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rfc:rfc3657

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.

Moriai & Kato Standards Track [Page 1] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

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.

Moriai & Kato Standards Track [Page 2] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

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) }

Moriai & Kato Standards Track [Page 3] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

   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

Moriai & Kato Standards Track [Page 4] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

 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]

Moriai & Kato Standards Track [Page 5] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

 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]}.

Moriai & Kato Standards Track [Page 6] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

 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)

Moriai & Kato Standards Track [Page 7] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

 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

Moriai & Kato Standards Track [Page 8] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

 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.

Moriai & Kato Standards Track [Page 9] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

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.

Moriai & Kato Standards Track [Page 10] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

 [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.

Moriai & Kato Standards Track [Page 11] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

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) }

Moriai & Kato Standards Track [Page 12] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

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

Moriai & Kato Standards Track [Page 13] RFC 3657 Use of the Camellia Algorithm in CMS January 2004

Full Copyright Statement

 Copyright (C) The Internet Society (2004).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
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 Internet organizations, except as needed for the purpose of
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 The limited permissions granted above are perpetual and will not be
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Acknowledgement

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

Moriai & Kato Standards Track [Page 14]

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