Network Working Group                                         P. Hoffman
Internet-Draft                                            VPN Consortium
Expires: March 28, 2005                               September 27, 2004


          Algorithms for Internet Key Exchange version 1 (IKEv1)
                  draft-hoffman-ikev1-algorithms-00.txt

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Copyright Notice

    Copyright (C) The Internet Society (2004).

Abstract

    The required and suggested algorithms in the original IKEv1
    specification does not reflect the current reality of IPsec market.
    It requires allowing weak security and suggests algorithms that are
    thinly implemented.  This document updates the original specification
    and is intended for all IKEv1 implementations deployed today.






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.  Introduction

    The original IKEv1 definition, RFC 2409 [RFC2409], has a set of
    MUST-level and SHOULD-level requirements that do not match the needs
    of IPsec users.  This document updates RFC by changing the algorithm
    requirements defined there.

    The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
    SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
    document, are to be interpreted as described in RFC 2119 [RFC2119].

.  Old algorithm requirements

    RFC 2409 has the following MUST-level and SHOULD-level requirements:

    o  DES for encryption MUST be supported
    o  MD5 and SHA-1 for hashing MUST be supported
    o  Diffie-Hellman MODP group 1 (discrete log 768 bits) MUST be
       supported
    o  TripleDES for encryption SHOULD be supported
    o  Tiger for hashing SHOULD be supported
    o  DSA and RSA for authentication with signatures SHOULD be supported
    o  RSA for authentication with encryption SHOULD be supported
    o  Diffie-Hellman MODP group 2 (discrete log 1024 bits) SHOULD be
       supported

    RFC 2409 gives two conflicting requirement levels for Diffie-Hellman
    MODP groups with elliptic curves.  Section 4 of that specification
    says "IKE implementations ...  MAY support ECP and EC2N groups", but
    Sections 6.3 and 6.4 say that MODP groups 3 and 4 for EC2N groups
    SHOULD be supported.

.  New algorithm requirements

    The new requirements for IKEv1 are:

    o  TripleDES for encryption MUST be supported
    o  SHA-1 for hashing MUST be supported
    o  Diffie-Hellman MODP group 2 (discrete log 1024 bits) MUST be
       supported
    o  RSA for authentication with signatures SHOULD be supported

    The other algorithms that were listed at MUST-level and SHOULD-level
    in RFC 2409 are now MAY-level.  This includes DES for encryption, MD5
    and Tiger for hashing, Diffie-Hellman MODP group 1, Diffie-Hellman
    MODP groups with elliptic curves, DSA for authentication with
    signatures, and RSA for authentication with encryption.  Some of
    these are dropped to MAY due to cryptographic weakness, while others



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    are dropped due to lack of any significant deployment and
    interoperability.

    Note that additional algorithms have been developed since the time of
    RFC 2409 that many people consider SHOULD-level or MUST-level.  Most
    notable among these are discrete log MODP groups with longer key
    lengths, AES-128 for encryption, and SHA-256 for hashing.  They are
    not included in this document because doing so would cause this
    document to be an extension to RFC 2409 instead of an update of RFC
    2409.

.  Security Considerations

    This document is all about security.  All the algorithms that are
    either MUST-level or SHOULD-level in the "new algoritm requirements"
    section of this document are believed to be robust and secure at the
    time of this writing.

  Normative References

    [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

    [RFC2409]  Harkins, D. and D. Carrel, "The Internet Key Exchange
               (IKE)", RFC 2409, November 1998.


Author's Address

    Paul Hoffman
    VPN Consortium
    127 Segre Place
    Santa Cruz, CA  95060
    US

    EMail: paul.hoffman@vpnc.org















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