





Network Working Group                                            A. Kato
Request for Comments: 4312                      NTT Software Corporation
Category: Standards Track                                      S. Moriai
                                        Sony Computer Entertainment Inc.
                                                                M. Kanda
                              Nippon Telegraph and Telephone Corporation
                                                           December 2005


          The Camellia Cipher Algorithm and Its Use With IPsec

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 (2005).

Abstract

   This document describes the use of the Camellia block cipher
   algorithm in Cipher Block Chaining Mode, with an explicit
   Initialization Vector, as a confidentiality mechanism within the
   context of the IPsec Encapsulating Security Payload (ESP).

1.  Introduction

   This document describes the use of the Camellia block cipher
   algorithm in Cipher Block Chaining Mode, with an explicit
   Initialization Vector, as a confidentiality mechanism within the
   context of the IPsec Encapsulating Security Payload (ESP).

   Camellia was selected as a recommended cryptographic primitive by the
   EU NESSIE (New European Schemes for Signatures, Integrity and
   Encryption) project [NESSIE] and was included in the list of
   cryptographic techniques for Japanese e-Government systems that was
   selected by the Japan CRYPTREC (Cryptography Research, Evaluation
   Committees) [CRYPTREC].  Camellia has been submitted to several other
   standardization bodies, such as ISO (ISO/IEC 18033) and the IETF
   S/MIME Mail Security Working Group [Camellia-CMS].






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   Camellia supports 128-bit block size and 128-, 192-, and 256-bit key
   lengths, i.e., the same interface specifications as the Advanced
   Encryption Standard (AES) [AES].

   Camellia is a symmetric cipher with a Feistel structure.  Camillia
   was developed jointly by NTT and Mitsubishi Electric Corporation in
   2000.  It was designed to withstand all known cryptanalytic attacks,
   and it has been scrutinized by worldwide cryptographic experts.
   Camellia is suitable for implementation in software and hardware,
   offering encryption speed in software and hardware implementations
   that is comparable to AES.

   The Camellia homepage [Camellia-Web] contains a wealth of information
   about camellia, including detailed specification, security analysis,
   performance figures, reference implementation, test vectors, and
   intellectual property information.

   The remainder of this document specifies the use of Camellia within
   the context of IPsec ESP.  For further information on how the various
   pieces of ESP fit together to provide security services, please refer
   to [ARCH], [ESP], and [ROAD].

1.1.  Specification of Requirements

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" that
   appear in this document are to be interpreted as described in
   [RFC-2119].

2.  The Camellia Cipher Algorithm

   All symmetric block cipher algorithms share common characteristics
   and variables, including mode, key size, weak keys, block size, and
   rounds.  The following sections contain descriptions of the relevant
   characteristics of Camellia.

   The algorithm specification and object identifiers are described in
   [Camellia-Desc].

2.1.  Mode

   NIST has defined five modes of operation for AES and other FIPS-
   approved ciphers [SP800-38a]: CBC (Cipher Block Chaining), ECB
   (Electronic CodeBook), CFB (Cipher FeedBack), OFB (Output FeedBack),
   and CTR (Counter).  The CBC mode is well defined and well understood
   for symmetric ciphers, and it is currently required for all other ESP
   ciphers.  This document specifies the use of the Camellia cipher in
   CBC mode within ESP.  This mode requires an Initialization Vector



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   (IV) size that is the same as the block size.  Use of a randomly
   generated IV prevents generation of identical cipher text from
   packets that have identical data spanning the first block of the
   cipher algorithm's block size.

   The CBC IV is XOR'd with the first plaintext block before it is
   encrypted.  Then, for successive blocks, the previous cipher text
   block is XOR'd with the current plain text before it is encrypted.
   More information on CBC mode can be obtained in [SP800-38a,
   CRYPTO-S].

2.2.  Key Size

   Camellia supports three key sizes: 128 bits, 192 bits, and 256 bits.
   The default key size is 128 bits, and all implementations MUST
   support this key size.  Implementations MAY also support key sizes of
   192 bits and 256 bits.

   Camellia uses a different number of rounds for each of the defined
   key sizes.  When a 128-bit key is used, implementations MUST use 18
   rounds.  When a 192-bit key is used, implementations MUST use 24
   rounds.  When a 256-bit key is used, implementations MUST use 24
   rounds.

2.3.  Weak Keys

   At the time of writing this document, there are no known weak keys
   for Camellia.

2.4.  Block Size and Padding

   Camellia uses a block size of sixteen octets (128 bits).

   Padding is required by the algorithms to maintain a 16-octet
   (128-bit) block size.  Padding MUST be added, as specified in [ESP],
   such that the data to be encrypted (which includes the ESP Pad Length
   and Next Header fields) is a multiple of 16 octets.

   Because of the algorithm-specific padding requirement, no additional
   padding is required to ensure that the ciphertext terminates on a
   4-octet boundary.  That is, maintaining a 16-octet block size
   guarantees that the ESP Pad Length and Next Header fields will be
   right-aligned within a 4-octet word).  Additional padding MAY be
   included, as specified in [ESP], as long as the 16-octet block size
   is maintained.






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2.5.  Performance

   Performance figures of Camellia are available at [Camellia-Web].
   This web site also includes performance comparison with the AES
   cipher and other AES finalists.  The NESSIE project [NESSIE] has
   reported performance of Optimized Implementations independently.

3.  ESP Payload

   The ESP payload is made up of the IV followed by raw cipher-text.
   Thus, the payload field, as defined in [ESP], is broken down
   according to the following diagram:

   +---------------+---------------+---------------+---------------+
   |                                                               |
   +               Initialization Vector (16 octets)               +
   |                                                               |
   +---------------+---------------+---------------+---------------+
   |                                                               |
   ~ Encrypted Payload (variable length, a multiple of 16 octets)  ~
   |                                                               |
   +---------------------------------------------------------------+

   The IV field MUST be the same size as the block size of the cipher
   algorithm being used.  The IV MUST be chosen at random, and MUST be
   unpredictable.

   Including the IV in each datagram ensures that each received datagram
   can be decrypted, even when some datagrams are dropped or re-ordered
   in transit.

   To avoid CBC encryption of very similar plaintext blocks in different
   packets, implementations MUST NOT use a counter or other low
   Hamming-distance source for IVs.

3.1.  ESP Algorithmic Interactions

   Currently, there are no known issues regarding interactions between
   the Camellia and other aspects of ESP, such as the use of certain
   authentication schemes.

3.2.  Keying Material

   The minimum number of bits sent from the key exchange protocol to the
   ESP algorithm must be greater than or equal to the key size.  The
   cipher's encryption and decryption key is taken from the first 128,
   192, or 256 bits of the keying material.




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4.  Interaction with Internet Key Exchange [IKE]

   Camellia was designed to follow the same API as the AES cipher.
   Therefore, this section defines only Phase 1 Identifier and Phase 2
   Identifier.  Any other consideration related to interaction with IKE
   is the same as that of the AES cipher.  Details can be found in
   [AES-IPSEC].

4.1.  Phase 1 Identifier

   For Phase 1 negotiations, IANA has assigned an Encryption Algorithm
   ID of 8 for CAMELLIA-CBC.

4.2.  Phase 2 Identifier

   For Phase 2 negotiations, IANA has assigned an ESP Transform
   Identifier of 22 for ESP_CAMELLIA.

5.  Security Considerations

   Implementations are encouraged to use the largest key sizes they can,
   taking into account performance considerations for their particular
   hardware and software configuration.  Note that encryption
   necessarily affects both sides of a secure channel, so such
   consideration must take into account not only the client side, but
   also the server.  However, a key size of 128 bits is considered
   secure for the foreseeable future.

   No security problem has been found on Camellia [CRYPTREC][NESSIE].

6.  IANA Considerations

   IANA has assigned Encryption Algorithm ID = 8 to CAMELLIA-CBC.

   IANA has assigned ESP Transform Identifier = 22 to ESP_CAMELLIA.

7.  Acknowledgements

    Portions of this text were unabashedly borrowed from [AES-IPSEC].
    This work was done when the first author worked for NTT.











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8.  References

8.1.  Normative References

   [Camellia-Desc]  Matsui, M., Nakajima, J., and S. Moriai, "A
                    Description of the Camellia Encryption Algorithm",
                    RFC 3713, April 2004.

   [ESP]            Kent, S., "IP Encapsulating Security Payload (ESP)",
                    RFC 4303, December 2005.

8.2.  Informative References

   [AES]            NIST, FIPS PUB 197, "Advanced Encryption Standard
                    (AES)," November 2001.
                    http://csrc.nist.gov/publications/fips/fips197/
                    fips-197.{ps,pdf}.

   [AES-IPSEC]      Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC
                    Cipher Algorithm and Its Use With IPsec," RFC 3602,
                    September 2003.

   [ARCH]           Kent, S. and R. Atkinson, "Security Architecture for
                    the Internet Protocol", RFC 2401, November 1998.

   [Camellia-CMS]   Moriai, S. and A. Kato, "Use of the Camellia
                    Encryption Algorithm in Cryptographic Message Syntax
                    (CMS)", RFC 3657, January 2004.

   [Camellia-Web]   Camellia web site:
                    http://info.isl.ntt.co.jp/camellia/.

   [CRYPTO-S]       Schneier, B., "Applied Cryptography Second Edition",
                    John Wiley & Sons, New York, NY, 1995, ISBN 0-471-
                    12845-7.

   [CRYPTREC]       Information-technology Promotion Agency (IPA),
                    Japan, CRYPTREC.
                    http://www.ipa.go.jp/security/enc/CRYPTREC/ index-
                    e.html.

   [IKE]            Harkins, D. and D. Carrel, "The Internet Key
                    Exchange (IKE)", RFC 2409, November 1998.

   [SP800-38a]      Dworkin, M., "Recommendation for Block Cipher Modes
                    of Operation - Methods and Techniques", NIST Special
                    Publication 800-38A, December 2001.




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   [NESSIE]         The NESSIE project (New European Schemes for
                    Signatures, Integrity and Encryption),
                    http://www.cosic.esat.kuleuven.ac.be/nessie/.

   [ROAD]           Thayer, R., Doraswamy, N., and R. Glenn, "IP
                    Security Document Roadmap", RFC 2411, November 1998.

   [RFC-2119]       Bradner, S., "Key words for use in RFCs to Indicate
                    Requirement Levels", BCP 14, RFC 2119, March 1997.

Authors' Addresses

   Akihiro Kato
   NTT Software Corporation

   Phone: +81-45-212-7934
   Fax:   +81-45-212-7410
   EMail: akato@po.ntts.co.jp


   Shiho Moriai
   Sony Computer Entertainment Inc.

   Phone: +81-3-6438-7523
   Fax:   +81-3-6438-8629
   EMail: camellia@isl.ntt.co.jp (Camellia team)
          shiho@rd.scei.sony.co.jp (Shiho Moriai)


   Masayuki Kanda
   Nippon Telegraph and Telephone Corporation

   Phone: +81-46-859-2437
   Fax:   +81-46-859-3365
   EMail: kanda@isl.ntt.co.jp
















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Full Copyright Statement

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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.







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