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rfc:rfc3826

Network Working Group U. Blumenthal Request for Comments: 3826 Lucent Technologies Category: Standards Track F. Maino

                                                 Andiamo Systems, Inc.
                                                         K. McCloghrie
                                                   Cisco Systems, Inc.
                                                             June 2004
      The Advanced Encryption Standard (AES) Cipher Algorithm
               in the SNMP User-based Security Model

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 (2004).

Abstract

 This document describes a symmetric encryption protocol that
 supplements the protocols described in the User-based Security Model
 (USM), which is a Security Subsystem for version 3 of the Simple
 Network Management Protocol for use in the SNMP Architecture.  The
 symmetric encryption protocol described in this document is based on
 the Advanced Encryption Standard (AES) cipher algorithm used in
 Cipher FeedBack Mode (CFB), with a key size of 128 bits.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . .    2
     1.1.  Goals and Constraints. . . . . . . . . . . . . . . . .    2
     1.2.  Key Localization . . . . . . . . . . . . . . . . . . .    3
     1.3.  Password Entropy and Storage . . . . . . . . . . . . .    3
 2.  Definitions. . . . . . . . . . . . . . . . . . . . . . . . .    4
 3.  CFB128-AES-128 Symmetric Encryption Protocol . . . . . . . .    5
     3.1.  Mechanisms . . . . . . . . . . . . . . . . . . . . . .    5
           3.1.1. The AES-based Symmetric Encryption Protocol . .    6
           3.1.2. Localized Key, AES Encryption Key and
                  Initialization Vector . . . . . . . . . . . . .    7
           3.1.3. Data Encryption . . . . . . . . . . . . . . . .    8
           3.1.4. Data Decryption . . . . . . . . . . . . . . . .    8

Blumenthal, et al. Standards Track [Page 1] RFC 3826 AES for SNMP's USM June 2004

     3.2.  Elements of the AES Privacy Protocol . . . . . . . . .    9
           3.2.1. Users . . . . . . . . . . . . . . . . . . . . .    9
           3.2.2. msgAuthoritativeEngineID. . . . . . . . . . . .    9
           3.2.3. SNMP Messages Using this Privacy Protocol . . .   10
           3.2.4. Services provided by the AES Privacy Modules. .   10
     3.3.  Elements of Procedure. . . . . . . . . . . . . . . . .   11
           3.3.1. Processing an Outgoing Message. . . . . . . . .   12
           3.3.2. Processing an Incoming Message. . . . . . . . .   12
 4.  Security Considerations. . . . . . . . . . . . . . . . . . .   13
 5.  IANA Considerations. . . . . . . . . . . . . . . . . . . . .   13
 6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .   14
 7.  References . . . . . . . . . . . . . . . . . . . . . . . . .   14
     7.1.  Normative References . . . . . . . . . . . . . . . . .   14
     7.2.  Informative References . . . . . . . . . . . . . . . .   14
 8.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . .   15
 9.  Full Copyright Statement . . . . . . . . . . . . . . . . . .   16

1. Introduction

 Within the Architecture for describing Internet Management Frameworks
 [RFC3411], the User-based Security Model (USM) [RFC3414] for SNMPv3
 is defined as a Security Subsystem within an SNMP engine.  RFC 3414
 describes the use of HMAC-MD5-96 and HMAC-SHA-96 as the initial
 authentication protocols, and the use of CBC-DES as the initial
 privacy protocol.  The User-based Security Model, however, allows for
 other such protocols to be used instead of, or concurrently with,
 these protocols.
 This memo describes the use of CFB128-AES-128 as an alternative
 privacy protocol for the User-based Security Model.  The key words
 "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
 "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this document
 are to be interpreted as described in [RFC2119].

1.1. Goals and Constraints

 The main goal of this memo is to provide a new privacy protocol for
 the USM based on the Advanced Encryption Standard (AES) [FIPS-AES].
 The major constraint is to maintain a complete interchangeability of
 the new protocol defined in this memo with existing authentication
 and privacy protocols already defined in USM.
 For a given user, the AES-based privacy protocol MUST be used with
 one of the authentication protocols defined in RFC 3414 or an
 algorithm/protocol providing equivalent functionality.

Blumenthal, et al. Standards Track [Page 2] RFC 3826 AES for SNMP's USM June 2004

1.2. Key Localization

 As defined in [RFC3414], a localized key is a secret key shared
 between a user U and one authoritative SNMP engine E.  Even though a
 user may have only one pair of authentication and privacy passwords
 (and consequently only one pair of keys) for the entire network, the
 actual secrets shared between the user and each authoritative SNMP
 engine will be different.  This is achieved by key localization.
 If the authentication protocol defined for a user U at the
 authoritative SNMP engine E is one of the authentication protocols
 defined in [RFC3414], the key localization is performed according to
 the two-step process described in section 2.6 of [RFC3414].

1.3. Password Entropy and Storage

 The security of various cryptographic functions lies both in the
 strength of the functions themselves against various forms of attack,
 and also, perhaps more importantly, in the keying material that is
 used with them.  While theoretical attacks against cryptographic
 functions are possible, it is more probable that key guessing is the
 main threat.
 The following are recommended in regard to user passwords:
  1. Password length SHOULD be at least 12 octets.
  2. Password sharing SHOULD be prohibited so that passwords are not

shared among multiple SNMP users.

  1. Implementations SHOULD support the use of randomly generated

passwords as a stronger form of security.

 It is worth remembering that, as specified in [RFC3414], if a user's
 password or a non-localized key is disclosed, then key localization
 will not help and network security may be compromised.  Therefore, a
 user's password or non-localized key MUST NOT be stored on a managed
 device/node.  Instead, the localized key SHALL be stored (if at all)
 so that, in case a device does get compromised, no other managed or
 managing devices get compromised.

Blumenthal, et al. Standards Track [Page 3] RFC 3826 AES for SNMP's USM June 2004

2. Definitions

 This MIB is written in SMIv2 [RFC2578].

SNMP-USM-AES-MIB DEFINITIONS ::= BEGIN

  IMPORTS
      MODULE-IDENTITY, OBJECT-IDENTITY,
      snmpModules             FROM SNMPv2-SMI          -- [RFC2578]
      snmpPrivProtocols       FROM SNMP-FRAMEWORK-MIB; -- [RFC3411]

snmpUsmAesMIB MODULE-IDENTITY

  LAST-UPDATED "200406140000Z"
  ORGANIZATION "IETF"
  CONTACT-INFO "Uri Blumenthal
                Lucent Technologies / Bell Labs
                67 Whippany Rd.
                14D-318
                Whippany, NJ  07981, USA
                973-386-2163
                uri@bell-labs.com
                Fabio Maino
                Andiamo Systems, Inc.
                375 East Tasman Drive
                San Jose, CA  95134, USA
                408-853-7530
                fmaino@andiamo.com
                Keith McCloghrie
                Cisco Systems, Inc.
                170 West Tasman Drive
                San Jose, CA  95134-1706, USA
                408-526-5260
                kzm@cisco.com"
  DESCRIPTION  "Definitions of Object Identities needed for
                the use of AES by SNMP's User-based Security
                Model.
                Copyright (C) The Internet Society (2004).
          This version of this MIB module is part of RFC 3826;
          see the RFC itself for full legal notices.
          Supplementary information may be available on
          http://www.ietf.org/copyrights/ianamib.html."

Blumenthal, et al. Standards Track [Page 4] RFC 3826 AES for SNMP's USM June 2004

  REVISION     "200406140000Z"
  DESCRIPTION  "Initial version, published as RFC3826"
  ::= { snmpModules 20 }

usmAesCfb128Protocol OBJECT-IDENTITY

  STATUS        current
  DESCRIPTION  "The CFB128-AES-128 Privacy Protocol."
  REFERENCE    "- Specification for the ADVANCED ENCRYPTION
                  STANDARD. Federal Information Processing
                  Standard (FIPS) Publication 197.
                  (November 2001).
  1. Dworkin, M., NIST Recommendation for Block

Cipher Modes of Operation, Methods and

                  Techniques. NIST Special Publication 800-38A
                  (December 2001).
               "
  ::= { snmpPrivProtocols 4 }

END

3. CFB128-AES-128 Symmetric Encryption Protocol

 This section describes a Symmetric Encryption Protocol based on the
 AES cipher algorithm [FIPS-AES], used in Cipher Feedback Mode as
 described in [AES-MODE], using encryption keys with a size of 128
 bits.
 This protocol is identified by usmAesCfb128PrivProtocol.
 The protocol usmAesCfb128PrivProtocol is an alternative to the
 privacy protocol defined in [RFC3414].

3.1. Mechanisms

 In support of data confidentiality, an encryption algorithm is
 required.  An appropriate portion of the message is encrypted prior
 to being transmitted.  The User-based Security Model specifies that
 the scopedPDU is the portion of the message that needs to be
 encrypted.
 A secret value is shared by all SNMP engines which can legitimately
 originate messages on behalf of the appropriate user.  This secret
 value, in combination with a timeliness value and a 64-bit integer,
 is used to create the (localized) en/decryption key and the
 initialization vector.

Blumenthal, et al. Standards Track [Page 5] RFC 3826 AES for SNMP's USM June 2004

3.1.1. The AES-based Symmetric Encryption Protocol

 The Symmetric Encryption Protocol defined in this memo provides
 support for data confidentiality.  The designated portion of an SNMP
 message is encrypted and included as part of the message sent to the
 recipient.
 The AES (Advanced Encryption Standard) is the symmetric cipher
 algorithm that the NIST (National Institute of Standards and
 Technology) has selected in a four-year competitive process as
 Replacement for DES (Data Encryption Standard).
 The AES homepage, http://www.nist.gov/aes, contains a wealth of
 information on AES including the Federal Information Processing
 Standard [FIPS-AES] that fully specifies the Advanced Encryption
 Standard.
 The following subsections contain descriptions of the relevant
 characteristics of the AES ciphers used in the symmetric encryption
 protocol described in this memo.

3.1.1.1. Mode of operation

 The NIST Special Publication 800-38A [AES-MODE] recommends five
 confidentiality modes of operation for use with AES: Electronic
 Codebook (ECB), Cipher Block Chaining (CBC), Cipher Feedback (CFB),
 Output Feedback (OFB), and Counter (CTR).
 The symmetric encryption protocol described in this memo uses AES in
 CFB mode with the parameter S (number of bits fed back) set to 128
 according to the definition of CFB mode given in [AES-MODE].  This
 mode requires an Initialization Vector (IV) that is the same size as
 the block size of the cipher algorithm.

3.1.1.2. Key Size

 In the encryption protocol described by this memo AES is used with a
 key size of 128 bits, as recommended in [AES-MODE].

3.1.1.3. Block Size and Padding

 The block size of the AES cipher algorithms used in the encryption
 protocol described by this memo is 128 bits, as recommended in [AES-
 MODE].

Blumenthal, et al. Standards Track [Page 6] RFC 3826 AES for SNMP's USM June 2004

3.1.1.4. Rounds

 This parameter determines how many times a block is encrypted.  The
 encryption protocol described in this memo uses 10 rounds, as
 recommended in [AES-MODE].

3.1.2. Localized Key, AES Encryption Key, and Initialization Vector

 The size of the Localized Key (Kul) of an SNMP user, as described in
 [RFC3414], depends on the authentication protocol defined for that
 user U at the authoritative SNMP engine E.
 The encryption protocol defined in this memo MUST be used with an
 authentication protocol that generates a localized key with at least
 128 bits.  The authentication protocols described in [RFC3414]
 satisfy this requirement.

3.1.2.1. AES Encryption Key and IV

 The first 128 bits of the localized key Kul are used as the AES
 encryption key.  The 128-bit IV is obtained as the concatenation of
 the authoritative SNMP engine's 32-bit snmpEngineBoots, the SNMP
 engine's 32-bit snmpEngineTime, and a local 64-bit integer.  The 64-
 bit integer is initialized to a pseudo-random value at boot time.
 The IV is concatenated as follows: the 32-bit snmpEngineBoots is
 converted to the first 4 octets (Most Significant Byte first), the
 32-bit snmpEngineTime is converted to the subsequent 4 octets (Most
 Significant Byte first), and the 64-bit integer is then converted to
 the last 8 octets (Most Significant Byte first).  The 64-bit integer
 is then put into the msgPrivacyParameters field encoded as an OCTET
 STRING of length 8 octets.  The integer is then modified for the
 subsequent message.  We recommend that it is incremented by one until
 it reaches its maximum value, at which time it is wrapped.
 An implementation can use any method to vary the value of the local
 64-bit integer, providing the chosen method never generates a
 duplicate IV for the same key.
 A duplicated IV can result in the very unlikely event that multiple
 managers, communicating with a single authoritative engine, both
 accidentally select the same 64-bit integer within a second.  The
 probability of such an event is very low, and does not significantly
 affect the robustness of the mechanisms proposed.

Blumenthal, et al. Standards Track [Page 7] RFC 3826 AES for SNMP's USM June 2004

 The 64-bit integer must be placed in the privParameters field to
 enable the receiving entity to compute the correct IV and to decrypt
 the message.  This 64-bit value is called the "salt" in this
 document.
 Note that the sender and receiver must use the same IV value, i.e.,
 they must both use the same values of the individual components used
 to create the IV.  In particular, both sender and receiver must use
 the values of snmpEngineBoots, snmpEngineTime, and the 64-bit integer
 which are contained in the relevant message (in the
 msgAuthoritativeEngineBoots, msgAuthoritativeEngineTime, and
 privParameters fields respectively).

3.1.3. Data Encryption

 The data to be encrypted is treated as a sequence of octets.
 The data is encrypted in Cipher Feedback mode with the parameter s
 set to 128 according to the definition of CFB mode given in Section
 6.3 of [AES-MODE].  A clear diagram of the encryption and decryption
 process is given in Figure 3 of [AES-MODE].
 The plaintext is divided into 128-bit blocks.  The last block may
 have fewer than 128 bits, and no padding is required.
 The first input block is the IV, and the forward cipher operation is
 applied to the IV to produce the first output block.  The first
 ciphertext block is produced by exclusive-ORing the first plaintext
 block with the first output block.  The ciphertext block is also used
 as the input block for the subsequent forward cipher operation.
 The process is repeated with the successive input blocks until a
 ciphertext segment is produced from every plaintext segment.
 The last ciphertext block is produced by exclusive-ORing the last
 plaintext segment of r bits (r is less than or equal to 128) with the
 segment of the r most significant bits of the last output block.

3.1.4. Data Decryption

 In CFB decryption, the IV is the first input block, the first
 ciphertext is used for the second input block, the second ciphertext
 is used for the third input block, etc.  The forward cipher function
 is applied to each input block to produce the output blocks.  The
 output blocks are exclusive-ORed with the corresponding ciphertext
 blocks to recover the plaintext blocks.

Blumenthal, et al. Standards Track [Page 8] RFC 3826 AES for SNMP's USM June 2004

 The last ciphertext block (whose size r is less than or equal to 128)
 is exclusive-ORed with the segment of the r most significant bits of
 the last output block to recover the last plaintext block of r bits.

3.2. Elements of the AES Privacy Protocol

 This section contains definitions required to realize the privacy
 modules defined by this memo.

3.2.1. Users

 Data en/decryption using this Symmetric Encryption Protocol makes use
 of a defined set of userNames.  For any user on whose behalf a
 message must be en/decrypted at a particular SNMP engine, that SNMP
 engine must have knowledge of that user.  An SNMP engine that needs
 to communicate with another SNMP engine must also have knowledge of a
 user known to that SNMP engine, including knowledge of the applicable
 attributes of that user.
 A user and its attributes are defined as follows:
 <userName>
    An octet string representing the name of the user.
 <privAlg>
    The algorithm used to protect messages generated on behalf of the
    user from disclosure.
 <privKey>
    The user's secret key to be used as input to the generation of the
    localized key for encrypting/decrypting messages generated on
    behalf of the user.  The length of this key MUST be greater than
    or equal to 128 bits (16 octets).
 <authAlg>
    The algorithm used to authenticate messages generated on behalf of
    the user, which is also used to generate the localized version of
    the secret key.

3.2.2. msgAuthoritativeEngineID

 The msgAuthoritativeEngineID value contained in an authenticated
 message specifies the authoritative SNMP engine for that particular
 message (see the definition of SnmpEngineID in the SNMP Architecture
 document [RFC3411]).

Blumenthal, et al. Standards Track [Page 9] RFC 3826 AES for SNMP's USM June 2004

 The user's (private) privacy key is different at each authoritative
 SNMP engine, and so the snmpEngineID is used to select the proper key
 for the en/decryption process.

3.2.3. SNMP Messages Using this Privacy Protocol

 Messages using this privacy protocol carry a msgPrivacyParameters
 field as part of the msgSecurityParameters.  For this protocol, the
 privParameters field is the serialized OCTET STRING representing the
 "salt" that was used to create the IV.

3.2.4. Services provided by the AES Privacy Modules

 This section describes the inputs and outputs that the AES Privacy
 module expects and produces when the User-based Security module
 invokes one of the AES Privacy modules for services.

3.2.4.1. Services for Encrypting Outgoing Data

 The AES privacy protocol assumes that the selection of the privKey is
 done by the caller, and that the caller passes the localized secret
 key to be used.
 Upon completion, the privacy module returns statusInformation and, if
 the encryption process was successful, the encryptedPDU and the
 msgPrivacyParameters encoded as an OCTET STRING.  The abstract
 service primitive is:
    statusInformation =              -- success or failure
      encryptData(
      IN    encryptKey               -- secret key for encryption
      IN    dataToEncrypt            -- data to encrypt (scopedPDU)
      OUT   encryptedData            -- encrypted data (encryptedPDU)
      OUT   privParameters           -- filled in by service provider
            )
 The abstract data elements are:
 statusInformation
    An indication of the success or failure of the encryption process.
    In case of failure, it is an indication of the error.
 encryptKey
    The secret key to be used by the encryption algorithm.  The length
    of this key MUST be 16 octets.
 dataToEncrypt
    The data that must be encrypted.

Blumenthal, et al. Standards Track [Page 10] RFC 3826 AES for SNMP's USM June 2004

 encryptedData
    The encrypted data upon successful completion.
 privParameters
    The privParameters encoded as an OCTET STRING.

3.2.4.2. Services for Decrypting Incoming Data

 This AES privacy protocol assumes that the selection of the privKey
 is done by the caller and that the caller passes the localized secret
 key to be used.
 Upon completion the privacy module returns statusInformation and, if
 the decryption process was successful, the scopedPDU in plain text.
 The abstract service primitive is:
    statusInformation =
      decryptData(
      IN    decryptKey               -- secret key for decryption
      IN    privParameters           -- as received on the wire
      IN    encryptedData            -- encrypted data (encryptedPDU)
      OUT   decryptedData            -- decrypted data (scopedPDU)
            )
 The abstract data elements are:
 statusInformation
    An indication of whether the data was successfully decrypted, and
    if not, an indication of the error.
 decryptKey
    The secret key to be used by the decryption algorithm.  The length
    of this key MUST be 16 octets.
 privParameters
    The 64-bit integer to be used to calculate the IV.
 encryptedData
    The data to be decrypted.
 decryptedData
    The decrypted data.

3.3. Elements of Procedure

 This section describes the procedures for the AES privacy protocol
 for SNMP's User-based Security Model.

Blumenthal, et al. Standards Track [Page 11] RFC 3826 AES for SNMP's USM June 2004

3.3.1. Processing an Outgoing Message

 This section describes the procedure followed by an SNMP engine
 whenever it must encrypt part of an outgoing message using the
 usmAesCfb128PrivProtocol.
 1) The secret encryptKey is used to construct the AES encryption key,
    as described in section 3.1.2.1.
 2) The privParameters field is set to the serialization according to
    the rules in [RFC3417] of an OCTET STRING representing the 64-bit
    integer that will be used in the IV as described in section
    3.1.2.1.
 3) The scopedPDU is encrypted (as described in section 3.1.3) and the
    encrypted data is serialized according to the rules in [RFC3417]
    as an OCTET STRING.
 4) The serialized OCTET STRING representing the encrypted scopedPDU
    together with the privParameters and statusInformation indicating
    success is returned to the calling module.

3.3.2. Processing an Incoming Message

 This section describes the procedure followed by an SNMP engine
 whenever it must decrypt part of an incoming message using the
 usmAesCfb128PrivProtocol.
 1) If the privParameters field is not an 8-octet OCTET STRING, then
    an error indication (decryptionError) is returned to the calling
    module.
 2) The 64-bit integer is extracted from the privParameters field.
 3) The secret decryptKey and the 64-bit integer are then used to
    construct the AES decryption key and the IV that is computed as
    described in section 3.1.2.1.
 4) The encryptedPDU is then decrypted (as described in section
    3.1.4).
 5) If the encryptedPDU cannot be decrypted, then an error indication
    (decryptionError) is returned to the calling module.
 6) The decrypted scopedPDU and statusInformation indicating success
    are returned to the calling module.

Blumenthal, et al. Standards Track [Page 12] RFC 3826 AES for SNMP's USM June 2004

4. Security Considerations

 The security of the cryptographic functions defined in this document
 lies both in the strength of the functions themselves against various
 forms of attack, and also, perhaps more importantly, in the keying
 material that is used with them.  The recommendations in Section 1.3
 SHOULD be followed to ensure maximum entropy to the selected
 passwords, and to protect the passwords while stored.
 The security of the CFB mode relies upon the use of a unique IV for
 each message encrypted with the same key [CRYPTO-B].  If the IV is
 not unique, a cryptanalyst can recover the corresponding plaintext.
 Section 3.1.2.1 defines a procedure to derive the IV from a local
 64-bit integer (the salt) initialized to a pseudo-random value at
 boot time.  An implementation can use any method to vary the value of
 the local 64-bit integer, providing the chosen method never generates
 a duplicate IV for the same key.
 The procedure of section 3.1.2.1 suggests a method to vary the local
 64-bit integer value that generates unique IVs for every message.
 This method can result in a duplicated IV in the very unlikely event
 that multiple managers, communicating with a single authoritative
 engine, both accidentally select the same 64-bit integer within a
 second.  The probability of such an event is very low, and does not
 significantly affect the robustness of the mechanisms proposed.
 This AES-based privacy protocol MUST be used with one of the
 authentication protocols defined in RFC 3414 or with an
 algorithm/protocol providing equivalent functionality (including
 integrity), because CFB encryption mode does not detect ciphertext
 modifications.
 For further security considerations, the reader is encouraged to read
 [RFC3414], and the documents that describe the actual cipher
 algorithms.

5. IANA Considerations

 IANA has assigned OID 20 for the snmpUsmAesMIB module under the
 snmpModules subtree, maintained in the registry at
 http://www.iana.org/assignments/smi-numbers.
 IANA has assigned OID 4 for the usmAesCfb128Protocol under the
 snmpPrivProtocols registration point, as defined in RFC 3411
 [RFC3411].

Blumenthal, et al. Standards Track [Page 13] RFC 3826 AES for SNMP's USM June 2004

6. Acknowledgements

 Portions of this text, as well as its general structure, were
 unabashedly lifted from [RFC3414].  The authors are grateful to many
 of the SNMPv3 WG members for their help, especially Wes Hardaker,
 Steve Moulton, Randy Presuhn, David Town, and Bert Wijnen.  Security
 discussions with Steve Bellovin helped to streamline this protocol.

7. References

7.1. Normative References

 [AES-MODE] Dworkin, M., "NIST Recommendation for Block Cipher Modes
            of Operation, Methods and Techniques", NIST Special
            Publication 800-38A, December 2001.
 [FIPS-AES] "Specification for the ADVANCED ENCRYPTION STANDARD
            (AES)", Federal Information Processing Standard (FIPS)
            Publication 197, November 2001.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2578]  McCloghrie, K., Perkins, D. and J. Schoenwaelder,
            "Structure of Management Information Version 2 (SMIv2)",
            STD 58, RFC 2578, April 1999.
 [RFC3411]  Harrington, D., Presuhn, R. and B. Wijnen, "An
            Architecture for Describing Simple Network Management
            Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
            December 2002.
 [RFC3414]  Blumenthal, U. and B. Wijnen, "User-based Security Model
            (USM) for version 3 of the Simple Network Management
            Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
 [RFC3417]  Presuhn, R., Ed., "Transport Mappings for the Simple
            Network Management Protocol (SNMP)", STD 62, RFC 3417,
            December 2002.

7.2. Informative References

 [CRYPTO-B] Bellovin, S., "Probable Plaintext Cryptanalysis of the IP
            Security Protocols", Proceedings of the Symposium on
            Network and Distributed System Security, San Diego, CA,
            pp. 155-160, February 1997.

Blumenthal, et al. Standards Track [Page 14] RFC 3826 AES for SNMP's USM June 2004

8. Authors' Addresses

 Uri Blumenthal
 Lucent Technologies / Bell Labs
 67 Whippany Rd.
 14D-318
 Whippany, NJ  07981, USA
 Phone:  +1-973-386-2163
 EMail:  uri@bell-labs.com
 Fabio Maino
 Andiamo Systems, Inc.
 375 East Tasman Drive
 San Jose, CA. 95134 USA
 Phone:  +1-408-853-7530
 EMail:  fmaino@andiamo.com
 Keith McCloghrie
 Cisco Systems, Inc.
 170 East Tasman Drive
 San Jose, CA. 95134-1706 USA
 Phone:  +1-408-526-5260
 EMail:  kzm@cisco.com

Blumenthal, et al. Standards Track [Page 15] RFC 3826 AES for SNMP's USM June 2004

9. Full Copyright Statement

 Copyright (C) The Internet Society (2004).  This document is subject
 to the rights, licenses and restrictions contained in BCP 78, and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM 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.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

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

Blumenthal, et al. Standards Track [Page 16]

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