Camellia CMS: Use of the Camellia Encryption Algorithm in Cryptographic Message Syntax (CMS)

Network Working Group                                          S. Moriai
Request for Comments: 3657              Sony Computer Entertainment Inc.
Category: Standards Track                                        A. Kato
                                                NTT Software Corporation
                                                            January 2004


               Use of the Camellia Encryption Algorithm
                 in Cryptographic Message Syntax (CMS)

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 (2004).  All Rights Reserved.

Abstract

   This document specifies the conventions for using the Camellia
   encryption algorithm for encryption with the Cryptographic Message
   Syntax (CMS).

1.  Introduction

   This document specifies the conventions for using the Camellia
   encryption algorithm [CamelliaSpec] for encryption with the
   Cryptographic Message Syntax (CMS) [CMS].  The relevant object
   identifiers (OIDs) and processing steps are provided so that Camellia
   may be used in the CMS specification (RFC 3369, RFC 3370) for content
   and key encryption.

   Note:  This work was done when the first author worked for NTT.

1.1.  Camellia

   Camellia was jointly developed by Nippon Telegraph and Telephone
   Corporation and Mitsubishi Electric Corporation in 2000.  Camellia
   specifies the 128-bit block size and 128-, 192-, and 256-bit key
   sizes, the same interface as the Advanced Encryption Standard (AES).
   Camellia is characterized by its suitability for both software and
   hardware implementations as well as its high level of security.  From
   a practical viewpoint, it is designed to enable flexibility in
   software and hardware implementations on 32-bit processors widely
   used over the Internet and many applications, 8-bit processors used
   in smart cards, cryptographic hardware, embedded systems, and so on
   [CamelliaTech].  Moreover, its key setup time is excellent, and its
   key agility is superior to that of AES.

   Camellia has been scrutinized by the wide cryptographic community
   during several projects for evaluating crypto algorithms.  In
   particular, Camellia was selected as a recommended cryptographic
   primitive by the EU NESSIE (New European Schemes for Signatures,
   Integrity and Encryption) project [NESSIE] and also included in the
   list of cryptographic techniques for Japanese e-Government systems
   which were selected by the Japan CRYPTREC (Cryptography Research and
   Evaluation Committees) [CRYPTREC].

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
   "RECOMMENDED", "MAY", and "OPTIONAL" in this document (in uppercase,
   as shown) are to be interpreted as described in [RFC2119].

2.  Object Identifiers for Content and Key Encryption

   This section provides the OIDs and processing information necessary
   for Camellia to be used for content and key encryption in CMS.

   Camellia is added to the set of optional symmetric encryption
   algorithms in CMS by providing two classes of unique object
   identifiers (OIDs).  One OID class defines the content encryption
   algorithms and the other defines the key encryption algorithms.  Thus
   a CMS agent can apply Camellia either for content or key encryption
   by selecting the corresponding object identifier, supplying the
   required parameter, and starting the program code.

2.1.  OIDs for Content Encryption

   Camellia is added to the set of symmetric content encryption
   algorithms defined in [CMSALG].  The Camellia content-encryption
   algorithm, in Cipher Block Chaining (CBC) mode, for the three
   different key sizes are identified by the following object
   identifiers:

      id-camellia128-cbc OBJECT IDENTIFIER ::=
          { iso(1) member-body(2) 392 200011 61 security(1)
            algorithm(1) symmetric-encryption-algorithm(1)
            camellia128-cbc(2) }

      id-camellia192-cbc OBJECT IDENTIFIER ::=
          { iso(1) member-body(2) 392 200011 61 security(1)
            algorithm(1) symmetric-encryption-algorithm(1)
            camellia192-cbc(3) }

      id-camellia256-cbc OBJECT IDENTIFIER ::=
          { iso(1) member-body(2) 392 200011 61 security(1)
            algorithm(1) symmetric-encryption-algorithm(1)
            camellia256-cbc(4) }

   The AlgorithmIdentifier parameters field MUST be present, and the
   parameters field MUST contain the value of IV:

      CamelliaCBCParameter ::= CamelliaIV  --  Initialization Vector

      CamelliaIV ::= OCTET STRING (SIZE(16))

   The plain text is padded according to Section 6.3 of [CMS].

2.2.  OIDs for Key Encryption

   The key-wrap/unwrap procedures used to encrypt/decrypt a Camellia
   content-encryption key (CEK) with a Camellia key-encryption key (KEK)
   are specified in Section 3.  Generation and distribution of key-
   encryption keys are beyond the scope of this document.

   The Camellia key-encryption algorithm has the following object
   identifier:

     id-camellia128-wrap OBJECT IDENTIFIER ::=
                 { iso(1) member-body(2) 392 200011 61 security(1)
                   algorithm(1) key-wrap-algorithm(3)
                   camellia128-wrap(2) }

     id-camellia192-wrap OBJECT IDENTIFIER ::=
                 { iso(1) member-body(2) 392 200011 61 security(1)
                    algorithm(1) key-wrap-algorithm(3)
                    camellia192-wrap(3) }

     id-camellia256-wrap OBJECT IDENTIFIER ::=
                 { iso(1) member-body(2) 392 200011 61 security(1)
                   algorithm(1) key-wrap-algorithm(3)
                   camellia256-wrap(4) }

   In all cases the parameters field of AlgorithmIdentifier MUST be
   ABSENT, because the key wrapping procedure itself defines how and
   when to use an IV.  The OID gives the KEK key size, but does not make
   any statements as to the size of the wrapped Camellia CEK.
   Implementations MAY use different KEK and CEK sizes.  Implementations
   MUST support the CEK and the KEK having the same length.  If
   different lengths are supported, the KEK MUST be of equal or greater
   length than the CEK.

3.  Key Wrap Algorithm

   Camellia key wrapping and unwrapping are done in conformance with the
   AES key wrap algorithm [RFC3394], because Camellia and AES have the
   same block and key sizes, i.e., the block size of 128 bits and key
   sizes of 128, 192, and 256 bits.

3.1.  Notation and Definitions

   The following notation is used in the description of the key wrapping
   algorithms:

   Camellia(K, W)
                 Encrypt W using the Camellia codebook with key K
   Camellia-1(K, W)
                   Decrypt W using the Camellia codebook with key K
   MSB(j, W)     Return the most significant j bits of W
   LSB(j, W)     Return the least significant j bits of W
   B1 ^ B2       The bitwise exclusive or (XOR) of B1 and B2
   B1 | B2       Concatenate B1 and B2
   K             The key-encryption key K
   n             The number of 64-bit key data blocks
   s             The number of steps in the wrapping process, s = 6n
   P[i]          The ith plaintext key data block
   C[i]          The ith ciphertext data block
   A             The 64-bit integrity check register
   R[i]          An array of 64-bit registers where
                     i = 0, 1, 2, ..., n

   A[t], R[t][i] The contents of registers A and R[i] after encryption
                     step t.
   IV            The 64-bit initial value used during the wrapping
                     process.

   In the key wrap algorithm, the concatenation function will be used to
   concatenate 64-bit quantities to form the 128-bit input to the
   Camellia codebook.  The extraction functions will be used to split
   the 128-bit output from the Camellia codebook into two 64-bit
   quantities.

3.2.  Camellia Key Wrap

   Key wrapping with Camellia is identical to Section 2.2.1 of [RFC3394]
   with "AES" replaced by "Camellia".

   The inputs to the key wrapping process are the KEK and the plaintext
   to be wrapped.  The plaintext consists of n 64-bit blocks, containing
   the key data being wrapped.  The key wrapping process is described
   below.

   Inputs:      Plaintext, n 64-bit values {P[1], P[2], ..., P[n]},
                and Key, K (the KEK).
   Outputs:     Ciphertext, (n+1) 64-bit values {C[0], C[1], ...,
                C[n]}.

   1) Initialize variables.

       Set A[0] to an initial value (see Section 3.4)
       For i = 1 to n
            R[0][i] = P[i]

   2) Calculate intermediate values.

       For t = 1 to s, where s = 6n
           A[t] = MSB(64, Camellia(K, A[t-1] | R[t-1][1])) ^ t
           For i = 1 to n-1
               R[t][i] = R[t-1][i+1]
           R[t][n] = LSB(64, Camellia(K, A[t-1] | R[t-1][1]))

   3) Output the results.

       Set C[0] = A[t]
       For i = 1 to n
           C[i] = R[t][i]

   An alternative description of the key wrap algorithm involves
   indexing rather than shifting.  This approach allows one to calculate
   the wrapped key in place, avoiding the rotation in the previous
   description.  This produces identical results and is more easily
   implemented in software.

   Inputs:  Plaintext, n 64-bit values {P[1], P[2], ..., P[n]},
            and Key, K (the KEK).
   Outputs: Ciphertext, (n+1) 64-bit values {C[0], C[1], ...,
            C[n]}.

   1) Initialize variables.

       Set A = IV, an initial value (see Section 3.4)
       For i = 1 to n
           R[i] = P[i]

   2) Calculate intermediate values.

       For j = 0 to 5
           For i=1 to n
               B = Camellia(K, A | R[i])
               A = MSB(64, B) ^ t where t = (n*j)+i
               R[i] = LSB(64, B)

   3) Output the results.

       Set C[0] = A
       For i = 1 to n
           C[i] = R[i]

3.3.  Camellia Key Unwrap

   Key unwrapping with Camellia is identical to Section 2.2.2 of
   [RFC3394], with "AES" replaced by "Camellia".

   The inputs to the unwrap process are the KEK and (n+1) 64-bit blocks
   of ciphertext consisting of previously wrapped key.  It returns n
   blocks of plaintext consisting of the n 64-bit blocks of the
   decrypted key data.

   Inputs:  Ciphertext, (n+1) 64-bit values {C[0], C[1], ..., C[n]},
            and Key, K (the KEK).
   Outputs: Plaintext, n 64-bit values {P[1], P[2], ..., P[n]}.

   1) Initialize variables.

       Set A[s] = C[0] where s = 6n
       For i = 1 to n
           R[s][i] = C[i]

   2) Calculate the intermediate values.

       For t = s to 1
           A[t-1] = MSB(64, Camellia-1(K, ((A[t] ^ t) | R[t][n]))
           R[t-1][1] = LSB(64, Camellia-1(K, ((A[t]^t) | R[t][n]))
           For i = 2 to n
               R[t-1][i] = R[t][i-1]

   3) Output the results.

       If A[0] is an appropriate initial value (see Section 3.4),
       Then
           For i = 1 to n
               P[i] = R[0][i]
       Else
           Return an error

   The unwrap algorithm can also be specified as an index based
   operation, allowing the calculations to be carried out in place.
   Again, this produces the same results as the register shifting
   approach.

   Inputs:  Ciphertext, (n+1) 64-bit values {C[0], C[1], ..., C[n]},
            and Key, K (the KEK).
   Outputs: Plaintext, n 64-bit values {P[0], P[1], ..., P[n]}.

   1) Initialize variables.

       Set A = C[0]
       For i = 1 to n
           R[i] = C[i]

   2) Calculate intermediate values.

       For j = 5 to 0
           For i = n to 1
               B = Camellia-1(K, (A ^ t) | R[i]) where t = n*j+i
               A = MSB(64, B)
               R[i] = LSB(64, B)

   3) Output results.

   If A is an appropriate initial value (see Section 3.4),
   Then
       For i = 1 to n
           P[i] = R[i]
   Else
       Return an error

3.4.  Key Data Integrity -- the Initial Value

   The initial value (IV) refers to the value assigned to A[0] in the
   first step of the wrapping process.  This value is used to obtain an
   integrity check on the key data.  In the final step of the unwrapping
   process, the recovered value of A[0] is compared to the expected
   value of A[0].  If there is a match, the key is accepted as valid,
   and the unwrapping algorithm returns it.  If there is not a match,
   then the key is rejected, and the unwrapping algorithm returns an
   error.

   The exact properties achieved by this integrity check depend on the
   definition of the initial value.  Different applications may call for
   somewhat different properties; for example, whether there is need to
   determine the integrity of key data throughout its lifecycle or just
   when it is unwrapped.  This specification defines a default initial
   value that supports integrity of the key data during the period it is
   wrapped (in Section 3.4.1).  Provision is also made to support
   alternative initial values (in Section 3.4.2).

3.4.1.  Default Initial Value

   The default initial value (IV) is defined to be the hexadecimal
   constant:

      A[0] = IV = A6A6A6A6A6A6A6A6

   The use of a constant as the IV supports a strong integrity check on
   the key data during the period that it is wrapped.  If unwrapping
   produces A[0] = A6A6A6A6A6A6A6A6, then the chance that the key data
   is corrupt is 2^-64.  If unwrapping produces A[0] any other value,
   then the unwrap must return an error and not return any key data.

3.4.2.  Alternative Initial Values

   When the key wrap is used as part of a larger key management protocol
   or system, the desired scope for data integrity may be more than just
   the key data or the desired duration for more than just the period
   that it is wrapped.  Also, if the key data is not just a Camellia
   key, it may not always be a multiple of 64 bits.  Alternative
   definitions of the initial value can be used to address such
   problems.  According to [RFC3394], NIST will define alternative
   initial values in future key management publications as needed.  In
   order to accommodate a set of alternatives that may evolve over time,
   key wrap implementations that are not application-specific will
   require some flexibility in the way that the initial value is set and
   tested.

4.  SMIMECapabilities Attribute

   An S/MIME client SHOULD announce the set of cryptographic functions
   it supports by using the S/MIME capabilities attribute.  This
   attribute provides a partial list of OIDs of cryptographic functions
   and MUST be signed by the client.  The functions' OIDs SHOULD be
   logically separated in functional categories and MUST be ordered with
   respect to their preference.

   RFC 2633 [RFC2633], Section 2.5.2 defines the SMIMECapabilities
   signed attribute (defined as a SEQUENCE of SMIMECapability SEQUENCEs)
   to be used to specify a partial list of algorithms that the software
   announcing the SMIMECapabilities can support.

   If an S/MIME client is required to support symmetric encryption with
   Camellia, the capabilities attribute MUST contain the Camellia OID
   specified above in the category of symmetric algorithms.  The
   parameter associated with this OID MUST be CamelliaSMimeCapability.

      CamelliaSMimeCapabilty ::= NULL

   The SMIMECapability SEQUENCE representing Camellia MUST be DER-
   encoded as the following hexadecimal strings:

      Key Size                   Capability
       128          30 0f 06 0b 2a 83 08 8c 9a 4b 3d 01 01 01 02 05 00
       196          30 0f 06 0b 2a 83 08 8c 9a 4b 3d 01 01 01 03 05 00
       256          30 0f 06 0b 2a 83 08 8c 9a 4b 3d 01 01 01 04 05 00

   When a sending agent creates an encrypted message, it has to decide
   which type of encryption algorithm to use.  In general the decision
   process involves information obtained from the capabilities lists
   included in messages received from the recipient, as well as other
   information such as private agreements, user preferences, legal
   restrictions, and so on.  If users require Camellia for symmetric
   encryption, it MUST be supported by the S/MIME clients on both the
   sending and receiving side, and it MUST be set in the user
   preferences.

5.  Security Considerations

   This document specifies the use of Camellia for encrypting the
   content of a CMS message and for encrypting the symmetric key used to
   encrypt the content of a CMS message, and the other mechanisms are
   the same as the existing ones.  Therefore, the security
   considerations described in the CMS specifications [CMS][CMSALG] and
   the AES key wrap algorithm [RFC3394] can be applied to this document.
   No security problem has been found on Camellia [CRYPTREC][NESSIE].

6.  Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

   The IETF has been notified of intellectual property rights claimed in
   regard to some or all of the specification contained in this
   document.  For more information consult the online list of claimed
   rights.

7.  References

7.1.  Normative References

   [CamelliaSpec] Aoki, K., Ichikawa, T., Kanda, M., Matsui, M., Moriai,
                  S., Nakajima, J., and Tokita, T., "Specification of
                  Camellia - a 128-bit Block Cipher".
                  http://info.isl.ntt.co.jp/camellia/

   [CMS]          Housley, R., "Cryptographic Message Syntax", RFC 3369,
                  August 2002.

   [CMSALG]       Housley, R., "Cryptographic Message Syntax (CMS)
                  Algorithms", RFC 3370, August 2002.

   [RFC2633]      Ramsdell, B., Editor, "S/MIME Version 3 Message
                  Specification", RFC 2633, June 1999.

   [RFC3565]      Schaad, J., "Use of the Advanced Encryption Standard
                  (AES) Encryption Algorithm in Cryptographic Message
                  Syntax (CMS)", RFC 3565, July 2003.

   [RFC3394]      Schaad, J. and R. Housley, "Advanced Encryption
                  Standard (AES) Key Wrap Algorithm", RFC 3394,
                  September 2002.

7.2.  Informative References

   [DES]          National Institute of Standards and Technology.  FIPS
                  Pub 46: Data Encryption Standard.  15 January 1977.

   [CamelliaTech] Aoki, K., Ichikawa, T., Kanda, M., Matsui, M., Moriai,
                  S., Nakajima, J., and Tokita, T., "Camellia: A 128-Bit
                  Block Cipher Suitable for Multiple Platforms - Design
                  and Analysis -", In Selected Areas in Cryptography,
                  7th Annual International Workshop, SAC 2000, August
                  2000, Proceedings, Lecture Notes in Computer Science
                  2012, pp.39-56, Springer-Verlag, 2001.

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

   [NESSIE]       New European Schemes for Signatures, Integrity and
                  Encryption (NESSIE) project.
                  http://www.cryptonessie.org

   [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.

Appendix A  ASN.1 Module

CamelliaEncryptionAlgorithmInCMS
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
      pkcs9(9) smime(16) modules(0) id-mod-cms-camellia(23) }

DEFINITIONS IMPLICIT TAGS ::=
BEGIN

-- Camellia using CBC-chaining mode for key sizes of 128, 192, 256

id-camellia128-cbc OBJECT IDENTIFIER ::=
    { iso(1) member-body(2) 392 200011 61 security(1)
      algorithm(1) symmetric-encryption-algorithm(1)
      camellia128-cbc(2) }

id-camellia192-cbc OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) 392 200011 61 security(1)
     algorithm(1) symmetric-encryption-algorithm(1)
     camellia192-cbc(3) }

id-camellia256-cbc OBJECT IDENTIFIER ::=
   { iso(1) member-body(2) 392 200011 61 security(1)
     algorithm(1) symmetric-encryption-algorithm(1)
     camellia256-cbc(4) }

-- Camellia-IV is the parameter for all the above object identifiers.

Camellia-IV ::= OCTET STRING (SIZE(16))

-- Camellia S/MIME Capabilty parameter for all the above object
-- identifiers.

CamelliaSMimeCapability ::= NULL

-- Camellia Key Wrap Algorithm identifiers - Parameter is absent.

id-camellia128-wrap OBJECT IDENTIFIER ::=
    { iso(1) member-body(2) 392 200011 61 security(1)
      algorithm(1) key-wrap-algorithm(3)
      camellia128-wrap(2) }

id-camellia192-wrap OBJECT IDENTIFIER ::=
    { iso(1) member-body(2) 392 200011 61 security(1)
      algorithm(1) key-wrap-algorithm(3)
      camellia192-wrap(3) }

id-camellia256-wrap OBJECT IDENTIFIER ::=
    { iso(1) member-body(2) 392 200011 61 security(1)
      algorithm(1) key-wrap-algorithm(3)
      camellia256-wrap(4) }

END

Authors' Addresses

   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)


   Akihiro Kato
   NTT Software Corporation
   Phone: +81-45-212-7934
   Fax:   +81-45-212-9800
   EMail: akato@po.ntts.co.jp

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