Telnet Encryption: DES3 64 bit Cipher Feedback
RFC 2947
Document | Type |
RFC - Proposed Standard
(September 2000; No errata)
Was draft-altman-telnet-enc-des3-cfb (individual)
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Author | Jeffrey Altman | ||
Last updated | 2013-03-02 | ||
Stream | Legacy stream | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 2947 (Proposed Standard) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group J. Altman Request for Comments: 2947 Columbia University Category: Standards Track September 2000 Telnet Encryption: DES3 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 Triple-DES (data encryption standard) encryption algorithm in cipher feedback mode with the telnet encryption option. 1. Command Names and Codes Encryption Type DES3_CFB64 3 Suboption Commands CFB64_IV 1 CFB64_IV_OK 2 CFB64_IV_BAD 3 2. Command Meanings IAC SB ENCRYPT IS DES3_CFB64 CFB64_IV <initial vector> 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 [Page 1] RFC 2947 DES3 64 bit Cipher Feedback September 2000 IAC SB ENCRYPT REPLY DES3_CFB64 CFB64_IV_OK IAC SE IAC SB ENCRYPT REPLY DES3_CFB64 CFB64_IV_BAD IAC SE 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 DES3 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 keyid sent (received) in the last START command. If encryption (decryption) is not enabled when a CFB64_IV command is sent (received), the encryption (decryption) machine must be re- initialized after the next START command, with the keyid sent (received) in that START command, and the initial vector sent (received) in this CFB64_IV command. Altman Standards Track [Page 2] RFC 2947 DES3 64 bit Cipher Feedback September 2000 4. Algorithm DES3 64 bit Cipher Feedback key1 key2 key3 | | | v v v +-------+ +-------+ +-------+ +->| DES-e |->| DES-d |->| DES-e |-- + | +-------+ +-------+ +-------+ | | v INPUT --(-------------------------------->(+)+---> DATA | | +------------------------------------+ Given: iV: Initial vector, 64 bits (8 bytes) long. Dn: the nth chunk of 64 bits (8 bytes) of data to encrypt (decrypt). On: the nth chunk of 64 bits (8 bytes) of encrypted (decrypted) output. V0 = DES-e(DES-d(DES-e(iV, key1),key2),key3) On = Dn ^ Vn V(n+1) = DES-e(DES-d(DES-e(On, key1),key2),key3) 5. Integration with the AUTHENTICATION telnet option As noted in the telnet ENCRYPTION option specifications, a keyid value of zero indicates the default encryption key, as might beShow full document text