Network Working Group
Internet Draft A. Kato
January 2005 NTT Software Corporation
Expiration Date: June 2005 S. Moriai
Sony Computer Entertainment Inc.
M. Kanda
Nippon Telegraph and Telephone Corporation
January 2005
The Camellia Cipher Algorithm and Its Use With IPsec
<draft-kato-ipsec-ciph-camellia-00.txt>
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Copyright (C) The Internet Society (2005). All Rights Reserved.
Abstract
This document describes the use of the Camellia block cipher
algorithm in Cipher Block Chaining Mode, with an explicit IV, as
a confidentiality mechanism within the context of the IPsec
Encapsulating Security Payload (ESP).
1. Introduction
Camellia was selected as a recommended cryptographic primitive by
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the EU NESSIE (New European Schemes for Signatures, Integrity and
Encryption) project [NESSIE] and included in the list of
cryptographic techniques for Japanese e-Government systems, which
were selected by the Japan CRYPTREC (Cryptography Research,
Evaluation Committees) [CRYPTREC] . Camellia has been submitted to
other several standardization bodies such as ISO (ISO/IEC 18033) and
IETF S/MIME Mail Security Working Group [Camellia-CMS].
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 was jointly developed by NTT and Mitsubishi Electric
Corporation in 2000. It was carefully designed to withstand all
known cryptanalytic attacks and even to have a sufficiently large
security leeway. It has been scrutinized by worldwide
cryptographic experts.
Camellia was also designed to have suitability for both software
and hardware implementations and to cover all possible encryption
applications that range from low-cost smart cards to high-speed
network systems. Compared to the AES, Camellia offers at least
comparable encryption speed in software and hardware. Camellia has a
Feistel structure, which is different from AES. It is rich for the
IPsec community that has block cipher in which was well verified by
the cryptographic expert with another structure. In addition, a
distinguishing feature is its small hardware design.
Camellia perfectly meets one of the current IPsec market
requirements, where low power consumption is a mandatory
condition.
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].
The Camellia homepage, http://info.isl.ntt.co.jp/camellia/,
contains a wealth of information about camellia, including
detailed specification, security analysis, performance figures,
reference implementation, test vectors, and intellectual property
information.
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
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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 5 modes of operation for AES and other FIPS-approved
ciphers [MODES]: 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 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
(IV) that is the same size as the block size. Use of a randomly
generated IV prevents generation of identical cipher text from
packets, which have identical data that spans the first block of the
cipher algorithm's block size.
The 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 [MODES, CRYPTO-S].
For the use of CBC mode in ESP with 64-bit ciphers, please see [CBC].
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) has a length that is a multiple of 16 octets.
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Because of the algorithm specific padding requirement, no additional
padding is required to ensure that the ciphertext terminates on a
4-octet boundary (i.e. 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.
2.6. Performance
Performance figures of Camellia are available at
http://info.isl.ntt.co.jp/camellia/. It also includes performance
comparison with the AES cipher and other AES finalists.
[NESSIE] project 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 decryption of each
received datagram can be performed, even when some datagrams are
dropped, or datagrams are 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 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.
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The cipher's encryption and decryption key is taken from the first
<x> bits of the keying material, where <x> represents the required
key size.
4. Interaction with 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 (TBD1) for CAMELLIA-CBC.
4.2. Phase 2 Identifier
For Phase 2 negotiations, IANA has assigned an ESP Transform
Identifier of (TBD2) for ESP_CAMELLIA.
5. Security Considerations
Implementations are encouraged to use the largest key sizes they can
when 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
the server as well. 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 (TBD1) to CAMELLIA-CBC.
IANA has assigned ESP Transform Identifier (TBD2) to ESP_CAMELLIA.
7. Acknowledgments
Portions of this text were unabashedly borrowed from [AES-IPSEC].
This work was done when the first author worked for NTT.
8. References
8.1. Normative References
[Camellia-Desc]
Matsui, M., Nakajima, J., Moriai, S., "A Description of
the Camellia Encryption Algorithm", RFC3713, April 2004.
[ESP] Kent, S. and R. Atkinson, "IP Encapsulating Security
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Payload (ESP)", RFC 2406, November 1998.
[CBC] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher
Algorithms," RFC 2451, November 1998.
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., S. Kelly, and R. Glenn, "The AES 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 Kato, A., "Use of the Camellia
Encryption Algorithm in CMS", January 2004, RFC3657.
[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.
[MODES] Symmetric Key Block Cipher Modes of Operation,
http://www.nist.gov/modes/.
[NESSIE] The NESSIE project (New European Schemes for
Signatures, Integrity and Encryption),
http://www.cosic.esat.kuleuven.ac.be/nessie/.
[ROAD] Thayer, R., N. Doraswamy 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", RFC-2119, March 1997.
9. Authors' Addresses
Akihiro Kato
NTT Software Corporation
Phone: +81-45-212-7934
FAX: +81-45-212-7410
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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 "at" 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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