draft-ietf-dnsext-rfc2539bis-dhk-06.txt

bind 源码 最新实现 linux/unix/windows平台

INTERNET-DRAFT                     Diffie-Hellman Information in the DNS
OBSOLETES: RFC 2539                               Donald E. Eastlake 3rd
                                                   Motorola Laboratories
Expires: January 2006                                          July 2005




        Storage of Diffie-Hellman Keying Information in the DNS
        ------- -- -------------- ------ ----------- -- --- ---
               <draft-ietf-dnsext-rfc2539bis-dhk-06.txt>



Status of This Document

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Distribution of this document is unlimited. Comments should be sent
   to the DNS extensions working group mailing list
   <[e-mail]>.

   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
   material or to cite them other than a "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html


Abstract

   The standard method for encoding Diffie-Hellman keys in the Domain
   Name System is specified.



Copyright

   Copyright (C) The Internet Society 2005.



D. Eastlake 3rd                                                 [Page 1]


INTERNET-DRAFT                     Diffie-Hellman Information in the DNS


Acknowledgements

   Part of the format for Diffie-Hellman keys and the description
   thereof was taken from a work in progress by Ashar Aziz, Tom Markson,
   and Hemma Prafullchandra.  In addition, the following persons
   provided useful comments that were incorporated into the predecessor
   of this document: Ran Atkinson, Thomas Narten.



Table of Contents

      Status of This Document....................................1
      Abstract...................................................1
      Copyright..................................................1

      Acknowledgements...........................................2
      Table of Contents..........................................2

      1. Introduction............................................3
      1.1 About This Document....................................3
      1.2 About Diffie-Hellman...................................3
      2. Encoding Diffie-Hellman Keying Information..............4
      3. Performance Considerations..............................5
      4. IANA Considerations.....................................5
      5. Security Considerations.................................5
      Copyright and Disclaimer...................................5

      Normative References.......................................7
      Informative Refences.......................................7

      Author Address.............................................8
      Expiration and File Name...................................8

      Appendix A: Well known prime/generator pairs...............9
      A.1. Well-Known Group 1:  A 768 bit prime..................9
      A.2. Well-Known Group 2:  A 1024 bit prime.................9
      A.3. Well-Known Group 3:  A 1536 bit prime................10














D. Eastlake 3rd                                                 [Page 2]


INTERNET-DRAFT                     Diffie-Hellman Information in the DNS


1. Introduction

   The Domain Name System (DNS) is the global hierarchical replicated
   distributed database system for Internet addressing, mail proxy, and
   similar information [RFC 1034, 1035]. The DNS has been extended to
   include digital signatures and cryptographic keys as described in
   [RFC 4033, 4034, 4035] and additonal work is underway which would use
   the storage of keying information in the DNS.



1.1 About This Document

   This document describes how to store Diffie-Hellman keys in the DNS.
   Familiarity with the Diffie-Hellman key exchange algorithm is assumed
   [Schneier, RFC 2631].



1.2 About Diffie-Hellman

   Diffie-Hellman requires two parties to interact to derive keying
   information which can then be used for authentication.  Thus Diffie-
   Hellman is inherently a key agreement algorithm. As a result, no
   format is defined for Diffie-Hellman "signature information".  For
   example, assume that two parties have local secrets "i" and "j".
   Assume they each respectively calculate X and Y as follows:

        X = g**i ( mod p )

        Y = g**j ( mod p )

   They exchange these quantities and then each calculates a Z as
   follows:

        Zi = Y**i ( mod p )

        Zj = X**j ( mod p )

   Zi and Zj will both be equal to g**(i*j)(mod p) and will be a shared
   secret between the two parties that an adversary who does not know i
   or j will not be able to learn from the exchanged messages (unless
   the adversary can derive i or j by performing a discrete logarithm
   mod p which is hard for strong p and g).

   The private key for each party is their secret i (or j).  The public
   key is the pair p and g, which must be the same for the parties, and
   their individual X (or Y).

   For further information about Diffie-Hellman and precautions to take


D. Eastlake 3rd                                                 [Page 3]


INTERNET-DRAFT                     Diffie-Hellman Information in the DNS


   in deciding on a p and g, see [RFC 2631].



2. Encoding Diffie-Hellman Keying Information

   When Diffie-Hellman keys appear within the RDATA portion of a RR,
   they are encoded as shown below.

   The period of key validity is not included in this data but is
   indicated separately, for example by an RR such as RRSIG which signs
   and authenticates the RR containing the keying information.

                            1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           KEY flags           |    protocol   |  algorithm=2  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     prime length (or flag)    |  prime (p) (or special)       /
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       /  prime (p)  (variable length) |       generator length        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | generator (g) (variable length)                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     public value length       | public value (variable length)/
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       /  public value (g^i mod p)    (variable length)                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Prime length is the length of the Diffie-Hellman prime (p) in bytes
   if it is 16 or greater.  Prime contains the binary representation of
   the Diffie-Hellman prime with most significant byte first (i.e., in
   network order). If "prime length" field is 1 or 2, then the "prime"
   field is actually an unsigned index into a table of 65,536
   prime/generator pairs and the generator length SHOULD be zero.  See
   Appedix A for defined table entries and Section 4 for information on
   allocating additional table entries.  The meaning of a zero or 3
   through 15 value for "prime length" is reserved.

   Generator length is the length of the generator (g) in bytes.
   Generator is the binary representation of generator with most
   significant byte first.  PublicValueLen is the Length of the Public
   Value (g**i (mod p)) in bytes.  PublicValue is the binary
   representation of the DH public value with most significant byte
   first.







D. Eastlake 3rd                                                 [Page 4]


INTERNET-DRAFT                     Diffie-Hellman Information in the DNS


3. Performance Considerations

   Current DNS implementations are optimized for small transfers,
   typically less than 512 bytes including DNS overhead.  Larger
   transfers will perform correctly and extensions have been
   standardized [RFC 2671] to make larger transfers more efficient. But
   it is still advisable at this time to make reasonable efforts to
   minimize the size of RR sets containing keying information consistent
   with adequate security.



4. IANA Considerations

   Assignment of meaning to Prime Lengths of 0 and 3 through 15 requires
   an IETF consensus as defined in [RFC 2434].

   Well known prime/generator pairs number 0x0000 through 0x07FF can
   only be assigned by an IETF standards action. [RFC 2539], the
   Proposed Standard predecessor of this document, assigned 0x0001
   through 0x0002. This document additionally assigns 0x0003.  Pairs
   number 0s0800 through 0xBFFF can be assigned based on RFC
   documentation. Pairs number 0xC000 through 0xFFFF are available for
   private use and are not centrally coordinated. Use of such private
   pairs outside of a closed environment may result in conflicts and/or
   security failures.



5. Security Considerations

   Keying information retrieved from the DNS should not be trusted
   unless (1) it has been securely obtained from a secure resolver or
   independently verified by the user and (2) this secure resolver and
   secure obtainment or independent verification conform to security
   policies acceptable to the user.  As with all cryptographic
   algorithms, evaluating the necessary strength of the key is important
   and dependent on security policy.

   In addition, the usual Diffie-Hellman key strength considerations
   apply. (p-1)/2 should also be prime, g should be primitive mod p, p
   should be "large", etc. See [RFC 2631, Schneier].



Copyright and Disclaimer

   Copyright (C) The Internet Society (2005).  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.


D. Eastlake 3rd                                                 [Page 5]