RFC 2631 (rfc2631) - Page 1 of 13

Diffie-Hellman Key Agreement Method

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Network Working Group                                       E. Rescorla
Request for Comments: 2631                                    RTFM Inc.
Category: Standards Track                                     June 1999


                  Diffie-Hellman Key Agreement Method

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

   This document standardizes one particular Diffie-Hellman variant,
   based on the ANSI X9.42 draft, developed by the ANSI X9F1 working
   group. Diffie-Hellman is a key agreement algorithm used by two
   parties to agree on a shared secret. An algorithm for converting the
   shared secret into an arbitrary amount of keying material is
   provided. The resulting keying material is used as a symmetric
   encryption key.  The Diffie-Hellman variant described requires the
   recipient to have a certificate, but the originator may have a static
   key pair (with the public key placed in a certificate) or an
   ephemeral key pair.

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . .   2
   1.1. Requirements Terminology  . . . . . . . . . . . . . . . .   2
   2. Overview Of Method  . . . . . . . . . . . . . . . . . . . .   2
   2.1. Key Agreement . . . . . . . . . . . . . . . . . . . . . .   2
   2.1.1. Generation of ZZ  . . . . . . . . . . . . . . . . . . .   3
   2.1.2. Generation of Keying Material . . . . . . . . . . . . .   3
   2.1.3. KEK Computation . . . . . . . . . . . . . . . . . . . .   4
   2.1.4. Keylengths for common algorithms  . . . . . . . . . . .   5
   2.1.5. Public Key Validation . . . . . . . . . . . . . . . . .   5
   2.1.6. Example 1 . . . . . . . . . . . . . . . . . . . . . . .   5
   2.1.7. Example 2 . . . . . . . . . . . . . . . . . . . . . . .   6
   2.2. Key and Parameter Requirements  . . . . . . . . . . . . .   7
   2.2.1. Group Parameter Generation  . . . . . . . . . . . . . .   7
   2.2.1.1. Generation of p, q  . . . . . . . . . . . . . . . . .   8



Rescorla                    Standards Track
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