draft-ietf-dnsext-rfc2539bis-dhk-00.txt

bind-3.2.

INTERNET-DRAFT                            Diffie-Hellman Keys in the DNS
OBSOLETES: RFC 2539                                  Donald Eastlake 3rd
                                                                Motorola
Expires: January 2002                                          July 2001




     Storage of Diffie-Hellman Keys in the Domain Name System (DNS)
     ------- -- -------------- ---- -- --- ------ ---- ------ -----
               <draft-ietf-dnsext-rfc2539bis-dhk-00.txt>

                         Donald E. Eastlake 3rd


Status of This Document

   This draft is intended to be become a Draft Standard RFC.
   Distribution of this document is unlimited. Comments should be sent
   to the DNS extensions working group mailing list
   <[e-mail]> or to the author.

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.  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 as "work in progress."

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

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

















Donald Eastlake 3rd                                             [Page 1]


INTERNET-DRAFT                            Diffie-Hellman Keys in the DNS


Abstract

   A standard method for storing Diffie-Hellman keys in the Domain Name
   System is described which utilizes DNS KEY resource records.



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.




































Donald Eastlake 3rd                                             [Page 2]


INTERNET-DRAFT                            Diffie-Hellman Keys in the DNS


Table of Contents

      Status of This Document....................................1

      Abstract...................................................2
      Acknowledgements...........................................2

      Table of Contents..........................................3

      1. Introduction............................................4
      1.1 About This Document....................................4
      1.2 About Diffie-Hellman...................................4
      2. Diffie-Hellman KEY Resource Records.....................5
      3. Performance Considerations..............................6
      4. IANA Considerations.....................................6
      5. Security Considerations.................................6

      References.................................................7
      Author's Address...........................................7
      Expiration and File Name...................................7

      Appendix A: Well known prime/generator pairs...............8
      A.1. Well-Known Group 1:  A 768 bit prime..................8
      A.2. Well-Known Group 2:  A 1024 bit prime.................8
      A.3. Well-Known Group 3:  A 1536 bit prime.................9



























Donald Eastlake 3rd                                             [Page 3]


INTERNET-DRAFT                            Diffie-Hellman Keys in the DNS


1. Introduction

   The Domain Name System (DNS) is the current global hierarchical
   replicated distributed database system for Internet addressing, mail
   proxy, and similar information. The DNS has been extended to include
   digital signatures and cryptographic keys as described in [RFC 2535].
   Thus the DNS can now be used for secure key distribution.



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].



1.2 About Diffie-Hellman

   Diffie-Hellman requires two parties to interact to derive keying
   information which can then be used for authentication.  Since DNS SIG
   RRs are primarily used as stored authenticators of zone information
   for many different resolvers, no Diffie-Hellman algorithm SIG RR is
   defined. 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**(ij)(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
   in deciding on a p and g, see [RFC 2631].


Donald Eastlake 3rd                                             [Page 4]


INTERNET-DRAFT                            Diffie-Hellman Keys in the DNS


2. Diffie-Hellman KEY Resource Records

   Diffie-Hellman keys are stored in the DNS as KEY RRs using algorithm
   number 2.  The structure of the RDATA portion of this RR is as shown
   below.  The first 4 octets, including the flags, protocol, and
   algorithm fields are common to all KEY RRs as described in [RFC
   2535].  The remainder, from prime length through public value is the
   "public key" part of the KEY RR. The period of key validity is not in
   the KEY RR but is indicated by the SIG RR(s) which signs and
   authenticates the KEY RR(s) at that domain name.

                            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)                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+