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Keywords: cipher block chaining mode, initialization vector, iv, esp, encapsulating security payload, ip security
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].
Kato, et al. Standards Track [Page 1]
RFC 4312 Camellia Cipher December 2005
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
Kato, et al. Standards Track [Page 2]
RFC 4312 Camellia Cipher December 2005
(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.
Kato, et al. Standards Track [Page 3]
RFC 4312 Camellia Cipher December 2005
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.
Kato, et al. Standards Track [Page 4]
RFC 4312 Camellia Cipher December 2005
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.
Kato, et al. Standards Track [Page 5]
RFC 4312 Camellia Cipher December 2005
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.
Kato, et al. Standards Track [Page 6]
RFC 4312 Camellia Cipher December 2005
[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
Kato, et al. Standards Track [Page 7]
RFC 4312 Camellia Cipher December 2005
Full Copyright Statement
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Kato, et al. Standards Track [Page 8]