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172 lines
5.0 KiB
Plaintext
172 lines
5.0 KiB
Plaintext
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Network Working Group D. Shaw
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Request for Comments: 5581 June 2009
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Updates: 4880
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Category: Informational
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The Camellia Cipher in OpenPGP
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Status of This Memo
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This memo provides information for the Internet community. It does
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not specify an Internet standard of any kind. Distribution of this
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memo is unlimited.
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Copyright Notice
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Copyright (c) 2009 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Provisions Relating to IETF Documents in effect on the date of
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publication of this document (http://trustee.ietf.org/license-info).
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Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document.
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Abstract
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This document presents the necessary information to use the Camellia
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symmetric block cipher in the OpenPGP protocol.
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Table of Contents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
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2. Requirements Notation . . . . . . . . . . . . . . . . . . . . . 2
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3. Camellia . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
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4. Security Considerations . . . . . . . . . . . . . . . . . . . . 2
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5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
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6. Normative References . . . . . . . . . . . . . . . . . . . . . 3
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Shaw Informational [Page 1]
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RFC 5581 The Camellia Cipher in OpenPGP June 2009
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1. Introduction
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The OpenPGP protocol [RFC4880] can support many different symmetric
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ciphers. This document presents the necessary information to use the
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Camellia [RFC3713] symmetric cipher in the OpenPGP protocol.
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2. Requirements Notation
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in [RFC2119].
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3. Camellia
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Camellia is specified in [RFC3713]. It is a 128-bit symmetric block
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cipher (as are AES and Twofish in OpenPGP) that supports 128-bit,
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192-bit, and 256-bit keys. This document defines the use of Camellia
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in OpenPGP.
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+---------------------+----------------------------------------+
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| Camellia Key Length | OpenPGP Symmetric-Key Algorithm Number |
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+---------------------+----------------------------------------+
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| 128 | 11 |
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| 192 | 12 |
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| 256 | 13 |
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+---------------------+----------------------------------------+
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OpenPGP applications MAY implement Camellia. If implemented,
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Camellia may be used in any place in OpenPGP where a symmetric cipher
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is usable, and it is subject to the same usage requirements (such as
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its presence in the Preferred Symmetric Algorithms signature
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subpacket) as the other symmetric ciphers in OpenPGP.
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While the OpenPGP algorithm preferences system prevents
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interoperability problems with public key encrypted messages, if
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Camellia (or any other optional cipher) is used for encrypting
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private keys, there could be interoperability problems when migrating
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a private key from one system to another. A similar issue can arise
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when using an optional cipher for symmetrically encrypted messages,
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as this OpenPGP message type does not use the algorithm preferences
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system. Those using optional ciphers in this manner should take care
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they are using a cipher that their intended recipient can decrypt.
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4. Security Considerations
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At publication time, there are no known weak keys for Camellia, and
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the Camellia algorithm is believed to be strong. However, as with
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any technology involving cryptography, implementers should check the
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Shaw Informational [Page 2]
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RFC 5581 The Camellia Cipher in OpenPGP June 2009
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current literature, as well as the Camellia home page at
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http://info.isl.ntt.co.jp/camellia/ to determine if Camellia has been
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found to be vulnerable to attack.
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5. IANA Considerations
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IANA assigned three algorithm numbers from the registry of OpenPGP
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Symmetric-Key Algorithms that was created by [RFC4880].
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6. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3713] Matsui, M., Nakajima, J., and S. Moriai, "A Description of
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the Camellia Encryption Algorithm", RFC 3713, April 2004.
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[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
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Thayer, "OpenPGP Message Format", RFC 4880, November 2007.
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Author's Address
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David Shaw
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EMail: dshaw@jabberwocky.com
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Shaw Informational [Page 3]
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