RFC 2950 (rfc2950) - Page 1 of 5
Telnet Encryption: CAST-128 64 bit Cipher Feedback
Alternative Format: Original Text Document
Network Working Group J. Altman
Request for Comments: 2950 Columbia University
Category: Standards Track September 2000
Telnet Encryption: CAST-128 64 bit Cipher 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 cipher 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_CFB64 8
CAST128_CFB64 10
Suboption Commands
CFB64_IV 1
CFB64_IV_OK 2
CFB64_IV_BAD 3
2. Command Meanings
IAC SB ENCRYPT IS CAST5_40_CFB64 CFB64_IV IAC SE
IAC SB ENCRYPT IS CAST128_CFB64 CFB64_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
CFB64_IV command. The initial vector is sent in clear text. Only
the side of the connection that is WILL ENCRYPT may send the
CFB64_IV command.
Altman Standards Track
