.
 $ PKIX
    (I) (1.) A contraction of "Public-Key Infrastructure (X.509)", the
    name of the IETF working group that is specifying an architecture
    and set of protocols needed to support an X.509-based PKI for the
    Internet. (2.) A collective name for that architecture and set of
    protocols.
    (C) The goal of PKIX is to facilitate the use of X.509 public-key
    certificates in multiple Internet applications and to promote
    interoperability between different implementations that use those
    certificates. The resulting PKI is intended to provide a framework
    that supports a range of trust and hierarchy environments and a
    range of usage environments. PKIX specifies (a) profiles of the v3
    X.509 public-key certificate standards and the v2 X.509 CRL
    standards for the Internet; (b) operational protocols used by
    relying parties to obtain information such as certificates or
    certificate status; (c) management protocols used by system
    entities to exchange information needed for proper management of
    the PKI; and (d) information about certificate policies and CPSs,
    covering the areas of PKI security not directly addressed in the
    rest of PKIX.
 $ PKIX private extension
    (I) PKIX defines a private extension to identify an on-line
    verification service supporting the issuing CA.

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 $ plaintext
    (I) Data that is input to and transformed by an encryption
    process, or that is output by a decryption process.
    (C) Usually, the plaintext input to an encryption operation is
    cleartext. But in some cases, the input is ciphertext that was
    output from another encryption operation. (See: superencryption.)
 $ Point-to-Point Protocol (PPP)
    (I) An Internet Standard protocol [R1661] for encapsulation and
    full-duplex transportation of network layer (mainly OSI layer 3)
    protocol data packets over a link between two peers, and for
    multiplexing different network layer protocols over the same link.
    Includes optional negotiation to select and use a peer entity
    authentication protocol to authenticate the peers to each other
    before they exchange network layer data. (See: CHAP, EAP, PAP.)
 $ Point-to-Point Tunneling Protocol (PPTP)
    (I) An Internet client-server protocol (originally developed by
    Ascend and Microsoft) that enables a dial-up user to create a
    virtual extension of the dial-up link across a network by
    tunneling PPP over IP. (See: L2TP.)
    (C) PPP can encapsulate any Internet Protocol Suite network layer
    protocol (or OSI layer 3 protocol). Therefore, PPTP does not
    specify security services; it depends on protocols above and below
    it to provide any needed security. PPTP makes it possible to
    divorce the location of the initial dial-up server (i.e., the PPTP
    Access Concentrator, the client, which runs on a special-purpose
    host) from the location at which the dial-up protocol (PPP)
    connection is terminated and access to the network is provided
    (i.e., the PPTP Network Server, which runs on a general-purpose
    host).
 $ policy
    (D) ISDs SHOULD NOT use this word as an abbreviation for either
    "security policy" or "certificate policy". Instead, to avoid
    misunderstanding, use the fully qualified term, at least at the
    point of first usage.
 $ policy approving authority (PAA)
    (O) MISSI usage: The top-level signing authority of a MISSI
    certification hierarchy. The term refers both to that
    authoritative office or role and to the person who plays that
    role. (See: root registry.)

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    (C) A PAA registers MISSI PCAs and signs their X.509 public-key
    certificates. A PAA issues CRLs but does not issue a CKL. A PAA
    may issue cross-certificates to other PAAs.
 $ policy certification authority (Internet PCA)
    (I) An X.509-compliant CA at the second level of the Internet
    certification hierarchy, under the Internet Policy Registration
    Authority (IPRA). Each PCA operates in accordance with its
    published security policy (see: certification practice statement)
    and within constraints established by the IPRA for all PCAs.
    [R1422]. (See: policy creation authority.)
 $ policy creation authority (MISSI PCA)
    (O) MISSI usage: The second level of a MISSI certification
    hierarchy; the administrative root of a security policy domain of
    MISSI users and other, subsidiary authorities. The term refers
    both to that authoritative office or role and to the person who
    fills that office. (See: policy certification authority.)
    (C) A MISSI PCA's certificate is issued by a policy approving
    authority. The PCA registers the CAs in its domain, defines their
    configurations, and issues their X.509 public-key certificates.
    (The PCA may also issue certificates for SCAs, ORAs, and other end
    entities, but a PCA does not usually do this.) The PCA
    periodically issues CRLs and CKLs for its domain.
 $ Policy Management Authority
    (N) Canadian usage: An organization responsible for PKI oversight
    and policy management in the Government of Canada.
 $ policy mapping
    (I) "Recognizing that, when a CA in one domain certifies a CA in
    another domain, a particular certificate policy in the second
    domain may be considered by the authority of the first domain to
    be equivalent (but not necessarily identical in all respects) to a
    particular certificate policy in the first domain." [X509]
 $ POP3
    See: Post Office Protocol, version 3.
 $ POP3 APOP
    (I) A POP3 "command" (better described as a transaction type, or a
    protocol-within-a-protocol) by which a POP3 client optionally uses
    a keyed hash (based on MD5) to authenticate itself to a POP3
    server and, depending on the server implementation, to protect
    against replay attacks. (See: CRAM, POP3 AUTH, IMAP4
    AUTHENTICATE.)

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    (C) The server includes a unique timestamp in its greeting to the
    client. The subsequent APOP command sent by the client to the
    server contains the client's name and the hash result of applying
    MD5 to a string formed from both the timestamp and a shared secret
    that is known only to the client and the server. APOP was designed
    to provide as an alternative to using POP3's USER and PASS (i.e.,
    password) command pair, in which the client sends a cleartext
    password to the server.
 $ POP3 AUTH
    (I) A "command" [R1734] (better described as a transaction type,
    or a protocol-within-a-protocol) in POP3, by which a POP3 client
    optionally proposes a mechanism to a POP3 server to authenticate
    the client to the server and provide other security services.
    (See: POP3 APOP, IMAP4 AUTHENTICATE.)
    (C) If the server accepts the proposal, the command is followed by
    performing a challenge-response authentication protocol and,
    optionally, negotiating a protection mechanism for subsequent POP3
    interactions. The security mechanisms used by POP3 AUTH are those
    used by IMAP4.
 $ port scan
    (I) An attack that sends client requests to a range of server port
    addresses on a host, with the goal of finding an active port and
    exploiting a known vulnerability of that service.
 $ POSIX
    (N) Portable Operating System Interface for Computer Environments,
    a standard [FP151, IS9945-1] (originally IEEE Standard P1003.1)
    that defines an operating system interface and environment to
    support application portability at the source code level. It is
    intended to be used by both application developers and system
    implementers.
    (C) P1003.1 supports security functionality like those on most
    UNIX systems, including discretionary access control and
    privilege. IEEE Draft Standard P1003.6.1 specifies additional
    functionality not provided in the base standard, including (a)
    discretionary access control, (b) audit trail mechanisms, (c)
    privilege mechanisms, (d) mandatory access control, and (e)
    information label mechanisms.
 $ Post Office Protocol, version 3 (POP3)
    (I) An Internet Standard protocol [R1939] by which a client
    workstation can dynamically access a mailbox on a server host to
    retrieve mail messages that the server has received and is holding
    for the client. (See: IMAP4.)

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    (C) POP3 has mechanisms for optionally authenticating a client to
    a server and providing other security services. (See: POP3 APOP,
    POP3 AUTH.)
 $ PPP
    See: Point-to-Point Protocol.
 $ PPTP
    See: Point-to-Point Tunneling Protocol.
 $ pre-authorization
    (I) A capability of a CAW that enables certification requests to
    be automatically validated against data provided in advance to the
    CA by an authorizing entity.
 $ Pretty Good Privacy(trademark) (PGP(trademark))
    (O) Trademarks of Network Associates, Inc., referring to a
    computer program (and related protocols) that uses cryptography to
    provide data security for electronic mail and other applications
    on the Internet. (See: MOSS, PEM, S/MIME.)
    (C) PGP encrypts messages with IDEA in CFB mode, distributes the
    IDEA keys by encrypting them with RSA, and creates digital
    signatures on messages with MD5 and RSA. To establish ownership of
    public keys, PGP depends on the web of trust. (See: Privacy
    Enhanced Mail.)
 $ primary account number (PAN)
    (O) SET usage: "The assigned number that identifies the card
    issuer and cardholder. This account number is composed of an
    issuer identification number, an individual account number
    identification, and an accompanying check digit as defined by ISO
    7812-1985." [SET2, IS7812] (See: bank identification number.)
    (C) The PAN is embossed, encoded, or both on a magnetic-strip-
    based credit card. The PAN identifies the issuer to which a
    transaction is to be routed and the account to which it is to be
    applied unless specific instructions indicate otherwise. The
    authority that assigns the bank identification number part of the
    PAN is the American Bankers Association.
 $ privacy
    (I) The right of an entity (normally a person), acting in its own
    behalf, to determine the degree to which it will interact with its
    environment, including the degree to which the entity is willing
    to share information about itself with others. (See: anonymity.)

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    (O) "The right of individuals to control or influence what
    information related to them may be collected and stored and by
    whom and to whom that information may be disclosed." [I7498 Part
    2]
    (D) ISDs SHOULD NOT use this term as a synonym for "data
    confidentiality" or "data confidentiality service", which are
    different concepts. Privacy is a reason for security rather than a
    kind of security. For example, a system that stores personal data
    needs to protect the data to prevent harm, embarrassment,
    inconvenience, or unfairness to any person about whom data is
    maintained, and to protect the person's privacy. For that reason,
    the system may need to provide data confidentiality service.
 $ Privacy Enhanced Mail (PEM)
    (I) An Internet protocol to provide data confidentiality, data
    integrity, and data origin authentication for electronic mail.
    [R1421, R1422]. (See: MOSS, MSP, PGP, S/MIME.)
    (C) PEM encrypts messages with DES in CBC mode, provides key
    distribution of DES keys by encrypting them with RSA, and signs
    messages with RSA over either MD2 or MD5. To establish ownership
    of public keys, PEM uses a certification hierarchy, with X.509
    public-key certificates and X.509 CRLs that are signed with RSA
    and MD2. (See: Pretty Good Privacy.)
    (C) PEM is designed to be compatible with a wide range of key
    management methods, but is limited to specifying security services
    only for text messages and, like MOSS, has not been widely
    implemented in the Internet.
 $ private component
    (I) A synonym for "private key".
    (D) In most cases, ISDs SHOULD NOT use this term; to avoid
    confusing readers, use "private key" instead. However, the term
    MAY be used when specifically discussing a key pair; e.g., "A key
    pair has a public component and a private component."
 $ private extension
    See: (secondary definition under) extension.
 $ private key
    (I) The secret component of a pair of cryptographic keys used for
    asymmetric cryptography. (See: key pair, public key.)
    (O) "(In a public key cryptosystem) that key of a user's key pair
    which is known only by that user." [X509]

Shirey Informational [Page 131] RFC 2828 Internet Security Glossary May 2000

 $ privilege
    (I) An authorization or set of authorizations to perform security-
    relevant functions, especially in the context of a computer
    operating system.
 $ privilege management infrastructure
    (N) "The complete set of processes required to provide an
    authorization service", i.e., processes concerned with attribute
    certificates. [FPDAM] (See: PKI.)
    (D) ISDs SHOULD NOT use this term and its definition because the
    definition is vague, and there is no consensus on an alternate
    definition.
 $ privileged process
    (I) An computer process that is authorized (and, therefore,
    trusted) to perform some security-relevant functions that ordinary
    processes are not. (See: privilege, trusted process.)
 $ procedural security
    (D) ISDs SHOULD NOT use this term as a synonym for "administrative
    security". Any type of security may involve procedures; therefore,
    the term may be misleading. Instead, use "administrative
    security", "communication security", "computer security",
    "emanations security", "personnel security", "physical security",
    or whatever specific type is meant. (See: security architecture.)
 $ proprietary
    (I) Refers to information (or other property) that is owned by an
    individual or organization and for which the use is restricted by
    that entity.
 $ protected checksum
    (I) A checksum that is computed for a data object by means that
    protect against active attacks that would attempt to change the
    checksum to make it match changes made to the data object. (See:
    digital signature, keyed hash, (discussion under) checksum.
 $ protected distribution system
    (I) A wireline or fiber-optic system that includes sufficient
    safeguards (acoustic, electric, electromagnetic, and physical) to
    permit its use for unencrypted transmission of (cleartext) data.
 $ protection authority
    See: (secondary definition under) Internet Protocol Security
    Option.

Shirey Informational [Page 132] RFC 2828 Internet Security Glossary May 2000

 $ protection ring
    (I) One of a hierarchy of privileged operation modes of a system
    that gives certain access rights to processes authorized to
    operate in that mode.
 $ protocol
    (I) A set of rules (i.e., formats and procedures) to implement and
    control some type of association (e.g., communication) between
    systems. (E.g., see: Internet Protocol.)
    (C) In particular, a series of ordered steps involving computing
    and communication that are performed by two or more system
    entities to achieve a joint objective. [A9042]
 $ protocol suite
    (I) A complementary collection of communication protocols used in
    a computer network. (See: Internet, OSI.)
 $ proxy server
    (I) A computer process--often used as, or as part of, a firewall--
    that relays a protocol between client and server computer systems,
    by appearing to the client to be the server and appearing to the
    server to be the client. (See: SOCKS.)
    (C) In a firewall, a proxy server usually runs on a bastion host,
    which may support proxies for several protocols (e.g., FTP, HTTP,
    and TELNET). Instead of a client in the protected enclave
    connecting directly to an external server, the internal client
    connects to the proxy server which in turn connects to the
    external server. The proxy server waits for a request from inside
    the firewall, forwards the request to the remote server outside
    the firewall, gets the response, then sends the response back to
    the client. The proxy may be transparent to the clients, or they
    may need to connect first to the proxy server, and then use that
    association to also initiate a connection to the real server.
    (C) Proxies are generally preferred over SOCKS for their ability
    to perform caching, high-level logging, and access control. A
    proxy can provide security service beyond that which is normally
    part of the relayed protocol, such as access control based on peer
    entity authentication of clients, or peer entity authentication of
    servers when clients do not have that capability. A proxy at OSI
    layer 7 can also provide finer-grained security service than can a
    filtering router at OSI layer 3. For example, an FTP proxy could
    permit transfers out of, but not into, a protected network.

Shirey Informational [Page 133] RFC 2828 Internet Security Glossary May 2000

 $ pseudo-random
    (I) A sequence of values that appears to be random (i.e.,
    unpredictable) but is actually generated by a deterministic
    algorithm. (See: random.)
 $ pseudo-random number generator
    (I) A process used to deterministically generate a series of
    numbers (usually integers) that appear to be random according to
    certain statistical tests, but actually are pseudo-random.
    (C) Pseudo-random number generators are usually implemented in
    software.
 $ public component
    (I) A synonym for "public key".
    (D) In most cases, ISDs SHOULD NOT use this term; to avoid
    confusing readers, use "private key" instead. However, the term
    MAY be used when specifically discussing a key pair; e.g., "A key
    pair has a public component and a private component."
 $ public key
    (I) The publicly-disclosable component of a pair of cryptographic
    keys used for asymmetric cryptography. (See: key pair, private
    key.)
    (O) "(In a public key cryptosystem) that key of a user's key pair
    which is publicly known." [X509]
 $ public-key certificate
    (I) A digital certificate that binds a system entity's identity to
    a public key value, and possibly to additional data items; a
    digitally-signed data structure that attests to the ownership of a
    public key. (See: X.509 public-key certificate.)
    (C) The digital signature on a public-key certificate is
    unforgeable. Thus, the certificate can be published, such as by
    posting it in a directory, without the directory having to protect
    the certificate's data integrity.
    (O) "The public key of a user, together with some other
    information, rendered unforgeable by encipherment with the private
    key of the certification authority which issued it." [X509]
 $ public-key cryptography
    (I) The popular synonym for "asymmetric cryptography".

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 $ Public-Key Cryptography Standards (PKCS)
    (I) A series of specifications published by RSA Laboratories for
    data structures and algorithm usage for basic applications of
    asymmetric cryptography. (See: PKCS #7, PKCS #10, PKCS #11.)
    (C) The PKCS were begun in 1991 in cooperation with industry and
    academia, originally including Apple, Digital, Lotus, Microsoft,
    Northern Telecom, Sun, and MIT. Today, the specifications are
    widely used, but they are not sanctioned by an official standards
    organization, such as ANSI, ITU-T, or IETF. RSA Laboratories
    retains sole decision-making authority over the PKCS.
 $ public-key forward secrecy (PFS)
    (I) For a key agreement protocol based on asymmetric cryptography,
    the property that ensures that a session key derived from a set of
    long-term public and private keys will not be compromised if one
    of the private keys is compromised in the future.
    (C) Some existing RFCs use the term "perfect forward secrecy" but
    either do not define it or do not define it precisely. While
    preparing this Glossary, we tried to find a good definition for
    that term, but found this to be a muddled area. Experts did not
    agree. For all practical purposes, the literature defines "perfect
    forward secrecy" by stating the Diffie-Hellman algorithm. The term
    "public-key forward secrecy" (suggested by Hilarie Orman) and the
    "I" definition stated for it here were crafted to be compatible
    with current Internet documents, yet be narrow and leave room for
    improved terminology.
    (C) Challenge to the Internet security community: We need a
    taxonomy--a family of mutually exclusive and collectively
    exhaustive terms and definitions to cover the basic properties
    discussed here--for the full range of cryptographic algorithms and
    protocols used in Internet Standards:
    (C) Involvement of session keys vs. long-term keys: Experts
    disagree about the basic ideas involved.
  1. One concept of "forward secrecy" is that, given observations of

the operation of a key establishment protocol up to time t, and

    given some of the session keys derived from those protocol runs,
    you cannot derive unknown past session keys or future session
    keys.
  1. A related property is that, given observations of the protocol

and knowledge of the derived session keys, you cannot derive one

    or more of the long-term private keys.

Shirey Informational [Page 135] RFC 2828 Internet Security Glossary May 2000

  1. The "I" definition presented above involves a third concept of

"forward secrecy" that refers to the effect of the compromise of

    long-term keys.
  1. All three concepts involve the idea that a compromise of "this"

encryption key is not supposed to compromise the "next" one. There

    also is the idea that compromise of a single key will compromise
    only the data protected by the single key. In Internet literature,
    the focus has been on protection against decryption of back
    traffic in the event of a compromise of secret key material held
    by one or both parties to a communication.
    (C) Forward vs. backward: Experts are unhappy with the word
    "forward", because compromise of "this" encryption key also is not
    supposed to compromise the "previous" one, which is "backward"
    rather than forward. In S/KEY, if the key used at time t is
    compromised, then all keys used prior to that are compromised. If
    the "long-term" key (i.e., the base of the hashing scheme) is
    compromised, then all keys past and future are compromised; thus,
    you could say that S/KEY has neither forward nor backward secrecy.
    (C) Asymmetric cryptography vs. symmetric: Experts disagree about
    forward secrecy in the context of symmetric cryptographic systems.
    In the absence of asymmetric cryptography, compromise of any long-
    term key seems to compromise any session key derived from the
    long-term key. For example, Kerberos isn't forward secret, because
    compromising a client's password (thus compromising the key shared
    by the client and the authentication server) compromises future
    session keys shared by the client and the ticket-granting server.
    (C) Ordinary forward secrecy vs. "perfect" forward secret: Experts
    disagree about the difference between these two. Some say there is
    no difference, and some say that the initial naming was
    unfortunate and suggest dropping the word "perfect". Some suggest
    using "forward secrecy" for the case where one long-term private
    key is compromised, and adding "perfect" for when both private
    keys (or, when the protocol is multi-party, all private keys) are
    compromised.
    (C) Acknowledgements: Bill Burr, Burt Kaliski, Steve Kent, Paul
    Van Oorschot, Michael Wiener, and, especially, Hilarie Orman
    contributed ideas to this discussion.
 $ public-key infrastructure (PKI)
    (I) A system of CAs (and, optionally, RAs and other supporting
    servers and agents) that perform some set of certificate
    management, archive management, key management, and token

Shirey Informational [Page 136] RFC 2828 Internet Security Glossary May 2000

    management functions for a community of users in an application of
    asymmetric cryptography. (See: hierarchical PKI, mesh PKI,
    security management infrastructure, trust-file PKI.)
    (O) PKIX usage: The set of hardware, software, people, policies,
    and procedures needed to create, manage, store, distribute, and
    revoke digital certificates based on asymmetric cryptography.
    (C) The core PKI functions are (a) to register users and issue
    their public-key certificates, (b) to revoke certificates when
    required, and (c) to archive data needed to validate certificates
    at a much later time. Key pairs for data confidentiality may be
    generated (and perhaps escrowed) by CAs or RAs, but requiring a
    PKI client to generate its own digital signature key pair helps
    maintain system integrity of the cryptographic system, because
    then only the client ever possesses the private key it uses. Also,
    an authority may be established to approve or coordinate CPSs,
    which are security policies under which components of a PKI
    operate.
    (C) A number of other servers and agents may support the core PKI,
    and PKI clients may obtain services from them. The full range of
    such services is not yet fully understood and is evolving, but
    supporting roles may include archive agent, certified delivery
    agent, confirmation agent, digital notary, directory, key escrow
    agent, key generation agent, naming agent who ensures that issuers
    and subjects have unique identifiers within the PKI, repository,
    ticket-granting agent, and time stamp agent.
 $ RA
    See: registration authority.
 $ RA domains
    (I) A capability of a CAW that allows a CA to divide the
    responsibility for certification requests among multiple RAs.
    (C) This capability might be used to restrict access to private
    authorization data that is provided with a certification request,
    and to distribute the responsibility to review and approve
    certification requests in high volume environments. RA domains
    might segregate certification requests according to an attribute
    of the certificate subject, such as an organizational unit.
 $ RADIUS
    See: Remote Authentication Dial-In User Service.

Shirey Informational [Page 137] RFC 2828 Internet Security Glossary May 2000

 $ Rainbow Series
    (O) A set of more than 30 technical and policy documents with
    colored covers, issued by the NCSC, that discuss in detail the
    TCSEC and provide guidance for meeting and applying the criteria.
    (See: Green Book, Orange Book, Red Book, Yellow Book.)
 $ random
    (I) General usage: In mathematics, random means "unpredictable". A
    sequence of values is called random if each successive value is
    obtained merely by chance and does not depend on the preceding
    values of the sequence, and a selected individual value is called
    random if each of the values in the total population of
    possibilities has equal probability of being selected. [Knuth]
    (See: cryptographic key, pseudo-random, random number generator.)
    (I) Security usage: In cryptography and other security
    applications, random means not only unpredictable, but also
    "unguessable". When selecting data values to use for cryptographic
    keys, "the requirement is for data that an adversary has a very
    low probability of guessing or determining." It is not sufficient
    to use data that "only meets traditional statistical tests for
    randomness or which is based on limited range sources, such as
    clocks. Frequently such random quantities are determinable [i.e.,
    guessable] by an adversary searching through an embarrassingly
    small space of possibilities." [R1750]
 $ random number generator
    (I) A process used to generate an unpredictable, uniformly
    distributed series of numbers (usually integers). (See: pseudo-
    random, random.)
    (C) True random number generators are hardware-based devices that
    depend on the output of a "noisy diode" or other physical
    phenomena. [R1750]
 $ RBAC
    See: Role-Based Access Control.
 $ RC2
 $ RC4
    See: Rivest Cipher #2, Rivest Cipher #4.
 $ realm
    (O) Kerberos usage: The domain of authority of a Kerberos server
    (consisting of an authentication server and a ticket-granting
    server), including the Kerberized clients and the Kerberized
    application servers

Shirey Informational [Page 138] RFC 2828 Internet Security Glossary May 2000

 $ RED
    (I) Designation for information system equipment or facilities
    that handle (and for data that contains) only plaintext (or,
    depending on the context, classified information), and for such
    data itself. This term derives from U.S. Government COMSEC
    terminology. (See: BLACK, RED/BLACK separation.)
 $ Red Book
    (D) ISDs SHOULD NOT use this term as a synonym for "Trusted
    Network Interpretation of the Trusted Computer System Evaluation
    Criteria" [NCS05]. Instead, use the full proper name of the
    document or, in subsequent references, a more conventional
    abbreviation. (See: TCSEC, Rainbow Series, (usage note under)
    Green Book.)
 $ RED/BLACK separation
    (I) An architectural concept for cryptographic systems that
    strictly separates the parts of a system that handle plaintext
    (i.e., RED information) from the parts that handle ciphertext
    (i.e., BLACK information). This term derives from U.S. Government
    COMSEC terminology. (See: BLACK, RED.)
 $ reference monitor
    (I) "An access control concept that refers to an abstract machine
    that mediates all accesses to objects by subjects." [NCS04] (See:
    security kernel.)
    (C) A reference monitor should be (a) complete (i.e., it mediates
    every access), (b) isolated (i.e., it cannot be modified by other
    system entities), and (c) verifiable (i.e., small enough to be
    subjected to analysis and tests to ensure that it is correct).
 $ reflection attack
    (I) A type of replay attack in which transmitted data is sent back
    to its originator.
 $ register
 $ registration
    (I) An administrative act or process whereby an entity's name and
    other attributes are established for the first time at a CA, prior
    to the CA issuing a digital certificate that has the entity's name
    as the subject. (See: registration authority.)
    (C) Registration may be accomplished either directly, by the CA,
    or indirectly, by a separate RA. An entity is presented to the CA
    or RA, and the authority either records the name(s) claimed for
    the entity or assigns the entity's name(s). The authority also
    determines and records other attributes of the entity that are to

Shirey Informational [Page 139] RFC 2828 Internet Security Glossary May 2000

    be bound in a certificate (such as a public key or authorizations)
    or maintained in the authority's database (such as street address
    and telephone number). The authority is responsible, possibly
    assisted by an RA, for authenticating the entity's identity and
    verifying the correctness of the other attributes, in accordance
    with the CA's CPS.
    (C) Among the registration issues that a CPS may address are the
    following [R2527]:
  1. How a claimed identity and other attributes are verified.
  2. How organization affiliation or representation is verified.
  3. What forms of names are permitted, such as X.500 DN, domain

name, or IP address.

  1. Whether names are required to be meaningful or unique, and

within what domain.

  1. How naming disputes are resolved, including the role of

trademarks.

  1. Whether certificates are issued to entities that are not

persons.

  1. Whether a person is required to appear before the CA or RA, or

can instead be represented by an agent.

  1. Whether and how an entity proves possession of the private key

matching a public key.

 $ registration authority (RA)
    (I) An optional PKI entity (separate from the CAs) that does not
    sign either digital certificates or CRLs but has responsibility
    for recording or verifying some or all of the information
    (particularly the identities of subjects) needed by a CA to issue
    certificates and CRLs and to perform other certificate management
    functions. (See: organizational registration authority,
    registration.)
    (C) Sometimes, a CA may perform all certificate management
    functions for all end users for which the CA signs certificates.
    Other times, such as in a large or geographically dispersed
    community, it may be necessary or desirable to offload secondary
    CA functions and delegate them to an assistant, while the CA
    retains the primary functions (signing certificates and CRLs). The
    tasks that are delegated to an RA by a CA may include personal
    authentication, name assignment, token distribution, revocation
    reporting, key generation, and archiving. An RA is an optional PKI
    component, separate from the CA, that is assigned secondary
    functions. The duties assigned to RAs vary from case to case but
    may include the following:

Shirey Informational [Page 140] RFC 2828 Internet Security Glossary May 2000

  1. Verifying a subject's identity, i.e., performing personal

authentication functions.

  1. Assigning a name to a subject. (See: distinguished name.)
  2. Verifying that a subject is entitled to have the attributes

requested for a certificate.

  1. Verifying that a subject possesses the private key that matches

the public key requested for a certificate.

  1. Performing functions beyond mere registration, such as

generating key pairs, distributing tokens, and handling

       revocation reports. (Such functions may be assigned to a PKI
       element that is separate from both the CA and the RA.)
    (I) PKIX usage: An optional PKI component, separate from the
    CA(s). The functions that the RA performs will vary from case to
    case but may include identity authentication and name assignment,
    key generation and archiving of key pairs, token distribution, and
    revocation reporting. [R2510]
    (O) SET usage: "An independent third-party organization that
    processes payment card applications for multiple payment card
    brands and forwards applications to the appropriate financial
    institutions." [SET2]
 $ regrade
    (I) Deliberately change the classification level of information in
    an authorized manner.
 $ rekey
    (I) Change the value of a cryptographic key that is being used in
    an application of a cryptographic system. (See: certificate
    rekey.)
    (C) For example, rekey is required at the end of a cryptoperiod or
    key lifetime.
 $ reliability
    (I) The ability of a system to perform a required function under
    stated conditions for a specified period of time. (See:
    availability, survivability.)
 $ relying party
    (N) A synonym for "certificate user". Used in a legal context to
    mean a recipient of a certificate who acts in reliance on that
    certificate. (See: ABA Guidelines.)
 $ Remote Authentication Dial-In User Service (RADIUS)
    (I) An Internet protocol [R2138] for carrying dial-in users'
    authentication information and configuration information between a

Shirey Informational [Page 141] RFC 2828 Internet Security Glossary May 2000

    shared, centralized authentication server (the RADIUS server) and
    a network access server (the RADIUS client) that needs to
    authenticate the users of its network access ports. (See: TACACS.)
    (C) A user of the RADIUS client presents authentication
    information to the client, and the client passes that information
    to the RADIUS server. The server authenticates the client using a
    shared secret value, then checks the user's authentication
    information, and finally returns to the client all authorization
    and configuration information needed by the client to deliver
    service to the user.
 $ renew
    See: certificate renewal.
 $ replay attack
    (I) An attack in which a valid data transmission is maliciously or
    fraudulently repeated, either by the originator or by an adversary
    who intercepts the data and retransmits it, possibly as part of a
    masquerade attack. (See: active wiretapping.)
 $ repository
    (I) A system for storing and distributing digital certificates and
    related information (including CRLs, CPSs, and certificate
    policies) to certificate users. (See: directory.)
    (O) "A trustworthy system for storing and retrieving certificates
    or other information relevant to certificates." [ABA]
    (C) A certificate is published to those who might need it by
    putting it in a repository. The repository usually is a publicly
    accessible, on-line server. In the Federal Public-key
    Infrastructure, for example, the expected repository is a
    directory that uses LDAP, but also may be the X.500 Directory that
    uses DAP, or an HTTP server, or an FTP server that permits
    anonymous login.
 $ repudiation
    (I) Denial by a system entity that was involved in an association
    (especially an association that transfers information) of having
    participated in the relationship. (See: accountability, non-
    repudiation service.)
    (O) "Denial by one of the entities involved in a communication of
    having participated in all or part of the communication." [I7498
    Part 2]

Shirey Informational [Page 142] RFC 2828 Internet Security Glossary May 2000

 $ Request for Comment (RFC)
    (I) One of the documents in the archival series that is the
    official channel for ISDs and other publications of the Internet
    Engineering Steering Group, the Internet Architecture Board, and
    the Internet community in general. [R2026, R2223] (See: Internet
    Standard.)
    (C) This term is *not* a synonym for "Internet Standard".
 $ residual risk
    (I) The risk that remains after countermeasures have been applied.
 $ restore
    See: card restore.
 $ revocation
    See: certificate revocation.
 $ revocation date
    (N) In an X.509 CRL entry, a date-time field that states when the
    certificate revocation occurred, i.e., when the CA declared the
    digital certificate to be invalid. (See: invalidity date.)
    (C) The revocation date may not resolve some disputes because, in
    the worst case, all signatures made during the validity period of
    the certificate may have to be considered invalid. However, it may
    be desirable to treat a digital signature as valid even though the
    private key used to sign was compromised after the signing. If
    more is known about when the compromise actually occurred, a
    second date-time, an "invalidity date", can be included in an
    extension of the CRL entry.
 $ revocation list
    See: certificate revocation list.
 $ revoke
    See: certificate revocation.
 $ RFC
    See: Request for Comment.
 $ risk
    (I) An expectation of loss expressed as the probability that a
    particular threat will exploit a particular vulnerability with a
    particular harmful result.

Shirey Informational [Page 143] RFC 2828 Internet Security Glossary May 2000

    (O) SET usage: "The possibility of loss because of one or more
    threats to information (not to be confused with financial or
    business risk)." [SET2]
 $ risk analysis
 $ risk assessment
    (I) A process that systematically identifies valuable system
    resources and threats to those resources, quantifies loss
    exposures (i.e., loss potential) based on estimated frequencies
    and costs of occurrence, and (optionally) recommends how to
    allocate resources to countermeasures so as to minimize total
    exposure.
    (C) The analysis lists risks in order of cost and criticality,
    thereby determining where countermeasures should be applied first.
    It is usually financially and technically infeasible to counteract
    all aspects of risk, and so some residual risk will remain, even
    after all available countermeasures have been deployed. [FP031,
    R2196]
 $ risk management
    (I) The process of identifying, controlling, and eliminating or
    minimizing uncertain events that may affect system resources.
    (See: risk analysis.)
 $ Rivest Cipher #2 (RC2)
    (N) A proprietary, variable-key-length block cipher invented by
    Ron Rivest for RSA Data Security, Inc. (now a wholly-owned
    subsidiary of Security Dynamics, Inc.).
 $ Rivest Cipher #4 (RC4)
    (N) A proprietary, variable-key-length stream cipher invented by
    Ron Rivest for RSA Data Security, Inc. (now a wholly-owned
    subsidiary of Security Dynamics, Inc.).
 $ Rivest-Shamir-Adleman (RSA)
    (N) An algorithm for asymmetric cryptography, invented in 1977 by
    Ron Rivest, Adi Shamir, and Leonard Adleman [RSA78, Schn].
    (C) RSA uses exponentiation modulo the product of two large prime
    numbers. The difficulty of breaking RSA is believed to be
    equivalent to the difficulty of factoring integers that are the
    product of two large prime numbers of approximately equal size.
    (C) To create an RSA key pair, randomly choose two large prime
    numbers, p and q, and compute the modulus, n = pq. Randomly choose
    a number e, the public exponent, that is less than n and
    relatively prime to (p-1)(q-1). Choose another number d, the

Shirey Informational [Page 144] RFC 2828 Internet Security Glossary May 2000

    private exponent, such that ed-1 evenly divides (p-1)(q-1). The
    public key is the set of numbers (n,e), and the private key is the
    set (n,d).
    (C) It is assumed to be difficult to compute the private key (n,d)
    from the public key (n,e). However, if n can be factored into p
    and q, then the private key d can be computed easily. Thus, RSA
    security depends on the assumption that it is computationally
    difficult to factor a number that is the product of two large
    prime numbers. (Of course, p and q are treated as part of the
    private key, or else destroyed after computing n.)
    (C) For encryption of a message, m, to be sent to Bob, Alice uses
    Bob's public key (n,e) to compute m**e (mod n) = c. She sends c to
    Bob. Bob computes c**d (mod n) = m. Only Bob knows d, so only Bob
    can compute c**d (mod n) = m to recover m.
    (C) To provide data origin authentication of a message, m, to be
    sent to Bob, Alice computes m**d (mod n) = s, where (d,n) is
    Alice's private key. She sends m and s to Bob. To recover the
    message that only Alice could have sent, Bob computes s**e (mod n)
    = m, where (e,n) is Alice's public key.
    (C) To ensure data integrity in addition to data origin
    authentication requires extra computation steps in which Alice and
    Bob use a cryptographic hash function h (as explained for digital
    signature). Alice computes the hash value h(m) = v, and then
    encrypts v with her private key to get s. She sends m and s. Bob
    receives m' and s', either of which might have been changed from
    the m and s that Alice sent. To test this, he decrypts s' with
    Alice's public key to get v'. He then computes h(m') = v". If v'
    equals v", Bob is assured that m' is the same m that Alice sent.
 $ role-based access control (RBAC)
    (I) A form of identity-based access control where the system
    entities that are identified and controlled are functional
    positions in an organization or process.
 $ root
    (I) A CA that is directly trusted by an end entity. Acquiring the
    value of a root CA's public key involves an out-of-band procedure.
    (I) Hierarchical PKI usage: The CA that is the highest level (most
    trusted) CA in a certification hierarchy; i.e., the authority upon
    whose public key all certificate users base their trust. (See: top
    CA.)

Shirey Informational [Page 145] RFC 2828 Internet Security Glossary May 2000

    (C) In a hierarchical PKI, a root issues public-key certificates
    to one or more additional CAs that form the second highest level.
    Each of these CAs may issue certificates to more CAs at the third
    highest level, and so on. To initialize operation of a
    hierarchical PKI, the root's initial public key is securely
    distributed to all certificate users in a way that does not depend
    on the PKI's certification relationships. The root's public key
    may be distributed simply as a numerical value, but typically is
    distributed in a self-signed certificate in which the root is the
    subject. The root's certificate is signed by the root itself
    because there is no higher authority in a certification hierarchy.
    The root's certificate is then the first certificate in every
    certification path.
    (O) MISSI usage: A name previously used for a MISSI policy
    creation authority, which is not a root as defined above for
    general usage, but is a CA at the second level of the MISSI
    hierarchy, immediately subordinate to a MISSI policy approving
    authority.
    (O) UNIX usage: A user account (also called "superuser") that has
    all privileges (including all security-related privileges) and
    thus can manage the system and its other user accounts.
 $ root certificate
    (I) A certificate for which the subject is a root.
    (I) Hierarchical PKI usage: The self-signed public-key certificate
    at the top of a certification hierarchy.
 $ root key
    (I) A public key for which the matching private key is held by a
    root.
 $ root registry
    (O) MISSI usage: A name previously used for a MISSI policy
    approving authority.
 $ router
    (I) A computer that is a gateway between two networks at OSI layer
    3 and that relays and directs data packets through that
    internetwork. The most common form of router operates on IP
    packets. (See: bridge.)
    (I) Internet usage: In the context of the Internet protocol suite,
    a networked computer that forwards Internet Protocol packets that
    are not addressed to the computer itself. (See: host.)

Shirey Informational [Page 146] RFC 2828 Internet Security Glossary May 2000

 $ RSA
    See: Rivest-Shamir-Adleman.
 $ rule-based security policy
    (I) "A security policy based on global rules imposed for all
    users. These rules usually rely on comparison of the sensitivity
    of the resource being accessed and the possession of corresponding
    attributes of users, a group of users, or entities acting on
    behalf of users." [I7498 Part 2] (See: identity-based security
    policy.)
 $ safety
    (I) The property of a system being free from risk of causing harm
    to system entities and outside entities.
 $ SAID
    See: security association identifier.
 $ salt
    (I) A random value that is concatenated with a password before
    applying the one-way encryption function used to protect passwords
    that are stored in the database of an access control system. (See:
    initialization value.)
    (C) Salt protects a password-based access control system against a
    dictionary attack.
 $ sanitize
    (I) Delete sensitive data from a file, a device, or a system; or
    modify data so as to be able to downgrade its classification
    level.
 $ SASL
    See: Simple Authentication and Security Layer.
 $ SCA
    See: subordinate certification authority.
 $ scavenging
    See: (secondary definition under) threat consequence.
 $ screening router
    (I) A synonym for "filtering router".
 $ SDE
    See: Secure Data Exchange.

Shirey Informational [Page 147] RFC 2828 Internet Security Glossary May 2000

 $ SDNS
    See: Secure Data Network System.
 $ seal
    (O) To use cryptography to provide data integrity service for a
    data object. (See: sign, wrap.)
    (D) ISDs SHOULD NOT use this definition; instead, use language
    that is more specific with regard to the mechanism(s) used, such
    as "sign" when the mechanism is digital signature.
 $ secret
    (I) (1.) Adjective: The condition of information being protected
    from being known by any system entities except those who are
    intended to know it. (2.) Noun: An item of information that is
    protected thusly.
    (C) This term applies to symmetric keys, private keys, and
    passwords.
 $ secret-key cryptography
    (I) A synonym for "symmetric cryptography".
 $ Secure Data Exchange (SDE)
    (N) A local area network security protocol defined by the IEEE
    802.10 standard.
 $ Secure Data Network System (SDNS)
    (N) An NSA program that developed security protocols for
    electronic mail (Message Security Protocol), OSI layer 3 (SP3),
    OSI layer 4 (SP4), and key management (KMP).
 $ Secure Hash Standard (SHS)
    (N) The U.S. Government standard [FP180] that specifies the Secure
    Hash Algorithm (SHA-1), a cryptographic hash function that
    produces a 160-bit output (hash result) for input data of any
    length < 2**64 bits.
 $ Secure Hypertext Transfer Protocol (Secure-HTTP, S-HTTP)
    (I) A Internet protocol for providing client-server security
    services for HTTP communications. (See: https.)
    (C) S-HTTP was originally specified by CommerceNet, a coalition of
    businesses interested in developing the Internet for commercial
    uses. Several message formats may be incorporated into S-HTTP
    clients and servers, particularly CMS and MOSS. S-HTTP supports
    choice of security policies, key management mechanisms, and
    cryptographic algorithms through option negotiation between

Shirey Informational [Page 148] RFC 2828 Internet Security Glossary May 2000

    parties for each transaction. S-HTTP supports both asymmetric and
    symmetric key operation modes. S-HTTP attempts to avoid presuming
    a particular trust model, but it attempts to facilitate multiply-
    rooted hierarchical trust and anticipates that principals may have
    many public key certificates.
 $ Secure/MIME (S/MIME)
    (I) Secure/Multipurpose Internet Mail Extensions, an Internet
    protocol [R2633] to provide encryption and digital signatures for
    Internet mail messages.
 $ Secure Sockets Layer (SSL)
    (N) An Internet protocol (originally developed by Netscape
    Communications, Inc.) that uses connection-oriented end-to-end
    encryption to provide data confidentiality service and data
    integrity service for traffic between a client (often a web
    browser) and a server, and that can optionally provide peer entity
    authentication between the client and the server. (See: Transport
    Layer Security.)
    (C) SSL is layered below HTTP and above a reliable transport
    protocol (TCP). SSL is independent of the application it
    encapsulates, and any higher level protocol can layer on top of
    SSL transparently. However, many Internet applications might be
    better served by IPsec.
    (C) SSL has two layers: (a) SSL's lower layer, the SSL Record
    Protocol, is layered on top of the transport protocol and
    encapsulates higher level protocols. One such encapsulated
    protocol is SSL Handshake Protocol. (b) SSL's upper layer provides
    asymmetric cryptography for server authentication (verifying the
    server's identity to the client) and optional client
    authentication (verifying the client's identity to the server),
    and also enables them to negotiate a symmetric encryption
    algorithm and secret session key (to use for data confidentiality)
    before the application protocol transmits or receives data. A
    keyed hash provides data integrity service for encapsulated data.
 $ secure state
    (I) A system condition in which no subject can access any object
    in an unauthorized manner. (See: (secondary definition under)
    Bell-LaPadula Model, clean system.)
 $ security
    (I) (1.) Measures taken to protect a system. (2.) The condition of
    a system that results from the establishment and maintenance of

Shirey Informational [Page 149] RFC 2828 Internet Security Glossary May 2000

    measures to protect the system. (3.) The condition of system
    resources being free from unauthorized access and from
    unauthorized or accidental change, destruction, or loss.
 $ security architecture
    (I) A plan and set of principles that describe (a) the security
    services that a system is required to provide to meet the needs of
    its users, (b) the system elements required to implement the
    services, and (c) the performance levels required in the elements
    to deal with the threat environment. (See: (discussion under)
    security policy.)
    (C) A security architecture is the result of applying the system
    engineering process. A complete system security architecture
    includes administrative security, communication security, computer
    security, emanations security, personnel security, and physical
    security (e.g., see: [R2179]). A complete security architecture
    needs to deal with both intentional, intelligent threats and
    accidental kinds of threats.
 $ security association
    (I) A relationship established between two or more entities to
    enable them to protect data they exchange. The relationship is
    used to negotiate characteristics of protection mechanisms, but
    does not include the mechanisms themselves. (See: association.)
    (C) A security association describes how entities will use
    security services. The relationship is represented by a set of
    information that is shared between the entities and is agreed upon
    and considered a contract between them.
    (O) IPsec usage: A simplex (uni-directional) logical connection
    created for security purposes and implemented with either AH or
    ESP (but not both). The security services offered by a security
    association depend on the protocol selected, the IPsec mode
    (transport or tunnel), the endpoints, and the election of optional
    services within the protocol. A security association is identified
    by a triple consisting of (a) a destination IP address, (b) a
    protocol (AH or ESP) identifier, and (c) a Security Parameter
    Index.
 $ security association identifier (SAID)
    (I) A data field in a security protocol (such as NLSP or SDE),
    used to identify the security association to which a protocol data
    unit is bound. The SAID value is usually used to select a key for
    decryption or authentication at the destination. (See: Security
    Parameter Index.)

Shirey Informational [Page 150] RFC 2828 Internet Security Glossary May 2000

 $ security audit
    (I) An independent review and examination of a system's records
    and activities to determine the adequacy of system controls,
    ensure compliance with established security policy and procedures,
    detect breaches in security services, and recommend any changes
    that are indicated for countermeasures. [I7498 Part 2, NCS01]
    (C) The basic audit objective is to establish accountability for
    system entities that initiate or participate in security-relevant
    events and actions. Thus, means are needed to generate and record
    a security audit trail and to review and analyze the audit trail
    to discover and investigate attacks and security compromises.
 $ security audit trail
    (I) A chronological record of system activities that is sufficient
    to enable the reconstruction and examination of the sequence of
    environments and activities surrounding or leading to an
    operation, procedure, or event in a security-relevant transaction
    from inception to final results. [NCS04] (See: security audit.)
 $ security class
    (D) A synonym for "security level". For consistency, ISDs SHOULD
    use "security level" instead of "security class".
 $ security clearance
    (I) A determination that a person is eligible, under the standards
    of a specific security policy, for authorization to access
    sensitive information or other system resources. (See: clearance
    level.)
 $ security compromise
    (I) A security violation in which a system resource is exposed, or
    is potentially exposed, to unauthorized access. (See: data
    compromise, violation.)
 $ security domain
    See: domain.
 $ security environment
    (I) The set of external entities, procedures, and conditions that
    affect secure development, operation, and maintenance of a system.
 $ security event
    (I) A occurrence in a system that is relevant to the security of
    the system. (See: security incident.)

Shirey Informational [Page 151] RFC 2828 Internet Security Glossary May 2000

    (C) The term includes both events that are security incidents and
    those that are not. In a CA workstation, for example, a list of
    security events might include the following:
  1. Performing a cryptographic operation, e.g., signing a digital

certificate or CRL.

  1. Performing a cryptographic card operation: creation, insertion,

removal, or backup.

  1. Performing a digital certificate lifecycle operation: rekey,

renewal, revocation, or update.

  1. Posting information to an X.500 Directory.
  2. Receiving a key compromise notification.
  3. Receiving an improper certification request.
  4. Detecting an alarm condition reported by a cryptographic

module.

  1. Logging the operator in or out.
  2. Failing a built-in hardware self-test or a software system

integrity check.

 $ security fault analysis
    (I) A security analysis, usually performed on hardware at a logic
    gate level, gate-by-gate, to determine the security properties of
    a device when a hardware fault is encountered.
 $ security gateway
    (I) A gateway that separates trusted (or relatively more trusted)
    hosts on the internal network side from untrusted (or less
    trusted) hosts on the external network side. (See: firewall and
    guard.)
    (O) IPsec usage: "An intermediate system that implements IPsec
    protocols." [R2401] Normally, AH or ESP is implemented to serve a
    set of internal hosts, providing security services for the hosts
    when they communicate with other, external hosts or gateways that
    also implement IPsec.
 $ security incident
    (I) A security event that involves a security violation. (See:
    CERT, GRIP, security event, security intrusion, security
    violation.)
    (C) In other words, a security-relevant system event in which the
    system's security policy is disobeyed or otherwise breached.
    (O) "Any adverse event which compromises some aspect of computer
    or network security." [R2350]

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    (D) ISDs SHOULD NOT use this "O" definition because (a) a security
    incident may occur without actually being harmful (i.e., adverse)
    and (b) this Glossary defines "compromise" more narrowly in
    relation to unauthorized access.
 $ security intrusion
    (I) A security event, or a combination of multiple security
    events, that constitutes a security incident in which an intruder
    gains, or attempts to gain, access to a system (or system
    resource) without having authorization to do so.
 $ security kernel
    (I) "The hardware, firmware, and software elements of a trusted
    computing base that implement the reference monitor concept. It
    must mediate all accesses, be protected from modification, and be
    verifiable as correct." [NCS04] (See: reference monitor.)
    (C) That is, a security kernel is an implementation of a reference
    monitor for a given hardware base.
 $ security label
    (I) A marking that is bound to a system resource and that names or
    designates the security-relevant attributes of that resource.
    [I7498 Part 2, R1457]
    (C) The recommended definition is usefully broad, but usually the
    term is understood more narrowly as a marking that represents the
    security level of an information object, i.e., a marking that
    indicates how sensitive an information object is. [NCS04]
    (C) System security mechanisms interpret security labels according
    to applicable security policy to determine how to control access
    to the associated information, otherwise constrain its handling,
    and affix appropriate security markings to visible (printed and
    displayed) images thereof. [FP188]
 $ security level
    (I) The combination of a hierarchical classification level and a
    set of non-hierarchical category designations that represents how
    sensitive information is. (See: (usage note under) classification
    level, dominate, lattice model.)
 $ security management infrastructure (SMI)
    (I) System elements and activities that support security policy by
    monitoring and controlling security services and mechanisms,
    distributing security information, and reporting security events.
    The associated functions are as follows [I7498-4]:

Shirey Informational [Page 153] RFC 2828 Internet Security Glossary May 2000

  1. Controlling (granting or restricting) access to system

resources: This includes verifying authorizations and

    identities, controlling access to sensitive security data, and
    modifying access priorities and procedures in the event of
    attacks.
  1. Retrieving (gathering) and archiving (storing) security

information: This includes logging security events and

    analyzing the log, monitoring and profiling usage, and
    reporting security violations.
  1. Managing and controlling the encryption process: This includes

performing the functions of key management and reporting on key

    management problems. (See: public-key infrastructure.)
 $ security mechanism
    (I) A process (or a device incorporating such a process) that can
    be used in a system to implement a security service that is
    provided by or within the system. (See: (discussion under)
    security policy.)
    (C) Some examples of security mechanisms are authentication
    exchange, checksum, digital signature, encryption, and traffic
    padding.
 $ security model
    (I) A schematic description of a set of entities and relationships
    by which a specified set of security services are provided by or
    within a system. (See: (discussion under) security policy.)
    (C) An example is the Bell-LaPadula Model.
 $ security parameters index (SPI)
    (I) IPsec usage: The type of security association identifier used
    in IPsec protocols. A 32-bit value used to distinguish among
    different security associations terminating at the same
    destination (IP address) and using the same IPsec security
    protocol (AH or ESP). Carried in AH and ESP to enable the
    receiving system to determine under which security association to
    process a received packet.
 $ security perimeter
    (I) The boundary of the domain in which a security policy or
    security architecture applies; i.e., the boundary of the space in
    which security services protect system resources.

Shirey Informational [Page 154] RFC 2828 Internet Security Glossary May 2000

 $ security policy
    (I) A set of rules and practices that specify or regulate how a
    system or organization provides security services to protect
    sensitive and critical system resources. (See: identity-based
    security policy, rule-based security policy, security
    architecture, security mechanism, security model.)
    (O) "The set of rules laid down by the security authority
    governing the use and provision of security services and
    facilities." [X509]
    (C) Ravi Sandhu notes that security policy is one of four layers
    of the security engineering process (as shown in the following
    diagram). Each layer provides a different view of security,
    ranging from what services are needed to how services are
    implemented.
       What Security Services Should Be Provided?
        ^
        | + - - - - - - - - - - - +
        | | Security Policy       |
        | + - - - - - - - - - - - +    + - - - - - - - - - - - - - - +
        | | Security Model        |    | A "top-level specification" |
        | + - - - - - - - - - - - + <- | is at a level below "model" |
        | | Security Architecture |    | but above "architecture".   |
        | + - - - - - - - - - - - +    + - - - - - - - - - - - - - - +
        | | Security Mechanism    |
        | + - - - - - - - - - - - +
        v
       How Are Security Services Implemented?
 $ Security Protocol 3 (SP3)
    (O) A protocol [SDNS3] developed by SDNS to provide connectionless
    data security at the top of OSI layer 3. (See: NLSP.)
 $ Security Protocol 4 (SP4)
    (O) A protocol [SDNS4] developed by SDNS to provide either
    connectionless or end-to-end connection-oriented data security at
    the bottom of OSI layer 4. (See: TLSP.)
 $ security-relevant event
    See: security event.
 $ security service
    (I) A processing or communication service that is provided by a
    system to give a specific kind of protection to system resources.
    (See: access control service, audit service, availability service,

Shirey Informational [Page 155] RFC 2828 Internet Security Glossary May 2000

    data confidentiality service, data integrity service, data origin
    authentication service, non-repudiation service, peer entity
    authentication service, system integrity service.)
    (O) "A service, provided by a layer of communicating open systems,
    which ensures adequate security of the systems or the data
    transfers." [I7498 Part 2]
    (C) Security services implement security policies, and are
    implemented by security mechanisms.
 $ security situation
    (I) ISAKMP usage: The set of all security-relevant information--
    e.g., network addresses, security classifications, manner of
    operation (normal or emergency)--that is needed to decide the
    security services that are required to protect the association
    that is being negotiated.
 $ security token
    See: token.
 $ security violation
    (I) An act or event that disobeys or otherwise breaches security
    policy. (See: compromise, penetration, security incident.)
 $ self-signed certificate
    (I) A public-key certificate for which the public key bound by the
    certificate and the private key used to sign the certificate are
    components of the same key pair, which belongs to the signer.
    (See: root certificate.)
    (C) In a self-signed X.509 public-key certificate, the issuer's DN
    is the same as the subject's DN.
 $ semantic security
    (I) An attribute of a encryption algorithm that is a formalization
    of the notion that the algorithm not only hides the plaintext but
    also reveals no partial information about the plaintext. Whatever
    is efficiently computable about the plaintext when given the
    ciphertext, is also efficiently computable without the ciphertext.
    (See: indistinguishability.)
 $ sensitive (information)
    (I) Information is sensitive if disclosure, alteration,
    destruction, or loss of the information would adversely affect the
    interests or business of its owner or user. (See: critical.)

Shirey Informational [Page 156] RFC 2828 Internet Security Glossary May 2000

 $ separation of duties
    (I) The practice of dividing the steps in a system function among
    different individuals, so as to keep a single individual from
    subverting the process. (See: dual control, administrative
    security.)
 $ serial number
    See: certificate serial number.
 $ server
    (I) A system entity that provides a service in response to
    requests from other system entities called clients.
 $ session key
    (I) In the context of symmetric encryption, a key that is
    temporary or is used for a relatively short period of time. (See:
    ephemeral key, key distribution center, master key.)
    (C) Usually, a session key is used for a defined period of
    communication between two computers, such as for the duration of a
    single connection or transaction set, or the key is used in an
    application that protects relatively large amounts of data and,
    therefore, needs to be rekeyed frequently.
 $ SET
    See: SET Secure Electronic Transaction(trademark).
 $ SET private extension
    (O) One of the private extensions defined by SET for X.509
    certificates. Carries information about hashed root key,
    certificate type, merchant data, cardholder certificate
    requirements, encryption support for tunneling, or message support
    for payment instructions.
 $ SET qualifier
    (O) A certificate policy qualifier that provides information about
    the location and content of a SET certificate policy.
    (C) In addition to the policies and qualifiers inherited from its
    own certificate, each CA in the SET certification hierarchy may
    add one qualifying statement to the root policy when the CA issues
    a certificate. The additional qualifier is a certificate policy
    for that CA. Each policy in a SET certificate may have these
    qualifiers:
  1. A URL where a copy of the policy statement may be found.
  2. An electronic mail address where a copy of the policy statement

may be found.

Shirey Informational [Page 157] RFC 2828 Internet Security Glossary May 2000

  1. A hash result of the policy statement, computed using the

indicated algorithm.

  1. A statement declaring any disclaimers associated with the

issuing of the certificate.

 $ SET Secure Electronic Transaction(trademark) or SET(trademark)
    (N) A protocol developed jointly by MasterCard International and
    Visa International and published as an open standard to provide
    confidentiality of transaction information, payment integrity, and
    authentication of transaction participants for payment card
    transactions over unsecured networks, such as the Internet. [SET1]
    (See: acquirer, brand, cardholder, dual signature, electronic
    commerce, issuer, merchant, payment gateway, third party.)
    (C) This term and acronym are trademarks of SETCo. MasterCard and
    Visa announced the SET standard on 1 February 1996. On 19 December
    1997, MasterCard and Visa formed SET Secure Electronic Transaction
    LLC (commonly referred to as "SETCo") to implement the SET 1.0
    specification. A memorandum of understanding adds American Express
    and JCB Credit Card Company as co-owners of SETCo.
 $ SETCo
    See: (secondary definition under) SET Secure Electronic
    Transaction.
 $ SHA-1
    See: Secure Hash Standard.
 $ shared secret
    (I) A synonym for "keying material" or "cryptographic key".
 $ S-HTTP
    See: Secure HTTP.
 $ sign
    (I) Create a digital signature for a data object.
 $ signature
    See: digital signature, electronic signature.
 $ signature certificate
    (I) A public-key certificate that contains a public key that is
    intended to be used for verifying digital signatures, rather than
    for encrypting data or performing other cryptographic functions.
    (C) A v3 X.509 public-key certificate may have a "keyUsage"
    extension which indicates the purpose for which the certified
    public key is intended.

Shirey Informational [Page 158] RFC 2828 Internet Security Glossary May 2000

 $ signer
    (N) A human being or an organization entity that uses its private
    key to create a digital signature for a data object. [ABA]
 $ SILS
    See: Standards for Interoperable LAN/MAN Security.
 $ simple authentication
    (I) An authentication process that uses a password as the
    information needed to verify an identity claimed for an entity.
    (See: strong authentication.)
    (O) "Authentication by means of simple password arrangements."
    [X509]
 $ Simple Authentication and Security Layer (SASL)
    (I) An Internet specification [R2222] for adding authentication
    service to connection-based protocols. To use SASL, a protocol
    includes a command for authenticating a user to a server and for
    optionally negotiating protection of subsequent protocol
    interactions. The command names a registered security mechanism.
    SASL mechanisms include Kerberos, GSSAPI, S/KEY, and others. Some
    protocols that use SASL are IMAP4 and POP3.
 $ Simple Key-management for Internet Protocols (SKIP)
    (I) A key distribution protocol that uses hybrid encryption to
    convey session keys that are used to encrypt data in IP packets.
    [R2356] (See: IKE, IPsec.)
    (C) SKIP uses the Diffie-Hellman algorithm (or could use another
    key agreement algorithm) to generate a key-encrypting key for use
    between two entities. A session key is used with a symmetric
    algorithm to encrypt data in one or more IP packets that are to be
    sent from one of the entities to the other. The KEK is used with a
    symmetric algorithm to encrypt the session key, and the encrypted
    session key is placed in a SKIP header that is added to each IP
    packet that is encrypted with that session key.
 $ Simple Mail Transfer Protocol (SMTP)
    (I) A TCP-based, application-layer, Internet Standard protocol
    [R0821] for moving electronic mail messages from one computer to
    another.
 $ Simple Network Management Protocol (SNMP)
    (I) A UDP-based, application-layer, Internet Standard protocol
    [R2570, R2574] for conveying management information between
    managers and agents.

Shirey Informational [Page 159] RFC 2828 Internet Security Glossary May 2000

    (C) SNMP version 1 uses cleartext passwords for authentication and
    access control. (See: community string.) Version 2 adds
    cryptographic mechanisms based on DES and MD5. Version 3 provides
    enhanced, integrated support for security services, including data
    confidentiality, data integrity, data origin authentication, and
    message timeliness and limited replay protection.
 $ simple security property
    See: (secondary definition under) Bell-LaPadula Model.
 $ single sign-on
    (I) A system that enables a user to access multiple computer
    platforms (usually a set of hosts on the same network) or
    application systems after being authenticated just one time. (See:
    Kerberos.)
    (C) Typically, a user logs in just once, and then is transparently
    granted access to a variety of permitted resources with no further
    login being required until after the user logs out. Such a system
    has the advantages of being user friendly and enabling
    authentication to be managed consistently across an entire
    enterprise, and has the disadvantage of requiring all hosts and
    applications to trust the same authentication mechanism.
 $ situation
    See: security situation.
 $ S/Key
    (I) A security mechanism that uses a cryptographic hash function
    to generate a sequence of 64-bit, one-time passwords for remote
    user login. [R1760]
    (C) The client generates a one-time password by applying the MD4
    cryptographic hash function multiple times to the user's secret
    key. For each successive authentication of the user, the number of
    hash applications is reduced by one. (Thus, an intruder using
    wiretapping cannot compute a valid password from knowledge of one
    previously used.) The server verifies a password by hashing the
    currently presented password (or initialization value) one time
    and comparing the hash result with the previously presented
    password.
 $ SKIP
    See: Simple Key-management for IP.

Shirey Informational [Page 160] RFC 2828 Internet Security Glossary May 2000

 $ SKIPJACK
    (N) A Type II block cipher [NIST] with a block size of 64 bits and
    a key size of 80 bits, that was developed by NSA and formerly
    classified at the U.S. Department of Defense "Secret" level. (See:
    CAPSTONE, CLIPPER, FORTEZZA, Key Exchange Algorithm.)
    (C) On 23 June 1998, NSA announced that SKIPJACK had been
    declassified.
 $ slot
    (O) MISSI usage: One of the FORTEZZA PC card storage areas that
    are each able to hold an X.509 certificate and additional data
    that is associated with the certificate, such as the matching
    private key.
 $ smart card
    (I) A credit-card sized device containing one or more integrated
    circuit chips, which perform the functions of a computer's central
    processor, memory, and input/output interface. (See: PC card.)
    (C) Sometimes this term is used rather strictly to mean a card
    that closely conforms to the dimensions and appearance of the kind
    of plastic credit card issued by banks and merchants. At other
    times, the term is used loosely to include cards that are larger
    than credit cards, especially cards that are thicker, such as PC
    cards.
    (C) A "smart token" is a device that conforms to the definition of
    smart card except that rather than having standard credit card
    dimensions, the token is packaged in some other form, such as a
    dog tag or door key shape.
 $ smart token
    See: (secondary definition under) smart card.
 $ SMI
    See: security management infrastructure.
 $ S/MIME
    See: Secure/MIME.
 $ SMTP
    See: Simple Mail Transfer Protocol.
 $ smurf
    (I) Software that mounts a denial-of-service attack ("smurfing")
    by exploiting IP broadcast addressing and ICMP ping packets to
    cause flooding. (See: flood, ICMP flood.)

Shirey Informational [Page 161] RFC 2828 Internet Security Glossary May 2000

    (D) ISDs SHOULD NOT use this term because it is not listed in most
    dictionaries and could confuse international readers.
    (C) A smurf program builds a network packet that appears to
    originate from another address, that of the "victim", either a
    host or an IP router. The packet contains an ICMP ping message
    that is addressed to an IP broadcast address, i.e., to all IP
    addresses in a given network. The echo responses to the ping
    message return to the victim's address. The goal of smurfing may
    be either to deny service at a particular host or to flood all or
    part of an IP network.
 $ sniffing
    (C) A synonym for "passive wiretapping". (See: password sniffing.)
    (D) ISDs SHOULD NOT use this term because it unnecessarily
    duplicates the meaning of a term that is better established. (See:
    (usage note under) Green Book.
 $ SNMP
    See: Simple Network Management Protocol.
 $ social engineering
    (I) A euphemism for non-technical or low-technology means--such as
    lies, impersonation, tricks, bribes, blackmail, and threats--used
    to attack information systems. (See: masquerade attack.)
    (D) ISDs SHOULD NOT use this term because it is vague; instead,
    use a term that is specific with regard to the means of attack.
 $ SOCKS
    (I) An Internet protocol [R1928] that provides a generalized proxy
    server that enables client-server applications--such as TELNET,
    FTP, and HTTP; running over either TCP or UDP--to use the services
    of a firewall.
    (C) SOCKS is layered under the application layer and above the
    transport layer. When a client inside a firewall wishes to
    establish a connection to an object that is reachable only through
    the firewall, it uses TCP to connect to the SOCKS server,
    negotiates with the server for the authentication method to be
    used, authenticates with the chosen method, and then sends a relay
    request. The SOCKS server evaluates the request, typically based
    on source and destination addresses, and either establishes the
    appropriate connection or denies it.

Shirey Informational [Page 162] RFC 2828 Internet Security Glossary May 2000

 $ soft TEMPEST
    (O) The use of software techniques to reduce the radio frequency
    information leakage from computer displays and keyboards. [Kuhn]
    (See: TEMPEST.)
 $ software
    (I) Computer programs (which are stored in and executed by
    computer hardware) and associated data (which also is stored in
    the hardware) that may be dynamically written or modified during
    execution. (See: firmware, hardware.)
 $ SORA
    See: SSO-PIN ORA.
 $ source authentication
    (D) ISDs SHOULD NOT use this term because it is ambiguous. If the
    intent is to authenticate the original creator or packager of data
    received, then say "data origin authentication". If the intent is
    to authenticate the identity of the sender of data, then say "peer
    entity authentication". (See: data origin authentication, peer
    entity authentication).
 $ source integrity
    (I) The degree of confidence that can be placed in information
    based on the trustworthiness of its sources. (See: integrity.)
 $ SP3
    See: Security Protocol 3.
 $ SP4
    See: Security Protocol 4.
 $ spam
    (I) (1.) Verb: To indiscriminately send unsolicited, unwanted,
    irrelevant, or inappropriate messages, especially commercial
    advertising in mass quantities. (2.) Noun: electronic "junk mail".
    [R2635]
    (D) This term SHOULD NOT be written in upper-case letters, because
    SPAM(trademark) is a trademark of Hormel Foods Corporation. Hormel
    says, "We do not object to use of this slang term [spam] to
    describe [unsolicited commercial email (UCE)], although we do
    object to the use of our product image in association with that
    term. Also, if the term is to be used, it should be used in all
    lower-case letters to distinguish it from our trademark SPAM,
    which should be used with all uppercase letters."

Shirey Informational [Page 163] RFC 2828 Internet Security Glossary May 2000

    (C) In sufficient volume, spam can cause denial of service. (See:
    flooding.) According to the SPAM Web site, the term was adopted as
    a result of the Monty Python skit in which a group of Vikings sang
    a chorus of 'SPAM, SPAM, SPAM . . .' in an increasing crescendo,
    drowning out other conversation. Hence, the analogy applied
    because UCE was drowning out normal discourse on the Internet.
 $ SPC
    See: software publisher certificate.
 $ SPI
    See: Security Parameters Index.
 $ split key
    (I) A cryptographic key that is divided into two or more separate
    data items that individually convey no knowledge of the whole key
    that results from combining the items. (See: dual control, split
    knowledge.)
 $ split knowledge
    (I) A security technique in which two or more entities separately
    hold data items that individually convey no knowledge of the
    information that results from combining the items. (See: dual
    control, split key.)
    (O) "A condition under which two or more entities separately have
    key components which individually convey no knowledge of the
    plaintext key which will be produced when the key components are
    combined in the cryptographic module." [FP140]
 $ spoofing attack
    (I) A synonym for "masquerade attack".
 $ SSH
    (I) A protocol for secure remote login and other secure network
    services over an insecure network.
    (C) Consists of three major components:
  1. Transport layer protocol: Provides server authentication,

confidentiality, and integrity. It may optionally also provide

       compression. The transport layer will typically be run over a
       TCP/IP connection, but might also be used on top of any other
       reliable data stream.
  1. User authentication protocol: Authenticates the client-side

user to the server. It runs over the transport layer protocol.

Shirey Informational [Page 164] RFC 2828 Internet Security Glossary May 2000

  1. Connection protocol: Multiplexes the encrypted tunnel into

several logical channels. It runs over the user authentication

       protocol.
 $ SSL
    See: Secure Sockets Layer, Standard Security Label.
 $ SSO
    See: system security officer.
 $ SSO PIN
    (O) MISSI usage: One of two personal identification numbers that
    control access to the functions and stored data of a FORTEZZA PC
    card. Knowledge of the SSO PIN enables the card user to perform
    the FORTEZZA functions intended for use by an end user and also
    the functions intended for use by a MISSI certification authority.
    (See: user PIN.)
 $ SSO-PIN ORA (SORA)
    (O) MISSI usage: A MISSI organizational RA that operates in a mode
    in which the ORA performs all card management functions and,
    therefore, requires knowledge of the SSO PIN for an end user's
    FORTEZZA PC card.
 $ Standards for Interoperable LAN/MAN Security (SILS)
    (N) (1.) The IEEE 802.10 standards committee. (2.) A developing
    set of IEEE standards, which has eight parts: (a) Model, including
    security management, (b) Secure Data Exchange protocol, (c) Key
    Management, (d) [has been incorporated in (a)], (e) SDE Over
    Ethernet 2.0, (f) SDE Sublayer Management, (g) SDE Security
    Labels, and (h) SDE PICS Conformance. Parts b, e, f, g, and h are
    incorporated in IEEE Standard 802.10-1998.
 $ star property
    (I) (Written "*-property".) See: "confinement property" under
    Bell-LaPadula Model.
 $ Star Trek attack
    (C) An attack that penetrates your system where no attack has ever
    gone before.
 $ steganography
    (I) Methods of hiding the existence of a message or other data.
    This is different than cryptography, which hides the meaning of a
    message but does not hide the message itself. (See: cryptology.)
    (C) An example of a steganographic method is "invisible" ink.
    (See: digital watermark.)

Shirey Informational [Page 165] RFC 2828 Internet Security Glossary May 2000

 $ storage channel
    See: (secondary definition under) covert channel.
 $ stream cipher
    (I) An encryption algorithm that breaks plaintext into a stream of
    successive bits (or characters) and encrypts the n-th plaintext
    bit with the n-th element of a parallel key stream, thus
    converting the plaintext bit stream into a ciphertext bit stream.
    [Schn] (See: block cipher.)
 $ strong authentication
    (I) An authentication process that uses cryptography--particularly
    public-key certificates--to verify the identity claimed for an
    entity. (See: X.509.)
    (O) "Authentication by means of cryptographically derived
    credentials." [X509]
 $ subject
    1. (I) In a computer system: A system entity that causes
    information to flow among objects or changes the system state;
    technically, a process-domain pair. (See: Bell-LaPadula Model.)
    2. (I) Of a certificate: The entity name that is bound to the data
    items in a digital certificate, and particularly a name that is
    bound to a key value in a public-key certificate.
 $ subnetwork
    (N) An OSI term for a system of packet relays and connecting links
    that implement the lower three protocol layers of the OSIRM to
    provide a communication service that interconnects attached end
    systems. Usually the relays operate at OSI layer 3 and are all of
    the same type (e.g., all X.25 packet switches, or all interface
    units in an IEEE 802.3 LAN). (See: gateway, internet, router.)
 $ subordinate certification authority (SCA)
    (I) A CA whose public-key certificate is issued by another
    (superior) CA. (See: certification hierarchy.)
    (O) MISSI usage: The fourth-highest (bottom) level of a MISSI
    certification hierarchy; a MISSI CA whose public-key certificate
    is signed by a MISSI CA rather than by a MISSI PCA. A MISSI SCA is
    the administrative authority for a subunit of an organization,
    established when it is desirable to organizationally distribute or
    decentralize the CA service. The term refers both to that
    authoritative office or role, and to the person who fills that

Shirey Informational [Page 166] RFC 2828 Internet Security Glossary May 2000

    office. A MISSI SCA registers end users and issues their
    certificates and may also register ORAs, but may not register
    other CAs. An SCA periodically issues a CRL.
 $ subordinate distinguished name
    (I) An X.500 DN is subordinate to another X.500 DN if it begins
    with a set of attributes that is the same as the entire second DN
    except for the terminal attribute of the second DN (which is
    usually the name of a CA). For example, the DN <C=FooLand, O=Gov,
    OU=Treasurer, CN=DukePinchpenny> is subordinate to the DN
    <C=FooLand, O=Gov, CN=KingFooCA>.
 $ superencryption
    (I) An encryption operation for which the plaintext input to be
    transformed is the ciphertext output of a previous encryption
    operation.
 $ survivability
    (I) The ability of a system to remain in operation or existence
    despite adverse conditions, including both natural occurrences,
    accidental actions, and attacks on the system. (See: availability,
    reliability.)
 $ symmetric cryptography
    (I) A branch of cryptography involving algorithms that use the
    same key for two different steps of the algorithm (such as
    encryption and decryption, or signature creation and signature
    verification). (See: asymmetric cryptography.)
    (C) Symmetric cryptography has been used for thousands of years
    [Kahn]. A modern example of a symmetric encryption algorithm is
    the U.S. Government's Data Encryption Algorithm. (See: DEA, DES.)
    (C) Symmetric cryptography is sometimes called "secret-key
    cryptography" (versus public-key cryptography) because the
    entities that share the key, such as the originator and the
    recipient of a message, need to keep the key secret. For example,
    when Alice wants to ensure confidentiality for data she sends to
    Bob, she encrypts the data with a secret key, and Bob uses the
    same key to decrypt. Keeping the shared key secret entails both
    cost and risk when the key is distributed to both Alice and Bob.
    Thus, symmetric cryptography has a key management disadvantage
    compared to asymmetric cryptography.
 $ symmetric key
    (I) A cryptographic key that is used in a symmetric cryptographic
    algorithm.

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 $ SYN flood
    (I) A denial of service attack that sends a host more TCP SYN
    packets (request to synchronize sequence numbers, used when
    opening a connection) than the protocol implementation can handle.
    (See: flooding.)
 $ system
    (C) In this Glossary, the term is mainly used as an abbreviation
    for "automated information system".
 $ system entity
    (I) An active element of a system--e.g., an automated process, a
    subsystem, a person or group of persons--that incorporates a
    specific set of capabilities.
 $ system high
    (I) The highest security level supported by a system at a
    particular time or in a particular environment. (See: system high
    security mode.)
 $ system high security mode
    (I) A mode of operation of an information system, wherein all
    users having access to the system possess a security clearance or
    authorization, but not necessarily a need-to-know, for all data
    handled by the system. (See: mode of operation.)
    (C) This mode is defined formally in U.S. Department of Defense
    policy regarding system accreditation [DOD2], but the term is
    widely used outside the Defense Department and outside the
    Government.
 $ system integrity
    (I) "The quality that a system has when it can perform its
    intended function in a unimpaired manner, free from deliberate or
    inadvertent unauthorized manipulation." [NCS04] (See: system
    integrity service.)
 $ system integrity service
    (I) A security service that protects system resources in a
    verifiable manner against unauthorized or accidental change, loss,
    or destruction. (See: system integrity.)
 $ system low
    (I) The lowest security level supported by a system at a
    particular time or in a particular environment. (See: system
    high.)

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 $ system resource
    (I) Data contained in an information system; or a service provided
    by a system; or a system capability, such as processing power or
    communication bandwidth; or an item of system equipment (i.e., a
    system component--hardware, firmware, software, or documentation);
    or a facility that houses system operations and equipment.
 $ system security officer (SSO)
    (I) A person responsible for enforcement or administration of the
    security policy that applies to the system.
 $ system verification
    See: (secondary definition under) verification.
 $ TACACS
 $ TACACS+
    See: Terminal Access Controller (TAC) Access Control System.
 $ tamper
    (I) Make an unauthorized modification in a system that alters the
    system's functioning in a way that degrades the security services
    that the system was intended to provide.
 $ TCB
    See: trusted computing base.
 $ TCP
    See: Transmission Control Protocol.
 $ TCP/IP
    (I) A synonym for "Internet Protocol Suite", in which the
    Transmission Control Protocol (TCP) and the Internet Protocol (IP)
    are important parts.
 $ TCSEC
    See: Trusted Computer System Evaluation Criteria.
 $ TELNET
    (I) A TCP-based, application-layer, Internet Standard protocol
    [R0854] for remote login from one host to another.
 $ TEMPEST
    (O) A nickname for specifications and standards for limiting the
    strength of electromagnetic emanations from electrical and
    electronic equipment and thus reducing vulnerability to
    eavesdropping. This term originated in the U.S. Department of
    Defense. [Army, Kuhn, Russ] (See: emanation security, soft
    tempest.)

Shirey Informational [Page 169] RFC 2828 Internet Security Glossary May 2000

    (D) ISDs SHOULD NOT use this term as a synonym for
    "electromagnetic emanations security".
 $ Terminal Access Controller (TAC) Access Control System (TACACS)
    (I) A UDP-based authentication and access control protocol [R1492]
    in which a network access server receives an identifier and
    password from a remote terminal and passes them to a separate
    authentication server for verification.
    (C) TACACS was developed for ARPANET and has evolved for use in
    commercial equipment. TACs were a type of network access server
    computer used to connect terminals to the early Internet, usually
    using dial-up modem connections. TACACS used centralized
    authentication servers and served not only network access servers
    like TACs but also routers and other networked computing devices.
    TACs are no longer in use, but TACACS+ is. [R1983]
  1. "XTACACS": The name of Cisco Corporation's implementation,

which enhances and extends the original TACACS.

  1. "TACACS+": A TCP-based protocol that improves on TACACS and

XTACACS by separating the functions of authentication,

       authorization, and accounting and by encrypting all traffic
       between the network access server and authentication server. It
       is extensible to allow any authentication mechanism to be used
       with TACACS+ clients.
 $ TESS
    See: The Exponential Encryption System.
 $ The Exponential Encryption System (TESS)
    (I) A system of separate but cooperating cryptographic mechanisms
    and functions for the secure authenticated exchange of
    cryptographic keys, the generation of digital signatures, and the
    distribution of public keys. TESS employs asymmetric cryptography,
    based on discrete exponentiation, and a structure of self-
    certified public keys. [R1824]
 $ threat
    (I) A potential for violation of security, which exists when there
    is a circumstance, capability, action, or event that could breach
    security and cause harm. (See: attack, threat action, threat
    consequence.)
    (C) That is, a threat is a possible danger that might exploit a
    vulnerability. A threat can be either "intentional" (i.e.,
    intelligent; e.g., an individual cracker or a criminal

Shirey Informational [Page 170] RFC 2828 Internet Security Glossary May 2000

    organization) or "accidental" (e.g., the possibility of a computer
    malfunctioning, or the possibility of an "act of God" such as an
    earthquake, a fire, or a tornado).
    (C) In some contexts, such as the following, the term is used
    narrowly to refer only to intelligent threats:
    (N) U. S. Government usage: The technical and operational
    capability of a hostile entity to detect, exploit, or subvert
    friendly information systems and the demonstrated, presumed, or
    inferred intent of that entity to conduct such activity.
 $ threat action
    (I) An assault on system security. (See: attack, threat, threat
    consequence.)
    (C) A complete security architecture deals with both intentional
    acts (i.e. attacks) and accidental events [FIPS31]. Various kinds
    of threat actions are defined as subentries under "threat
    consequence".
 $ threat analysis
    (I) An analysis of the probability of occurrences and consequences
    of damaging actions to a system.
 $ threat consequence
    (I) A security violation that results from a threat action.
    Includes disclosure, deception, disruption, and usurpation. (See:
    attack, threat, threat action.)
    (C) The following subentries describe four kinds of threat
    consequences, and also list and describe the kinds of threat
    actions that cause each consequence. Threat actions that are
    accidental events are marked by "*".
    1. "(Unauthorized) Disclosure" (a threat consequence): A
       circumstance or event whereby an entity gains access to data
       for which the entity is not authorized. (See: data
       confidentiality.) The following threat actions can cause
       unauthorized disclosure:
       A. "Exposure": A threat action whereby sensitive data is
          directly released to an unauthorized entity. This includes:
          a. "Deliberate Exposure": Intentional release of sensitive
             data to an unauthorized entity.

Shirey Informational [Page 171] RFC 2828 Internet Security Glossary May 2000

          b. "Scavenging": Searching through data residue in a system
             to gain unauthorized knowledge of sensitive data.
          c* "Human error": Human action or inaction that
             unintentionally results in an entity gaining unauthorized
             knowledge of sensitive data.
          d* "Hardware/software error". System failure that results in
             an entity gaining unauthorized knowledge of sensitive
             data.
       B. "Interception": A threat action whereby an unauthorized
          entity directly accesses sensitive data traveling between
          authorized sources and destinations. This includes:
          a. "Theft": Gaining access to sensitive data by stealing a
             shipment of a physical medium, such as a magnetic tape or
             disk, that holds the data.
          b. "Wiretapping (passive)": Monitoring and recording data
             that is flowing between two points in a communication
             system. (See: wiretapping.)
          c. "Emanations analysis": Gaining direct knowledge of
             communicated data by monitoring and resolving a signal
             that is emitted by a system and that contains the data
             but is not intended to communicate the data. (See:
             emanation.)
       C. "Inference": A threat action whereby an unauthorized entity
          indirectly accesses sensitive data (but not necessarily the
          data contained in the communication) by reasoning from
          characteristics or byproducts of communications. This
          includes:
          a. Traffic analysis: Gaining knowledge of data by observing
             the characteristics of communications that carry the
             data. (See: (main Glossary entry for) traffic analysis.)
          b. "Signals analysis": Gaining indirect knowledge of
             communicated data by monitoring and analyzing a signal
             that is emitted by a system and that contains the data
             but is not intended to communicate the data. (See:
             emanation.)
       D. "Intrusion": A threat action whereby an unauthorized entity
          gains access to sensitive data by circumventing a system's
          security protections. This includes:

Shirey Informational [Page 172] RFC 2828 Internet Security Glossary May 2000

          a. "Trespass": Gaining unauthorized physical access to
             sensitive data by circumventing a system's protections.
          b. "Penetration": Gaining unauthorized logical access to
             sensitive data by circumventing a system's protections.
          c. "Reverse engineering": Acquiring sensitive data by
             disassembling and analyzing the design of a system
             component.
          d. Cryptanalysis: Transforming encrypted data into plaintext
             without having prior knowledge of encryption parameters
             or processes. (See: (main Glossary entry for)
             cryptanalysis.)
    2. "Deception" (a threat consequence): A circumstance or event
       that may result in an authorized entity receiving false data
       and believing it to be true. The following threat actions can
       cause deception:
       A. "Masquerade": A threat action whereby an unauthorized entity
          gains access to a system or performs a malicious act by
          posing as an authorized entity. (See: (main Glossary entry
          for) masquerade attack.)
          a. "Spoof": Attempt by an unauthorized entity to gain access
             to a system by posing as an authorized user.
          b. "Malicious logic": In context of masquerade, any
             hardware, firmware, or software (e.g., Trojan horse) that
             appears to perform a useful or desirable function, but
             actually gains unauthorized access to system resources or
             tricks a user into executing other malicious logic. (See:
             (main Glossary entry for) malicious logic.)
       B. "Falsification": A threat action whereby false data deceives
          an authorized entity. (See: active wiretapping.)
          a. "Substitution": Altering or replacing valid data with
             false data that serves to deceive an authorized entity.
          b. "Insertion": Introducing false data that serves to
             deceive an authorized entity.
       C. "Repudiation": A threat action whereby an entity deceives
          another by falsely denying responsibility for an act. (See:
          non-repudiation service, (main Glossary entry for)
          repudiation.)

Shirey Informational [Page 173] RFC 2828 Internet Security Glossary May 2000

          a. "False denial of origin": Action whereby the originator
             of data denies responsibility for its generation.
          b. "False denial of receipt": Action whereby the recipient
             of data denies receiving and possessing the data.
    3. "Disruption" (a threat consequence): A circumstance or event
       that interrupts or prevents the correct operation of system
       services and functions. (See: denial of service.) The following
       threat actions can cause disruption:
       A. "Incapacitation": A threat action that prevents or
          interrupts system operation by disabling a system component.
          a. "Malicious logic": In context of incapacitation, any
             hardware, firmware, or software (e.g., logic bomb)
             intentionally introduced into a system to destroy system
             functions or resources. (See: (main Glossary entry for)
             malicious logic.)
          b. "Physical destruction": Deliberate destruction of a
             system component to interrupt or prevent system
             operation.
          c* "Human error": Action or inaction that unintentionally
             disables a system component.
          d* "Hardware or software error": Error that causes failure
             of a system component and leads to disruption of system
             operation.
          e* "Natural disaster": Any "act of God" (e.g., fire, flood,
             earthquake, lightning, or wind) that disables a system
             component. [FP031 section 2]
       B. "Corruption": A threat action that undesirably alters system
          operation by adversely modifying system functions or data.
          a. "Tamper": In context of corruption, deliberate alteration
             of a system's logic, data, or control information to
             interrupt or prevent correct operation of system
             functions.
          b. "Malicious logic": In context of corruption, any
             hardware, firmware, or software (e.g., a computer virus)
             intentionally introduced into a system to modify system
             functions or data. (See: (main Glossary entry for)
             malicious logic.)

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          c* "Human error": Human action or inaction that
             unintentionally results in the alteration of system
             functions or data.
          d* "Hardware or software error": Error that results in the
             alteration of system functions or data.
          e* "Natural disaster": Any "act of God" (e.g., power surge
             caused by lightning) that alters system functions or
             data. [FP031 section 2]
       C. "Obstruction": A threat action that interrupts delivery of
          system services by hindering system operations.
          a. "Interference": Disruption of system operations by
             blocking communications or user data or control
             information.
          b. "Overload": Hindrance of system operation by placing
             excess burden on the performance capabilities of a system
             component. (See: flooding.)
    4. "Usurpation" (a threat consequence): A circumstance or event
       that results in control of system services or functions by an
       unauthorized entity. The following threat actions can cause
       usurpation:
       A. "Misappropriation": A threat action whereby an entity
          assumes unauthorized logical or physical control of a system
          resource.
          a. "Theft of service": Unauthorized use of service by an
             entity.
          b. "Theft of functionality": Unauthorized acquisition of
             actual hardware, software, or firmware of a system
             component.
          c. "Theft of data": Unauthorized acquisition and use of
             data.
       B. "Misuse": A threat action that causes a system component to
          perform a function or service that is detrimental to system
          security.
          a. "Tamper": In context of misuse, deliberate alteration of
             a system's logic, data, or control information to cause
             the system to perform unauthorized functions or services.

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          b. "Malicious logic": In context of misuse, any hardware,
             software, or firmware intentionally introduced into a
             system to perform or control execution of an unauthorized
             function or service.
          c. "Violation of permissions": Action by an entity that
             exceeds the entity's system privileges by executing an
             unauthorized function.
 $ thumbprint
    (I) A pattern of curves formed by the ridges on the tip of a
    thumb. (See: biometric authentication, fingerprint.)
    (D) ISDs SHOULD NOT use this term as a synonym for "hash result"
    because that meaning mixes concepts in a potentially misleading
    way.
 $ ticket
    (I) A synonym for "capability". (See: Kerberos.)
    (C) A ticket is usually granted by a centralized access control
    server (ticket-granting agent) to authorize access to a system
    resource for a limited time. Tickets have been implemented with
    symmetric cryptography, but can also be implemented as attribute
    certificates using asymmetric cryptography.
 $ timing channel
    See: (secondary definition under) covert channel.
 $ TLS
    See: Transport Layer Security. (See: TLSP.)
 $ TLSP
    See: Transport Layer Security Protocol. (See: TLS.)
 $ token
    1. (I) General usage: An object that is used to control access and
    is passed between cooperating entities in a protocol that
    synchronizes use of a shared resource. Usually, the entity that
    currently holds the token has exclusive access to the resource.
    2. (I) Authentication usage: A data object or a portable, user-
    controlled, physical device used to verify an identity in an
    authentication process. (See: authentication information, dongle.)
    3. (I) Cryptographic usage: See: cryptographic token.

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    4. (O) SET usage: "A portable device [e.g., smart card or PCMCIA
    card] specifically designed to store cryptographic information and
    possibly perform cryptographic functions in a secure manner."
    [SET2]
 $ token backup
    (I) A token management operation that stores sufficient
    information in a database (e.g., in a CAW) to recreate or restore
    a security token (e.g., a smart card) if it is lost or damaged.
 $ token copy
    (I) A token management operation that copies all the personality
    information from one security token to another. However, unlike in
    a token restore operation, the second token is initialized with
    its own, different local security values such as PINs and storage
    keys.
 $ token management
    (I) The process of initializing security tokens (e.g., see: smart
    card), loading data into the tokens, and controlling the tokens
    during their life cycle. May include performing key management and
    certificate management functions; generating and installing PINs;
    loading user personality data; performing card backup, card copy,
    and card restore operations; and updating firmware.
 $ token restore
    (I) A token management operation that loads a security token with
    data for the purpose of recreating (duplicating) the contents
    previously held by that or another token.
 $ token storage key
    (I) A cryptography key used to protect data that is stored on a
    security token.
 $ top CA
    (I) A CA that is the highest level (i.e., is the most trusted CA)
    in a certification hierarchy. (See: root.)
 $ top-level specification
    (I) "A non-procedural description of system behavior at the most
    abstract level; typically a functional specification that omits
    all implementation details." [NCS04] (See: (discussion under)
    security policy.)
    (C) A top-level specification may be descriptive or formal:

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  1. "Descriptive top-level specification": One that is written in a

natural language like English or an informal design notation.

  1. "Formal top-level specification": One that is written in a

formal mathematical language to enable theorems to be proven that

    show that the specification correctly implements a set of formal
    requirements or a formal security model. (See: correctness proof.)
 $ traffic analysis
    (I) Inference of information from observable characteristics of
    data flow(s), even when the data is encrypted or otherwise not
    directly available. Such characteristics include the identities
    and locations of the source(s) and destination(s), and the
    presence, amount, frequency, and duration of occurrence. (See:
    wiretapping.)
    (O) "The inference of information from observation of traffic
    flows (presence, absence, amount, direction, and frequency)."
    [I7498 Part 2]
 $ traffic flow confidentiality
    (I) A data confidentiality service to protect against traffic
    analysis.
    (O) "A confidentiality service to protect against traffic
    analysis." [I7498 Part 2]
 $ traffic padding
    (I) "The generation of spurious instances of communication,
    spurious data units, and/or spurious data within data units."
    [I7498 Part 2]
 $ tranquillity property
    See: (secondary definition under) Bell-LaPadula Model.
 $ Transmission Control Protocol (TCP)
    (I) An Internet Standard protocol [R0793] that reliably delivers a
    sequence of datagrams (discrete sets of bits) from one computer to
    another in a computer network. (See: TCP/IP.)
    (C) TCP is designed to fit into a layered hierarchy of protocols
    that support internetwork applications. TCP assumes it can obtain
    a simple, potentially unreliable datagram service (such as the
    Internet Protocol) from the lower-layer protocols.
 $ Transport Layer Security (TLS)
    (I) TLS Version 1.0 is an Internet protocol [R2246] based-on and
    very similar to SSL Version 3.0. (See: TLSP.)

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    (C) The TLS protocol is misnamed, because it operates well above
    the transport layer (OSI layer 4).
 $ Transport Layer Security Protocol (TLSP)
    (I) An end-to-end encryption protocol(ISO Standard 10736) that
    provides security services at the bottom of OSI layer 4, i.e.,
    directly above layer 3. (See: TLS.)
    (C) TLSP evolved directly from the SP4 protocol of SDNS.
 $ transport mode vs. tunnel mode
    (I) IPsec usage: Two ways to apply IPsec protocols (AH and ESP) to
    protect communications:
  1. "Transport mode": The protection applies to (i.e., the IPsec

protocol encapsulates) the packets of upper-layer protocols,

       the ones that are carried above IP.
  1. "Tunnel mode": The protection applies to (i.e., the IPsec

protocol encapsulates) IP packets.

    (C) A transport mode security association is always between two
    hosts. In a tunnel mode security association, each end may be
    either a host or a gateway. Whenever either end of an IPsec
    security association is a security gateway, the association is
    required to be in tunnel mode.
 $ trap door
    (I) A hidden computer flaw known to an intruder, or a hidden
    computer mechanism (usually software) installed by an intruder,
    who can activate the trap door to gain access to the computer
    without being blocked by security services or mechanisms. (See:
    back door, Trojan horse.)
 $ triple DES
    (I) A block cipher, based on DES, that transforms each 64-bit
    plaintext block by applying the Data Encryption Algorithm three
    successive times, using either two or three different keys, for an
    effective key length of 112 or 168 bits. [A9052] (See: DES.)
    (C) IPsec usage: The algorithm variation proposed for ESP uses a
    168-bit key, consisting of three independent 56-bit quantities
    used by the Data Encryption Algorithm, and a 64-bit initialization
    value. Each datagram contains an IV to ensure that each received
    datagram can be decrypted even when other datagrams are dropped or
    a sequence of datagrams is reordered in transit. [R1851]

Shirey Informational [Page 179] RFC 2828 Internet Security Glossary May 2000

 $ triple-wrapped
    (I) S/MIME usage: Data that has been signed with a digital
    signature, and then encrypted, and then signed again. [R2634]
 $ Trojan horse
    (I) A computer program that appears to have a useful function, but
    also has a hidden and potentially malicious function that evades
    security mechanisms, sometimes by exploiting legitimate
    authorizations of a system entity that invokes the program.
 $ trust
    1. (I) Information system usage: The extent to which someone who
    relies on a system can have confidence that the system meets its
    specifications, i.e., that the system does what it claims to do
    and does not perform unwanted functions. (See: trust level.)
    (C) "trusted vs. trustworthy": In discussing a system or system
    process or object, this Glossary (and industry usage) prefers the
    term "trusted" to describe a system that operates as expected,
    according to design and policy. When the trust can also be
    guaranteed in some convincing way, such as through formal analysis
    or code review, the system is termed "trustworthy"; this differs
    from the ABA Guidelines definition (see: trustworthy system).
    2. (I) PKI usage: A relationship between a certificate user and a
    CA in which the user acts according to the assumption that the CA
    creates only valid digital certificates.
    (O) "Generally, an entity can be said to 'trust' a second entity
    when it (the first entity) makes the assumption that the second
    entity will behave exactly as the first entity expects. This trust
    may apply only for some specific function. The key role of trust
    in [X.509] is to describe the relationship between an entity and a
    [certification] authority; an entity shall be certain that it can
    trust the certification authority to create only valid and
    reliable certificates." [X509]
 $ trust chain
    (D) ISDs SHOULD NOT use this term as a synonym for "certification
    path" because it mixes concepts in a potentially misleading way.
    (See: trust.)
 $ trust-file PKI
    (I) A non-hierarchical PKI in which each certificate user has a
    local file (which is used by application software) of public-key
    certificates that the user trusts as starting points (i.e., roots)
    for certification paths. (See: hierarchical PKI, mesh PKI, root,
    web of trust.)

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    (C) For example, popular browsers are distributed with an initial
    file of trusted certificates, which often are self-signed
    certificates. Users can add certificates to the file or delete
    from it. The file may be directly managed by the user, or the
    user's organization may manage it from a centralized server.
 $ trust hierarchy
    (D) ISDs SHOULD NOT use this term as a synonym for "certification
    hierarchy" because this term mixes concepts (see: trust) in a
    potentially misleading way and duplicates the meaning of another,
    standardized term. (See: trust, web of trust.)
 $ trust level
    (I) A characterization of a standard of security protection to be
    met by a computer system.
    (C) The TCSEC defines eight trust levels. From the lowest to the
    highest, they are D, C1, C2, B1, B2, B3, and A1. A trust level is
    based not only on the presence of security mechanisms but also on
    the use of systems engineering discipline to properly structure
    the system and implementation analysis to ensure that the system
    provides an appropriate degree of trust.
 $ trusted
    See: (discussion under) trust.
 $ trusted certificate
    (I) A certificate upon which a certificate user relies as being
    valid without the need for validation testing; especially a
    public-key certificate that is used to provide the first public
    key in a certification path. (See: certification path, root
    certificate, validation.)
    (C) A trusted public-key certificate might be (a) the root
    certificate in a hierarchical PKI, (b) the certificate of the CA
    that issued the user's own certificate in a mesh PKI, or (c)
    any certificate accepted by the user in a trust-file PKI.
 $ trusted computer system
    (I) Multilevel security usage: "A system that employs sufficient
    hardware and software assurance measures to allow its use for
    simultaneous processing of a range of sensitive or classified
    information." [NCS04] (See: (discussion under) trust.)
 $ Trusted Computer System Evaluation Criteria (TCSEC)
    (N) A standard for evaluating the security provided by operating
    systems [CSC001, DOD1]. Informally called the "Orange Book"

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    because of the color of its cover; first document in the Rainbow
    Series. (See: Common Criteria, (usage note under) Green Book,
    Orange Book, trust level.)
 $ trusted computing base (TCB)
    (I) "The totality of protection mechanisms within a computer
    system, including hardware, firmware, and software, the
    combination of which is responsible for enforcing a security
    policy." [NCS04] (See: (discussion of "trusted" under) trust.)
 $ trusted distribution
    (I) "A trusted method for distributing the TCB hardware, software,
    and firmware components, both originals and updates, that provides
    methods for protecting the TCB from modification during
    distribution and for detection of any changes to the TCB that may
    occur." [NCS04]
 $ trusted key
    (I) A public key upon which a user relies; especially a public key
    that can be used as the first public key in a certification path.
    (See: certification path, root key, validation.)
    (C) A trusted public key might be (a) the root key in a
    hierarchical PKI, (b) the key of the CA that issued the user's own
    certificate in a mesh PKI, or (c) any key accepted by the user in
    a trust-file PKI.
 $ trusted path
    (I) COMPUSEC usage: A mechanism by which a computer system user
    can communicate directly and reliably with the trusted computing
    base (TCB) and that can only be activated by the user or the TCB
    and cannot be imitated by untrusted software within the computer.
    [NCS04]
    (I) COMSEC usage: A mechanism by which a person or process can
    communicate directly with a cryptographic module and that can only
    be activated by the person, process, or module, and cannot be
    imitated by untrusted software within the module. [FP140]
 $ trusted process
    (I) A system process that has privileges that enable it to affect
    the state of system security and that can, therefore, through
    incorrect or malicious execution, violate the system's security
    policy. (See: privileged process, (discussion of "trusted" under)
    trust.)

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 $ trusted subnetwork
    (I) A subnetwork containing hosts and routers that trust each
    other not to engage in active or passive attacks. (There also is
    an assumption that the underlying communication channels--e.g.,
    telephone lines, or a LAN--are protected from attack by some
    means.)
 $ trusted system
    See: (discussion under) trust, trusted computer system,
    trustworthy system.
 $ Trusted Systems Interoperability Group (TSIG)
    (N) A forum of computer vendors, system integrators, and users
    devoted to promoting interoperability of trusted computer systems.
    TSIG meetings are open to all persons who are working in the
    INFOSEC area.
 $ trustworthy system
    (O) ABA usage: "Computer hardware, software, and procedures that:
    (a) are reasonably secure from intrusion and misuse; (b) provide a
    reasonably reliable level of availability, reliability, and
    correct operation; (c) are reasonably suited to performing their
    intended functions; and (d) adhere to generally accepted security
    principles." [ABA] This differs somewhat from other industry
    usage. (See: (discussion of "trusted vs. trustworthy" under)
    trust.)
 $ TSIG
    See: Trusted System Interoperability Group.
 $ tunnel
    (I) A communication channel created in a computer network by
    encapsulating (carrying, layering) a communication protocol's data
    packets in (on top of) a second protocol that normally would be
    carried above, or at the same layer as, the first one. (See: L2TP,
    VPN.)
    (C) Tunneling can involve almost any OSI or TCP/IP protocol
    layers; for example, a TCP connection between two hosts could
    conceivably be tunneled through email messages across the
    Internet. Most often, a tunnel is a logical point-to-point link--
    i.e., an OSI layer 2 connection--created by encapsulating the
    layer 2 protocol in a transport protocol (such as TCP), in a
    network or internetwork layer protocol (such as IP), or in another
    link layer protocol. Often, encapsulation is accomplished with an
    extra, intermediate protocol, i.e., a tunneling protocol (such as
    L2TP) that is layered between the tunneled layer 2 protocol and
    the encapsulating protocol.

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    (C) Tunneling can move data between computers that use a protocol
    not supported by the network connecting them. Tunneling also can
    enable a computer network to use the services of a second network
    as though the second network were a set of point-to-point links
    between the first network's nodes. (See: virtual private network.)
    (O) SET usage: The name of a SET private extension that indicates
    whether the CA or the payment gateway supports passing encrypted
    messages to the cardholder through the merchant. If so, the
    extension lists OIDs of symmetric encryption algorithms that are
    supported.
 $ tunnel mode
    (I) IPsec usage: See: transport mode vs. tunnel mode.
 $ two-person control
    (I) The close surveillance and control of a system, process, or
    materials (especially with regard to cryptography) at all times by
    a minimum of two appropriately authorized persons, each capable of
    detecting incorrect and unauthorized procedures with respect to
    the tasks to be performed and each familiar with established
    security requirements. (See: dual control, no-lone zone.)
 $ Type I cryptography
    (O) A cryptographic algorithm or device approved by NSA for
    protecting classified information.
 $ Type II cryptography
    (O) A cryptographic algorithm or device approved by NSA for
    protecting sensitive unclassified information (as specified in
    section 2315 of Title 10 United States Code, or section 3502(2) of
    Title 44, United States Code.)
 $ Type III cryptography
    (O) A cryptographic algorithm or device approved as a Federal
    Information Processing Standard.
 $ UDP
    See: User Datagram Protocol.
 $ unclassified
    (I) Not classified.
 $ unencrypted
    (I) Not encrypted.

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 $ unforgeable
    (I) Cryptographic usage: The property of a cryptographic data
    structure (i.e., a data structure that is defined using one or
    more cryptographic functions) that makes it computationally
    infeasible to construct (i.e., compute) an unauthorized but
    correct value of the structure without having knowledge of one of
    more keys. (E.g., see: digital certificate.)
    (C) This definition is narrower than general English usage, where
    "unforgeable" means unable to be fraudulently created or
    duplicated. In that broader sense, anyone can forge a digital
    certificate containing any set of data items whatsoever by
    generating the to-be-signed certificate and signing it with any
    private key whatsoever. But for PKI purposes, the forged data
    structure is invalid if it is not signed with the true private key
    of the claimed issuer; thus, the forgery will be detected when a
    certificate user uses the true public key of the claimed issuer to
    verify the signature.
 $ uniform resource identifier (URI)
    (I) A type of formatted identifier that encapsulates the name of
    an Internet object, and labels it with an identification of the
    name space, thus producing a member of the universal set of names
    in registered name spaces and of addresses referring to registered
    protocols or name spaces. [R1630]
    (C) URIs are used in HTML to identify the target of hyperlinks. In
    common practice, URIs include uniform resource locators [R2368]
    and relative URLs, and may be URNs. [R1808]
 $ uniform resource locator (URL)
    (I) A type of formatted identifier that describes the access
    method and location of an information resource object on the
    Internet. [R1738]
    (C) A URL is a URI that provides explicit instructions on how to
    access the named object. For example,
    "ftp://bbnarchive.bbn.com/foo/bar/picture/cambridge.zip" is a URL.
    The part before the colon specifies the access scheme or protocol,
    and the part after the colon is interpreted according to that
    access method. Usually, two slashes after the colon indicate the
    host name of a server (written as a domain name). In an FTP or
    HTTP URL, the host name is followed by the path name of a file on
    the server. The last (optional) part of a URL may be either a
    fragment identifier that indicates a position in the file, or a
    query string.

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 $ uniform resource name (URN)
    (I) A URI that has an institutional commitment to persistence and
    availability.
 $ untrusted process
    (I) A system process that is not able to affect the state of
    system security through incorrect or malicious operation, usually
    because its operation is confined by a security kernel. (See:
    trusted process.)
 $ UORA
    See: user-PIN ORA.
 $ update
    See: certificate update and key update.
 $ URI
    See: uniform resource identifier.
 $ URL
    See: uniform resource locator.
 $ URN
    See: uniform resource name.
 $ user
    (I) A person, organization entity, or automated process that
    accesses a system, whether authorized to do so or not. (See:
    [R2504].)
    (C) Any ISD that uses this term SHOULD provide an explicit
    definition, because this term is used in many ways and can easily
    be misunderstood.
 $ User Datagram Protocol (UDP)
    (I) An Internet Standard protocol [R0768] that provides a datagram
    mode of packet-switched computer communication in an internetwork.
    (C) UDP is a transport layer protocol, and it assumes that IP is
    the underlying protocol. UDP enables application programs to send
    transaction-oriented data to other programs with minimal protocol
    mechanism. UDP does not provide reliable delivery, flow control,
    sequencing, or other end-to-end services that TCP provides.
 $ user identifier
    (I) A character string or symbol that is used in a system to
    uniquely name a specific user or group of users.

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    (C) Often verified by a password in an authentication process.
 $ user PIN
    (O) MISSI usage: One of two personal identification numbers that
    control access to the functions and stored data of a FORTEZZA PC
    card. Knowledge of the user PIN enables the card user to perform
    the FORTEZZA functions that are intended for use by an end user.
    (See: SSO PIN.)
 $ user-PIN ORA (UORA)
    (O) A MISSI organizational RA that operates in a mode in which the
    ORA performs only the subset of card management functions that are
    possible with knowledge of the user PIN for a FORTEZZA PC card.
    (See: no-PIN ORA, SSO-PIN ORA.)
 $ usurpation
    See: (secondary definition under) threat consequence.
 $ UTCTime
    (N) The ASN.1 data type "UTCTime" contains a calendar date
    (YYMMDD) and a time to a precision of either one minute (HHMM) or
    one second (HHMMSS), where the time is either (a) Coordinated
    Universal Time or (b) the local time followed by an offset that
    enables Coordinated Universal Time to be calculated. Note: UTCTime
    has the Year 2000 problem. (See: Coordinated Universal Time,
    GeneralizedTime.)
 $ v1 certificate
    (C) Ambiguously refers to either an X.509 public-key certificate
    in its version 1 format, or an X.509 attribute certificate in its
    version 1 format. However, many people who use this term are not
    aware that X.509 specifies attribute certificates that do not
    contain a public key. Therefore, ISDs MAY use this term as an
    abbreviation for "version 1 X.509 public-key certificate", but
    only after using the full term at the first instance.
    (D) ISDs SHOULD NOT use this term as an abbreviation for "version
    1 X.509 attribute certificate".
 $ v1 CRL
    (I) An abbreviation for "X.509 CRL in version 1 format".
    (C) ISDs should use this abbreviation only after using the full
    term at its first occurrence and defining the abbreviation.
 $ v2 certificate
    (I) An abbreviation for "X.509 public-key certificate in version 2
    format".

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    (C) ISDs should use this abbreviation only after using the full
    term at its first occurrence and defining the abbreviation.
 $ v2 CRL
    (I) An abbreviation for "X.509 CRL in version 2 format".
    (C) ISDs should use this abbreviation only after using the full
    term at its first occurrence and defining the abbreviation.
 $ v3 certificate
    (I) An abbreviation for "X.509 public-key certificate in version 3
    format".
    (C) ISDs should use this abbreviation only after using the full
    term at its first occurrence and defining the abbreviation.
 $ valid certificate
    (I) A digital certificate for which the binding of the data items
    can be trusted; one that can be validated successfully. (See:
    validate vs. verify.)
 $ valid signature
    (D) ISDs SHOULD NOT use this term; instead, use "authentic
    signature". This Glossary recommends saying "validate the
    certificate" and "verify the signature"; therefore, it would be
    inconsistent to say that a signature is "valid". (See: validate
    vs. verify.)
 $ validate vs. verify
    (C) The PKI community uses words inconsistently when describing
    what a certificate user does to make certain that a digital
    certificate can be trusted. Usually, we say "verify the signature"
    but say "validate the certificate"; i.e., we "verify" atomic
    truths but "validate" data structures, relationships, and systems
    that are composed of or depend on verified items. Too often,
    however, verify and validate are used interchangeably.
    ISDs SHOULD comply with the following two rules to ensure
    consistency and to align Internet security terminology with
    ordinary English:
  1. Rule 1: Use "validate" when referring to a process intended to

establish the soundness or correctness of a construct. (E.g.,

       see: certificate validation.)
  1. Rule 2: Use "verify" when referring to a process intended to

test or prove the truth or accuracy of a fact or value. (E.g.,

       see: authenticate.)

Shirey Informational [Page 188] RFC 2828 Internet Security Glossary May 2000

    The rationale for Rule 1 is that "valid" derives from a word that
    means "strong" in Latin. Thus, to validate means to make sure that
    a construction is sound. A certificate user validates a public-key
    certificate to establish trust in the binding that the certificate
    asserts between an identity and a key. (To validate can also mean
    to officially approve something; e.g., NIST validates
    cryptographic modules for conformance with FIPS PUB 140-1.)
    The rationale for Rule 2 is that "verify" derives from a word that
    means "true" in Latin. Thus, to verify means to prove the truth of
    an assertion by examining evidence or performing tests. To verify
    an identity, an authentication process examines identification
    information that is presented or generated. To validate a
    certificate, a certificate user verifies the digital signature on
    the certificate by performing calculations; verifies that the
    current time is within the certificate's validity period; and may
    need to validate a certification path involving additional
    certificates.
 $ validation
    See: validate vs. verify.
 $ validity period
    (I) A data item in a digital certificate that specifies the time
    period for which the binding between data items (especially
    between the subject name and the public key value in a public-key
    certificate) is valid, except if the certificate appears on a CRL
    or the key appears on a CKL.
 $ value-added network (VAN)
    (I) A computer network or subnetwork (which is usually a
    commercial enterprise) that transmits, receives, and stores EDI
    transactions on behalf of its customers.
    (C) A VAN may also provide additional services, ranging from EDI
    format translation, to EDI-to-FAX conversion, to integrated
    business systems.
 $ VAN
    See: value-added network.
 $ verification
    1. System verification: The process of comparing two levels of
    system specification for proper correspondence, such as comparing
    a security policy with a top-level specification, a top-level
    specification with source code, or source code with object code.
    [NCS04]

Shirey Informational [Page 189] RFC 2828 Internet Security Glossary May 2000

    2. Identification verification: Presenting information to
    establish the truth of a claimed identity.
 $ verify
    See: validate vs. verify.
 $ violation
    See: security violation.
 $ virtual private network (VPN)
    (I) A restricted-use, logical (i.e., artificial or simulated)
    computer network that is constructed from the system resources of
    a relatively public, physical (i.e., real) network (such as the
    Internet), often by using encryption (located at hosts or
    gateways), and often by tunneling links of the virtual network
    across the real network.
    (C) For example, if a corporation has LANs at several different
    sites, each connected to the Internet by a firewall, the
    corporation could create a VPN by (a) using encrypted tunnels to
    connect from firewall to firewall across the Internet and (b) not
    allowing any other traffic through the firewalls. A VPN is
    generally less expensive to build and operate than a dedicated
    real network, because the virtual network shares the cost of
    system resources with other users of the real network.
 $ virus
    (I) A hidden, self-replicating section of computer software,
    usually malicious logic, that propagates by infecting--i.e.,
    inserting a copy of itself into and becoming part of--another
    program. A virus cannot run by itself; it requires that its host
    program be run to make the virus active.
 $ VPN
    See: virtual private network.
 $ vulnerability
    (I) A flaw or weakness in a system's design, implementation, or
    operation and management that could be exploited to violate the
    system's security policy.
    (C) Most systems have vulnerabilities of some sort, but this does
    not mean that the systems are too flawed to use. Not every threat
    results in an attack, and not every attack succeeds. Success
    depends on the degree of vulnerability, the strength of attacks,
    and the effectiveness of any countermeasures in use. If the
    attacks needed to exploit a vulnerability are very difficult to
    carry out, then the vulnerability may be tolerable. If the

Shirey Informational [Page 190] RFC 2828 Internet Security Glossary May 2000

    perceived benefit to an attacker is small, then even an easily
    exploited vulnerability may be tolerable. However, if the attacks
    are well understood and easily made, and if the vulnerable system
    is employed by a wide range of users, then it is likely that there
    will be enough benefit for someone to make an attack.
 $ W3
    See: World Wide Web.
 $ war dialer
    (I) A computer program that automatically dials a series of
    telephone numbers to find lines connected to computer systems, and
    catalogs those numbers so that a cracker can try to break into the
    systems.
 $ Wassenaar Arrangement
    (N) The Wassenaar Arrangement on Export Controls for Conventional
    Arms and Dual-Use Goods and Technologies is a global, multilateral
    agreement approved by 33 countries in July 1996 to contribute to
    regional and international security and stability, by promoting
    information exchange concerning, and greater responsibility in,
    transfers of arms and dual-use items, thus preventing
    destabilizing accumulations. (See: International Traffic in Arms
    Regulations.)
    (C) The Arrangement began operations in September 1996. The
    participating countries are Argentina, Australia, Austria,
    Belgium, Bulgaria, Canada, Czech Republic, Denmark, Finland,
    France, Germany, Greece, Hungary, Ireland, Italy, Japan,
    Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal,
    Republic of Korea, Romania, Russian Federation, Slovak Republic,
    Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, and
    United States. Participants meet on a regular basis in Vienna,
    where the Arrangement has its headquarters.
    Participating countries seek through their national policies to
    ensure that transfers do not contribute to the development or
    enhancement of military capabilities that undermine the goals of
    the arrangement, and are not diverted to support such
    capabilities. The countries maintain effective export controls for
    items on the agreed lists, which are reviewed periodically to
    account for technological developments and experience gained.
    Through transparency and exchange of views and information,
    suppliers of arms and dual-use items can develop common
    understandings of the risks associated with their transfer and
    assess the scope for coordinating national control policies to
    combat these risks. Members provide semi-annual notification of
    arms transfers, covering seven categories derived from the UN

Shirey Informational [Page 191] RFC 2828 Internet Security Glossary May 2000

    Register of Conventional Arms. Members also report transfers or
    denials of transfers of certain controlled dual-use items.
    However, the decision to transfer or deny transfer of any item is
    the sole responsibility of each participating country. All
    measures undertaken with respect to the arrangement are in
    accordance with national legislation and policies and are
    implemented on the basis of national discretion.
 $ watermarking
    See: digital watermarking.
 $ web of trust
    (O) PGP usage: A trust-file PKI technique used in PGP for building
    a file of validated public keys by making personal judgments about
    being able to trust certain people to be holding properly
    certified keys of other people. (See: certification hierarchy,
    mesh PKI.)
 $ web server
    (I) A software process that runs on a host computer connected to
    the Internet to respond to HTTP requests for documents from client
    web browsers.
 $ web vs. Web
    1. (I) Capitalized: ISDs SHOULD capitalize "Web" when using the
    term (as either a noun or an adjective) to refer specifically to
    the World Wide Web. (Similarly, see: internet vs. Internet.)
    2. (C) Not capitalized: ISDs SHOULD NOT capitalize "web" when
    using the term (usually as an adjective) to refer generically to
    technology--such as web browsers, web servers, HTTP, and HTML--
    that is used in the Web or similar networks.
    (C) IETF documents SHOULD spell out "World Wide Web" fully at the
    first instance of usage and SHOULD Use "Web" and "web" especially
    carefully where confusion with the PGP "web of trust" is possible.
 $ wiretapping
    (I) An attack that intercepts and accesses data and other
    information contained in a flow in a communication system.
    (C) Although the term originally referred to making a mechanical
    connection to an electrical conductor that links two nodes, it is
    now used to refer to reading information from any sort of medium
    used for a link or even directly from a node, such as gateway or
    subnetwork switch.

Shirey Informational [Page 192] RFC 2828 Internet Security Glossary May 2000

    (C) "Active wiretapping" attempts to alter the data or otherwise
    affect the flow; "passive wiretapping" only attempts to observe
    the flow and gain knowledge of information it contains. (See:
    active attack, end-to-end encryption, passive attack.)
 $ work factor
    (I) General security usage: The estimated amount of effort or time
    that can be expected to be expended by a potential intruder to
    penetrate a system, or defeat a particular countermeasure, when
    using specified amounts of expertise and resources.
    (I) Cryptography usage: The estimated amount of computing time and
    power needed to break a cryptographic system.
 $ World Wide Web ("the Web", WWW, W3)
    (N) The global, hypermedia-based collection of information and
    services that is available on Internet servers and is accessed by
    browsers using Hypertext Transfer Protocol and other information
    retrieval mechanisms. (See: web vs. Web, [R2084].)
 $ worm
    (I) A computer program that can run independently, can propagate a
    complete working version of itself onto other hosts on a network,
    and may consume computer resources destructively. (See: Morris
    Worm, virus.)
 $ wrap
    (O) To use cryptography to provide data confidentiality service
    for a data object. (See: encrypt, seal.)
    (D) ISDs SHOULD NOT use this term with this definition because it
    duplicates the meaning of other, standard terms. Instead, use
    "encrypt" or use a term that is specific with regard to the
    mechanism used.
 $ WWW
    See: World Wide Web.
 $ X.400
    (N) An ITU-T Recommendation [X400] that is one part of a joint
    ITU-T/ISO multi-part standard (X.400-X.421) that defines the
    Message Handling Systems. (The ISO equivalent is IS 10021, parts
    1-7.) (See: Message Handling Systems.)
 $ X.500
 $ X.500 Directory
    (N) An ITU-T Recommendation [X500] that is one part of a joint
    ITU-T/ISO multi-part standard (X.500-X.525) that defines the X.500

Shirey Informational [Page 193] RFC 2828 Internet Security Glossary May 2000

    Directory, a conceptual collection of systems that provide
    distributed directory capabilities for OSI entities, processes,
    applications, and services. (The ISO equivalent is IS 9594-1 and
    related standards, IS 9594-x.) (See: directory vs. Directory,
    X.509.)
    (C) The X.500 Directory is structured as a tree (the Directory
    Information Tree), and information is stored in directory entries.
    Each entry is a collection of information about one object, and
    each object has a DN. A directory entry is composed of attributes,
    each with a type and one or more values. For example, if a PKI
    uses the Directory to distribute certificates, then the X.509
    public-key certificate of an end user is normally stored as a
    value of an attribute of type "userCertificate" in the Directory
    entry that has the DN that is the subject of the certificate.
 $ X.509
    (N) An ITU-T Recommendation [X509] that defines a framework to
    provide and support data origin authentication and peer entity
    authentication services, including formats for X.509 public-key
    certificates, X.509 attribute certificates, and X.509 CRLs. (The
    ISO equivalent is IS 9498-4.) (See: X.500.)
    (C) X.509 describes two levels of authentication: simple
    authentication based on a password, and strong authentication
    based on a public-key certificate.
 $ X.509 attribute certificate
    (N) An attribute certificate in the version 1 (v1) format defined
    by X.509. (The v1 designation for an X.509 attribute certificate
    is disjoint from the v1 designation for an X.509 public-key
    certificate, and from the v1 designation for an X.509 CRL.)
    (C) An X.509 attribute certificate has a subject field, but the
    attribute certificate is a separate data structure from that
    subject's public-key certificate. A subject may have multiple
    attribute certificates associated with each of its public-key
    certificates, and an attribute certificate may be issued by a
    different CA than the one that issued the associated public-key
    certificate.
    (C) An X.509 attribute certificate contains a sequence of data
    items and has a digital signature that is computed from that
    sequence. In addition to the signature, an attribute certificate
    contains items 1 through 9 listed below:

Shirey Informational [Page 194] RFC 2828 Internet Security Glossary May 2000

    1. version                Identifies v1.
    2. subject                Is one of the following:
       2a. baseCertificateID   - Issuer and serial number of an
                                 X.509 public-key certificate.
       2b. subjectName         - DN of the subject.
    3. issuer                 DN of the issuer (the CA who signed).
    4. signature              OID of algorithm that signed the cert.
    5. serialNumber           Certificate serial number;
                              an integer assigned by the issuer.
    6. attCertValidityPeriod  Validity period; a pair of UTCTime
                              values: "not before" and "not after".
    7. attributes             Sequence of attributes describing the
                              subject.
    8. issuerUniqueId         Optional, when a DN is not sufficient.
    9. extensions             Optional.
 $ X.509 authority revocation list
    (N) An ARL in one of the formats defined by X.509--version 1 (v1)
    or version 2 (v2). A specialized kind of certificate revocation
    list.
 $ X.509 certificate
    (N) Either an X.509 public-key certificate or an X.509 attribute
    certificate.
    (C) This Glossary uses the term with the precise meaning
    recommended here. However, some who use the term may not be aware
    that X.509 specifies attribute certificates that do not contain a
    public key. Even among those who are aware, this term is commonly
    used as an abbreviation to mean "X.509 public-key certificate".
    ISDs MAY use the term as an abbreviation for "X.509 public-key
    certificate", but only after using the full term at the first
    instance.
    (D) ISDs SHOULD NOT use this term as an abbreviation to mean
    "X.509 attribute certificate".
 $ X.509 certificate revocation list (CRL)
    (N) A CRL in one of the formats defined by X.509--version 1 (v1)
    or version 2 (v2). (The v1 and v2 designations for an X.509 CRL
    are disjoint from the v1 and v2 designations for an X.509 public-
    key certificate, and from the v1 designation for an X.509
    attribute certificate.) (See: certificate revocation.)
    (C) ISDs SHOULD NOT refer to an X.509 CRL as a digital
    certificate, but note that an X.509 CRL does meet this Glossary's
    definition of "digital certificate". Like a digital certificate,

Shirey Informational [Page 195] RFC 2828 Internet Security Glossary May 2000

    an X.509 CRL makes an assertion and is signed by a CA. But instead
    of binding a key or other attributes to a subject, an X.509 CRL
    asserts that certain previously-issued X.509 certificates have
    been revoked.
    (C) An X.509 CRL contains a sequence of data items and has a
    digital signature computed on that sequence. In addition to the
    signature, both v1 and v2 contain items 2 through 6b listed below.
    Version 2 contains item 1 and may optionally contain 6c and 7.
    1. version                Optional. If present, identifies v2.
    2. signature              OID of the algorithm that signed CRL.
    3. issuer                 DN of the issuer (the CA who signed).
    4. thisUpdate             A UTCTime value.
    5. nextUpdate             A UTCTime value.
    6. revokedCertificates    3-tuples of 6a, 6b, and (optional) 6c:
       6a. userCertificate    A certificate's serial number.
       6b. revocationDate     UTCTime value for the revocation date.
       6c. crlEntryExtensions Optional.
    7. crlExtensions          Optional.
 $ X.509 public-key certificate
    (N) A public-key certificate in one of the formats defined by
    X.509--version 1 (v1), version 2 (v2), or version 3 (v3). (The v1
    and v2 designations for an X.509 public-key certificate are
    disjoint from the v1 and v2 designations for an X.509 CRL, and
    from the v1 designation for an X.509 attribute certificate.)
    (C) An X.509 public-key certificate contains a sequence of data
    items and has a digital signature computed on that sequence. In
    addition to the signature, all three versions contain items 1
    through 7 listed below. Only v2 and v3 certificates may also
    contain items 8 and 9, and only v3 may contain item 10.
    1. version                 Identifies v1, v2, or v3.
    2. serialNumber            Certificate serial number;
                               an integer assigned by the issuer.
    3. signature               OID of algorithm that was used to
                               sign the certificate.
    4. issuer                  DN of the issuer (the CA who signed).
    5. validity                Validity period; a pair of UTCTime
                               values: "not before" and "not after".
    6. subject                 DN of entity who owns the public key.
    7. subjectPublicKeyInfo    Public key value and algorithm OID.
    8. issuerUniqueIdentifier  Defined for v2, v3; optional.
    9. subjectUniqueIdentifier Defined for v2, v2; optional.
    10. extensions             Defined only for v3; optional.

Shirey Informational [Page 196] RFC 2828 Internet Security Glossary May 2000

 $ XTACACS
    See: (secondary definition under) Terminal Access Controller (TAC)
    Access Control System.
 $ Yellow Book
    (D) ISDs SHOULD NOT use this term as a synonym for "Computer
    Security Requirements: Guidance for Applying the Department of
    Defense Trusted Computer System Evaluation Criteria in Specific
    Environments" [CSC3]. Instead, use the full proper name of the
    document or, in subsequent references, a conventional
    abbreviation. (See: (usage note under) Green Book, Rainbow
    Series.)
 $ zeroize
    (I) Use erasure or other means to render stored data unusable and
    unrecoverable, particularly a key stored in a cryptographic module
    or other device.
    (O) Erase electronically stored data by altering the contents of
    the data storage so as to prevent the recovery of the data.
    [FP140]

4. References

 This Glossary focuses on the Internet Standards Process. Therefore,
 this set of references emphasizes international, governmental, and
 industry standards documents; only a few other texts are listed. RFCs
 are listed, but not Internet-Drafts, because the latter are not an
 archival document series and should not be cited or quoted in an RFC.
 [A3092]  American National Standards Institute, "American National
          Standard Data Encryption Algorithm", ANSI X3.92-1981, 30 Dec
          1980.
 [A9009]  ---, "Financial Institution Message Authentication
          (Wholesale)", ANSI X9.9-1986, 15 Aug 1986.
 [A9017]  ---, "Financial Institution Key Management (Wholesale)",
          X9.17, 4 Apr 1985. [Defines procedures for the manual and
          automated management of keying material and uses DES to
          provide key management for a variety of operational
          environments.]
 [A9042]  ---, "Public key Cryptography for the Financial Service
          Industry: Agreement of Symmetric Keys Using Diffie-Hellman
          and MQV Algorithms", X9.42, 29 Jan 1999.

Shirey Informational [Page 197] RFC 2828 Internet Security Glossary May 2000

 [A9052]  ---, "Triple Data Encryption Algorithm Modes of Operation",
          X9.52-1998, ANSI approval 9 Nov 1998.
 [A9062]  ---, "Public Key Cryptography for the Financial Services
          Industry: The Elliptic Curve Digital Signature Algorithm
          (ECDSA)", X9.62-1998, ANSI approval 7 Jan 1999.
 [ABA]    American Bar Association, "Digital Signature Guidelines:
          Legal Infrastructure for Certification Authorities and
          Secure Electronic Commerce", Chicago, IL, 1 Aug 1996.
 [ACM]    Association for Computing Machinery, "Communications of the
          ACM", Jul 1998 issue with: Minerva M. Yeung, "Digital
          Watermarking"; Nasir Memom and Ping Wah Wong, "Protecting
          Digital Media Content"; and Scott Craver, Boon-Lock Yeo, and
          Minerva Yeung, "Technical Trials and Legal Tribulations".
 [Army]   U.S. Army Corps of Engineers, "Electromagnetic Pulse (EMP)
          and Tempest Protection for Facilities", EP 1110-3-2, 31 Dec
          1990.
 [B7799]  British Standards Institution, "Information Security
          Management, Part 1: Code of Practice for Information
          Security Management", BS 7799-1:1999, effective 15 May 1999.
  1. –, —, "Part 2: Specification for Information Security

Management Systems", BS 7799-2:1999, effective 15 May 1999.

 [Bell]   D. E. Bell and L. J. LaPadula, "Secure Computer Systems:
          Mathematical Foundations and Model", M74-244, The MITRE
          Corporation, Bedford, MA, May 1973. (Available as AD-771543,
          National Technical Information Service, Springfield, VA.)
 [CCIB]   Common Criteria Implementation Board, "Common Criteria for
          Information Technology Security Evaluation, Part 1:
          Introduction and General Model", ver. 2.1, CCIB-99-01, Aug
          1999.
 [CIPSO]  Trusted Systems Interoperability Working Group, "Common IP
          Security Option", ver. 2.3, 9 Mar 1993. [A "work in
          progress" that is probably defunct.]
 [CSC1]   U.S. Department of Defense Computer Security Center,
          "Department of Defense Trusted Computer System Evaluation
          Criteria", CSC-STD-001-83, 15 Aug 1983. (Superseded by
          [DOD1].)

Shirey Informational [Page 198] RFC 2828 Internet Security Glossary May 2000

 [CSC2]   ---, "Department of Defense Password Management Guideline",
          CSC-STD-002-85, 12 Apr 1985.
 [CSC3]   ---, "Computer Security Requirements: Guidance for Applying
          the Department of Defense Trusted Computer System Evaluation
          Criteria in Specific Environments", CSC-STD-003-85, 25 Jun
          1985.
 [CSOR]   U.S. Department of Commerce, "General Procedures for
          Registering Computer Security Objects", National Institute
          of Standards Interagency Report 5308, Dec 1993.
 [Denn]   D. E. Denning, "A Lattice Model of Secure Information Flow",
          in "Communications of the ACM", vol. 19, no. 5, May 1976,
          pp. 236-243.
 [DH76]   W. Diffie and M. H. Hellman, "New Directions in
          Cryptography" in "IEEE Transactions on Information Theory",
          vol. IT-22, no. 6, Nov 1976, pp. 644-654.
 [DOD1]   U.S. Department of Defense, "Department of Defense Trusted
          Computer System Evaluation Criteria", DoD 5200.28-STD, 26
          Dec 1985. (Supersedes [CSC1].)
 [DOD2]   ---, Directive 5200.28, "Security Requirements for Automated
          Information Systems (AISs)", 21 Mar 1988.
 [DOD3]   ---, "X.509 Certificate Policy", ver. 2, Mar 1999.
 [DOD4]   ---, "NSA Key Recovery Assessment Criteria", 8 Jun 1998.
 [ElGa]   T. El Gamal, "A Public-Key Cryptosystem and a Signature
          Scheme Based on Discrete Logarithms" in "IEEE Transactions
          on Information Theory", vol. IT-31, no. 4, 1985, pp. 469-
          472.
 [EMV1]   Europay International S.A., MasterCard International
          Incorporated, and Visa International Service Association,
          "EMV '96 Integrated Circuit Card Specification for Payment
          Systems", ver. 3.1.1, 31 May 1998.
 [EMV2]   ---, "EMV '96 Integrated Circuit Card Terminal Specification
          for Payment Systems", ver. 3.1.1, 31 May 1998.
 [EMV3]   ---, EMV '96 Integrated Circuit Card Application
          Specification for Payment Systems", ver. 3.1.1, 31 May 1998.

Shirey Informational [Page 199] RFC 2828 Internet Security Glossary May 2000

 [For94]  W. Ford, "Computer Communications Security: Principles,
          Standard Protocols and Techniques", ISBN 0-13-799453-2,
          1994.
 [For97]  W. Ford and M. Baum, "Secure Electronic Commerce: Building
          the Infrastructure for Digital Signatures and Encryption",
          ISBN 0-13-476342-4, 1994.
 [FP031]  U.S. Department of Commerce, "Guidelines for Automatic Data
          Processing Physical Security and Risk Management", Federal
          Information Processing Standards Publication (FIPS PUB) 31,
          Jun 1974.
 [FP039]  ---, "Glossary for Computer Systems Security", FIPS PUB 39,
          15 Feb 1976.
 [FP046]  ---, "Data Encryption Standard (DES)", FIPS PUB 46-2, 30 Dec
          1993.
 [FP081]  ---, "DES Modes of Operation", FIPS PUB 81, 2 Dec 1980.
 [FP102]  ---, "Guideline for Computer Security Certification and
          Accreditation", FIPS PUB 102, 27 Sep 1983.
 [FP113]  ---, "Computer Data Authentication", FIPS PUB 113, 30 May
          1985.
 [FP140]  ---, "Security Requirements for Cryptographic Modules", FIPS
          PUB 140-1, 11 Jan 1994.
 [FP151]  ---, "Portable Operating System Interface (POSIX)--System
          Application Program Interface [C Language]", FIPS PUB 151-2,
          12 May 1993
 [FP180]  ---, "Secure Hash Standard", FIPS PUB 180-1, 17 Apr 1995.
 [FP185]  ---, "Escrowed Encryption Standard", FIPS PUB 185, 9 Feb
          1994.
 [FP186]  ---, "Digital Signature Standard (DSS)", FIPS PUB 186, 19
          May 1994.
 [FP188]  ---, "Standard Security Label for Information Transfer",
          FIPS PUB 188, 6 Sep 1994.
 [FPDAM]  Collaborative ITU and ISO/IEC meeting on the Directory,
          "Final Proposed Draft Amendment on Certificate Extensions",
          April 1999. (This draft proposes changes to [X.509].)

Shirey Informational [Page 200] RFC 2828 Internet Security Glossary May 2000

 [FPKI]   U.S. Department of Commerce, "Public Key Infrastructure
          (PKI) Technical Specifications: Part A--Technical Concept of
          Operations", National Institute of Standards, 4 Sep 1998.
 [I3166]  International Standards Organization, "Codes for the
          Representation of Names of countries and Their Subdivisions
          --Part 1: Country Codes", ISO 3166-1:1997.
  1. –, — "Part 2: Country Subdivision Codes", ISO/DIS 3166-

2.

  1. –, — "Part 3: Codes for Formerly Used Names of

Countries", ISO/DIS 3166-3.

 [I7498]  ---, "Information Processing Systems--Open Systems
          Interconnection Reference Model--[Part 1:] Basic Reference
          Model", ISO/IEC 7498-1. (Equivalent to ITU-T Recommendation
          X.200.)
  1. –, — "Part 2: Security Architecture", ISO/IEC 7499-2.
  1. –, — "Part 4: Management Framework", ISO/IEC 7498-4.
 [I7812]  ---, "Identification cards--Identification of Issuers--Part
          1: Numbering System", ISO/IEC 7812-1:1993
  1. –, — "Part 2: Application and Registration Procedures",

ISO/IEC 7812-2:1993.

 [I9945]  ---, "Portable Operating System Interface for Computer
          Environments", ISO/IEC 9945-1:1990.
 [I15408] ---, "Information Technology--Security Techniques--
          Evaluation criteria for IT Security--Part 1: Introduction
          and General Model", ISO/IEC 15408-1:1999.
 [ITSEC]  "Information Technology Security Evaluation Criteria
          (ITSEC): Harmonised Criteria of France, Germany, the
          Netherlands, and the United Kingdom", ver. 1.2, U.K.
          Department of Trade and Industry, Jun 1991.
 [Kahn]   David Kahn, "The Codebreakers: The Story of Secret Writing",
          The Macmillan Company, New York, 1967.
 [Knuth]  D. E. Knuth, Chapter 3 ("Random Numbers") in Volume 2
          ("Seminumerical Algorithms") of "The Art of Computer
          Programming", Addison-Wesley, Reading, MA, 1969.

Shirey Informational [Page 201] RFC 2828 Internet Security Glossary May 2000

 [Kuhn]   Markus G. Kuhn and Ross J. Anderson, "Soft Tempest: Hidden
          Data Transmission Using Electromagnetic Emanations", in
          David Aucsmith, ed., "Information Hiding, Second
          International Workshop, IH'98", Portland, Oregon, USA, 15-17
          Apr 1998, LNCS 1525, Springer-Verlag, ISBN 3-540-65386-4,
          pp. 124-142.
 [MISPC]  U.S. Department of Commerce, "Minimum Interoperability
          Specification for PKI Components (MISPC), Version 1",
          National Institute of Standards Special Publication 800-15,
          Sep 1997.
 [NCS01]  National Computer Security Center, "A Guide to Understanding
          Audit in Trusted Systems", NCSC-TG-001, 1 Jun 1988. (Part of
          the Rainbow Series.)
 [NCS04]  ---, "Glossary of Computer Security Terms", NCSC-TG-004,
          ver. 1, 21 Oct 1988. (Part of the Rainbow Series.)
 [NCS05]  ---, "Trusted Network Interpretation of the Trusted Computer
          System Evaluation Criteria", NCSC-TG-005, ver. 1, 31 Jul
          1987. (Part of the Rainbow Series.)
 [NCS25]  ---, "A Guide to Understanding Data Remanence in Automated
          Information Systems", NCSC-TG-025, ver. 2, Sep 1991. (Part
          of the Rainbow Series.)
 [NIST]   National Institute of Standards and Technology, "SKIPJACK
          and KEA Algorithm Specifications", ver. 2, 29 May 1998.
          (http://csrc.nist.gov/encryption/skipjack-kea.htm)
 [PGP]    Simson Garfinkel, "PGP: Pretty Good Privacy", O'Reilly &
          Associates, Inc., Sebastopol, CA, 1995.
 [PKCS]   Burton S. Kaliski, Jr., "An Overview of the PKCS Standards",
          RSA Data Security, Inc., 3 Jun 1991.
 [PKC07]  RSA Laboratories, "PKCS #7: Cryptographic Message Syntax
          Standard", ver. 1.5, RSA Laboratories Technical Note, 1 Nov
          1993.
 [PKC10]  ---, "PKCS #10: Certification Request Syntax Standard", ver.
          1.0, RSA Laboratories Technical Note, 1 Nov 1993.
 [PKC11]  ---, "PKCS #11: Cryptographic Token Interface Standard",
          ver. 1.0, 28 Apr 1995.

Shirey Informational [Page 202] RFC 2828 Internet Security Glossary May 2000

 [R0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768, August
          1980.
 [R0791]  Postel, J., "Internet Protocol", STD 5, RFC 791, September
          1981.
 [R0792]  Postel, J., "Internet Control Message Protocol", STD 5, RFC
          792, September 1981. [See: RFC 1885.]
 [R0793]  Postel, J., ed., "Transmission Control Protocol", STD 7, RFC
          793, September 1981.
 [R0821]  Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC
          821, August 1982.
 [R0822]  Crocker, D., "Standard for the Format of ARPA Internet Text
          Messages", STD 11, RFC 822, August 1982.
 [R0854]  Postel, J. and J. Reynolds, "TELNET Protocol Specification",
          STD 8, RFC 854, May 1983.
 [R0959]  Postel, J. and J. Reynolds, "File Transfer Protocol (FTP)",
          STD 9, RFC 959, October 1985.
 [R1034]  Mockapetris, P., "Domain Names--Concepts and Facilities",
          STD 13, RFC 1034, November 1987.
 [R1157]  Case, J., Fedor, M., Schoffstall, M. and J. Davin, "A Simple
          Network Management Protocol (SNMP)" [version 1], STD 15, RFC
          1157, May 1990.
 [R1208]  Jacobsen O. and D. Lynch, "A Glossary of Networking Terms",
          RFC 1208, March 1991.
 [R1319]  Kaliski, B., "The MD2 Message-Digest Algorithm", RFC 1319,
          April 1992.
 [R1320]  Rivest, R., "The MD4 Message-Digest Algorithm", RFC 1320,
          April 1992.
 [R1321]  Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
          April 1992.
 [R1334]  Lloyd, B. and W. Simpson, "PPP Authentication Protocols",
          RFC 1334, October 1992.
 [R1413]  St. Johns, M., "Identification Protocol", RFC 1413, February
          1993.

Shirey Informational [Page 203] RFC 2828 Internet Security Glossary May 2000

 [R1421]  Linn, J., "Privacy Enhancement for Internet Electronic Mail,
          Part I: Message Encryption and Authentication Procedures",
          RFC 1421, February 1993.
 [R1422]  Kent, S., "Privacy Enhancement for Internet Electronic Mail,
          Part II: Certificate-Based Key Management", RFC 1422,
          February 1993.
 [R1455]  Eastlake, D., "Physical Link Security Type of Service", RFC
          1455, May 1993.
 [R1457]  Housley, R., "Security Label Framework for the Internet",
          RFC 1457, May 1993.
 [R1492]  Finseth, C., "An Access Control Protocol, Sometimes Called
          TACACS", RFC 1492, July 1993.
 [R1507]  Kaufman, C., "DASS: Distributed Authentication Security
          Service", RFC 1507, September 1993.
 [R1510]  Kohl, J. and C. Neuman, "The Kerberos Network Authentication
          Service (V5)", RFC 1510, September 1993.
 [R1591]  Kohl, J. and C. Neuman, "Domain Name System Structure and
          Delegation", March 1994.
 [R1630]  Berners-Lee, T., "Universal Resource Identifiers in WWW",
          RFC 1630, June 1994.
 [R1661]  Simpson, W., ed., " The Point-to-Point Protocol (PPP)", STD
          51, RFC 1661, July 1994.
 [R1731]  Myers, J., "IMAP4 Authentication Mechanisms", RFC 1731,
          December 1994.
 [R1734]  Myers, J., "POP3 AUTHentication Command", RFC 1734, December
          1994.
 [R1738]  Myers, J., Masinter, L. and M. McCahill, ed's., "Uniform
          Resource Locators (URL)", RFC 1738, December 1994.
 [R1750]  Eastlake, D., Crocker, S. and J. Schiller, "Randomness
          Recommendations for Security", RFC 1750, December 1994.
 [R1777]  Yeong, W., Howes, T. and S. Kille, "Lightweight Directory
          Access Protocol", RFC 1777, March 1995.

Shirey Informational [Page 204] RFC 2828 Internet Security Glossary May 2000

 [R1808]  Fielding, R., "Relative Uniform Resource Locators", RFC
          1808, June 1995.
 [R1824]  Danisch, H., "The Exponential Security System TESS: An
          Identity-Based Cryptographic Protocol for Authenticated Key-
          Exchange (E.I.S.S.-Report 1995/4)", RFC 1824, August 1995.
 [R1828]  Metzger, P. and W. Simpson, "IP Authentication using Keyed
          MD5", RFC 1828, August 1995.
 [R1829]  Karn, P., Metzger, P. and W. Simpson, "The ESP DES-CBC
          Transform", RFC 1829, August 1995.
 [R1848]  Crocker, S., Freed, N., Galvin, J. and S. Murphy, "MIME
          Object Security Services", RFC 1848, October 1995.
 [R1851]  Karn, P., Metzger, P. and W. Simpson, "The ESP Triple DES
          Transform", RFC 1851, September 1995.
 [R1866]  Berners-Lee, T., "Hypertext Markup Language--2.0", RFC 1866,
          November 1995.
 [R1885]  Conta, A. and S. Deering, "Internet Control Message Protocol
          (ICMPv6) for the Internet Protocol Version 6 (IPv6)
          Specification", RFC 1885, December 1995.
 [R1928]  Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D. and L.
          Jones, "SOCKS Protocol Version 5", RFC 1928, March 1996.
 [R1938]  Haller, N. and C. Metzion, "A One-Time Password System", RFC
          1938, May 1996.
 [R1939]  Myers, J. and M. Rose, "Post Office Protocol - Version 3",
          STD 53, RFC 1939, May 1996.
 [R1958]  Carpenter, B., ed., "Architectural Principles of the
          Internet", RFC 1958, June 1996.
 [R1983]  Malkin, G., ed., "Internet Users' Glossary", FYI 18, RFC
          1983, August 1996.
 [R1994]  Simpson, W. "PPP Challenge Handshake Authentication Protocol
          (CHAP)", RFC 1994, August 1996.
 [R2023]  Postel, J. and J. Reynolds, "Instructions to RFC Authors",
          RFC 2023, October 1997.

Shirey Informational [Page 205] RFC 2828 Internet Security Glossary May 2000

 [R2026]  Bradner, S., "The Internet Standards Process--Revision 3",
          BCP 9, RFC 2026, March 1994.
 [R2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
          Extensions (MIME) Part One: Format of Internet Message
          Bodies", RFC 2045, November 1996.
 [R2060]  Crispin, M., "Internet Message Access Protocol--Version 4
          Revision 1", RFC 2060, December 1996.
 [R2065]  Eastlake, D., 3rd, "Domain Name System Security Extensions",
          RFC 2065, January 1997.
 [R2078]  Linn, J., "Generic Security Service Application Program
          Interface, Version 2", RFC 2078, January 1997.
 [R2084]  Bossert, G., Cooper, S. and W. Drummond, "Considerations for
          Web Transaction Security", RFC 2084, January 1997.
 [R2104]  Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-
          Hashing for Message Authentication", RFC 2104, February
          1997.
 [R2119]  Bradner, S., "Key Words for Use in RFCs To Indicate
          Requirement Levels", BCP 14, RFC 2119, March 1997.
 [R2138]  Rigney, C., Rubens, A., Simpson, W. and S. Willens, "Remote
          Authentication Dial In User Service (RADIUS)", RFC 2138,
          April 1997.
 [R2137]  Eastlake, D., "Secure Domain Name System Dynamic Update",
          RFC 2137, April 1997.
 [R2179]  Gwinn, A., "Network Security For Trade Shows", RFC 2179,
          July 1997.
 [R2195]  Klensin, J., Catoe, R. and P. Krumviede, "IMAP/POP AUTHorize
          Extension for Simple Challenge/Response", RFC 2195, Sepember
          1997.
 [R2196]  Fraser, B., "Site Security Handbook", FYI 8, RFC 2196,
          Sepember 1997.
 [R2202]  Cheng, P. and R. Glenn, "Test Cases for HMAC-MD5 and HMAC-
          SHA-1", RFC 2202, Sepember 1997.

Shirey Informational [Page 206] RFC 2828 Internet Security Glossary May 2000

 [R2222]  Myers, J., "Simple Authentication and Security Layer
          (SASL)", RFC 2222, October 1997.
 [R2223]  Postel, J., "Instructions to RFC Authors", RFC 2223, October
          1997.
 [R2246]  Dierks, T. and C. Allen, "The TLS Protocol, Version 1.0",
          RFC 2246, January 1999.
 [R2284]  Blunk, L. and J. Vollbrecht, "PPP Extensible Authentication
          Protocol (EAP)", RFC 2284, March 1998.
 [R2315]  Kaliski, B., "PKCS #7: Cryptographic Message Syntax, Version
          1.5", RFC 2315, March 1998.
 [R2323]  Ramos, A., "IETF Identification and Security Guidelines",
          RFC 2323, 1 April 1998. [Intended for humorous entertainment
          ("please laugh loud and hard"); does not contain serious
          security information.]
 [R2350]  Brownlee, N. and E. Guttman, "Expectations for Computer
          Security Incident Response", RFC 2350, June 1998.
 [R2356]  Montenegro, C. and V. Gupta, "Sun's SKIP Firewall Traversal
          for Mobile IP", RFC 2356, June 1998.
 [R2373]  Hinden, R. and S. Deering, "IP Version 6 Addressing
          Architecture", RFC 2373, July 2998.
 [R2401]  Kent, S. and R. Atkinson, "Security Architecture for the
          Internet Protocol", RFC 2401, November 1998.
 [R2402]  Kent, S. and R. Atkinson, "IP Authentication Header", RFC
          2402, November 1998.
 [R2403]  Madson, C. and R. Glenn, "The Use of HMAC-MD5-96 within ESP
          and AH", RFC 2403, November 1998.
 [R2404]  Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
          ESP and AH", RFC 2404, November 1998.
 [R2405]  Madson, C. and N. Doraswamy, "The ESP DES-CBC Cipher
          Algorithm With Explicit IV", RFC 2405, November 1998.
 [R2406]  Kent, S. and R. Atkinson, "IP Encapsulating Security Payload
          (ESP)", RFC 2406, November 1998.

Shirey Informational [Page 207] RFC 2828 Internet Security Glossary May 2000

 [R2407]  Piper, D., "The Internet IP Security Domain of
          Interpretation for ISAKMP", RFC 2407, November 1998.
 [R2408]  Maughan, D., Schertler, M., Schneider, M. and J. Turner,
          "Internet Security Association and Key Management Protocol
          (ISAKMP)", RFC 2408, November 1998.
 [R2409]  Harkins, D. and D. Carrel, "The Internet Key Exchange
          (IKE)", RFC 2409, November 1998.
 [R2410]  Glenn, R. and S. Kent, "The NULL Encryption Algorithm and
          Its Use With IPsec", RFC 2410, November 1998.
 [R2412]  Orman, H., "The OAKLEY Key Determination Protocol", RFC
          2412, November 1998.
 [R2451]  Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher
          Algorithms", RFC 2451, November 1998.
 [R2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
          (IPv6) Specification", RFC 2460, December 1998.
 [R2504]  Guttman, E., Leong, L. and G. Malkin, "Users' Security
          Handbook", RFC 2504, February 1999.
 [R2510]  Adams, C. and S. Farrell, "Internet X.509 Public Key
          Infrastructure Certificate Management Protocols", RFC 2510,
          March 1999.
 [R2527]  Chokhani, S. and W. Ford, "Internet X.509 Public Key
          Infrastructure, Certificate Policy and Certification
          Practices Framework", RFC 2527, March 1999.
 [R2536]  EastLake, D., "DSA KEYs and SIGs in the Domain Name System
          (DNS)", RFC 2536, March 1999.
 [R2570]  Case, J., Mundy, R., Partain, D. and B. Stewart,
          "Introduction to Version 3 of the Internet-Standard Network
          Management Framework", RFC 2570, April 1999.
 [R2574]  Blumenthal, U. and B. Wijnen, "User-based Security Model
          (USM) for Version 3 of the Simple Network Management
          Protocol (SNMPv3)", RFC 2574, April 1999.
 [R2612]  Adams, C. and J. Gilchrist, "The CAST-256 Encryption
          Algorithm", RFC 2612, June 1999.

Shirey Informational [Page 208] RFC 2828 Internet Security Glossary May 2000

 [R2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter,
          L., Leach, P. and T. Berners-Lee, "Hypertext Transfer
          Protocol-- HTTP/1.1", RFC 2616, June 1999.
 [R2628]  Smyslov, V., "Simple Cryptographic Program Interface", RFC
          2628, June 1999.
 [R2630]  Housley, R., "Cryptographic Message Syntax", RFC 2630, June
          1999.
 [R2631]  Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC
          2631, June 1999.
 [R2633]  Ramsdell, B., ed., "S/MIME Version 3 Message Specification",
          RFC 2633, June 1999.
 [R2634]  Hoffman, P., ed., "Enhanced Security Services for S/MIME",
          RFC 2634, June 1999.
 [R2635]  Hambridge, S. and A. Lunde, "Don't Spew: A Set of Guidelines
          for Mass Unsolicited Mailings and Postings", RFC 2635, June
          1999.
 [Raym]   E. S. Raymond, ed., "The On-Line Hacker Jargon File", ver.
          4.0.0, 24 Jul 1996. (Also available as "The New Hacker's
          Dictionary", 2nd edition, MIT Press, Sep 1993, ISBN 0-262-
          18154-1. See: http://www.tuxedo.org/jargon/ for the latest
          version.)
 [Russ]   D. Russell and G. T. Gangemi Sr., Chapter 10 ("TEMPEST") in
          "Computer Security Basics", ISBN 0-937175-71-4, 1991.
 [Schn]   B. Schneier, "Applied Cryptography", John Wiley & Sons,
          Inc., New York, 1994.
 [SDNS3]  U.S. Department of Defense, National Security Agency,
          "Secure Data Network Systems, Security Protocol 3 (SP3)",
          document SDN.301, Revision 1.5, 15 May 1989.
 [SDNS4]  ---, ---, "Security Protocol 4 (SP4)", document SDN.401,
          Revision 1.2, 12 Jul 1988.
 [SDNS7]  ---, ---, "Secure data Network System, Message Security
          Protocol (MSP)", document SDN.701, Revision 4.0, 7 Jun 1996,
          with Corrections to Message Security Protocol, SDN.701, Rev
          4.0", 96-06-07, 30 Aug, 1996.

Shirey Informational [Page 209] RFC 2828 Internet Security Glossary May 2000

 [SET1]   MasterCard and Visa, "SET Secure Electronic Transaction
          Specification, Book 1: Business Description", ver. 1.0, 31
          May 1997.
 [SET2]   ---, "SET Secure Electronic Transaction Specification, Book
          2: Programmer's Guide", ver. 1.0, 31 May 1997.
 [Stei]   J. Steiner, C. Neuman, and J. Schiller, "Kerberos: An
          Authentication Service for Open Network Systems" in "Usenix
          Conference Proceedings", Feb 1988.
 [X400]   International Telecommunications Union--Telecommunication
          Standardization Sector (formerly "CCITT"), Recommendation
          X.400, "Message Handling Services: Message Handling System
          and Service Overview".
 [X500]   ---, Recommendation X.500, "Information Technology--Open
          Systems Interconnection--The Directory: Overview of
          Concepts, Models, and Services". (Equivalent to ISO 9594-1.)
 [X501]   ---, Recommendation X.501, "Information Technology--Open
          Systems Interconnection--The Directory: Models".
 [X509]   ---, Recommendation X.509, "Information Technology--Open
          Systems Interconnection--The Directory: Authentication
          Framework". (Equivalent to ISO 9594-8.)
 [X519]   ---, Recommendation X.519, "Information Technology--Open
          Systems Interconnection--The Directory: Protocol
          Specifications".
 [X520]   ---, Recommendation X.520, "Information Technology--Open
          Systems Interconnection--The Directory: Selected Attribute
          Types".
 [X680]   ---, Recommendation X.680, "Information Technology--Abstract
          Syntax Notation One (ASN.1)--Specification of Basic
          Notation", 15 Nov 1994. (Equivalent to ISO/IEC 8824-1.)
 [X690]   ---, Recommendation X.690, "Information Technology--ASN.1
          Encoding Rules--Specification of Basic Encoding Rules (BER),
          Canonical Encoding Rules (CER) and Distinguished Encoding
          Rules (DER)", 15 Nov 1994. (Equivalent to ISO/IEC 8825-1.)

Shirey Informational [Page 210] RFC 2828 Internet Security Glossary May 2000

5. Security Considerations

 This document only defines security terms and recommends how to use
 them. It does not describe in detail the vulnerabilities of, threats
 to, or mechanisms that protect specific Internet protocols.

6. Acknowledgments

 Pat Cain, Mike Kong, and Charles Lynn provided meticulous comments on
 an early draft.

7. Author's Address

 Please address all comments to:
 Robert W. Shirey                   GTE / BBN Technologies
 EMail: rshirey@bbn.com             Suite 1200, Mail Stop 30/12B2
 Phone: +1 (703) 284-4641           1300 Seventeenth Street North
 Fax:   +1 (703) 284-2766           Arlington, VA  22209-3801 USA

Shirey Informational [Page 211] RFC 2828 Internet Security Glossary May 2000

8. Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Shirey Informational [Page 212]

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