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rfc:rfc2411

Network Working Group R. Thayer Request for Comments: 2411 Sable Technology Corporation Category: Informational N. Doraswamy

                                                         Bay Networks
                                                             R. Glenn
                                                                 NIST
                                                        November 1998
                            IP Security
                          Document Roadmap

Status of this Memo

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

Copyright Notice

 Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

 The IPsec protocol suite is used to provide privacy and
 authentication services at the IP layer.  Several documents are used
 to describe this protocol suite.  The interrelationship and
 organization of the various documents covering the IPsec protocol are
 discussed here.  An explanation of what to find in which document,
 and what to include in new Encryption Algorithm and Authentication
 Algorithm documents are described.

Table of Contents

 1. Introduction ................................................2
 2. Interrelationship of IPsec Documents ........................2
 3. Keying Material .............................................4
 4. Recommended Content of Algorithm Documents ..................5
 4.1 Encryption and Authentication Algorithms ...................5
 4.2 Encryption Algorithms ......................................6
 4.3 Authentication Algorithms ..................................7
 5. Security Considerations .....................................8
 6. Acknowledgments .............................................8
 7. References ..................................................9
 8. Authors' Addresses .........................................10
 9. Full Copyright Statement ...................................11

Thayer, et. al. Informational [Page 1] RFC 2411 IP Security Document Roadmap November 1998

1. Introduction

 This document is intended to provide guidelines for the development
 of collateral specifications describing the use of new encryption and
 authentication algorithms with the ESP protocol, described in [ESP]
 and new authentication algorithms used with the AH protocol,
 described in [AH].  ESP and AH are part of the IP Security
 architecture described in [Arch].  There is a requirement for a
 well-known procedure that can be used to add new encryption
 algorithms or authentication algorithms to ESP and AH, not only while
 the initial document set is undergoing development but after the base
 documents have achieved RFC status.  Following the guidelines
 discussed below simplifies adding new algorithms and reduces that
 amount of redundant documentation.
 The goal in writing a new Encryption Algorithm or Authentication
 Algorithm document is to concentrate on the application of the
 specific algorithm within ESP and AH.  General ESP and AH concepts,
 definitions, and issues are covered in the ESP and AH documents. The
 algorithms themselves are not described in these documents.  This
 gives us the capability to add new algorithms and also specify how
 any given algorithm might interact with other algorithms. The intent
 is to achieve the goal of avoiding duplication of information and
 excessive numbers of documents, the so-called "draft explosion"
 effect.

2. Interrelationship of IPsec Documents

 The documents describing the set of IPsec protocols are divided into
 seven groups.  This is illustrated in Figure 1.  There is a main
 Architecture document which broadly covers the general concepts,
 security requirements, definitions, and mechanisms defining IPsec
 technology.
 There is an ESP Protocol document and an AH Protocol document which
 covers the packet format and general issues regarding the respective
 protocols.  These protocol documents also contain default values if
 appropriate, such as the default padding contents, and mandatory to
 implement algorithms.  These documents dictate some of the values in
 the Domain Of Interpretation document [DOI].  Note the DOI document
 is itself part of the IANA Assigned Numbers mechanism and so the
 values described in the DOI are well-known.  See [DOI] for more
 information on the mechanism.
 The "Encryption Algorithm" document set, shown on the left, is the
 set of documents describing how various encryption algorithms are
 used for ESP.  These documents are intended to fit in this roadmap,
 and should avoid overlap with the ESP protocol document and with the

Thayer, et. al. Informational [Page 2] RFC 2411 IP Security Document Roadmap November 1998

 Authentication Algorithm documents.  Examples of this document are
 the [DES-Detroit] and [CBC] documents.  When these or other
 encryption algorithms are used for ESP, the DOI document has to
 indicate certain values, such as an encryption algorithm identifier,
 so these documents provide input to the DOI.
 The "Authentication Algorithm" document set, shown on the right, is
 the set of documents describing how various authentication algorithms
 are used for both ESP and AH.  These documents are intended to fit in
 this roadmap, and should avoid overlap with the AH protocol document
 and with the Encryption Algorithm documents.  Examples of this
 document are the [HMAC-MD5], and [HMAC-SHA-1] documents.  When these
 or other algorithms are used for either ESP or AH, the DOI document
 has to indicate certain values, such as algorithm type, so these
 documents provide input to the DOI.
 The "Key Management Documents", shown at the bottom, are the
 documents describing the IETF standards-track key management schemes.
 These documents provide certain values for the DOI also.  Note that
 issues of key management should be indicated here and not in, for
 example, the ESP and AH protocol documents.  Currently this box
 represents [ISAKMP], [Oakley], and [Resolution].
 The DOI document, shown in the middle, contains values needed for the
 other documents to relate to each other.  This includes for example
 encryption algorithms, authentication algorithms, and operational
 parameters such as key lifetimes.

Thayer, et. al. Informational [Page 3] RFC 2411 IP Security Document Roadmap November 1998

                    +--------------+
                    | Architecture |
                    +--------------+
                      v          v
             +<-<-<-<-+          +->->->->+
             v                            v
    +----------+                       +----------+
    |   ESP    |                       |    AH    |
    | Protocol |                       | Protocol |
    +----------+                       +----------+
      v      v                           v       v
      v      +->->->->->->->->+          v       v
      v      v                v          v       v
      v      v                v          v       v
      v  +------------+     +----------------+   v
      v  | +------------+   | +----------------+ v
      v  | | Encryption |   | | Authentication | v
      v  +-| Algorithm  |   +-| Algorithm      | v
      v    +------------+     +----------------+ v
      v        v                       v         v
      v        v        +-----+        v         v
      +>->->->-+->->->->| DOI |<-<-<-<-+-<-<-<-<-+
                        +-----+
                           ^
                           ^
                     +------------+
                     |    KEY     |
                     | MANAGEMENT |
                     +------------+
            Figure 1. IPsec Document Roadmap.

3. Keying Material

 Describing the encryption and authentication algorithms in different
 documents raises the issue of how the key management protocols knows
 the required keying material length for the desired algorithms when
 used together with ESP.  It also raises the issue of how to divide
 the keying material.  This is known as the "slicing and dicing"
 information.
 Each Encryption Algorithm and Authentication Algorithm document
 should specify their respective key attributes (e.g. how to pad,
 location of parity bits, key order for multi-keyed algorithms, and
 length).  The key management protocols should use the length of the
 keys specified in the respective Algorithm documents to generate the
 keying material of required length.

Thayer, et. al. Informational [Page 4] RFC 2411 IP Security Document Roadmap November 1998

 The key management protocol generates keying material with enough
 strength and size to generate keys for individual algorithms. The
 IPsec Architecture document specifies how keys are extracted from a
 single block of keying material when multiple keys are required (e.g.
 ESP with authentication).  The Encryption Algorithm and
 Authentication Algorithm documents are responsible for specifying the
 key sizes and strengths for each algorithm. However, whether the
 entire keying material is passed down to the kernel to perform
 slicing and dicing or if the keys are sliced and diced by key
 management protocol is an implementation issue. The AH protocol
 document has no such requirement.

4. Recommended Content of Algorithm Documents

 The document describing how a specific encryption or authentication
 algorithm is used should contain information appropriate to that
 encryption or authentication algorithm.  This section enumerates what
 information should be provided.  It is the intention of the document
 roadmap that:
 .  General protocol information goes in the respective ESP or AH
    protocol documents.
 .  Key management information goes in the key management documents.
 .  Assigned values and constants of negotiable items go in the DOI
    document.
 Encryption and authentication algorithms require some set of optional
 parameters or have optional modes of operation (e.g. IVs,
 authentication data lengths, and key lengths).  To help eliminate
 some complexity involved with key management having to negotiate
 large numbers of algorithm-specific parameters, encryption and
 authentication algorithm documents will select fixed values for these
 parameters when it is deemed technically reasonable and feasible.
 Note, the following information is intended as a general guideline
 only.

4.1 Encryption and Authentication Algorithms

 This section describes the information that should be included in
 both Encryption Algorithm and Authentication Algorithm documents.
 Keying Material
 .  Size of keys, including minimum, maximum, recommended and/or
    required sizes.  Note: the security considerations section should
    address any weakness in specific sizes.

Thayer, et. al. Informational [Page 5] RFC 2411 IP Security Document Roadmap November 1998

 .  Recommended or required pseudo-random number generator techniques
    and attributes to provide sufficiently strong keys.  [RANDOM]
    provides recommendations on generating strong randomness for use
    with security.
 .  Format of keying material.
 .  Known weak keys or references to documentation on known weak keys.
 .  Recommended or required processing of input keying material such
    as parity generation or checking.
 .  Requirements and/or recommendations on how often the keying
    material should be refreshed.
 Performance Considerations
 .  Any available estimates on performance of this algorithm.
 .  Any available comparison data  (e.g., compared against DES or
    MD5).
 .  Input size or other considerations that could improve or degrade
    performance.
 ESP Environmental Considerations
 .  Any known issues regarding interactions between this algorithm and
    other aspects of ESP, such as use of certain authentication
    schemes.  Note:  As new encryption and authentication algorithms
    are applied to ESP, the later documents will be required to
    address interactions with previously specified algorithms.
 Payload Content and Format Description
 .  Specification of size, placement, and content of algorithm-
    specific fields not defined in the ESP or AH protocol documents
    (e.g., IV).
 Security Considerations
 .  Discuss any known attacks.
 .  Discuss any known common implementation pitfalls, such as use of
    weak random number generators.
 .  Discuss any relevant validation procedures, such as test vectors.
    [RFC-2202] is an example document containing test vectors for
    a set of authentication algorithms.

4.2 Encryption Algorithms

 This section describes the information that should be included in the
 Encryption Algorithm documents.
 Encryption Algorithm Description
 .  General information how this encryption algorithm is to be used in
    ESP.
 .  Description of background material and formal algorithm
    description.

Thayer, et. al. Informational [Page 6] RFC 2411 IP Security Document Roadmap November 1998

 .  Features of this encryption algorithm to be used by ESP, including
    encryption and/or authentication.
 .  Mention of any availability issues such as Intellectual Property
    considerations.
 .  References, in IETF style, to background material such as FIPS
    documents.
 Algorithm Modes of Operation
 .  Description of how the algorithm is operated, whether it is block
    mode or streaming mode or other.
 .  Requirements for input or output block format.
 .  Padding requirements of this algorithm.  Note: there is a default
    for padding, specified in the base ESP document, so this is only
    needed if the default cannot be used.
 .  Any algorithm-specific operating parameters, such as number of
    rounds.
 .  Identify optional parameters and optional methods of operation and
    pick reasonable fixed values and methods with explicit technical
    explanations.
 .  Identify those optional parameters in which values and methods
    should remain optional with explicit technical explanations on why
    fixed values and methods should not be used.
 .  Defaults and mandatory ranges on algorithm-specific optional
    parameters that could not be fixed.

4.3 Authentication Algorithms

 This section describes the information that should be included in the
 Authentication Algorithm documents.  In most cases, an authentication
 algorithm will operate the same whether it is used for ESP or AH.
 This should be represented in a single Authentication Algorithm
 document.
 Authentication Algorithm Description
 .  General information on how this authentication algorithm is to be
    used with ESP and AH.
 .  Description of background material and formal algorithm
    description.
 .  Features of this authentication algorithm.
 .  Mention of any availability issues such as Intellectual Property
    considerations.
 .  References, in IETF style, to background material such as
    FIPS documents and definitive descriptions of underlying
    algorithms.
 Algorithm Modes of Operation
 .  Description of how the algorithm is operated.

Thayer, et. al. Informational [Page 7] RFC 2411 IP Security Document Roadmap November 1998

 .  Algorithm-specific operating parameters, such as number of
    rounds, and input or output block format.
 .  Implicit and explicit padding requirements of this algorithm.
    Note: There is a default method for padding of the
    authentication data field specified in the AH protocol document.
    This is only needed if the default cannot be used.
 .  Identify optional parameters and optional methods of operation and
    pick reasonable fixed values and methods with explicit technical
    explanations.
 .  Identify those optional parameters in which values and methods
    should remain optional with explicit technical explanations on why
    fixed values and methods should not be used.
 .  Defaults and mandatory ranges on algorithm-specific optional
    parameters that could not be fixed.
 .  Authentication data comparison criteria for this algorithm.  Note:
    There is a default method for verifying the authentication data
    specified in the AH protocol document.  This is only needed if the
    default cannot be used (e.g. when using a signed hash).

5. Security Considerations

 This document provides a roadmap and guidelines for writing
 Encryption and Authentication Algorithm documents. The reader should
 follow all the security procedures and guidelines described in the
 IPsec Architecture, ESP Protocol, AH Protocol, Encryption Algorithm,
 and Authentication Algorithm documents.  Note that many encryption
 algorithms are not considered secure if they are not used with some
 sort of authentication mechanism.

6. Acknowledgments

 Several Internet drafts were referenced in writing this document.
 Depending on where the documents are on (or off) the IETF standards
 track these may not be available through the IETF RFC repositories.
 In certain cases the reader may want to know what version of these
 documents were referenced. These documents are:
 .  DES-Detroit: this is the ANX Workshop style of ESP, based on the
    Hughes draft as modified by Cheryl Madson and published on the ANX
    mailing list.
 .  DOI: draft-ietf-ipsec-ipsec-doi-02.txt.
 .  3DES: this is <the Triple-DES shim document>.
 .  CAST: this is draft-ietf-ipsec-esp-cast-128-cbc-00.txt, as revised
    to relate to this document.
 .  ESP: draft-ietf-ipsec-esp-04.txt, mailed to the IETF mailing list
    in May/June 1997.
 .  AH: draft-ietf-ipsec-auth-05.txt, mailed to the IETF mailing list
    in May/June 1997.

Thayer, et. al. Informational [Page 8] RFC 2411 IP Security Document Roadmap November 1998

 .  HUGHES: this is draft-ietf-ipsec-esp-des-md5-03.txt
 .  ISAKMP: There are three documents describing ISAKMP.  These are
    draft-ietf-ipsec-isakmp-07.txt, draft-ietf-ipsec-isakmp-oakley-
    03.txt, and draft-ietf-ipsec-ipsec-doi-02.txt.

7. References

 [CBC]         Periera, R., and R. Adams, "The ESP CBC-Mode Cipher
               Algorithms", RFC 2451, November 1998.
 [Arch]        Kent, S., and R.  Atkinson, "Security Architecture for
               the Internet Protocol", RFC 2401, November 1998.
 [DES-Detroit] Madson, C., and N. Doraswamy, "The ESP DES-CBC Cipher
               Algorithm With Explicit IV", RFC 2405, November 1998.
 [DOI]         Piper, D., "The Internet IP Security Domain of
               Interpretation for ISAKMP", RFC 2407, November 1998.
 [AH]          Kent, S., and R. Atkinson, "IP Authentication Header",
               RFC 2402, November 1998.
 [ESP]         Kent, S., and R. Atkinson, "IP Encapsulating Security
               Payload (ESP)", RFC 2406, November 1998.
 [HMAC]        Krawczyk, K., Bellare, M., and R. Canetti, "HMAC:
               Keyed-Hashing for Message Authentication", RFC 2104,
               February 1997.
 [HMAC-MD5]    Madson, C., and R. Glenn, "The Use of HMAC-MD5 within
               ESP and AH", RFC 2403, November 1998.
 [HMAC-SHA-1]  Madson, C., and R. Glenn, "The Use of HMAC-SHA-1 within
               ESP and AH", RFC 2404, November 1998.
 [RANDOM]      Eastlake, D., Crocker, S., and J. Schiller, "Randomness
               Recommendations for Security", RFC 1750, December 1994.
 [RFC-2202]    Cheng, P., and R. Glenn, "Test Cases for HMAC-MD5 and
               HMAC-SHA-1", RFC 2202, March 1997.

Thayer, et. al. Informational [Page 9] RFC 2411 IP Security Document Roadmap November 1998

8. Authors' Addresses

 Rodney Thayer
 Sable Technology Corporation
 246 Walnut Street
 Newton, Massachusetts  02160
 EMail: mailto:rodney@sabletech.com
 Naganand Doraswamy
 Bay Networks
 EMail: naganand@baynetworks.com
 Rob Glenn
 NIST
 EMail: rob.glenn@nist.gov

Thayer, et. al. Informational [Page 10] RFC 2411 IP Security Document Roadmap November 1998

9. Full Copyright Statement

 Copyright (C) The Internet Society (1998).  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.

Thayer, et. al. Informational [Page 11]

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