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rfc:rfc2510

Network Working Group C. Adams Request for Comments: 2510 Entrust Technologies Category: Standards Track S. Farrell

                                                                    SSE
                                                             March 1999
              Internet X.509 Public Key Infrastructure
                  Certificate Management Protocols

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

 This document describes the Internet X.509 Public Key Infrastructure
 (PKI) Certificate Management Protocols. Protocol messages are defined
 for all relevant aspects of certificate creation and management.
 Note that "certificate" in this document refers to an X.509v3
 Certificate as defined in [COR95, X509-AM].
 The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
 "RECOMMENDED", "MAY", and "OPTIONAL" in this document (in uppercase,
 as shown) are to be interpreted as described in [RFC2119].

Introduction

 The layout of this document is as follows:
  1. Section 1 contains an overview of PKI management;
  2. Section 2 contains discussion of assumptions and restrictions;
  3. Section 3 contains data structures used for PKI management messages;
  4. Section 4 defines the functions that are to be carried out in PKI

management by conforming implementations;

  1. Section 5 describes a simple protocol for transporting PKI messages;
  2. the Appendices specify profiles for conforming implementations and

provide an ASN.1 module containing the syntax for all messages

   defined in this specification.

Adams & Farrell Standards Track [Page 1] RFC 2510 PKI Certificate Management Protocols March 1999

1 PKI Management Overview

 The PKI must be structured to be consistent with the types of
 individuals who must administer it.  Providing such administrators
 with unbounded choices not only complicates the software required but
 also increases the chances that a subtle mistake by an administrator
 or software developer will result in broader compromise. Similarly,
 restricting administrators with cumbersome mechanisms will cause them
 not to use the PKI.
 Management protocols are REQUIRED to support on-line interactions
 between Public Key Infrastructure (PKI) components.  For example, a
 management protocol might be used between a Certification Authority
 (CA) and a client system with which a key pair is associated, or
 between two CAs that issue cross-certificates for each other.

1.1 PKI Management Model

 Before specifying particular message formats and procedures we first
 define the entities involved in PKI management and their interactions
 (in terms of the PKI management functions required).  We then group
 these functions in order to accommodate different identifiable types
 of end entities.

1.2 Definitions of PKI Entities

 The entities involved in PKI management include the end entity (i.e.,
 the entity to be named in the subject field of a certificate) and the
 certification authority (i.e., the entity named in the issuer field
 of a certificate). A registration authority MAY also be involved in
 PKI management.

1.2.1 Subjects and End Entities

 The term "subject" is used here to refer to the entity named in the
 subject field of a certificate; when we wish to distinguish the tools
 and/or software used by the subject (e.g., a local certificate
 management module) we will use the term "subject equipment". In
 general, the term "end entity" (EE) rather than subject is preferred
 in order to avoid confusion with the field name.
 It is important to note that the end entities here will include not
 only human users of applications, but also applications themselves
 (e.g., for IP security). This factor influences the protocols which
 the PKI management operations use; for example, application software
 is far more likely to know exactly which certificate extensions are
 required than are human users. PKI management entities are also end
 entities in the sense that they are sometimes named in the subject

Adams & Farrell Standards Track [Page 2] RFC 2510 PKI Certificate Management Protocols March 1999

 field of a certificate or cross-certificate. Where appropriate, the
 term "end-entity" will be used to refer to end entities who are not
 PKI management entities.
 All end entities require secure local access to some information --
 at a minimum, their own name and private key, the name of a CA which
 is directly trusted by this entity and that CA's public key (or a
 fingerprint of the public key where a self-certified version is
 available elsewhere). Implementations MAY use secure local storage
 for more than this minimum (e.g., the end entity's own certificate or
 application-specific information). The form of storage will also vary
 -- from files to tamper-resistant cryptographic tokens.  Such local
 trusted storage is referred to here as the end entity's Personal
 Security Environment (PSE).
 Though PSE formats are beyond the scope of this document (they are
 very dependent on equipment, et cetera), a generic interchange format
 for PSEs is defined here - a certification response message MAY be
 used.

1.2.2 Certification Authority

 The certification authority (CA) may or may not actually be a real
 "third party" from the end entity's point of view. Quite often, the
 CA will actually belong to the same organization as the end entities
 it supports.
 Again, we use the term CA to refer to the entity named in the issuer
 field of a certificate; when it is necessary to distinguish the
 software or hardware tools used by the CA we use the term "CA
 equipment".
 The CA equipment will often include both an "off-line" component and
 an "on-line" component, with the CA private key only available to the
 "off-line" component. This is, however, a matter for implementers
 (though it is also relevant as a policy issue).
 We use the term "root CA" to indicate a CA that is directly trusted
 by an end entity; that is, securely acquiring the value of a root CA
 public key requires some out-of-band step(s). This term is not meant
 to imply that a root CA is necessarily at the top of any hierarchy,
 simply that the CA in question is trusted directly.
 A "subordinate CA" is one that is not a root CA for the end entity in
 question. Often, a subordinate CA will not be a root CA for any
 entity but this is not mandatory.

Adams & Farrell Standards Track [Page 3] RFC 2510 PKI Certificate Management Protocols March 1999

1.2.3 Registration Authority

 In addition to end-entities and CAs, many environments call for the
 existence of a Registration Authority (RA) separate from the
 Certification Authority. The functions which the registration
 authority may carry out will vary from case to case but MAY include
 personal authentication, token distribution, revocation reporting,
 name assignment, key generation, archival of key pairs, et cetera.
 This document views the RA as an OPTIONAL component - when it is not
 present the CA is assumed to be able to carry out the RA's functions
 so that the PKI management protocols are the same from the end-
 entity's point of view.
 Again, we distinguish, where necessary, between the RA and the tools
 used (the "RA equipment").
 Note that an RA is itself an end entity. We further assume that all
 RAs are in fact certified end entities and that RAs have private keys
 that are usable for signing. How a particular CA equipment identifies
 some end entities as RAs is an implementation issue (i.e., this
 document specifies no special RA certification operation). We do not
 mandate that the RA is certified by the CA with which it is
 interacting at the moment (so one RA may work with more than one CA
 whilst only being certified once).
 In some circumstances end entities will communicate directly with a
 CA even where an RA is present. For example, for initial registration
 and/or certification the subject may use its RA, but communicate
 directly with the CA in order to refresh its certificate.

1.3 PKI Management Requirements

 The protocols given here meet the following requirements on PKI
 management.
    1. PKI management must conform to the ISO 9594-8 standard and the
       associated amendments (certificate extensions)
    2. PKI management must conform to the other parts of this series.
    3. It must be possible to regularly update any key pair without
       affecting any other key pair.
    4. The use of confidentiality in PKI management protocols must be
       kept to a minimum in order to ease regulatory problems.

Adams & Farrell Standards Track [Page 4] RFC 2510 PKI Certificate Management Protocols March 1999

    5. PKI management protocols must allow the use of different
       industry-standard cryptographic algorithms, (specifically
       including RSA, DSA, MD5, SHA-1) -- this means that any given
       CA, RA, or end entity may, in principle, use whichever
       algorithms suit it for its own key pair(s).
    6. PKI management protocols must not preclude the generation of
       key pairs by the end-entity concerned, by an RA, or by a CA --
       key generation may also occur elsewhere, but for the purposes
       of PKI management we can regard key generation as occurring
       wherever the key is first present at an end entity, RA, or CA.
    7. PKI management protocols must support the publication of
       certificates by the end-entity concerned, by an RA, or by a CA.
       Different implementations and different environments may choose
       any of the above approaches.
    8. PKI management protocols must support the production of
       Certificate Revocation Lists (CRLs) by allowing certified end
       entities to make requests for the revocation of certificates -
       this must be done in such a way that the denial-of-service
       attacks which are possible are not made simpler.
    9. PKI management protocols must be usable over a variety of
       "transport" mechanisms, specifically including mail, http,
       TCP/IP and ftp.
    10. Final authority for certification creation rests with the CA;
        no RA or end-entity equipment can assume that any certificate
        issued by a CA will contain what was requested -- a CA may
        alter certificate field values or may add, delete or alter
        extensions according to its operating policy. In other words,
        all PKI entities (end-entities, RAs, and CAs) must be capable
        of handling responses to requests for certificates in which
        the actual certificate issued is different from that requested
        (for example, a CA may shorten the validity period requested).
        Note that policy may dictate that the CA must not publish or
        otherwise distribute the certificate until the requesting
        entity has reviewed and accepted the newly-created certificate
        (typically through use of the PKIConfirm message).
    11. A graceful, scheduled change-over from one non-compromised CA
        key pair to the next (CA key update) must be supported (note
        that if the CA key is compromised, re-initialization must be
        performed for all entities in the domain of that CA). An end
        entity whose PSE contains the new CA public key (following a
        CA key update) must also be able to verify certificates
        verifiable using the old public key. End entities who directly

Adams & Farrell Standards Track [Page 5] RFC 2510 PKI Certificate Management Protocols March 1999

        trust the old CA key pair must also be able to verify
        certificates signed using the new CA private key.  (Required
        for situations where the old CA public key is "hardwired" into
        the end entity's cryptographic equipment).
    12. The Functions of an RA may, in some implementations or
        environments, be carried out by the CA itself. The protocols
        must be designed so that end entities will use the same
        protocol (but, of course, not the same key!) regardless of
        whether the communication is with an RA or CA.
    13. Where an end entity requests a certificate containing a given
        public key value, the end entity must be ready to demonstrate
        possession of the corresponding private key value. This may be
        accomplished in various ways, depending on the type of
        certification request. See Section 2.3, "Proof of Possession
        of Private Key", for details of the in-band methods defined
        for the PKIX-CMP (i.e., Certificate Management Protocol)
        messages.

PKI Management Operations

 The following diagram shows the relationship between the entities
 defined above in terms of the PKI management operations. The letters
 in the diagram indicate "protocols" in the sense that a defined set
 of PKI management messages can be sent along each of the lettered
 lines.

Adams & Farrell Standards Track [Page 6] RFC 2510 PKI Certificate Management Protocols March 1999

    +---+     cert. publish        +------------+      j
    |   |  <---------------------  | End Entity | <-------
    | C |             g            +------------+      "out-of-band"
    |   |                            | ^                loading
    | e |                            | |      initial
    | r |                          a | | b     registration/
    | t |                            | |       certification
    |   |                            | |      key pair recovery
    | / |                            | |      key pair update
    |   |                            | |      certificate update
    | C |  PKI "USERS"               V |      revocation request
    | R | -------------------+-+-----+-+------+-+-------------------
    | L |  PKI MANAGEMENT    | ^              | ^
    |   |    ENTITIES      a | | b          a | | b
    |   |                    V |              | |
    | R |             g   +------+    d       | |
    | e |   <------------ | RA   | <-----+    | |
    | p |      cert.      |      | ----+ |    | |
    | o |       publish   +------+   c | |    | |
    | s |                              | |    | |
    | i |                              V |    V |
    | t |          g                 +------------+   i
    | o |   <------------------------|     CA     |------->
    | r |          h                 +------------+  "out-of-band"
    | y |      cert. publish              | ^         publication
    |   |      CRL publish                | |
    +---+                                 | |    cross-certification
                                        e | | f  cross-certificate
                                          | |       update
                                          | |
                                          V |
                                        +------+
                                        | CA-2 |
                                        +------+
                         Figure 1 - PKI Entities
 At a high level the set of operations for which management messages
 are defined can be grouped as follows.
    1 CA establishment: When establishing a new CA, certain steps are
      required (e.g., production of initial CRLs, export of CA public
      key).
    2 End entity initialization: this includes importing a root CA
      public key and requesting information about the options
      supported by a PKI management entity.

Adams & Farrell Standards Track [Page 7] RFC 2510 PKI Certificate Management Protocols March 1999

    3 Certification: various operations result in the creation of new
      certificates:
      3.1 initial registration/certification: This is the process
          whereby  an end entity first makes itself known to a CA or
          RA, prior to the CA issuing a certificate or certificates
          for that end entity. The end result of this process (when it
          is successful) is that a CA issues a certificate for an end
          entity's public key, and returns that certificate to the end
          entity and/or posts that certificate in a public repository.
          This process may, and typically will, involve multiple
          "steps", possibly including an initialization of the end
          entity's equipment. For example, the end entity's equipment
          must be securely initialized with the public key of a CA, to
          be used in validating certificate paths.  Furthermore, an
          end entity typically needs to be initialized with its own
          key pair(s).
      3.2 key pair update:  Every key pair needs to be updated
          regularly (i.e., replaced with a new key pair), and a new
          certificate needs to be issued.
      3.3 certificate update: As certificates expire they may be
          "refreshed" if nothing relevant in the environment has
          changed.
      3.4 CA key pair update: As with end entities, CA key pairs need
          to be updated regularly; however, different mechanisms are
          required.
      3.5 cross-certification request:  One CA requests issuance of a
          cross-certificate from another CA.  For the purposes of this
          standard, the following terms are defined.  A "cross-
          certificate" is a certificate in which the subject CA and
          the issuer CA are distinct and SubjectPublicKeyInfo contains
          a verification key (i.e., the certificate has been issued
          for the subject CA's signing key pair).  When it is
          necessary to distinguish more finely, the following terms
          may be used: a cross-certificate is called an "inter-domain
          cross-certificate" if the subject and issuer CAs belong to
          different administrative domains; it is called an "intra-
          domain cross-certificate" otherwise.

Adams & Farrell Standards Track [Page 8] RFC 2510 PKI Certificate Management Protocols March 1999

 Notes:
 Note 1. The above definition of "cross-certificate" aligns with the
 defined term "CA-certificate" in X.509.  Note that this term is not
 to be confused with the X.500 "cACertificate" attribute type, which
 is unrelated.
 Note 2. In many environments the term "cross-certificate", unless
 further qualified, will be understood to be synonymous with "inter-
 domain cross-certificate" as defined above.
 Note 3. Issuance of cross-certificates may be, but is not
 necessarily, mutual; that is, two CAs may issue cross-certificates
 for each other.
      3.6 cross-certificate update: Similar to a normal certificate
          update but involving a cross-certificate.
    4 Certificate/CRL discovery operations: some PKI management
      operations result in the publication of certificates or CRLs:
      4.1 certificate publication: Having gone to the trouble of
          producing a certificate, some means for publishing it is
          needed.  The "means" defined in PKIX MAY involve the
          messages specified in Sections 3.3.13 - 3.3.16, or MAY
          involve other methods (LDAP, for example) as described in
          the "Operational Protocols" documents of the PKIX series of
          specifications.
      4.2 CRL publication: As for certificate publication.
    5 Recovery operations: some PKI management operations are used
      when an end entity has "lost" its PSE:
      5.1 key pair recovery:  As an option, user client key materials
          (e.g., a user's private key used for decryption purposes)
          MAY be backed up by a CA, an RA, or a key backup system
          associated with a CA or RA. If an entity needs to recover
          these backed up key materials (e.g., as a result of a
          forgotten password or a lost key chain file), a  protocol
          exchange may be needed to support such recovery.
    6 Revocation operations: some PKI operations result in the
      creation of new CRL entries and/or new CRLs:
      6.1 revocation request:  An authorized person advises a CA of an
          abnormal situation requiring certificate revocation.

Adams & Farrell Standards Track [Page 9] RFC 2510 PKI Certificate Management Protocols March 1999

    7 PSE operations: whilst the definition of PSE operations (e.g.,
      moving a PSE, changing a PIN, etc.) are beyond the scope of this
      specification, we do define a PKIMessage (CertRepMessage) which
      can form the basis of such operations.
 Note that on-line protocols are not the only way of implementing the
 above operations.  For all operations there are off-line methods of
 achieving the same result, and this specification does not mandate
 use of on-line protocols.  For example, when hardware tokens are
 used, many of the operations MAY be achieved as part of the physical
 token delivery.
 Later sections define a set of standard messages supporting the above
 operations.  The protocols for conveying these exchanges in different
 environments (file based, on-line, E-mail, and WWW) is also
 specified.

2. Assumptions and restrictions

2.1 End entity initialization

 The first step for an end entity in dealing with PKI management
 entities is to request information about the PKI functions supported
 and to securely acquire a copy of the relevant root CA public key(s).

2.2 Initial registration/certification

 There are many schemes that can be used to achieve initial
 registration and certification of end entities. No one method is
 suitable for all situations due to the range of policies which a CA
 may implement and the variation in the types of end entity which can
 occur.
 We can however, classify the initial registration / certification
 schemes that are supported by this specification. Note that the word
 "initial", above, is crucial - we are dealing with the situation
 where the end entity in question has had no previous contact with the
 PKI. Where the end entity already possesses certified keys then some
 simplifications/alternatives are possible.
 Having classified the schemes that are supported by this
 specification we can then specify some as mandatory and some as
 optional. The goal is that the mandatory schemes cover a sufficient
 number of the cases which will arise in real use, whilst the optional
 schemes are available for special cases which arise less frequently.
 In this way we achieve a balance between flexibility and ease of
 implementation.

Adams & Farrell Standards Track [Page 10] RFC 2510 PKI Certificate Management Protocols March 1999

 We will now describe the classification of initial registration /
 certification schemes.

2.2.1 Criteria used

2.2.1.1 Initiation of registration / certification

 In terms of the PKI messages which are produced we can regard the
 initiation of the initial registration / certification exchanges as
 occurring wherever the first PKI message relating to the end entity
 is produced. Note that the real-world initiation of the registration
 / certification procedure may occur elsewhere (e.g., a personnel
 department may telephone an RA operator).
 The possible locations are at the end entity, an RA, or a CA.

2.2.1.2 End entity message origin authentication

 The on-line messages produced by the end entity that requires a
 certificate may be authenticated or not. The requirement here is to
 authenticate the origin of any messages from the end entity to the
 PKI (CA/RA).
 In this specification, such authentication is achieved by the PKI
 (CA/RA) issuing the end entity with a secret value (initial
 authentication key) and reference value (used to identify the
 transaction) via some out-of-band means. The initial authentication
 key can then be used to protect relevant PKI messages.
 We can thus classify the initial registration/certification scheme
 according to whether or not the on-line end entity -> PKI messages
 are authenticated or not.
 Note 1: We do not discuss the authentication of the PKI -> end entity
 messages here as this is always REQUIRED. In any case, it can be
 achieved simply once the root-CA public key has been installed at the
 end entity's equipment or it can be based on the initial
 authentication key.
 Note 2: An initial registration / certification procedure can be
 secure where the messages from the end entity are authenticated via
 some out- of-band means (e.g., a subsequent visit).

2.2.1.3 Location of key generation

 In this specification, "key generation" is regarded as occurring
 wherever either the public or private component of a key pair first
 occurs in a PKIMessage. Note that this does not preclude a

Adams & Farrell Standards Track [Page 11] RFC 2510 PKI Certificate Management Protocols March 1999

 centralized key generation service - the actual key pair MAY have
 been generated elsewhere and transported to the end entity, RA, or CA
 using a (proprietary or standardized) key generation request/response
 protocol (outside the scope of this specification).
 There are thus three possibilities for the location of "key
 generation":  the end entity, an RA, or a CA.

2.2.1.4 Confirmation of successful certification

 Following the creation of an initial certificate for an end entity,
 additional assurance can be gained by having the end entity
 explicitly confirm successful receipt of the message containing (or
 indicating the creation of) the certificate. Naturally, this
 confirmation message must be protected (based on the initial
 authentication key or other means).
 This gives two further possibilities: confirmed or not.

2.2.2 Mandatory schemes

 The criteria above allow for a large number of initial registration /
 certification schemes. This specification mandates that conforming CA
 equipment, RA equipment, and EE equipment MUST support the second
 scheme listed below. Any entity MAY additionally support other
 schemes, if desired.

2.2.2.1 Centralized scheme

 In terms of the classification above, this scheme is, in some ways,
 the simplest possible, where:
  1. initiation occurs at the certifying CA;
  2. no on-line message authentication is required;
  3. "key generation" occurs at the certifying CA (see Section 2.2.1.3);
  4. no confirmation message is required.
 In terms of message flow, this scheme means that the only message
 required is sent from the CA to the end entity. The message must
 contain the entire PSE for the end entity. Some out-of-band means
 must be provided to allow the end entity to authenticate the message
 received and decrypt any encrypted values.

Adams & Farrell Standards Track [Page 12] RFC 2510 PKI Certificate Management Protocols March 1999

2.2.2.2 Basic authenticated scheme

 In terms of the classification above, this scheme is where:
  1. initiation occurs at the end entity;
  2. message authentication is REQUIRED;
  3. "key generation" occurs at the end entity (see Section 2.2.1.3);
  4. a confirmation message is REQUIRED.
 In terms of message flow, the basic authenticated scheme is as
 follows:
    End entity                                          RA/CA
    ==========                                      =============
         out-of-band distribution of Initial Authentication
         Key (IAK) and reference value (RA/CA -> EE)
    Key generation
    Creation of certification request
    Protect request with IAK
                  -->>--certification request-->>--
                                                   verify request
                                                   process request
                                                   create response
                  --<<--certification response--<<--
    handle response
    create confirmation
                  -->>--confirmation message-->>--
                                                   verify confirmation
 (Where verification of the confirmation message fails, the RA/CA MUST
 revoke the newly issued certificate if it has been published or
 otherwise made available.)

2.3 Proof of Possession (POP) of Private Key

 In order to prevent certain attacks and to allow a CA/RA to properly
 check the validity of the binding between an end entity and a key
 pair, the PKI management operations specified here make it possible
 for an end entity to prove that it has possession of (i.e., is able
 to use) the private key corresponding to the public key for which a
 certificate is requested.  A given CA/RA is free to choose how to
 enforce POP (e.g., out-of-band procedural means versus PKIX-CMP in-
 band messages) in its certification exchanges (i.e., this may be a
 policy issue).  However, it is REQUIRED that CAs/RAs MUST enforce POP
 by some means because there are currently many non-PKIX operational
 protocols in use (various electronic mail protocols are one example)
 that do not explicitly check the binding between the end entity and
 the private key.  Until operational protocols that do verify the

Adams & Farrell Standards Track [Page 13] RFC 2510 PKI Certificate Management Protocols March 1999

 binding (for signature, encryption, and key agreement key pairs)
 exist, and are ubiquitous, this binding can only be assumed to have
 been verified by the CA/RA. Therefore, if the binding is not verified
 by the CA/RA, certificates in the Internet Public-Key Infrastructure
 end up being somewhat less meaningful.
 POP is accomplished in different ways depending upon the type of key
 for which a certificate is requested. If a key can be used for
 multiple purposes (e.g., an RSA key) then any appropriate method MAY
 be used (e.g., a key which may be used for signing, as well as other
 purposes, SHOULD NOT be sent to the CA/RA in order to prove
 possession).
 This specification explicitly allows for cases where an end entity
 supplies the relevant proof to an RA and the RA subsequently attests
 to the CA that the required proof has been received (and validated!).
 For example, an end entity wishing to have a signing key certified
 could send the appropriate signature to the RA which then simply
 notifies the relevant CA that the end entity has supplied the
 required proof. Of course, such a situation may be disallowed by some
 policies (e.g., CAs may be the only entities permitted to verify POP
 during certification).

2.3.1 Signature Keys

 For signature keys, the end entity can sign a value to prove
 possession of the private key.

2.3.2 Encryption Keys

 For encryption keys, the end entity can provide the private key to
 the CA/RA, or can be required to decrypt a value in order to prove
 possession of the private key (see Section 3.2.8). Decrypting a value
 can be achieved either directly or indirectly.
 The direct method is for the RA/CA to issue a random challenge to
 which an immediate response by the EE is required.
 The indirect method is to issue a certificate which is encrypted for
 the end entity (and have the end entity demonstrate its ability to
 decrypt this certificate in the confirmation message). This allows a
 CA to issue a certificate in a form which can only be used by the
 intended end entity.
 This specification encourages use of the indirect method because this
 requires no extra messages to be sent (i.e., the proof can be
 demonstrated using the {request, response, confirmation} triple of
 messages).

Adams & Farrell Standards Track [Page 14] RFC 2510 PKI Certificate Management Protocols March 1999

2.3.3 Key Agreement Keys

 For key agreement keys, the end entity and the PKI management entity
 (i.e., CA or RA) must establish a shared secret key in order to prove
 that the end entity has possession of the private key.
 Note that this need not impose any restrictions on the keys that can
 be certified by a given CA -- in particular, for Diffie-Hellman keys
 the end entity may freely choose its algorithm parameters -- provided
 that the CA can generate a short-term (or one-time) key pair with the
 appropriate parameters when necessary.

2.4 Root CA key update

 This discussion only applies to CAs that are a root CA for some end
 entity.
 The basis of the procedure described here is that the CA protects its
 new public key using its previous private key and vice versa. Thus
 when a CA updates its key pair it must generate two extra
 cACertificate attribute values if certificates are made available
 using an X.500 directory (for a total of four:  OldWithOld;
 OldWithNew; NewWithOld; and NewWithNew).
 When a CA changes its key pair those entities who have acquired the
 old CA public key via "out-of-band" means are most affected. It is
 these end entities who will need access to the new CA public key
 protected with the old CA private key. However, they will only
 require this for a limited period (until they have acquired the new
 CA public key via the "out-of-band" mechanism). This will typically
 be easily achieved when these end entities' certificates expire.
 The data structure used to protect the new and old CA public keys is
 a standard certificate (which may also contain extensions). There are
 no new data structures required.
 Note 1. This scheme does not make use of any of the X.509 v3
 extensions as it must be able to work even for version 1
 certificates. The presence of the KeyIdentifier extension would make
 for efficiency improvements.
 Note 2. While the scheme could be generalized to cover cases where
 the CA updates its key pair more than once during the validity period
 of one of its end entities' certificates, this generalization seems
 of dubious value. Not having this generalization simply means that
 the validity period of a CA key pair must be greater than the
 validity period of any certificate issued by that CA using that key
 pair.

Adams & Farrell Standards Track [Page 15] RFC 2510 PKI Certificate Management Protocols March 1999

 Note 3.This scheme forces end entities to acquire the new CA public
 key on the expiry of the last certificate they owned that was signed
 with the old CA private key (via the "out-of-band" means).
 Certificate and/or key update operations occurring at other times do
 not necessarily require this (depending on the end entity's
 equipment).

2.4.1 CA Operator actions

 To change the key of the CA, the CA operator does the following:
    1. Generate a new key pair;
    2. Create a certificate containing the old CA public key signed
       with the new private key (the "old with new" certificate);
    3. Create a certificate containing the new CA public key signed
       with the old private key (the "new with old" certificate);
    4. Create a certificate containing the new CA public key signed
       with the new private key (the "new with new" certificate);
    5. Publish these new certificates via the directory and/or other
       means (perhaps using a CAKeyUpdAnn message);
    6. Export the new CA public key so that end entities may acquire
       it using the "out-of-band" mechanism (if required).
 The old CA private key is then no longer required. The old CA public
 key will however remain in use for some time. The time when the old
 CA public key is no longer required (other than for non-repudiation)
 will be when all end entities of this CA have securely acquired the
 new CA public key.
 The "old with new" certificate must have a validity period starting
 at the generation time of the old key pair and ending at the expiry
 date of the old public key.
 The "new with old" certificate must have a validity period starting
 at the generation time of the new key pair and ending at the time by
 which all end entities of this CA will securely possess the new CA
 public key (at the latest, the expiry date of the old public key).
 The "new with new" certificate must have a validity period starting
 at the generation time of the new key pair and ending at the time by
 which the CA will next update its key pair.

Adams & Farrell Standards Track [Page 16] RFC 2510 PKI Certificate Management Protocols March 1999

2.4.2 Verifying Certificates.

 Normally when verifying a signature, the verifier verifies (among
 other things) the certificate containing the public key of the
 signer. However, once a CA is allowed to update its key there are a
 range of new possibilities. These are shown in the table below.
             Repository contains NEW     Repository contains only OLD
               and OLD public keys        public key (due to, e.g.,
                                           delay in publication)
                PSE      PSE Contains  PSE Contains    PSE Contains
             Contains     OLD public    NEW public      OLD public
            NEW public       key            key            key
                key
 Signer's   Case 1:      Case 3:       Case 5:        Case 7:
 certifi-   This is      In this case  Although the   In this case
 cate is    the          the verifier  CA operator    the CA
 protected  standard     must access   has not        operator  has
 using NEW  case where   the           updated the    not updated
 public     the          directory in  directory the  the directory
 key        verifier     order to get  verifier can   and so the
            can          the value of  verify the     verification
            directly     the NEW       certificate    will FAIL
            verify the   public key    directly -
            certificate                this is thus
            without                    the same as
            using the                  case 1.
            directory
 Signer's   Case 2:      Case 4:       Case 6:        Case 8:
 certifi-   In this      In this case  The verifier   Although the
 cate is    case the     the verifier  thinks this    CA operator
 protected  verifier     can directly  is the         has not
 using OLD  must         verify the    situation of   updated the
 public     access the   certificate   case 2 and     directory the
 key        directory    without       will access    verifier can
            in order     using the     the            verify the
            to get the   directory     directory;     certificate
            value of                   however, the   directly -
            the OLD                    verification   this is thus
            public key                 will FAIL      the same as
                                                      case 4.

Adams & Farrell Standards Track [Page 17] RFC 2510 PKI Certificate Management Protocols March 1999

2.4.2.1 Verification in cases 1, 4, 5 and 8.

 In these cases the verifier has a local copy of the CA public key
 which can be used to verify the certificate directly. This is the
 same as the situation where no key change has occurred.
 Note that case 8 may arise between the time when the CA operator has
 generated the new key pair and the time when the CA operator stores
 the updated attributes in the directory. Case 5 can only arise if the
 CA operator has issued both the signer's and verifier's certificates
 during this "gap" (the CA operator SHOULD avoid this as it leads to
 the failure cases described below).

2.4.2.2 Verification in case 2.

 In case 2 the verifier must get access to the old public key of the
 CA. The verifier does the following:
    1. Look up the caCertificate attribute in the directory and pick
       the OldWithNew certificate (determined based on validity
       periods);
    2. Verify that this is correct using the new CA key (which the
       verifier has locally);
    3. If correct, check the signer's certificate using the old CA
       key.
 Case 2 will arise when the CA operator has issued the signer's
 certificate, then changed key and then issued the verifier's
 certificate, so it is quite a typical case.

2.4.2.3 Verification in case 3.

 In case 3 the verifier must get access to the new public key of the
 CA. The verifier does the following:
    1. Look up the CACertificate attribute in the directory and pick
       the NewWithOld certificate (determined based on validity
       periods);
    2. Verify that this is correct using the old CA key (which the
       verifier has stored locally);
    3. If correct, check the signer's certificate using the new CA
       key.
 Case 3 will arise when the CA operator has issued the verifier's
 certificate, then changed key and then issued the signer's
 certificate, so it is also quite a typical case.

Adams & Farrell Standards Track [Page 18] RFC 2510 PKI Certificate Management Protocols March 1999

2.4.2.4 Failure of verification in case 6.

 In this case the CA has issued the verifier's PSE containing the new
 key without updating the directory attributes. This means that the
 verifier has no means to get a trustworthy version of the CA's old
 key and so verification fails.
 Note that the failure is the CA operator's fault.

2.4.2.5 Failure of verification in case 7.

 In this case the CA has issued the signer's certificate protected
 with the new key without updating the directory attributes. This
 means that the verifier has no means to get a trustworthy version of
 the CA's new key and so verification fails.
 Note that the failure is again the CA operator's fault.

2.4.3 Revocation - Change of CA key

 As we saw above the verification of a certificate becomes more
 complex once the CA is allowed to change its key. This is also true
 for revocation checks as the CA may have signed the CRL using a newer
 private key than the one that is within the user's PSE.
 The analysis of the alternatives is as for certificate verification.

3. Data Structures

 This section contains descriptions of the data structures required
 for PKI management messages. Section 4 describes constraints on their
 values and the sequence of events for each of the various PKI
 management operations. Section 5 describes how these may be
 encapsulated in various transport mechanisms.

3.1 Overall PKI Message

 All of the messages used in this specification for the purposes of
 PKI management use the following structure:
   PKIMessage ::= SEQUENCE {
       header           PKIHeader,
       body             PKIBody,
       protection   [0] PKIProtection OPTIONAL,
       extraCerts   [1] SEQUENCE SIZE (1..MAX) OF Certificate OPTIONAL
   }

Adams & Farrell Standards Track [Page 19] RFC 2510 PKI Certificate Management Protocols March 1999

 The PKIHeader contains information which is common to many PKI
 messages.
 The PKIBody contains message-specific information.
 The PKIProtection, when used, contains bits that protect the PKI
 message.
 The extraCerts field can contain certificates that may be useful to
 the recipient. For example, this can be used by a CA or RA to present
 an end entity with certificates that it needs to verify its own new
 certificate (if, for example, the CA that issued the end entity's
 certificate is not a root CA for the end entity).  Note that this
 field does not necessarily contain a certification path - the
 recipient may have to sort, select from, or otherwise process the
 extra certificates in order to use them.

3.1.1 PKI Message Header

 All PKI messages require some header information for addressing and
 transaction identification. Some of this information will also be
 present in a transport-specific envelope; however, if the PKI message
 is protected then this information is also protected (i.e., we make
 no assumption about secure transport).
 The following data structure is used to contain this information:
   PKIHeader ::= SEQUENCE {
       pvno                INTEGER     { ietf-version2 (1) },
       sender              GeneralName,
       -- identifies the sender
       recipient           GeneralName,
       -- identifies the intended recipient
       messageTime     [0] GeneralizedTime         OPTIONAL,
       -- time of production of this message (used when sender
       -- believes that the transport will be "suitable"; i.e.,
       -- that the time will still be meaningful upon receipt)
       protectionAlg   [1] AlgorithmIdentifier     OPTIONAL,
       -- algorithm used for calculation of protection bits
       senderKID       [2] KeyIdentifier           OPTIONAL,
       recipKID        [3] KeyIdentifier           OPTIONAL,
       -- to identify specific keys used for protection
       transactionID   [4] OCTET STRING            OPTIONAL,
       -- identifies the transaction; i.e., this will be the same in
       -- corresponding request, response and confirmation messages
       senderNonce     [5] OCTET STRING            OPTIONAL,
       recipNonce      [6] OCTET STRING            OPTIONAL,
       -- nonces used to provide replay protection, senderNonce

Adams & Farrell Standards Track [Page 20] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - is inserted by the creator of this message; recipNonce
  2. - is a nonce previously inserted in a related message by
  3. - the intended recipient of this message

freeText [7] PKIFreeText OPTIONAL,

  1. - this may be used to indicate context-specific instructions
  2. - (this field is intended for human consumption)

generalInfo [8] SEQUENCE SIZE (1..MAX) OF

                              InfoTypeAndValue     OPTIONAL
       -- this may be used to convey context-specific information
       -- (this field not primarily intended for human consumption)
   }
   PKIFreeText ::= SEQUENCE SIZE (1..MAX) OF UTF8String
       -- text encoded as UTF-8 String (note:  each UTF8String SHOULD
       -- include an RFC 1766 language tag to indicate the language
       -- of the contained text)
 The pvno field is fixed (at one) for this version of this
 specification.
 The sender field contains the name of the sender of the PKIMessage.
 This name (in conjunction with senderKID, if supplied) should be
 usable to verify the protection on the message.  If nothing about the
 sender is known to the sending entity (e.g., in the init. req.
 message, where the end entity may not know its own Distinguished Name
 (DN), e-mail name, IP address, etc.), then the "sender" field MUST
 contain a "NULL" value; that is, the SEQUENCE OF relative
 distinguished names is of zero length. In such a case the senderKID
 field MUST hold an identifier (i.e., a reference number) which
 indicates to the receiver the appropriate shared secret information
 to use to verify the message.
 The recipient field contains the name of the recipient of the
 PKIMessage. This name (in conjunction with recipKID, if supplied)
 should be usable to verify the protection on the message.
 The protectionAlg field specifies the algorithm used to protect the
 message. If no protection bits are supplied (note that PKIProtection
 is OPTIONAL) then this field MUST be omitted; if protection bits are
 supplied then this field MUST be supplied.
 senderKID and recipKID are usable to indicate which keys have been
 used to protect the message (recipKID will normally only be required
 where protection of the message uses Diffie-Hellman (DH) keys).

Adams & Farrell Standards Track [Page 21] RFC 2510 PKI Certificate Management Protocols March 1999

 The transactionID field within the message header MAY be used to
 allow the recipient of a response message to correlate this with a
 previously issued request. For example, in the case of an RA there
 may be many requests "outstanding" at a given moment.
 The senderNonce and recipNonce fields protect the PKIMessage against
 replay attacks.
 The messageTime field contains the time at which the sender created
 the message. This may be useful to allow end entities to correct
 their local time to be consistent with the time on a central system.
 The freeText field may be used to send a human-readable message to
 the recipient (in any number of languages).  The first language used
 in this sequence indicates the desired language for replies.
 The generalInfo field may be used to send machine-processable
 additional data to the recipient.

3.1.2 PKI Message Body

   PKIBody ::= CHOICE {       -- message-specific body elements
       ir      [0]  CertReqMessages,        --Initialization Request
       ip      [1]  CertRepMessage,         --Initialization Response
       cr      [2]  CertReqMessages,        --Certification Request
       cp      [3]  CertRepMessage,         --Certification Response
       p10cr   [4]  CertificationRequest,   --PKCS #10 Cert. Req.
         -- the PKCS #10 certification request (see [PKCS10])
       popdecc [5]  POPODecKeyChallContent, --pop Challenge
       popdecr [6]  POPODecKeyRespContent,  --pop Response
       kur     [7]  CertReqMessages,        --Key Update Request
       kup     [8]  CertRepMessage,         --Key Update Response
       krr     [9]  CertReqMessages,        --Key Recovery Request
       krp     [10] KeyRecRepContent,       --Key Recovery Response
       rr      [11] RevReqContent,          --Revocation Request
       rp      [12] RevRepContent,          --Revocation Response
       ccr     [13] CertReqMessages,        --Cross-Cert. Request
       ccp     [14] CertRepMessage,         --Cross-Cert. Response
       ckuann  [15] CAKeyUpdAnnContent,     --CA Key Update Ann.
       cann    [16] CertAnnContent,         --Certificate Ann.
       rann    [17] RevAnnContent,          --Revocation Ann.
       crlann  [18] CRLAnnContent,          --CRL Announcement
       conf    [19] PKIConfirmContent,      --Confirmation
       nested  [20] NestedMessageContent,   --Nested Message
       genm    [21] GenMsgContent,          --General Message
       genp    [22] GenRepContent,          --General Response
       error   [23] ErrorMsgContent         --Error Message
   }

Adams & Farrell Standards Track [Page 22] RFC 2510 PKI Certificate Management Protocols March 1999

 The specific types are described in Section 3.3 below.

3.1.3 PKI Message Protection

 Some PKI messages will be protected for integrity. (Note that if an
 asymmetric algorithm is used to protect a message and the relevant
 public component has been certified already, then the origin of
 message can also be authenticated.  On the other hand, if the public
 component is uncertified then the message origin cannot be
 automatically authenticated, but may be authenticated via out-of-band
 means.)
 When protection is applied the following structure is used:
   PKIProtection ::= BIT STRING
 The input to the calculation of PKIProtection is the DER encoding of
 the following data structure:
   ProtectedPart ::= SEQUENCE {
       header    PKIHeader,
       body      PKIBody
   }
 There MAY be cases in which the PKIProtection BIT STRING is
 deliberately not used to protect a message (i.e., this OPTIONAL field
 is omitted) because other protection, external to PKIX, will instead
 be applied. Such a choice is explicitly allowed in this
 specification.  Examples of such external protection include PKCS #7
 [PKCS7] and Security Multiparts [RFC1847] encapsulation of the
 PKIMessage (or simply the PKIBody (omitting the CHOICE tag), if the
 relevant PKIHeader information is securely carried in the external
 mechanism); specification of external protection using PKCS #7 will
 be provided in a separate document.  It is noted, however, that many
 such external mechanisms require that the end entity already
 possesses a public-key certificate, and/or a unique Distinguished
 Name, and/or other such infrastructure-related information. Thus,
 they may not be appropriate for initial registration, key-recovery,
 or any other process with "boot-strapping" characteristics.  For
 those cases it may be necessary that the PKIProtection parameter be
 used.  In the future, if/when external mechanisms are modified to
 accommodate boot-strapping scenarios, the use of PKIProtection may
 become rare or non-existent.
 Depending on the circumstances the PKIProtection bits may contain a
 Message Authentication Code (MAC) or signature. Only the following
 cases can occur:

Adams & Farrell Standards Track [Page 23] RFC 2510 PKI Certificate Management Protocols March 1999

  1. shared secret information
 In this case the sender and recipient share secret information
 (established via out-of-band means or from a previous PKI management
 operation).  PKIProtection will contain a MAC value and the
 protectionAlg will be the following:
   PasswordBasedMac ::= OBJECT IDENTIFIER --{1 2 840 113533 7 66 13}
   PBMParameter ::= SEQUENCE {
       salt                OCTET STRING,
       owf                 AlgorithmIdentifier,
       -- AlgId for a One-Way Function (SHA-1 recommended)
       iterationCount      INTEGER,
       -- number of times the OWF is applied
       mac                 AlgorithmIdentifier
       -- the MAC AlgId (e.g., DES-MAC, Triple-DES-MAC [PKCS11],
   }   -- or HMAC [RFC2104, RFC2202])
 In the above protectionAlg the salt value is appended to the shared
 secret input. The OWF is then applied iterationCount times, where the
 salted secret is the input to the first iteration and, for each
 successive iteration, the input is set to be the output of the
 previous iteration. The output of the final iteration (called
 "BASEKEY" for ease of reference, with a size of "H") is what is used
 to form the symmetric key. If the MAC algorithm requires a K-bit key
 and K <= H, then the most significant K bits of BASEKEY are used. If
 K > H, then all of BASEKEY is used for the most significant H bits of
 the key, OWF("1" || BASEKEY) is used for the next most significant H
 bits of the key, OWF("2" || BASEKEY) is used for the next most
 significant H bits of the key, and so on, until all K bits have been
 derived. [Here "N" is the ASCII byte encoding the number N and "||"
 represents concatenation.]
  1. DH key pairs
 Where the sender and receiver possess Diffie-Hellman certificates
 with compatible DH parameters, then in order to protect the message
 the end entity must generate a symmetric key based on its private DH
 key value and the DH public key of the recipient of the PKI message.
 PKIProtection will contain a MAC value keyed with this derived
 symmetric key and the protectionAlg will be the following:

Adams & Farrell Standards Track [Page 24] RFC 2510 PKI Certificate Management Protocols March 1999

   DHBasedMac ::= OBJECT IDENTIFIER --{1 2 840 113533 7 66 30}
   DHBMParameter ::= SEQUENCE {
       owf                 AlgorithmIdentifier,
       -- AlgId for a One-Way Function (SHA-1 recommended)
       mac                 AlgorithmIdentifier
       -- the MAC AlgId (e.g., DES-MAC, Triple-DES-MAC [PKCS11],
   }   -- or HMAC [RFC2104, RFC2202])
 In the above protectionAlg OWF is applied to the result of the
 Diffie-Hellman computation. The OWF output (called "BASEKEY" for ease
 of reference, with a size of "H") is what is used to form the
 symmetric key. If the MAC algorithm requires a K-bit key and K <= H,
 then the most significant K bits of BASEKEY are used. If K > H, then
 all of BASEKEY is used for the most significant H bits of the key,
 OWF("1" || BASEKEY) is used for the next most significant H bits of
 the key, OWF("2" || BASEKEY) is used for the next most significant H
 bits of the key, and so on, until all K bits have been derived. [Here
 "N" is the ASCII byte encoding the number N and "||" represents
 concatenation.]
  1. signature
 Where the sender possesses a signature key pair it may simply sign
 the PKI message. PKIProtection will contain the signature value and
 the protectionAlg will be an AlgorithmIdentifier for a digital
 signature (e.g., md5WithRSAEncryption or dsaWithSha-1).
  1. multiple protection
 In cases where an end entity sends a protected PKI message to an RA,
 the RA MAY forward that message to a CA, attaching its own protection
 (which MAY be a MAC or a signature, depending on the information and
 certificates shared between the RA and the CA). This is accomplished
 by nesting the entire message sent by the end entity within a new PKI
 message. The structure used is as follows.
   NestedMessageContent ::= PKIMessage

3.2 Common Data Structures

 Before specifying the specific types that may be placed in a PKIBody
 we define some data structures that are used in more than one case.

Adams & Farrell Standards Track [Page 25] RFC 2510 PKI Certificate Management Protocols March 1999

3.2.1 Requested Certificate Contents

 Various PKI management messages require that the originator of the
 message indicate some of the fields that are required to be present
 in a certificate. The CertTemplate structure allows an end entity or
 RA to specify as much as it wishes about the certificate it requires.
 CertTemplate is identical to a Certificate but with all fields
 optional.
 Note that even if the originator completely specifies the contents of
 a certificate it requires, a CA is free to modify fields within the
 certificate actually issued.  If the modified certificate is
 unacceptable to the requester, the Confirmation message may be
 withheld, or an Error Message may be sent (with a PKIStatus of
 "rejection").
 See [CRMF] for CertTemplate syntax.

3.2.2 Encrypted Values

 Where encrypted values (restricted, in this specification, to be
 either private keys or certificates) are sent in PKI messages the
 EncryptedValue data structure is used.
 See [CRMF] for EncryptedValue syntax.
 Use of this data structure requires that the creator and intended
 recipient respectively be able to encrypt and decrypt. Typically,
 this will mean that the sender and recipient have, or are able to
 generate, a shared secret key.
 If the recipient of the PKIMessage already possesses a private key
 usable for decryption, then the encSymmKey field MAY contain a
 session key encrypted using the recipient's public key.

3.2.3 Status codes and Failure Information for PKI messages

 All response messages will include some status information. The
 following values are defined.
   PKIStatus ::= INTEGER {
       granted                (0),
       -- you got exactly what you asked for
       grantedWithMods        (1),
       -- you got something like what you asked for; the
       -- requester is responsible for ascertaining the differences
       rejection              (2),
       -- you don't get it, more information elsewhere in the message

Adams & Farrell Standards Track [Page 26] RFC 2510 PKI Certificate Management Protocols March 1999

       waiting                (3),
       -- the request body part has not yet been processed,
       -- expect to hear more later
       revocationWarning      (4),
       -- this message contains a warning that a revocation is
       -- imminent
       revocationNotification (5),
       -- notification that a revocation has occurred
       keyUpdateWarning       (6)
       -- update already done for the oldCertId specified in
       -- the key update request message
   }
 Responders may use the following syntax to provide more information
 about failure cases.
   PKIFailureInfo ::= BIT STRING {
   -- since we can fail in more than one way!
   -- More codes may be added in the future if/when required.
       badAlg           (0),
       -- unrecognized or unsupported Algorithm Identifier
       badMessageCheck  (1),
       -- integrity check failed (e.g., signature did not verify)
       badRequest       (2),
       -- transaction not permitted or supported
       badTime          (3),
       -- messageTime was not sufficiently close to the system time,
       -- as defined by local policy
       badCertId        (4),
       -- no certificate could be found matching the provided criteria
       badDataFormat    (5),
       -- the data submitted has the wrong format
       wrongAuthority   (6),
       -- the authority indicated in the request is different from the
       -- one creating the response token
       incorrectData    (7),
       -- the requester's data is incorrect (used for notary services)
       missingTimeStamp (8),
       -- when the timestamp is missing but should be there (by policy)
       badPOP           (9)
       -- the proof-of-possession failed
   }
   PKIStatusInfo ::= SEQUENCE {
       status        PKIStatus,
       statusString  PKIFreeText     OPTIONAL,
       failInfo      PKIFailureInfo  OPTIONAL
   }

Adams & Farrell Standards Track [Page 27] RFC 2510 PKI Certificate Management Protocols March 1999

3.2.4 Certificate Identification

 In order to identify particular certificates the CertId data
 structure is used.
 See [CRMF] for CertId syntax.

3.2.5 "Out-of-band" root CA public key

 Each root CA must be able to publish its current public key via some
 "out-of-band" means. While such mechanisms are beyond the scope of
 this document, we define data structures which can support such
 mechanisms.
 There are generally two methods available: either the CA directly
 publishes its self-signed certificate; or this information is
 available via the Directory (or equivalent) and the CA publishes a
 hash of this value to allow verification of its integrity before use.
   OOBCert ::= Certificate
 The fields within this certificate are restricted as follows:
  1. The certificate MUST be self-signed (i.e., the signature must be

verifiable using the SubjectPublicKeyInfo field);

  1. The subject and issuer fields MUST be identical;
  2. If the subject field is NULL then both subjectAltNames and

issuerAltNames extensions MUST be present and have exactly the same

   value;
 - The values of all other extensions must be suitable for a self-
   signed certificate (e.g., key identifiers for subject and issuer
   must be the same).
   OOBCertHash ::= SEQUENCE {
       hashAlg     [0] AlgorithmIdentifier     OPTIONAL,
       certId      [1] CertId                  OPTIONAL,
       hashVal         BIT STRING
       -- hashVal is calculated over the self-signed
       -- certificate with the identifier certID.
   }
 The intention of the hash value is that anyone who has securely
 received the hash value (via the out-of-band means) can verify a
 self- signed certificate for that CA.

Adams & Farrell Standards Track [Page 28] RFC 2510 PKI Certificate Management Protocols March 1999

3.2.6 Archive Options

 Requesters may indicate that they wish the PKI to archive a private
 key value using the PKIArchiveOptions structure
 See [CRMF] for PKIArchiveOptions syntax.

3.2.7 Publication Information

 Requesters may indicate that they wish the PKI to publish a
 certificate using the PKIPublicationInfo structure.
 See [CRMF] for PKIPublicationInfo syntax.

3.2.8 Proof-of-Possession Structures

 If the certification request is for a signing key pair (i.e., a
 request for a verification certificate), then the proof of possession
 of the private signing key is demonstrated through use of the
 POPOSigningKey structure.
 See [CRMF] for POPOSigningKey syntax, but note that
 POPOSigningKeyInput has the following semantic stipulations in this
 specification.
   POPOSigningKeyInput ::= SEQUENCE {
       authInfo            CHOICE {
           sender              [0] GeneralName,
           -- from PKIHeader (used only if an authenticated identity
           -- has been established for the sender (e.g., a DN from a
           -- previously-issued and currently-valid certificate))
           publicKeyMAC        [1] PKMACValue
           -- used if no authenticated GeneralName currently exists for
           -- the sender; publicKeyMAC contains a password-based MAC
           -- (using the protectionAlg AlgId from PKIHeader) on the
           -- DER-encoded value of publicKey
       },
       publicKey           SubjectPublicKeyInfo    -- from CertTemplate
   }
 On the other hand, if the certification request is for an encryption
 key pair (i.e., a request for an encryption certificate), then the
 proof of possession of the private decryption key may be demonstrated
 in one of three ways.
    1) By the inclusion of the private key (encrypted) in the
       CertRequest (in the PKIArchiveOptions control structure).

Adams & Farrell Standards Track [Page 29] RFC 2510 PKI Certificate Management Protocols March 1999

    2) By having the CA return not the certificate, but an encrypted
       certificate (i.e., the certificate encrypted under a randomly-
       generated symmetric key, and the symmetric key encrypted under
       the public key for which the certification request is being
       made) -- this is the "indirect" method mentioned previously in
       Section 2.3.2.  The end entity proves knowledge of the private
       decryption key to the CA by MACing the PKIConfirm message using
       a key derived from this symmetric key.  [Note that if more than
       one CertReqMsg is included in the PKIMessage, then the CA uses
       a different symmetric key for each CertReqMsg and the MAC uses
       a key derived from the concatenation of all these keys.]  The
       MACing procedure uses the PasswordBasedMac AlgId defined in
       Section 3.1.
    3) By having the end entity engage in a challenge-response
       protocol (using the messages POPODecKeyChall and
       POPODecKeyResp; see below) between CertReqMessages and
       CertRepMessage -- this is the "direct" method mentioned
       previously in Section 2.3.2.  [This method would typically be
       used in an environment in which an RA verifies POP and then
       makes a certification request to the CA on behalf of the end
       entity.  In such a scenario, the CA trusts the RA to have done
       POP correctly before the RA requests a certificate for the end
       entity.]  The complete protocol then looks as follows (note
       that req' does not necessarily encapsulate req as a nested
       message):
                      EE            RA            CA
                       ---- req ---->
                       <--- chall ---
                       ---- resp --->
                                     ---- req' --->
                                     <--- rep -----
                                     ---- conf --->
                       <--- rep -----
                       ---- conf --->
 This protocol is obviously much longer than the 3-way exchange given
 in choice (2) above, but allows a local Registration Authority to be
 involved and has the property that the certificate itself is not
 actually created until the proof of possession is complete.
 If the cert. request is for a key agreement key (KAK) pair, then the
 POP can use any of the 3 ways described above for enc. key pairs,
 with the following changes:  (1) the parenthetical text of bullet 2)
 is replaced with "(i.e., the certificate encrypted under the
 symmetric key derived from the CA's private KAK and the public key
 for which the certification request is being made)"; (2) the first

Adams & Farrell Standards Track [Page 30] RFC 2510 PKI Certificate Management Protocols March 1999

 parenthetical text of the challenge field of "Challenge" below is
 replaced with "(using PreferredSymmAlg (see Appendix B6) and a
 symmetric key derived from the CA's private KAK and the public key
 for which the certification request is being made)".  Alternatively,
 the POP can use the POPOSigningKey structure given in [CRMF] (where
 the alg field is DHBasedMAC and the signature field is the MAC) as a
 fourth alternative for demonstrating POP if the CA already has a D-H
 certificate that is known to the EE.
 The challenge-response messages for proof of possession of a private
 decryption key are specified as follows (see [MvOV97, p.404] for
 details).  Note that this challenge-response exchange is associated
 with the preceding cert. request message (and subsequent cert.
 response and confirmation messages) by the nonces used in the
 PKIHeader and by the protection (MACing or signing) applied to the
 PKIMessage.
   POPODecKeyChallContent ::= SEQUENCE OF Challenge
   -- One Challenge per encryption key certification request (in the
   -- same order as these requests appear in CertReqMessages).
   Challenge ::= SEQUENCE {
       owf                 AlgorithmIdentifier  OPTIONAL,
       -- MUST be present in the first Challenge; MAY be omitted in any
       -- subsequent Challenge in POPODecKeyChallContent (if omitted,
       -- then the owf used in the immediately preceding Challenge is
       -- to be used).
       witness             OCTET STRING,
       -- the result of applying the one-way function (owf) to a
       -- randomly-generated INTEGER, A.  [Note that a different
       -- INTEGER MUST be used for each Challenge.]
       challenge           OCTET STRING
       -- the encryption (under the public key for which the cert.
       -- request is being made) of Rand, where Rand is specified as
       --   Rand ::= SEQUENCE {
       --      int      INTEGER,
       --       - the randomly-generated INTEGER A (above)
       --      sender   GeneralName
       --       - the sender's name (as included in PKIHeader)
       --   }
   }
   POPODecKeyRespContent ::= SEQUENCE OF INTEGER
   -- One INTEGER per encryption key certification request (in the
   -- same order as these requests appear in CertReqMessages).  The
   -- retrieved INTEGER A (above) is returned to the sender of the
   -- corresponding Challenge.

Adams & Farrell Standards Track [Page 31] RFC 2510 PKI Certificate Management Protocols March 1999

3.3 Operation-Specific Data Structures

3.3.1 Initialization Request

 An Initialization request message contains as the PKIBody an
 CertReqMessages data structure which specifies the requested
 certificate(s).  Typically, SubjectPublicKeyInfo, KeyId, and Validity
 are the template fields which may be supplied for each certificate
 requested (see Appendix B profiles for further information).  This
 message is intended to be used for entities first initializing into
 the PKI.
 See [CRMF] for CertReqMessages syntax.

3.3.2 Initialization Response

 An Initialization response message contains as the PKIBody an
 CertRepMessage data structure which has for each certificate
 requested a PKIStatusInfo field, a subject certificate, and possibly
 a private key (normally encrypted with a session key, which is itself
 encrypted with the protocolEncKey).
 See Section 3.3.4 for CertRepMessage syntax.  Note that if the PKI
 Message Protection is "shared secret information" (see Section
 3.1.3), then any certificate transported in the caPubs field may be
 directly trusted as a root CA certificate by the initiator.

3.3.3 Registration/Certification Request

 A Registration/Certification request message contains as the PKIBody
 a CertReqMessages data structure which specifies the requested
 certificates.  This message is intended to be used for existing PKI
 entities who wish to obtain additional certificates.
 See [CRMF] for CertReqMessages syntax.
 Alternatively, the PKIBody MAY be a CertificationRequest (this
 structure is fully specified by the ASN.1 structure
 CertificationRequest given in [PKCS10]).  This structure may be
 required for certificate requests for signing key pairs when
 interoperation with legacy systems is desired, but its use is
 strongly discouraged whenever not absolutely necessary.

Adams & Farrell Standards Track [Page 32] RFC 2510 PKI Certificate Management Protocols March 1999

3.3.4 Registration/Certification Response

 A registration response message contains as the PKIBody a
 CertRepMessage data structure which has a status value for each
 certificate requested, and optionally has a CA public key, failure
 information, a subject certificate, and an encrypted private key.
CertRepMessage ::= SEQUENCE {
    caPubs          [1] SEQUENCE SIZE (1..MAX) OF Certificate OPTIONAL,
    response            SEQUENCE OF CertResponse
}
CertResponse ::= SEQUENCE {
    certReqId           INTEGER,
    -- to match this response with corresponding request (a value
    -- of -1 is to be used if certReqId is not specified in the
    -- corresponding request)
    status              PKIStatusInfo,
    certifiedKeyPair    CertifiedKeyPair    OPTIONAL,
    rspInfo             OCTET STRING        OPTIONAL
    -- analogous to the id-regInfo-asciiPairs OCTET STRING defined
    -- for regInfo in CertReqMsg [CRMF]
}
CertifiedKeyPair ::= SEQUENCE {
    certOrEncCert       CertOrEncCert,
    privateKey      [0] EncryptedValue      OPTIONAL,
    publicationInfo [1] PKIPublicationInfo  OPTIONAL
}
CertOrEncCert ::= CHOICE {
    certificate     [0] Certificate,
    encryptedCert   [1] EncryptedValue
}
 Only one of the failInfo (in PKIStatusInfo) and certificate (in
 CertifiedKeyPair) fields can be present in each CertResponse
 (depending on the status). For some status values (e.g., waiting)
 neither of the optional fields will be present.
 Given an EncryptedCert and the relevant decryption key the
 certificate may be obtained. The purpose of this is to allow a CA to
 return the value of a certificate, but with the constraint that only
 the intended recipient can obtain the actual certificate. The benefit
 of this approach is that a CA may reply with a certificate even in
 the absence of a proof that the requester is the end entity which can
 use the relevant private key (note that the proof is not obtained

Adams & Farrell Standards Track [Page 33] RFC 2510 PKI Certificate Management Protocols March 1999

 until the PKIConfirm message is received by the CA). Thus the CA will
 not have to revoke that certificate in the event that something goes
 wrong with the proof of possession.

3.3.5 Key update request content

 For key update requests the CertReqMessages syntax is used.
 Typically, SubjectPublicKeyInfo, KeyId, and Validity are the template
 fields which may be supplied for each key to be updated.  This
 message is intended to be used to request updates to existing (non-
 revoked and non-expired) certificates.
 See [CRMF] for CertReqMessages syntax.

3.3.6 Key Update response content

 For key update responses the CertRepMessage syntax is used.  The
 response is identical to the initialization response.
 See Section 3.3.4 for CertRepMessage syntax.

3.3.7 Key Recovery Request content

 For key recovery requests the syntax used is identical to the
 initialization request CertReqMessages.  Typically,
 SubjectPublicKeyInfo and KeyId are the template fields which may be
 used to supply a signature public key for which a certificate is
 required (see Appendix B profiles for further information).
 See [CRMF] for CertReqMessages syntax.  Note that if a key history is
 required, the requester must supply a Protocol Encryption Key control
 in the request message.

3.3.8 Key recovery response content

 For key recovery responses the following syntax is used.  For some
 status values (e.g., waiting) none of the optional fields will be
 present.
   KeyRecRepContent ::= SEQUENCE {
       status          PKIStatusInfo,
       newSigCert  [0] Certificate                   OPTIONAL,
       caCerts     [1] SEQUENCE SIZE (1..MAX) OF
                                    Certificate      OPTIONAL,
       keyPairHist [2] SEQUENCE SIZE (1..MAX) OF
                                    CertifiedKeyPair OPTIONAL
   }

Adams & Farrell Standards Track [Page 34] RFC 2510 PKI Certificate Management Protocols March 1999

3.3.9 Revocation Request Content

 When requesting revocation of a certificate (or several certificates)
 the following data structure is used. The name of the requester is
 present in the PKIHeader structure.
   RevReqContent ::= SEQUENCE OF RevDetails
   RevDetails ::= SEQUENCE {
       certDetails         CertTemplate,
       -- allows requester to specify as much as they can about
       -- the cert. for which revocation is requested
       -- (e.g., for cases in which serialNumber is not available)
       revocationReason    ReasonFlags      OPTIONAL,
       -- the reason that revocation is requested
       badSinceDate        GeneralizedTime  OPTIONAL,
       -- indicates best knowledge of sender
       crlEntryDetails     Extensions       OPTIONAL
       -- requested crlEntryExtensions
   }

3.3.10 Revocation Response Content

 The response to the above message. If produced, this is sent to the
 requester of the revocation. (A separate revocation announcement
 message MAY be sent to the subject of the certificate for which
 revocation was requested.)
RevRepContent ::= SEQUENCE {
    status        SEQUENCE SIZE (1..MAX) OF PKIStatusInfo,
    -- in same order as was sent in RevReqContent
    revCerts  [0] SEQUENCE SIZE (1..MAX) OF CertId OPTIONAL,
    -- IDs for which revocation was requested (same order as status)
    crls      [1] SEQUENCE SIZE (1..MAX) OF CertificateList  OPTIONAL
    -- the resulting CRLs (there may be more than one)
}

3.3.11 Cross certification request content

 Cross certification requests use the same syntax (CertReqMessages) as
 for normal certification requests with the restriction that the key
 pair MUST have been generated by the requesting CA and the private
 key MUST NOT be sent to the responding CA.
 See [CRMF] for CertReqMessages syntax.

Adams & Farrell Standards Track [Page 35] RFC 2510 PKI Certificate Management Protocols March 1999

3.3.12 Cross certification response content

 Cross certification responses use the same syntax (CertRepMessage) as
 for normal certification responses with the restriction that no
 encrypted private key can be sent.
 See Section 3.3.4 for CertRepMessage syntax.

3.3.13 CA Key Update Announcement content

 When a CA updates its own key pair the following data structure MAY
 be used to announce this event.
CAKeyUpdAnnContent ::= SEQUENCE {
    oldWithNew          Certificate, -- old pub signed with new priv
    newWithOld          Certificate, -- new pub signed with old priv
    newWithNew          Certificate  -- new pub signed with new priv
}

3.3.14 Certificate Announcement

 This structure MAY be used to announce the existence of certificates.
 Note that this message is intended to be used for those cases (if
 any) where there is no pre-existing method for publication of
 certificates; it is not intended to be used where, for example, X.500
 is the method for publication of certificates.
   CertAnnContent ::= Certificate

3.3.15 Revocation Announcement

 When a CA has revoked, or is about to revoke, a particular
 certificate it MAY issue an announcement of this (possibly upcoming)
 event.
   RevAnnContent ::= SEQUENCE {
       status              PKIStatus,
       certId              CertId,
       willBeRevokedAt     GeneralizedTime,
       badSinceDate        GeneralizedTime,
       crlDetails          Extensions  OPTIONAL
       -- extra CRL details(e.g., crl number, reason, location, etc.)
   }

Adams & Farrell Standards Track [Page 36] RFC 2510 PKI Certificate Management Protocols March 1999

 A CA MAY use such an announcement to warn (or notify) a subject that
 its certificate is about to be (or has been) revoked. This would
 typically be used where the request for revocation did not come from
 the subject concerned.
 The willBeRevokedAt field contains the time at which a new entry will
 be added to the relevant CRLs.

3.3.16 CRL Announcement

 When a CA issues a new CRL (or set of CRLs) the following data
 structure MAY be used to announce this event.
   CRLAnnContent ::= SEQUENCE OF CertificateList

3.3.17 PKI Confirmation content

 This data structure is used in three-way protocols as the final
 PKIMessage. Its content is the same in all cases - actually there is
 no content since the PKIHeader carries all the required information.
   PKIConfirmContent ::= NULL

3.3.18 PKI General Message content

InfoTypeAndValue ::= SEQUENCE {
    infoType               OBJECT IDENTIFIER,
    infoValue              ANY DEFINED BY infoType  OPTIONAL
}
-- Example InfoTypeAndValue contents include, but are not limited to:
--  { CAProtEncCert    = {id-it 1}, Certificate                     }
--  { SignKeyPairTypes = {id-it 2}, SEQUENCE OF AlgorithmIdentifier }
--  { EncKeyPairTypes  = {id-it 3}, SEQUENCE OF AlgorithmIdentifier }
--  { PreferredSymmAlg = {id-it 4}, AlgorithmIdentifier             }
--  { CAKeyUpdateInfo  = {id-it 5}, CAKeyUpdAnnContent              }
--  { CurrentCRL       = {id-it 6}, CertificateList                 }
-- where {id-it} = {id-pkix 4} = {1 3 6 1 5 5 7 4}
-- This construct MAY also be used to define new PKIX Certificate
-- Management Protocol request and response messages, or general-
-- purpose (e.g., announcement) messages for future needs or for
-- specific environments.
GenMsgContent ::= SEQUENCE OF InfoTypeAndValue
-- May be sent by EE, RA, or CA (depending on message content).
-- The OPTIONAL infoValue parameter of InfoTypeAndValue will typically
-- be omitted for some of the examples given above.  The receiver is

Adams & Farrell Standards Track [Page 37] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - free to ignore any contained OBJ. IDs that it does not recognize.
  2. - If sent from EE to CA, the empty set indicates that the CA may send
  3. - any/all information that it wishes.

3.3.19 PKI General Response content

GenRepContent ::= SEQUENCE OF InfoTypeAndValue
-- The receiver is free to ignore any contained OBJ. IDs that it does
-- not recognize.

3.3.20 Error Message content

   ErrorMsgContent ::= SEQUENCE {
       pKIStatusInfo          PKIStatusInfo,
       errorCode              INTEGER           OPTIONAL,
       -- implementation-specific error codes
       errorDetails           PKIFreeText       OPTIONAL
       -- implementation-specific error details
   }

4. Mandatory PKI Management functions

 The PKI management functions outlined in Section 1 above are
 described in this section.
 This section deals with functions that are "mandatory" in the sense
 that all end entity and CA/RA implementations MUST be able to provide
 the functionality described (perhaps via one of the transport
 mechanisms defined in Section 5). This part is effectively the
 profile of the PKI management functionality that MUST be supported.
 Note that not all PKI management functions result in the creation of
 a PKI message.

4.1 Root CA initialization

 [See Section 1.2.2 for this document's definition of "root CA".]
 A newly created root CA must produce a "self-certificate" which is a
 Certificate structure with the profile defined for the "newWithNew"
 certificate issued following a root CA key update.
 In  order to make the CA's self certificate useful to end entities
 that do not acquire the self certificate via "out-of-band" means, the
 CA must also produce a fingerprint for its public key.  End entities
 that acquire this fingerprint securely via some "out-of-band" means
 can then verify the CA's self-certificate and hence the other
 attributes contained therein.

Adams & Farrell Standards Track [Page 38] RFC 2510 PKI Certificate Management Protocols March 1999

 The data structure used to carry the fingerprint is the OOBCertHash.

4.2 Root CA key update

 CA keys (as all other keys) have a finite lifetime and will have to
 be updated on a periodic basis.  The certificates NewWithNew,
 NewWithOld, and OldWithNew (see Section 2.4.1) are issued by the CA
 to aid existing end entities who hold the current self-signed CA
 certificate (OldWithOld) to transition securely to the new self-
 signed CA certificate (NewWithNew), and to aid new end entities who
 will hold NewWithNew to acquire OldWithOld securely for verification
 of existing data.

4.3 Subordinate CA initialization

 [See Section 1.2.2 for this document's definition of "subordinate
 CA".]
 From the perspective of PKI management protocols the initialization
 of a subordinate CA is the same as the initialization of an end
 entity. The only difference is that the subordinate CA must also
 produce an initial revocation list.

4.4 CRL production

 Before issuing any certificates a newly established CA (which issues
 CRLs) must produce "empty" versions of each CRL which is to be
 periodically produced.

4.5 PKI information request

 When a PKI entity (CA, RA, or EE) wishes to acquire information about
 the current status of a CA it MAY send that CA a request for such
 information.
 The CA must respond to the request by providing (at least) all of the
 information requested by the requester.  If some of the information
 cannot be provided then an error must be conveyed to the requester.
 If PKIMessages are used to request and supply this PKI information,
 then the request must be the GenMsg message, the response must be the
 GenRep message, and the error must be the Error message.  These
 messages are protected using a MAC based on shared secret information
 (i.e., PasswordBasedMAC) or any other authenticated means (if the end
 entity has an existing certificate).

Adams & Farrell Standards Track [Page 39] RFC 2510 PKI Certificate Management Protocols March 1999

4.6 Cross certification

 The requester CA is the CA that will become the subject of the
 cross-certificate; the responder CA will become the issuer of the
 cross-certificate.
 The requester CA must be "up and running" before initiating the
 cross-certification operation.

4.6.1 One-way request-response scheme:

 The cross-certification scheme is essentially a one way operation;
 that is, when successful, this operation results in the creation of
 one new cross-certificate. If the requirement is that cross-
 certificates be created in "both directions" then each CA in turn
 must initiate a cross-certification operation (or use another
 scheme).
 This scheme is suitable where the two CAs in question can already
 verify each other's signatures (they have some common points of
 trust) or where there is an out-of-band verification of the origin of
 the certification request.
 Detailed Description:
 Cross certification is initiated at one CA known as the responder.
 The CA administrator for the responder identifies the CA it wants to
 cross certify and the responder CA equipment generates an
 authorization code.  The responder CA administrator passes this
 authorization code by out-of-band means to the requester CA
 administrator. The requester CA administrator enters the
 authorization code at the requester CA in order to initiate the on-
 line exchange.
 The authorization code is used for authentication and integrity
 purposes. This is done by generating a symmetric key based on the
 authorization code and using the symmetric key for generating Message
 Authentication Codes (MACs) on all messages exchanged.
 The requester CA initiates the exchange by generating a random number
 (requester random number). The requester CA then sends to the
 responder CA the cross certification request (ccr) message. The
 fields in this message are protected from modification with a MAC
 based on the authorization code.
 Upon receipt of the ccr message, the responder CA checks the protocol
 version, saves the requester random number, generates its own random
 number (responder random number) and validates the MAC. It then

Adams & Farrell Standards Track [Page 40] RFC 2510 PKI Certificate Management Protocols March 1999

 generates (and archives, if desired) a new requester certificate that
 contains the requester CA public key and is signed with the responder
 CA signature private key. The responder CA responds with the cross
 certification response (ccp) message. The fields in this message are
 protected from modification with a MAC based on the authorization
 code.
 Upon receipt of the ccp message, the requester CA checks that its own
 system time is close to the responder CA system time, checks the
 received random numbers and validates the MAC.  The requester CA
 responds with the PKIConfirm message. The fields in this message are
 protected from modification with a MAC based on the authorization
 code.  The requester CA writes the requester certificate to the
 Repository.
 Upon receipt of the PKIConfirm message, the responder CA checks the
 random numbers and validates the MAC.
 Notes:
 1. The ccr message must contain a "complete" certification request,
    that is, all fields (including, e.g., a BasicConstraints
    extension) must be specified by the requester CA.
 2. The ccp message SHOULD contain the verification certificate of the
    responder CA - if present, the requester CA must then verify this
    certificate (for example, via the "out-of-band" mechanism).

4.7 End entity initialization

 As with CAs, end entities must be initialized. Initialization of end
 entities requires at least two steps:
  1. acquisition of PKI information
  2. out-of-band verification of one root-CA public key
 (other possible steps include the retrieval of trust condition
 information and/or out-of-band verification of other CA public keys).

4.7.1 Acquisition of PKI information

 The information REQUIRED is:
  1. the current root-CA public key
  2. (if the certifying CA is not a root-CA) the certification path

from the root CA to the certifying CA together with appropriate

      revocation lists
    - the algorithms and algorithm parameters which the certifying CA
      supports for each relevant usage

Adams & Farrell Standards Track [Page 41] RFC 2510 PKI Certificate Management Protocols March 1999

 Additional information could be required (e.g., supported extensions
 or CA policy information) in order to produce a certification request
 which will be successful. However, for simplicity we do not mandate
 that the end entity acquires this information via the PKI messages.
 The end result is simply that some certification requests may fail
 (e.g., if the end entity wants to generate its own encryption key but
 the CA doesn't allow that).
 The required information MAY be acquired as described in Section 4.5.

4.7.2 Out-of-Band Verification of Root-CA Key

 An end entity must securely possess the public key of its root CA.
 One method to achieve this is to provide the end entity with the CA's
 self-certificate fingerprint via some secure "out-of-band" means. The
 end entity can then securely use the CA's self-certificate.
 See Section 4.1 for further details.

4.8 Certificate Request

 An initialized end entity MAY request a certificate at any time (as
 part of an update procedure, or for any other purpose).  This request
 will be made using the certification request (cr) message.  If the
 end entity already possesses a signing key pair (with a corresponding
 verification certificate), then this cr message will typically be
 protected by the entity's digital signature.  The CA returns the new
 certificate (if the request is successful) in a CertRepMessage.

4.9 Key Update

 When a key pair is due to expire the relevant end entity MAY request
 a key update - that is, it MAY request that the CA issue a new
 certificate for a new key pair.  The request is made using a key
 update request (kur) message.  If the end entity already possesses a
 signing key pair (with a corresponding verification certificate),
 then this message will typically be protected by the entity's digital
 signature. The CA returns the new certificate (if the request is
 successful) in a key update response (kup) message, which is
 syntactically identical to a CertRepMessage.

5. Transports

 The transport protocols specified below allow end entities, RAs and
 CAs to pass PKI messages between them. There is no requirement for
 specific security mechanisms to be applied at this level if the PKI
 messages are suitably protected (that is, if the OPTIONAL
 PKIProtection parameter is used as specified for each message).

Adams & Farrell Standards Track [Page 42] RFC 2510 PKI Certificate Management Protocols March 1999

5.1 File based protocol

 A file containing a PKI message MUST contain only the DER encoding of
 one PKI message, i.e., there MUST be no extraneous header or trailer
 information in the file.
 Such files can be used to transport PKI messages using, e.g., FTP.

5.2 Direct TCP-Based Management Protocol

 The following simple TCP-based protocol is to be used for transport
 of PKI messages. This protocol is suitable for cases where an end
 entity (or an RA) initiates a transaction and can poll to pick up the
 results.
 If a transaction is initiated by a PKI entity (RA or CA) then an end
 entity must either supply a listener process or be supplied with a
 polling reference (see below) in order to allow it to pick up the PKI
 message from the PKI management component.
 The protocol basically assumes a listener process on an RA or CA
 which can accept PKI messages on a well-defined port (port number
 829). Typically an initiator binds to this port and submits the
 initial PKI message for a given transaction ID. The responder replies
 with a PKI message and/or with a reference number to be used later
 when polling for the actual PKI message response.
 If a number of PKI response messages are to be produced for a given
 request (say if some part of the request is handled more quickly than
 another) then a new polling reference is also returned.
 When the final PKI response message has been picked up by the
 initiator then no new polling reference is supplied.
 The initiator of a transaction sends a "direct TCP-based PKI message"
 to the recipient. The recipient responds with a similar message.
 A "direct TCP-based PKI message" consists of:
       length (32-bits), flag (8-bits), value (defined below)
 The length field contains the number of octets of the remainder of
 the message (i.e., number of octets of "value" plus one).  All 32-bit
 values in this protocol are specified to be in network byte order.
  Message name   flag     value
  pkiMsg         '00'H    DER-encoded PKI message

Adams & Farrell Standards Track [Page 43] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - PKI message

pollRep '01'H polling reference (32 bits),

                          time-to-check-back (32 bits)
    -- poll response where no PKI message response ready; use polling
    -- reference value (and estimated time value) for later polling
  pollReq        '02'H    polling reference (32 bits)
    -- request for a PKI message response to initial message
  negPollRep     '03'H    '00'H
    -- no further polling responses (i.e., transaction complete)
  partialMsgRep  '04'H    next polling reference (32 bits),
                          time-to-check-back (32 bits),
                          DER-encoded PKI message
    -- partial response to initial message plus new polling reference
    -- (and estimated time value) to use to get next part of response
  finalMsgRep    '05'H    DER-encoded PKI message
    -- final (and possibly sole) response to initial message
  errorMsgRep    '06'H    human readable error message
    -- produced when an error is detected (e.g., a polling reference is
    -- received which doesn't exist or is finished with)
 Where a PKIConfirm message is to be transported (always from the
 initiator to the responder) then a pkiMsg message is sent and a
 negPollRep is returned.
 The sequence of messages which can occur is then:
 a) end entity sends pkiMsg and receives one of pollRep, negPollRep,
 partialMsgRep or finalMsgRep in response.  b) end entity sends
 pollReq message and receives one of negPollRep, partialMsgRep,
 finalMsgRep or errorMsgRep in response.
 The "time-to-check-back" parameter is a 32-bit integer, defined to be
 the number of seconds which have elapsed since midnight, January 1,
 1970, coordinated universal time.  It provides an estimate of the
 time that the end entity should send its next pollReq.

5.3 Management Protocol via E-mail

 This subsection specifies a means for conveying ASN.1-encoded
 messages for the protocol exchanges described in Section 4 via
 Internet mail.
 A simple MIME object is specified as follows.
    Content-Type: application/pkixcmp
    Content-Transfer-Encoding: base64
    <<the ASN.1 DER-encoded PKIX-CMP message, base64-encoded>>

Adams & Farrell Standards Track [Page 44] RFC 2510 PKI Certificate Management Protocols March 1999

 This MIME object can be sent and received using common MIME
 processing engines and provides a simple Internet mail transport for
 PKIX-CMP messages.  Implementations MAY wish to also recognize and
 use the "application/x-pkixcmp" MIME type (specified in earlier
 versions of this document) in order to support backward compatibility
 wherever applicable.

5.4 Management Protocol via HTTP

 This subsection specifies a means for conveying ASN.1-encoded
 messages for the protocol exchanges described in Section 4 via the
 HyperText Transfer Protocol.
 A simple MIME object is specified as follows.
    Content-Type: application/pkixcmp
    <<the ASN.1 DER-encoded PKIX-CMP message>>
 This MIME object can be sent and received using common HTTP
 processing engines over WWW links and provides a simple browser-
 server transport for PKIX-CMP messages.  Implementations MAY wish to
 also recognize and use the "application/x-pkixcmp" MIME type
 (specified in earlier versions of this document) in order to support
 backward compatibility wherever applicable.

SECURITY CONSIDERATIONS

 This entire memo is about security mechanisms.
 One cryptographic consideration is worth explicitly spelling out. In
 the protocols specified above, when an end entity is required to
 prove possession of a decryption key, it is effectively challenged to
 decrypt something (its own certificate). This scheme (and many
 others!) could be vulnerable to an attack if the possessor of the
 decryption key in question could be fooled into decrypting an
 arbitrary challenge and returning the cleartext to an attacker.
 Although in this specification a number of other failures in security
 are required in order for this attack to succeed, it is conceivable
 that some future services (e.g., notary, trusted time) could
 potentially be vulnerable to such attacks. For this reason we re-
 iterate the general rule that implementations should be very careful
 about decrypting arbitrary "ciphertext" and revealing recovered
 "plaintext" since such a practice can lead to serious security
 vulnerabilities.

Adams & Farrell Standards Track [Page 45] RFC 2510 PKI Certificate Management Protocols March 1999

 Note also that exposing a private key to the CA/RA as a proof-of-
 possession technique can carry some security risks (depending upon
 whether or not the CA/RA can be trusted to handle such material
 appropriately).  Implementers are advised to exercise caution in
 selecting and using this particular POP mechanism.

References

 [COR95]   ISO/IEC JTC 1/SC 21, Technical Corrigendum 2 to ISO/IEC
           9594-8: 1990 & 1993 (1995:E), July 1995.
 [CRMF]    Myers, M., Adams, C., Solo, D. and D. Kemp, "Certificate
           Request Message Format", RFC 2511, March 1999.
 [MvOV97]  A. Menezes, P. van Oorschot, S. Vanstone, "Handbook of
           Applied Cryptography", CRC Press, 1997.
 [PKCS7]   RSA Laboratories, "The Public-Key Cryptography Standards
           (PKCS)", RSA Data Security Inc., Redwood City, California,
           November 1993 Release.
 [PKCS10]  RSA Laboratories, "The Public-Key Cryptography Standards
           (PKCS)", RSA Data Security Inc., Redwood City, California,
           November 1993 Release.
 [PKCS11]  RSA Laboratories, "The Public-Key Cryptography Standards -
           PKCS #11:  Cryptographic token interface standard", RSA
           Data Security Inc., Redwood City, California, April 28,
           1995.
 [RFC1847] Galvin, J., Murphy, S. Crocker, S. and N. Freed, "Security
           Multiparts for MIME:  Multipart/Signed and Multipart/
           Encrypted", RFC 1847, October 1995.
 [RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC:  Keyed
           Hashing for Message Authentication", RFC 2104, February
           1997.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2202] Cheng, P. and R. Glenn, "Test Cases for HMAC-MD5 and HMAC-
           SHA-1", RFC 2202, September 1997.
 [X509-AM] ISO/IEC JTC1/SC 21, Draft Amendments DAM 4 to ISO/IEC
           9594-2, DAM 2 to ISO/IEC 9594-6, DAM 1 to ISO/IEC 9594-7,
           and DAM 1 to ISO/IEC 9594-8 on Certificate Extensions, 1
           December, 1996.

Adams & Farrell Standards Track [Page 46] RFC 2510 PKI Certificate Management Protocols March 1999

Acknowledgements

 The authors gratefully acknowledge the contributions of various
 members of the PKIX Working Group.  Many of these contributions
 significantly clarified and improved the utility of this
 specification.

Authors' Addresses

 Carlisle Adams
 Entrust Technologies
 750 Heron Road, Suite E08,
 Ottawa, Ontario
 Canada K1V 1A7
 EMail: cadams@entrust.com
 Stephen Farrell
 Software and Systems Engineering Ltd.
 Fitzwilliam Court
 Leeson Close
 Dublin 2
 IRELAND
 EMail: stephen.farrell@sse.ie

Adams & Farrell Standards Track [Page 47] RFC 2510 PKI Certificate Management Protocols March 1999

APPENDIX A: Reasons for the presence of RAs

 The reasons which justify the presence of an RA can be split into
 those which are due to technical factors and those which are
 organizational in nature. Technical reasons include the following.
  1. If hardware tokens are in use, then not all end entities will have

the equipment needed to initialize these; the RA equipment can

    include the necessary functionality (this may also be a matter of
    policy).
  1. Some end entities may not have the capability to publish

certificates; again, the RA may be suitably placed for this.

  1. The RA will be able to issue signed revocation requests on behalf

of end entities associated with it, whereas the end entity may not

    be able to do this (if the key pair is completely lost).
 Some of the organizational reasons which argue for the presence of an
 RA are the following.
  1. It may be more cost effective to concentrate functionality in the

RA equipment than to supply functionality to all end entities

    (especially if special token initialization equipment is to be
    used).
  1. Establishing RAs within an organization can reduce the number of

CAs required, which is sometimes desirable.

  1. RAs may be better placed to identify people with their

"electronic" names, especially if the CA is physically remote from

    the end entity.
  1. For many applications there will already be in place some

administrative structure so that candidates for the role of RA are

    easy to find (which may not be true of the CA).

Adams & Farrell Standards Track [Page 48] RFC 2510 PKI Certificate Management Protocols March 1999

Appendix B. PKI Management Message Profiles.

 This appendix contains detailed profiles for those PKIMessages which
 MUST be supported by conforming implementations (see Section 4).
 Profiles for the PKIMessages used in the following PKI management
 operations are provided:
  1. root CA key update
  2. information request/response
  3. cross-certification request/response (1-way)
  4. initial registration/certification
    1. basic authenticated scheme
  5. certificate request
  6. key update
 <<Later versions of this document may extend the above to include
 profiles for the operations listed below (along with other
 operations, if desired).>>
  1. revocation request
  2. certificate publication
  3. CRL publication

B1. General Rules for interpretation of these profiles.

 1. Where OPTIONAL or DEFAULT fields are not mentioned in individual
    profiles, they SHOULD be absent from the relevant message (i.e., a
    receiver can validly reject a message containing such fields as
    being syntactically incorrect).
    Mandatory fields are not mentioned if they have an obvious value
    (e.g., pvno).
 2. Where structures occur in more than one message, they are
    separately profiled as appropriate.
 3. The algorithmIdentifiers from PKIMessage structures are profiled
    separately.
 4. A "special" X.500 DN is called the "NULL-DN"; this means a DN
    containing a zero-length SEQUENCE OF RelativeDistinguishedNames
    (its DER encoding is then '3000'H).
 5. Where a GeneralName is required for a field but no suitable
    value is available (e.g., an end entity produces a request before
    knowing its name) then the GeneralName is to be an X.500 NULL-DN
    (i.e., the Name field of the CHOICE is to contain a NULL-DN).
    This special value can be called a "NULL-GeneralName".
 6. Where a profile omits to specify the value for a GeneralName
    then the NULL-GeneralName value is to be present in the relevant
    PKIMessage field. This occurs with the sender field of the
    PKIHeader for some messages.

Adams & Farrell Standards Track [Page 49] RFC 2510 PKI Certificate Management Protocols March 1999

 7. Where any ambiguity arises due to naming of fields, the profile
    names these using a "dot" notation (e.g., "certTemplate.subject"
    means the subject field within a field called certTemplate).
 8. Where a "SEQUENCE OF types" is part of a message, a zero-based
    array notation is used to describe fields within the SEQUENCE OF
    (e.g., crm[0].certReq.certTemplate.subject refers to a
    subfield of the first CertReqMsg contained in a request message).
 9. All PKI message exchanges in Sections B7-B10 require a PKIConfirm
    message to be sent by the initiating entity.  This message is not
    included in some of the profiles given since its body is NULL and
    its header contents are clear from the context.  Any authenticated
    means can be used for the protectionAlg (e.g., password-based MAC,
    if shared secret information is known, or signature).

B2. Algorithm Use Profile

 The following table contains definitions of algorithm uses within PKI
 management protocols.
 The columns in the table are:

Name: an identifier used for message profiles Use: description of where and for what the algorithm is used Mandatory: an AlgorithmIdentifier which MUST be supported by

         conforming implementations

Others: alternatives to the mandatory AlgorithmIdentifier

Name Use Mandatory Others

MSG_SIG_ALG Protection of PKI DSA/SHA-1 RSA/MD5…

              messages using signature

MSG_MAC_ALG protection of PKI PasswordBasedMac HMAC,

              messages using MACing                       X9.9...

SYM_PENC_ALG symmetric encryption of 3-DES (3-key- RC5,

              an end entity's private    EDE, CBC mode)   CAST-128...
              key where symmetric
              key is distributed
              out-of-band

PROT_ENC_ALG asymmetric algorithm D-H RSA

              used for encryption of
              (symmetric keys for
              encryption of) private
              keys transported in
              PKIMessages

PROT_SYM_ALG symmetric encryption 3-DES (3-key- RC5,

              algorithm used for         EDE, CBC mode)   CAST-128...
              encryption of private
              key bits (a key of this

Adams & Farrell Standards Track [Page 50] RFC 2510 PKI Certificate Management Protocols March 1999

              type is encrypted using
              PROT_ENC_ALG)

Mandatory AlgorithmIdentifiers and Specifications:

DSA/SHA-1:

AlgId:  {1 2 840 10040 4 3};
NIST, FIPS PUB 186: Digital Signature Standard, 1994;
Public Modulus size:  1024 bits.

PasswordBasedMac:

{1 2 840 113533 7 66 13}, with SHA-1 {1 3 14 3 2 26} as the owf
  parameter and HMAC-SHA1 {1 3 6 1 5 5 8 1 2} as the mac parameter;
(this specification), along with
NIST, FIPS PUB 180-1: Secure Hash Standard, April 1995;
H. Krawczyk, M. Bellare, R. Canetti, "HMAC:  Keyed-Hashing for Message
  Authentication", Internet Request for Comments 2104, February 1997.

3-DES:

{1 2 840 113549 3 7};
(used in RSA's BSAFE and in S/MIME).

D-H:

AlgId:  {1 2 840 10046 2 1};
ANSI X9.42;
Public Modulus Size:  1024 bits.
DHParameter ::= SEQUENCE {
  prime INTEGER, -- p
  base  INTEGER  -- g
}

B3. "Self-signed" certificates

 Profile of how a Certificate structure may be "self-signed". These
 structures are used for distribution of "root" CA public keys. This
 can occur in one of three ways (see Section 2.4 above for a
 description of the use of these structures):

Type Function

newWithNew a true "self-signed" certificate; the contained public

             key MUST be usable to verify the signature (though this
             provides only integrity and no authentication whatsoever)

oldWithNew previous root CA public key signed with new private key newWithOld new root CA public key signed with previous private key

Adams & Farrell Standards Track [Page 51] RFC 2510 PKI Certificate Management Protocols March 1999

 <<Such certificates (including relevant extensions) must contain
 "sensible" values for all fields.  For example, when present
 subjectAltName MUST be identical to issuerAltName, and when present
 keyIdentifiers must contain appropriate values, et cetera.>>

B4. Proof of Possession Profile

 POP fields for use (in signature field of pop field of
 ProofOfPossession structure) when proving possession of a private
 signing key which corresponds to a public verification key for which
 a certificate has been requested.
  Field               Value         Comment
  algorithmIdentifier MSG_SIG_ALG   only signature protection is
                                    allowed for this proof
  signature           present       bits calculated using MSG_SIG_ALG
 <<Proof of possession of a private decryption key which corresponds
 to a public encryption key for which a certificate has been requested
 does not use this profile; instead the method given in protectionAlg
 for PKIConfirm in Section B8 is used.>>
 Not every CA/RA will do Proof-of-Possession (of signing key,
 decryption key, or key agreement key) in the PKIX-CMP in-band
 certification request protocol (how POP is done MAY ultimately be a
 policy issue which is made explicit for any given CA in its
 publicized Policy OID and Certification Practice Statement).
 However, this specification MANDATES that CA/RA entities MUST do POP
 (by some means) as part of the certification process.  All end
 entities MUST be prepared to provide POP (i.e., these components of
 the PKIX-CMP protocol MUST be supported).

B5. Root CA Key Update

 A root CA updates its key pair. It then produces a CA key update
 announcement message which can be made available (via one of the
 transport mechanisms) to the relevant end entities.  A PKIConfirm
 message is NOT REQUIRED from the end entities.
 ckuann message:
  Field        Value                        Comment
  sender       CA name                      responding CA name
  body         ckuann(CAKeyUpdAnnContent)
  oldWithNew   present                      see Section B3 above

Adams & Farrell Standards Track [Page 52] RFC 2510 PKI Certificate Management Protocols March 1999

  newWithOld   present                      see Section B3 above
  newWithNew   present                      see Section B3 above
  extraCerts   optionally present           can be used to "publish"
                                            certificates (e.g.,
                                            certificates signed using
                                            the new private key)

B6. PKI Information request/response

 The end entity sends general message to the PKI requesting details
 which will be required for later PKI management operations.  RA/CA
 responds with general response. If an RA generates the response then
 it will simply forward the equivalent message which it previously
 received from the CA, with the possible addition of the certificates
 to the extraCerts fields of the PKIMessage.  A PKIConfirm message is
 NOT REQUIRED from the end entity.

Message Flows:

Step# End entity PKI

1     format genm
2                      ->      genm      ->
3                                                   handle genm
4                                                   produce genp
5                      <-      genp      <-
6     handle genp

genm:

Field Value

recipient CA name

  1. - the name of the CA as contained in issuerAltName extensions or
  2. - issuer fields within certificates

protectionAlg MSG_MAC_ALG or MSG_SIG_ALG

  1. - any authenticated protection alg.

SenderKID present if required

  1. - must be present if required for verification of message protection

freeText any valid value body genr (GenReqContent) GenMsgContent empty SEQUENCE

  1. - all relevant information requested

protection present

  1. - bits calculated using MSG_MAC_ALG or MSG_SIG_ALG

Adams & Farrell Standards Track [Page 53] RFC 2510 PKI Certificate Management Protocols March 1999

genp:

Field Value

sender CA name

  1. - name of the CA which produced the message

protectionAlg MSG_MAC_ALG or MSG_SIG_ALG

  1. - any authenticated protection alg.

senderKID present if required

  1. - must be present if required for verification of message protection

body genp (GenRepContent) CAProtEncCert present (object identifier one

                   of PROT_ENC_ALG), with relevant
                   value
-- to be used if end entity needs to encrypt information for the CA
-- (e.g., private key for recovery purposes)

SignKeyPairTypes present, with relevant value

  1. - the set of signature algorithm identifiers which this CA will
  2. - certify for subject public keys

EncKeyPairTypes present, with relevant value

  1. - the set of encryption/key agreement algorithm identifiers which
  2. - this CA will certify for subject public keys

PreferredSymmAlg present (object identifier one

                   of PROT_SYM_ALG) , with relevant
                   value
-- the symmetric algorithm which this CA expects to be used in later
-- PKI messages (for encryption)

CAKeyUpdateInfo optionally present, with

                   relevant value
-- the CA MAY provide information about a relevant root CA key pair
-- using this field (note that this does not imply that the responding
-- CA is the root CA in question)

CurrentCRL optionally present, with relevant value

  1. - the CA MAY provide a copy of a complete CRL (i.e., fullest possible
  2. - one)

protection present

  1. - bits calculated using MSG_MAC_ALG or MSG_SIG_ALG

extraCerts optionally present

  1. - can be used to send some certificates to the end entity. An RA MAY
  2. - add its certificate here.

B7. Cross certification request/response (1-way)

 Creation of a single cross-certificate (i.e., not two at once). The
 requesting CA MAY choose who is responsible for publication of the
 cross-certificate created by the responding CA through use of the
 PKIPublicationInfo control.

Adams & Farrell Standards Track [Page 54] RFC 2510 PKI Certificate Management Protocols March 1999

 Preconditions:
 1. Responding CA can verify the origin of the request (possibly
    requiring out-of-band means) before processing the request.
 2. Requesting CA can authenticate the authenticity of the origin of
    the response (possibly requiring out-of-band means) before
    processing the response

Message Flows:

Step# Requesting CA Responding CA

1     format ccr
2                        ->       ccr       ->
3                                                     handle ccr
4                                                     produce ccp
5                        <-       ccp       <-
6     handle ccp
7     format conf
8                        ->       conf      ->
9                                                     handle conf

ccr: Field Value

sender Requesting CA name

  1. - the name of the CA who produced the message

recipient Responding CA name

  1. - the name of the CA who is being asked to produce a certificate

messageTime time of production of message

  1. - current time at requesting CA

protectionAlg MSG_SIG_ALG

  1. - only signature protection is allowed for this request

senderKID present if required

  1. - must be present if required for verification of message protection

transactionID present

  1. - implementation-specific value, meaningful to requesting CA.
  2. - [If already in use at responding CA then a rejection message
  3. - MUST be produced by responding CA]

senderNonce present

  1. - 128 (pseudo-)random bits

freeText any valid value body ccr (CertReqMessages)

                    only one CertReqMsg
                    allowed
-- if multiple cross certificates are required they MUST be packaged
-- in separate PKIMessages

certTemplate present

Adams & Farrell Standards Track [Page 55] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - details follow

version v1 or v3

  1. - «v3 STRONGLY RECOMMENDED»

signingAlg present

  1. - the requesting CA must know in advance with which algorithm it
  2. - wishes the certificate to be signed

subject present

  1. - may be NULL-DN only if subjectAltNames extension value proposed

validity present

  1. - MUST be completely specified (i.e., both fields present)

issuer present

  1. - may be NULL-DN only if issuerAltNames extension value proposed

publicKey present

  1. - the key to be certified (which must be for a signing algorithm)

extensions optionally present

  1. - a requesting CA must propose values for all extensions which it
  2. - requires to be in the cross-certificate

POPOSigningKey present

  1. - see "Proof of possession profile" (Section B4)

protection present

  1. - bits calculated using MSG_SIG_ALG

extraCerts optionally present

  1. - MAY contain any additional certificates that requester wishes
  2. - to include

ccp: Field Value

sender Responding CA name

  1. - the name of the CA who produced the message

recipient Requesting CA name

  1. - the name of the CA who asked for production of a certificate

messageTime time of production of message

  1. - current time at responding CA

protectionAlg MSG_SIG_ALG

  1. - only signature protection is allowed for this message

senderKID present if required

  1. - must be present if required for verification of message
  2. - protection

recipKID present if required transactionID present

  1. - value from corresponding ccr message

senderNonce present

  1. - 128 (pseudo-)random bits

recipNonce present

Adams & Farrell Standards Track [Page 56] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - senderNonce from corresponding ccr message

freeText any valid value body ccp (CertRepMessage)

                    only one CertResponse allowed
-- if multiple cross certificates are required they MUST be packaged
-- in separate PKIMessages

response present status present PKIStatusInfo.status present

  1. - if PKIStatusInfo.status is one of:
  2. - granted, or
  3. - grantedWithMods,
  4. - then certifiedKeyPair MUST be present and failInfo MUST be absent

failInfo present depending on

                    PKIStatusInfo.status
-- if PKIStatusInfo.status is:
--   rejection
-- then certifiedKeyPair MUST be absent and failInfo MUST be present
-- and contain appropriate bit settings

certifiedKeyPair present depending on

                    PKIStatusInfo.status

certificate present depending on

                    certifiedKeyPair
-- content of actual certificate must be examined by requesting CA
-- before publication

protection present

  1. - bits calculated using MSG_SIG_ALG

extraCerts optionally present

  1. - MAY contain any additional certificates that responder wishes
  2. - to include

B8. Initial Registration/Certification (Basic Authenticated Scheme)

 An (uninitialized) end entity requests a (first) certificate from a
 CA. When the CA responds with a message containing a certificate, the
 end entity replies with a confirmation. All messages are
 authenticated.
 This scheme allows the end entity to request certification of a
 locally-generated public key (typically a signature key). The end
 entity MAY also choose to request the centralized generation and
 certification of another key pair (typically an encryption key pair).
 Certification may only be requested for one locally generated public
 key (for more, use separate PKIMessages).

Adams & Farrell Standards Track [Page 57] RFC 2510 PKI Certificate Management Protocols March 1999

 The end entity MUST support proof-of-possession of the private key
 associated with the locally-generated public key.
 Preconditions:
 1. The end entity can authenticate the CA's signature based on
    out-of-band means
 2. The end entity and the CA share a symmetric MACing key
 Message flow:
 Step#    End entity                                    PKI
   1      format ir
   2                         ->      ir       ->
   3                                                    handle ir
   4                                                    format ip
   5                         <-      ip       <-
   6      handle ip
   7      format conf
   8                         ->      conf     ->
   9                                                    handle conf
 For this profile, we mandate that the end entity MUST include all
 (i.e., one or two) CertReqMsg in a single PKIMessage and that the PKI
 (CA) MUST produce a single response PKIMessage which contains the
 complete response (i.e., including the OPTIONAL second key pair, if
 it was requested and if centralized key generation is supported). For
 simplicity, we also mandate that this message MUST be the final one
 (i.e., no use of "waiting" status value).

ir: Field Value

recipient CA name

  1. - the name of the CA who is being asked to produce a certificate

protectionAlg MSG_MAC_ALG

  1. - only MAC protection is allowed for this request, based on
  2. - initial authentication key

senderKID referenceNum

  1. - the reference number which the CA has previously issued to
  2. - the end entity (together with the MACing key)

transactionID present

  1. - implementation-specific value, meaningful to end entity.
  2. - [If already in use at the CA then a rejection message MUST be
  3. - produced by the CA]

senderNonce present

  1. - 128 (pseudo-)random bits

freeText any valid value

Adams & Farrell Standards Track [Page 58] RFC 2510 PKI Certificate Management Protocols March 1999

body ir (CertReqMessages)

                   only one or two CertReqMsg
                   are allowed
-- if more certificates are required requests MUST be packaged in
-- separate PKIMessages

CertReqMsg one or two present

  1. - see below for details, note: crm[0] means the first (which MUST
  2. - be present), crm[1] means the second (which is OPTIONAL, and used
  3. - to ask for a centrally-generated key)

crm[0].certReq. fixed value of zero

 certReqId
-- this is the index of the template within the message

crm[0].certReq present

 certTemplate
-- MUST include subject public key value, otherwise unconstrained

crm[0].pop… optionally present if public key

 POPOSigningKey    from crm[0].certReq.certTemplate is
                   a signing key
-- proof of possession MAY be required in this exchange (see Section
-- B4 for details)

crm[0].certReq. optionally present

 controls.archiveOptions
-- the end entity MAY request that the locally-generated private key
-- be archived

crm[0].certReq. optionally present

 controls.publicationInfo
-- the end entity MAY ask for publication of resulting cert.

crm[1].certReq fixed value of one

 certReqId
-- the index of the template within the message

crm[1].certReq present

 certTemplate
-- MUST NOT include actual public key bits, otherwise unconstrained
-- (e.g., the names need not be the same as in crm[0])

crm[0].certReq. present [object identifier MUST be PROT_ENC_ALG]

 controls.protocolEncKey
-- if centralized key generation is supported by this CA, this
-- short-term asymmetric encryption key (generated by the end entity)
-- will be used by the CA to encrypt (a symmetric key used to encrypt)
-- a private key generated by the CA on behalf of the end entity

crm[1].certReq. optionally present

 controls.archiveOptions

crm[1].certReq. optionally present

 controls.publicationInfo

protection present

  1. - bits calculated using MSG_MAC_ALG

Adams & Farrell Standards Track [Page 59] RFC 2510 PKI Certificate Management Protocols March 1999

ip: Field Value

sender CA name

  1. - the name of the CA who produced the message

messageTime present

  1. - time at which CA produced message

protectionAlg MS_MAC_ALG

  1. - only MAC protection is allowed for this response

recipKID referenceNum

  1. - the reference number which the CA has previously issued to the
  2. - end entity (together with the MACing key)

transactionID present

  1. - value from corresponding ir message

senderNonce present

  1. - 128 (pseudo-)random bits

recipNonce present

  1. - value from senderNonce in corresponding ir message

freeText any valid value body ir (CertRepMessage)

                   contains exactly one response
                   for each request
-- The PKI (CA) responds to either one or two requests as appropriate.
-- crc[0] denotes the first (always present); crc[1] denotes the
-- second (only present if the ir message contained two requests and
-- if the CA supports centralized key generation).

crc[0]. fixed value of zero

 certReqId
-- MUST contain the response to the first request in the corresponding
-- ir message

crc[0].status. present, positive values allowed:

 status               "granted", "grantedWithMods"
                   negative values allowed:
                      "rejection"

crc[0].status. present if and only if

 failInfo          crc[0].status.status is "rejection"

crc[0]. present if and only if

 certifiedKeyPair  crc[0].status.status is
                      "granted" or "grantedWithMods"

certificate present unless end entity's public

                   key is an encryption key and POP
                   is done in this in-band exchange

encryptedCert present if and only if end entity's

                   public key is an encryption key and
                   POP done in this in-band exchange

publicationInfo optionally present

  1. - indicates where certificate has been published (present at
  2. - discretion of CA)

Adams & Farrell Standards Track [Page 60] RFC 2510 PKI Certificate Management Protocols March 1999

crc[1]. fixed value of one

 certReqId
-- MUST contain the response to the second request in the
-- corresponding ir message

crc[1].status. present, positive values allowed:

 status               "granted", "grantedWithMods"
                   negative values allowed:
                      "rejection"

crc[1].status. present if and only if

 failInfo          crc[0].status.status is "rejection"

crc[1]. present if and only if

 certifiedKeyPair  crc[0].status.status is "granted"
                   or "grantedWithMods"

certificate present privateKey present publicationInfo optionally present

  1. - indicates where certificate has been published (present at
  2. - discretion of CA)

protection present

  1. - bits calculated using MSG_MAC_ALG

extraCerts optionally present

  1. - the CA MAY provide additional certificates to the end entity

conf: Field Value

recipient CA name

  1. - the name of the CA who was asked to produce a certificate

transactionID present

  1. - value from corresponding ir and ip messages

senderNonce present

  1. - value from recipNonce in corresponding ip message

recipNonce present

  1. - value from senderNonce in corresponding ip message

protectionAlg MSG_MAC_ALG

  1. - only MAC protection is allowed for this message. The MAC is
  2. - based on the initial authentication key if only a signing key
  3. - pair has been sent in ir for certification, or if POP is not
  4. - done in this in-band exchange. Otherwise, the MAC is based on
  5. - a key derived from the symmetric key used to decrypt the
  6. - returned encryptedCert.

senderKID referenceNum

  1. - the reference number which the CA has previously issued to the
  2. - end entity (together with the MACing key)

body conf (PKIConfirmContent)

  1. - this is an ASN.1 NULL

protection present

  1. - bits calculated using MSG_MAC_ALG

Adams & Farrell Standards Track [Page 61] RFC 2510 PKI Certificate Management Protocols March 1999

B9. Certificate Request

 An (initialized) end entity requests a certificate from a CA (for any
 reason). When the CA responds with a message containing a
 certificate, the end entity replies with a confirmation. All messages
 are authenticated.
 The profile for this exchange is identical to that given in Section
 B8 with the following exceptions:
  1. protectionAlg may be MSG_MAC_ALG or MSG_SIG_ALG in request,

response, and confirm messages (the determination in the confirm

     message being dependent upon POP considerations for key-
     encipherment and key- agreement certificate requests);
   - senderKID and recipKID are only present if required for message
     verification;
   - body is cr or cp;
     - protocolEncKey is not present;
   - protection bits are calculated according to the protectionAlg
     field.

B10. Key Update Request

 An (initialized) end entity requests a certificate from a CA (to
 update the key pair and corresponding certificate that it already
 possesses). When the CA responds with a message containing a
 certificate, the end entity replies with a confirmation. All messages
 are authenticated.
 The profile for this exchange is identical to that given in Section
 B8 with the following exceptions:
  1. protectionAlg may be MSG_MAC_ALG or MSG_SIG_ALG in request,

response, and confirm messages (the determination in the confirm

     message being dependent upon POP considerations for key-
     encipherment and key- agreement certificate requests);
   - senderKID and recipKID are only present if required for message
     verification;
   - body is kur or kup;
   - protection bits are calculated according to the protectionAlg
     field.

Adams & Farrell Standards Track [Page 62] RFC 2510 PKI Certificate Management Protocols March 1999

Appendix C: "Compilable" ASN.1 Module using 1988 Syntax

PKIXCMP {iso(1) identified-organization(3) dod(6) internet(1)
   security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-cmp(9)}
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
  1. - EXPORTS ALL –
IMPORTS
    Certificate, CertificateList, Extensions, AlgorithmIdentifier
           FROM PKIX1Explicit88 {iso(1) identified-organization(3)
           dod(6) internet(1) security(5) mechanisms(5) pkix(7)
           id-mod(0) id-pkix1-explicit-88(1)}}
    GeneralName, KeyIdentifier, ReasonFlags
           FROM PKIX1Implicit88 {iso(1) identified-organization(3)
           dod(6) internet(1) security(5) mechanisms(5) pkix(7)
           id-mod(0) id-pkix1-implicit-88(2)}
    CertTemplate, PKIPublicationInfo, EncryptedValue, CertId,
    CertReqMessages
           FROM PKIXCRMF {iso(1) identified-organization(3)
           dod(6) internet(1) security(5) mechanisms(5) pkix(7)
           id-mod(0) id-mod-crmf(5)}}
  1. - CertificationRequest
  2. - FROM PKCS10 {no standard ASN.1 module defined;
  3. - implementers need to create their own module to import
  4. - from, or directly include the PKCS10 syntax in this module}
  1. - Locally defined OIDs –
PKIMessage ::= SEQUENCE {
    header           PKIHeader,
    body             PKIBody,
    protection   [0] PKIProtection OPTIONAL,
    extraCerts   [1] SEQUENCE SIZE (1..MAX) OF Certificate OPTIONAL
}
PKIHeader ::= SEQUENCE {
    pvno                INTEGER     { ietf-version2 (1) },
    sender              GeneralName,
    -- identifies the sender
    recipient           GeneralName,

Adams & Farrell Standards Track [Page 63] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - identifies the intended recipient

messageTime [0] GeneralizedTime OPTIONAL,

  1. - time of production of this message (used when sender
  2. - believes that the transport will be "suitable"; i.e.,
  3. - that the time will still be meaningful upon receipt)

protectionAlg [1] AlgorithmIdentifier OPTIONAL,

  1. - algorithm used for calculation of protection bits

senderKID [2] KeyIdentifier OPTIONAL,

    recipKID        [3] KeyIdentifier           OPTIONAL,
    -- to identify specific keys used for protection
    transactionID   [4] OCTET STRING            OPTIONAL,
    -- identifies the transaction; i.e., this will be the same in
    -- corresponding request, response and confirmation messages
    senderNonce     [5] OCTET STRING            OPTIONAL,
    recipNonce      [6] OCTET STRING            OPTIONAL,
    -- nonces used to provide replay protection, senderNonce
    -- is inserted by the creator of this message; recipNonce
    -- is a nonce previously inserted in a related message by
    -- the intended recipient of this message
    freeText        [7] PKIFreeText             OPTIONAL,
    -- this may be used to indicate context-specific instructions
    -- (this field is intended for human consumption)
    generalInfo     [8] SEQUENCE SIZE (1..MAX) OF
                           InfoTypeAndValue     OPTIONAL
    -- this may be used to convey context-specific information
    -- (this field not primarily intended for human consumption)
}
PKIFreeText ::= SEQUENCE SIZE (1..MAX) OF UTF8String
    -- text encoded as UTF-8 String (note:  each UTF8String SHOULD
    -- include an RFC 1766 language tag to indicate the language
    -- of the contained text)
PKIBody ::= CHOICE {       -- message-specific body elements
    ir      [0]  CertReqMessages,        --Initialization Request
    ip      [1]  CertRepMessage,         --Initialization Response
    cr      [2]  CertReqMessages,        --Certification Request
    cp      [3]  CertRepMessage,         --Certification Response
    p10cr   [4]  CertificationRequest,   --imported from [PKCS10]
    popdecc [5]  POPODecKeyChallContent, --pop Challenge
    popdecr [6]  POPODecKeyRespContent,  --pop Response
    kur     [7]  CertReqMessages,        --Key Update Request
    kup     [8]  CertRepMessage,         --Key Update Response
    krr     [9]  CertReqMessages,        --Key Recovery Request
    krp     [10] KeyRecRepContent,       --Key Recovery Response
    rr      [11] RevReqContent,          --Revocation Request
    rp      [12] RevRepContent,          --Revocation Response

Adams & Farrell Standards Track [Page 64] RFC 2510 PKI Certificate Management Protocols March 1999

    ccr     [13] CertReqMessages,        --Cross-Cert. Request
    ccp     [14] CertRepMessage,         --Cross-Cert. Response
    ckuann  [15] CAKeyUpdAnnContent,     --CA Key Update Ann.
    cann    [16] CertAnnContent,         --Certificate Ann.
    rann    [17] RevAnnContent,          --Revocation Ann.
    crlann  [18] CRLAnnContent,          --CRL Announcement
    conf    [19] PKIConfirmContent,      --Confirmation
    nested  [20] NestedMessageContent,   --Nested Message
    genm    [21] GenMsgContent,          --General Message
    genp    [22] GenRepContent,          --General Response
    error   [23] ErrorMsgContent         --Error Message
}
PKIProtection ::= BIT STRING
ProtectedPart ::= SEQUENCE {
    header    PKIHeader,
    body      PKIBody
}
PasswordBasedMac ::= OBJECT IDENTIFIER --{1 2 840 113533 7 66 13}
PBMParameter ::= SEQUENCE {
    salt                OCTET STRING,
    owf                 AlgorithmIdentifier,
    -- AlgId for a One-Way Function (SHA-1 recommended)
    iterationCount      INTEGER,
    -- number of times the OWF is applied
    mac                 AlgorithmIdentifier
    -- the MAC AlgId (e.g., DES-MAC, Triple-DES-MAC [PKCS11],
}   -- or HMAC [RFC2104, RFC2202])
DHBasedMac ::= OBJECT IDENTIFIER --{1 2 840 113533 7 66 30}
DHBMParameter ::= SEQUENCE {
    owf                 AlgorithmIdentifier,
    -- AlgId for a One-Way Function (SHA-1 recommended)
    mac                 AlgorithmIdentifier
    -- the MAC AlgId (e.g., DES-MAC, Triple-DES-MAC [PKCS11],
}   -- or HMAC [RFC2104, RFC2202])
NestedMessageContent ::= PKIMessage
PKIStatus ::= INTEGER {
    granted                (0),
    -- you got exactly what you asked for
    grantedWithMods        (1),

Adams & Farrell Standards Track [Page 65] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - you got something like what you asked for; the
  2. - requester is responsible for ascertaining the differences

rejection (2),

  1. - you don't get it, more information elsewhere in the message

waiting (3),

  1. - the request body part has not yet been processed,
  2. - expect to hear more later

revocationWarning (4),

  1. - this message contains a warning that a revocation is
  2. - imminent

revocationNotification (5),

  1. - notification that a revocation has occurred

keyUpdateWarning (6)

  1. - update already done for the oldCertId specified in
  2. - CertReqMsg

}

PKIFailureInfo ::= BIT STRING {
-- since we can fail in more than one way!
-- More codes may be added in the future if/when required.
    badAlg           (0),
    -- unrecognized or unsupported Algorithm Identifier
    badMessageCheck  (1),
    -- integrity check failed (e.g., signature did not verify)
    badRequest       (2),
    -- transaction not permitted or supported
    badTime          (3),
    -- messageTime was not sufficiently close to the system time,
    -- as defined by local policy
    badCertId        (4),
    -- no certificate could be found matching the provided criteria
    badDataFormat    (5),
    -- the data submitted has the wrong format
    wrongAuthority   (6),
    -- the authority indicated in the request is different from the
    -- one creating the response token
    incorrectData    (7),
    -- the requester's data is incorrect (for notary services)
    missingTimeStamp (8),
    -- when the timestamp is missing but should be there (by policy)
    badPOP           (9)
    -- the proof-of-possession failed
}
PKIStatusInfo ::= SEQUENCE {
    status        PKIStatus,
    statusString  PKIFreeText     OPTIONAL,
    failInfo      PKIFailureInfo  OPTIONAL

Adams & Farrell Standards Track [Page 66] RFC 2510 PKI Certificate Management Protocols March 1999

}
OOBCert ::= Certificate
OOBCertHash ::= SEQUENCE {
    hashAlg     [0] AlgorithmIdentifier     OPTIONAL,
    certId      [1] CertId                  OPTIONAL,
    hashVal         BIT STRING
    -- hashVal is calculated over DER encoding of the
    -- subjectPublicKey field of the corresponding cert.
}
POPODecKeyChallContent ::= SEQUENCE OF Challenge
-- One Challenge per encryption key certification request (in the
-- same order as these requests appear in CertReqMessages).
Challenge ::= SEQUENCE {
    owf                 AlgorithmIdentifier  OPTIONAL,
    -- MUST be present in the first Challenge; MAY be omitted in any
    -- subsequent Challenge in POPODecKeyChallContent (if omitted,
    -- then the owf used in the immediately preceding Challenge is
    -- to be used).
    witness             OCTET STRING,
    -- the result of applying the one-way function (owf) to a
    -- randomly-generated INTEGER, A.  [Note that a different
    -- INTEGER MUST be used for each Challenge.]
    challenge           OCTET STRING
    -- the encryption (under the public key for which the cert.
    -- request is being made) of Rand, where Rand is specified as
    --   Rand ::= SEQUENCE {
    --      int      INTEGER,
    --       - the randomly-generated INTEGER A (above)
    --      sender   GeneralName
    --       - the sender's name (as included in PKIHeader)
    --   }
}
POPODecKeyRespContent ::= SEQUENCE OF INTEGER
-- One INTEGER per encryption key certification request (in the
-- same order as these requests appear in CertReqMessages).  The
-- retrieved INTEGER A (above) is returned to the sender of the
-- corresponding Challenge.
CertRepMessage ::= SEQUENCE {
    caPubs       [1] SEQUENCE SIZE (1..MAX) OF Certificate OPTIONAL,
    response         SEQUENCE OF CertResponse
}

Adams & Farrell Standards Track [Page 67] RFC 2510 PKI Certificate Management Protocols March 1999

CertResponse ::= SEQUENCE {
    certReqId           INTEGER,
    -- to match this response with corresponding request (a value
    -- of -1 is to be used if certReqId is not specified in the
    -- corresponding request)
    status              PKIStatusInfo,
    certifiedKeyPair    CertifiedKeyPair    OPTIONAL,
    rspInfo             OCTET STRING        OPTIONAL
    -- analogous to the id-regInfo-asciiPairs OCTET STRING defined
    -- for regInfo in CertReqMsg [CRMF]
}
CertifiedKeyPair ::= SEQUENCE {
    certOrEncCert       CertOrEncCert,
    privateKey      [0] EncryptedValue      OPTIONAL,
    publicationInfo [1] PKIPublicationInfo  OPTIONAL
}
CertOrEncCert ::= CHOICE {
    certificate     [0] Certificate,
    encryptedCert   [1] EncryptedValue
}
KeyRecRepContent ::= SEQUENCE {
    status                  PKIStatusInfo,
    newSigCert          [0] Certificate                   OPTIONAL,
    caCerts             [1] SEQUENCE SIZE (1..MAX) OF
                                        Certificate       OPTIONAL,
    keyPairHist         [2] SEQUENCE SIZE (1..MAX) OF
                                        CertifiedKeyPair  OPTIONAL
}
RevReqContent ::= SEQUENCE OF RevDetails
RevDetails ::= SEQUENCE {
    certDetails         CertTemplate,
    -- allows requester to specify as much as they can about
    -- the cert. for which revocation is requested
    -- (e.g., for cases in which serialNumber is not available)
    revocationReason    ReasonFlags      OPTIONAL,
    -- the reason that revocation is requested
    badSinceDate        GeneralizedTime  OPTIONAL,
    -- indicates best knowledge of sender
    crlEntryDetails     Extensions       OPTIONAL
    -- requested crlEntryExtensions
}
RevRepContent ::= SEQUENCE {

Adams & Farrell Standards Track [Page 68] RFC 2510 PKI Certificate Management Protocols March 1999

    status       SEQUENCE SIZE (1..MAX) OF PKIStatusInfo,
    -- in same order as was sent in RevReqContent
    revCerts [0] SEQUENCE SIZE (1..MAX) OF CertId OPTIONAL,
    -- IDs for which revocation was requested (same order as status)
    crls     [1] SEQUENCE SIZE (1..MAX) OF CertificateList  OPTIONAL
    -- the resulting CRLs (there may be more than one)
}
CAKeyUpdAnnContent ::= SEQUENCE {
    oldWithNew          Certificate, -- old pub signed with new priv
    newWithOld          Certificate, -- new pub signed with old priv
    newWithNew          Certificate  -- new pub signed with new priv
}
CertAnnContent ::= Certificate
RevAnnContent ::= SEQUENCE {
    status              PKIStatus,
    certId              CertId,
    willBeRevokedAt     GeneralizedTime,
    badSinceDate        GeneralizedTime,
    crlDetails          Extensions  OPTIONAL
    -- extra CRL details(e.g., crl number, reason, location, etc.)

}

CRLAnnContent ::= SEQUENCE OF CertificateList
PKIConfirmContent ::= NULL
InfoTypeAndValue ::= SEQUENCE {
    infoType               OBJECT IDENTIFIER,
    infoValue              ANY DEFINED BY infoType  OPTIONAL
}
-- Example InfoTypeAndValue contents include, but are not limited to:
--  { CAProtEncCert    = {id-it 1}, Certificate                     }
--  { SignKeyPairTypes = {id-it 2}, SEQUENCE OF AlgorithmIdentifier }
--  { EncKeyPairTypes  = {id-it 3}, SEQUENCE OF AlgorithmIdentifier }
--  { PreferredSymmAlg = {id-it 4}, AlgorithmIdentifier             }
--  { CAKeyUpdateInfo  = {id-it 5}, CAKeyUpdAnnContent              }
--  { CurrentCRL       = {id-it 6}, CertificateList                 }
-- where {id-it} = {id-pkix 4} = {1 3 6 1 5 5 7 4}
-- This construct MAY also be used to define new PKIX Certificate
-- Management Protocol request and response messages, or general-
-- purpose (e.g., announcement) messages for future needs or for
-- specific environments.
GenMsgContent ::= SEQUENCE OF InfoTypeAndValue

Adams & Farrell Standards Track [Page 69] RFC 2510 PKI Certificate Management Protocols March 1999

  1. - May be sent by EE, RA, or CA (depending on message content).
  2. - The OPTIONAL infoValue parameter of InfoTypeAndValue will typically
  3. - be omitted for some of the examples given above. The receiver is
  4. - free to ignore any contained OBJ. IDs that it does not recognize.
  5. - If sent from EE to CA, the empty set indicates that the CA may send
  6. - any/all information that it wishes.
GenRepContent ::= SEQUENCE OF InfoTypeAndValue
-- The receiver is free to ignore any contained OBJ. IDs that it does
-- not recognize.
ErrorMsgContent ::= SEQUENCE {
    pKIStatusInfo          PKIStatusInfo,
    errorCode              INTEGER           OPTIONAL,
    -- implementation-specific error codes
    errorDetails           PKIFreeText       OPTIONAL
    -- implementation-specific error details
}

– The following definition is provided for compatibility reasons with – 1988 and 1993 ASN.1 compilers which allow the use of UNIVERSAL class – tags (not a part of formal ASN.1); 1997 and subsequent compilers – SHOULD comment out this line.

UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING

END

Adams & Farrell Standards Track [Page 70] RFC 2510 PKI Certificate Management Protocols March 1999

Appendix D: Registration of MIME Type for Section 5

 To: ietf-types@iana.org
 Subject: Registration of MIME media type application/pkixcmp
 MIME media type name: application
 MIME subtype name: pkixcmp
 Required parameters: -
 Optional parameters: -
 Encoding considerations:
 Content may contain arbitrary octet values (the ASN.1 DER encoding of
 a PKI message, as defined in the IETF PKIX Working Group
 specifications).  base64 encoding is required for MIME e-mail; no
 encoding is necessary for HTTP.
 Security considerations:
 This MIME type may be used to transport Public-Key Infrastructure
 (PKI) messages between PKI entities.  These messages are defined by
 the IETF PKIX Working Group and are used to establish and maintain an
 Internet X.509 PKI.  There is no requirement for specific security
 mechanisms to be applied at this level if the PKI messages themselves
 are protected as defined in the PKIX specifications.
 Interoperability considerations: -
 Published specification: this document
 Applications which use this media type:
 Applications using certificate management, operational, or ancillary
 protocols (as defined by the IETF PKIX Working Group) to send PKI
 messages via E-Mail or HTTP.
 Additional information:
   Magic number (s): -
   File extension (s): ".PKI"
   Macintosh File Type Code (s): -
 Person and email address to contact for further information:
 Carlisle Adams, cadams@entrust.com
 Intended usage: COMMON
 Author/Change controller: Carlisle Adams

Adams & Farrell Standards Track [Page 71] RFC 2510 PKI Certificate Management Protocols March 1999

Full Copyright Statement

 Copyright (C) The Internet Society (1999).  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.

Adams & Farrell Standards Track [Page 72]

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