RFC 2403 (rfc2403) - Page 1 of 7

The Use of HMAC-MD5-96 within ESP and AH

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Network Working Group                                          C. Madson
Request for Comments: 2403                            Cisco Systems Inc.
Category: Standards Track                                       R. Glenn
                                                                    NIST
                                                           November 1998


                The Use of HMAC-MD5-96 within ESP and AH

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 (1998).  All Rights Reserved.

Abstract

   This memo describes the use of the HMAC algorithm [RFC-2104] in
   conjunction with the MD5 algorithm [RFC-1321] as an authentication
   mechanism within the revised IPSEC Encapsulating Security Payload
   [ESP] and the revised IPSEC Authentication Header [AH]. HMAC with MD5
   provides data origin authentication and integrity protection.

   Further information on the other components necessary for ESP and AH
   implementations is provided by [Thayer97a].

1.  Introduction

   This memo specifies the use of MD5 [RFC-1321] combined with HMAC
   [RFC-2104] as a keyed authentication mechanism within the context of
   the Encapsulating Security Payload and the Authentication Header.
   The goal of HMAC-MD5-96 is to ensure that the packet is authentic and
   cannot be modified in transit.

   HMAC is a secret key authentication algorithm. Data integrity and
   data origin authentication as provided by HMAC are dependent upon the
   scope of the distribution of the secret key. If only the source and
   destination know the HMAC key, this provides both data origin
   authentication and data integrity for packets sent between the two
   parties; if the HMAC is correct, this proves that it must have been
   added by the source.




Madson & Glenn              Standards Track
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