Network Working Group D. Shaw
Internet-Draft December 5, 2008
Updates: 4880 (if approved)
Intended status: Standards Track
Expires: June 8, 2009
The Camellia Cipher in OpenPGP
draft-ietf-openpgp-camellia-04
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Abstract
This document presents the necessary information to use the Camellia
symmetric block cipher in the OpenPGP protocol.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3
3. Camellia . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
6. Normative References . . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 4
Intellectual Property and Copyright Statements . . . . . . . . . . 5
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1. Introduction
The OpenPGP protocol [RFC4880] can support many different symmetric
ciphers. This document presents the necessary information to use the
Camellia [RFC3713] cipher in the OpenPGP protocol.
2. Requirements notation
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 [RFC2119].
3. Camellia
Camellia is specified in [RFC3713]. It is a 128-bit block cipher (as
are AES and Twofish in OpenPGP), that supports 128-bit, 192-bit, and
256-bit keys. This document defines the use of Camellia in OpenPGP.
+---------------------+----------------------------------------+
| Camellia Key Length | OpenPGP Symmetric-Key Algorithm Number |
+---------------------+----------------------------------------+
| 128 | XXXX |
| 192 | YYYY |
| 256 | ZZZZ |
+---------------------+----------------------------------------+
[[To be allocated by IANA. Please fill this in: presumably XXXX ==
11, YYYY == 12, and ZZZZ == 13]]
OpenPGP applications MAY implement Camellia. If implemented,
Camellia may be used in any place in OpenPGP where a symmetric cipher
is usable, and is subject to the same usage requirements (such as its
presence in the Preferred Symmetric Algorithms signature subpacket)
as the other symmetric ciphers in OpenPGP.
While the OpenPGP algorithm preferences system prevents
interoperability problems with public key encrypted messages, if
Camellia (or any other optional cipher) is used for encrypting
private keys, there could be interoperability problems when migrating
a private key from one system to another. A similar issue can arise
when using an optional cipher for symmetrically encrypted messages,
as this OpenPGP message type does not perform cipher negotiation.
Those using optional ciphers in this manner should take care they are
using a cipher that their intended recipient can decrypt.
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4. Security Considerations
At publication time, there are no known weak keys for Camellia, and
the Camellia algorithm is believed to be strong. However, as with
any technology involving cryptography, implementers should check the
current literature, as well as the Camellia home page at
<http://info.isl.ntt.co.jp/camellia/>, to determine if Camellia has
been found to be vulnerable to attack.
5. IANA Considerations
This document requires IANA to assign three algorithm numbers from
the registry of OpenPGP Symmetric-Key Algorithms that was created by
[RFC4880].
6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3713] Matsui, M., Nakajima, J., and S. Moriai, "A Description of
the Camellia Encryption Algorithm", RFC 3713, April 2004.
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
Thayer, "OpenPGP Message Format", RFC 4880, November 2007.
Author's Address
David Shaw
Email: dshaw@jabberwocky.com
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