RFC 2419 (rfc2419) - Page 2 of 12

The PPP DES Encryption Protocol, Version 2 (DESE-bis)

RFC 2419                 PPP DES Encryption v2            September 1998


   6. Encryption ..................................................  6
   6.1. Padding Considerations ....................................  7
   6.2. Generation of the Ciphertext ..............................  8
   6.3. Retrieval of the Plaintext ................................  8
   6.4. Recovery after Packet Loss ................................  8
   7. MRU Considerations ..........................................  9
   8. Differences from RFC 1969 ...................................  9
   8.1. When to Pad ...............................................  9
   8.2. Assigned Numbers ..........................................  9
   8.3. Minor Editorial Changes ...................................  9
   9. Security Considerations .....................................  9
   10. References ................................................. 10
   11. Authors' Addresses ......................................... 11
   12. Full Copyright Statement ................................... 12

1.  Introduction

1.1.  Motivation

   The purpose of this memo is two-fold: to show how one specifies the
   necessary details of a "data" or "bearer" protocol given the context
   of the generic PPP Encryption Control Protocol, and also to provide
   at least one commonly-understood means of secure data transmission
   between PPP implementations.

   The DES encryption algorithm is a well studied, understood and widely
   implemented encryption algorithm.  The DES cipher was designed for
   efficient implementation in hardware, and consequently may be
   relatively expensive to implement in software.  However, its
   pervasiveness makes it seem like a reasonable choice for a "model"
   encryption protocol.

   Source code implementing DES in the "Electronic Code Book Mode" can be
   found in [7].  US export laws forbid the inclusion of
   compilation-ready source code in this document.

1.2.  Conventions

   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 [8].

2.  General Overview

   The purpose of encrypting packets exchanged between two PPP
   implementations is to attempt to insure the privacy of communication
   conducted via the two implementations.  The encryption process
   depends on the specification of an encryption algorithm and a shared



Sklower & Meyer             Standards Track