RFC 2949 (rfc2949) - Page 1 of 5

Telnet Encryption: CAST-128 64 bit Output Feedback

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Network Working Group                                          J. Altman
Request for Comments: 2949                           Columbia University
Category: Standards Track                                 September 2000


           Telnet Encryption: CAST-128 64 bit Output Feedback

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 (2000).  All Rights Reserved.

Abstract

   This document specifies how to use the CAST-128 encryption algorithm
   in output feedback mode with the telnet encryption option.  Two key
   sizes are defined: 40 bit and 128 bit.

1.  Command Names and Codes

   Encryption Type

      CAST5_40_OFB64   9
      CAST128_OFB64   11

   Suboption Commands

      OFB64_IV         1
      OFB64_IV_OK      2
      OFB64_IV_BAD     3

2.  Command Meanings

   IAC SB ENCRYPT IS CAST5_40_OFB64 OFB64_IV  IAC SE
   IAC SB ENCRYPT IS CAST128_OFB64 OFB64_IV  IAC SE

     The sender of this command generates a random 8 byte initial
     vector, and sends it to the other side of the connection using the
     OFB64_IV command.  The initial vector is sent in clear text.  Only
     the side of the connection that is WILL ENCRYPT may send the
     OFB64_IV command.



Altman                      Standards Track
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