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Versions: 00 01 RFC 2411

Network  Working Group                                        R. Thayer
Internet Draft                                             N. Doraswamy
Category: Informational                                        R. Glenn
Expire in six months                                          July 1997


                              IP Security
                            Document Roadmap
                 <draft-ietf-ipsec-doc-roadmap-01.txt>




Status of This Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
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   To learn the current status of any Internet-Draft, please check the
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   ftp.isi.edu (US West Coast).

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

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.













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Contents

   Status of This Memo .................................................1

   Abstract ............................................................1

   Contents ............................................................2

   1. Introduction .....................................................3

   2. Interrelationship of IPsec Documents .............................3

   3. Keying Material ..................................................5

   4. Recommended Content of Algorithm Documents .......................6

   4.1 Encryption and Authentication Algorithms ........................6
   4.2 Encryption Algorithms ...........................................7
   4.3 Authentication Algorithms .......................................8

   5. Security Considerations ..........................................8

   6. Acknowledgments ..................................................9

   7. References .......................................................9

   8. Author's Addresses ..............................................10






























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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
   Authentication Algorithm documents.  Examples of this document are
   the [DES-1829], [DES-Detroit], [3DES], or [CAST] 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.




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   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.




































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                      +--------------+
                      | 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 lengths. The key management pro-
   tocols should use the length of the keys specified in the respective
   Algorithm documents to generate the keying material of required
   length.

   The key management protocol generates keying material with enough
   strength and size to generate keys for individual algorithms. The ESP
   protocol document is responsible for specifying how the keys are
   extracted from the keying material (sliced and diced). The Encryption
   Algorithm and Authentication Algorithm documents are responsible for
   specifying the key sizes and strengths for each algorithm. However,



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   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 docu-
   ment 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 go in the DOI document.

  Encryption and authentication algorithms require some set of optional
  parameters or have optional modes of operation (e.g. IVs, authentica-
  tion data lengths, and key lengths).  To help eliminate some complex-
  ity 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.
   .  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



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      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.

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.
   .  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.




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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 docu-
   ment.

   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.
   .  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 Encryp-
   tion 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 algo-
   rithms are not considered secure if they are not used with some sort
   of authentication mechanism.







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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:

   .  ARCH: draft-ietf-ipsec-arch-sec-01.txt.
   .  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.
   .  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

   [3DES]        Doraswamy, N., Metzger, P., Simpson, W.A., "The ESP
                 Triple DES Transform",
                 draft-ietf-ipsec-ciph-des3-00.txt, July 1997.

   [Arch]        Atkinson, R., "Security Architecture for the Internet
                 Protocol", RFC-1825, Naval Research Laboratory,
                 July 1995.

   [CAST]        Pereira, R., Carter, G., "The ESP CAST128-CBC
                 Algorithm", draft-ietf-ipsec-ciph-cast128-cbc-00.txt,
                 July 1997.

   [DES-Detroit] Madson, C., "The ESP DES-CBC Cipher Algorithm With
                 Explicit IV", draft-ietf-ipsec-ciph-des-expiv-00.txt,
                 July 1997.

   [DES-1829]    Metzger, P., Simpson, W.A., "The ESP DES-CBC
                 Transform", draft-ietf-ipsec-ciph-des-derived-00.txt,
                 July 1997.

   [DOI]         IP Security Domain of Interpretation, RFC-xxxx.

   [AH]          Kent, S., Atkinson, R., "IP Authentication Header",
                 draft-ietf-ipsec-auth-header-01.txt, July 1997.

   [ESP]         Kent, S., Atkinson, R., "IP Encapsulating Security
                 Payload (ESP)", draft-ietf-ipsec-esp-v2-00.txt,



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                 July 1997.

   [HMAC]        Krawczyk, K., Bellare, M., and Canetti R., "HMAC:
                 Keyed-Hashing for Message Authentication", RFC-2104,
                 February 1997.

   [HMAC-MD5]    Madson, C., Glenn, R., "The Use of HMAC-MD5 within ESP
                 and AH", draft-ietf-ipsec-hmac-md5-96-00.txt,
                 July 1997.

   [HMAC-SHA-1]  Madson, C., Glenn, R., "The Use of HMAC-SHA-1 within
                 ESP and AH", draft-ietf-ipsec-auth-hmac-sha196-00.txt,
                 July 1997.

   [RANDOM]      Eastlake, D., Crocker, S., Schiller, J., "Randomness
                 Recommendations for Security", RFC-1750,
                 December 1994.

8. Author's Addresses

   Rodney Thayer
   Sable Technology Corporation
   246 Walnut Street
   Newton, Massachusetts  02160
   <mailto:rodney@sabletech.com>

   Naganand Doraswamy
   Bay Networks
   e-mail: naganand@baynetworks.com

   Rob Glenn
   NIST
   e-mail: rob.glenn@nist.gov
























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