1. Introduction

This document describes the use of the DES Cipher algorithm in Cipher Block Chaining Mode as a confidentiality mechanism within the context of the Encapsulating Security Payload.

DES is a symmetric block cipher algorithm. The algorithm is described in [FIPS-46-2][FIPS-74][FIPS-81]. [Schneier96] provides a general description of Cipher Block Chaining Mode, a mode which is applicable to several encryption algorithms.

As specified in this memo, DES-CBC is not an authentication mechanism. [Although DES-MAC, described in [Schneier96] amongst other places, does provide authentication, DES-MAC is not discussed here.]

For further information on how the various pieces of ESP fit together to provide security services, refer to [ESP] and [road].

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC-2119].