Browse Prior Art Database

Telnet Encryption: DES 64 bit Cipher Feedback (RFC2952)

IP.com Disclosure Number: IPCOM000005145D
Original Publication Date: 2000-Sep-01
Included in the Prior Art Database: 2001-Aug-16
Document File: 6 page(s) / 9K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

T. Ts'o: AUTHOR

Abstract

This document specifies how to use the DES encryption algorithm in cipher feedback mode with the telnet encryption option.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 36% of the total text.

Network Working Group T. Ts'o Request for Comments: 2952 VA Linux Systems Category: Informational September 2000

Telnet Encryption: DES 64 bit Cipher Feedback

Status of this Memo

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. 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 DES encryption algorithm in cipher feedback mode with the telnet encryption option.

1. Command Names and Codes

Encryption Type

DES_CFB64 1

Suboption Commands

CFB64_IV 1 CFB64_IV_OK 2 CFB64_IV_BAD 3

2. Command Meanings

IAC SB ENCRYPT IS DES_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.

IAC SB ENCRYPT REPLY DES_CFB64 CFB64_IV_OK IAC SE IAC SB ENCRYPT REPLY DES_CFB64 CFB64_IV_BAD IAC SE

T'so Informational [Page 1]

RFC 2952 DES 64 bit Cipher Feedback September 2000

The sender of these commands either accepts or rejects the initial vector received in a CFB64_IV command. Only the side of the connection that is DO ENCRYPT may send the CFB64_IV_OK and CFB64_IV_BAD commands. The CFB64_IV_OK command MUST be sent for backwards compatibility with existing implementations; there really isn't any reason why a sender would need to send the CFB64_IV_BAD command except in the case of a protocol violation where the IV sent was not of the correct length (i.e., 8 bytes).

3. Implementation Rules

Once a CFB64_IV_OK command has been received, the WILL ENCRYPT side of the connection should do keyid negotiation using the ENC_KEYID command. Once the keyid negotiation has successfully identified a common keyid, then START and END commands may be sent by the side of the connection that is WILL ENCRYPT. Data will be encrypted using the DES 64 bit Cipher Feedback algorithm.

If encryption (decryption) is turned off and back on again, and the same keyid is used when re-starting the encryption (decryption), the intervening clear text must not change the state of the encryption (decryption) machine.

If a START command is sent (received) with a different keyid, the encryption (decryption) machine must be re-initialized immediately following the end of the START command with the new key and the initial vector sent (received) in the last CFB64_IV command.

If a new CFB64_IV command is sent (received), and encryption (decryption) is enabled, the encryption (decryption) machine must be re-initialized immediately following the end of the CFB64_IV command with the new initial vector, and the key...