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Versions: 00 RFC 6160

Network Working Group                                       Sean Turner
Internet Draft                                                     IECA
Intended Status: Standard Track                      September 23, 2010
Expires: March 23, 2010



             Algorithms for Cryptographic Message Syntax (CMS)
             Protection of Symmetric Key Package Content Types
             draft-turner-cms-symmetrickeypackage-algs-00.txt


Abstract

   This document describes the conventions for using several
   cryptographic algorithms with the Cryptographic Message Syntax (CMS)
   to protect the symmetric key package content type.  Specifically, it
   includes conventions necessary to implement SignedData,
   EnvelopedData, EncryptedData, and AuthEnvelopedData.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on March 23, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors. All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1. Introduction

   This document describes the conventions for using several
   cryptographic algorithms with the Cryptographic Message Syntax (CMS)
   [RFC5652] to protect the symmetric key package content type defined
   in [I-D.keyprov-symmetrickeyformat].  Specifically, it includes
   conventions necessary to implement the following CMS content types:
   SignedData [RFC5652], EnvelopedData [RFC5652], EncryptedData
   [RFC5652], and AuthEnvelopedData [RFC5083].  Familiarity with
   [RFC5083], [RFC5652], [RFC5753], and [I-D.keyprov-symmetrickeyformat]
   is assumed.

   This document does not define any new algorithms; instead it refers
   to previously defined algorithms.

1.1. Terminology

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

2. SignedData

   If an implementation supports SignedData, then it MUST support the
   signature scheme RSA [RFC3370] and SHOULD support the signature
   schemes RSASSA-PSS [RFC4056] and DSA [RFC3370].  Additionally,
   implementations MUST support in concert with these signature schemes
   the hash function SHA-256 [RFC5754] and they SHOULD support the hash
   function SHA-1 [RFC3370].  If an implementation supports SignedData,
   then it MAY support ECDSA [I-D.mcgrew-fundamental-ecc][RFC5753].

3. EnvelopedData

   If an implementation supports EnvelopedData, then it MUST implement
   key transport and it MAY implement key agreement.




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   When key transport is used, RSA encryption [RFC3370] MUST be
   supported and RSAES-OAEP [RFC3560] SHOULD be supported.

   When key agreement is used, Diffie-Hellman ephemeral-static [RFC3370]
   MUST be supported.  When key agreement is used, ECDH
   [I-D.mcgrew-fundamental-ecc][RFC5753] MAY be supported.

   Regardless of the key management technique choice, implementations
   MUST support AES-128 Key Wrap with Padding [RFC5649] as the content
   encryption algorithm.  Implementations SHOULD support AES-256 Key
   Wrap with Padding [RFC5649] as the content encryption algorithm.

   When key agreement is used, a key wrap algorithm is also specified to
   wrap the content encryption key.  If the content encryption algorithm
   is AES-128 Key Wrap with Padding, then the key wrap algorithm MUST be
   AES-128 Key Wrap with Padding [RFC5649].  If the content encryption
   algorithm is AES-256 Key Wrap with Padding, then the key wrap
   algorithm MUST be AES-256 Key Wrap with Padding [RFC5649].

4. EncryptedData

   If an implementation supports EncryptedData, then it MUST implement
   AES-128 Key Wrap with Padding [RFC5649] and SHOULD implement AES-256
   Key Wrap with Padding [RFC5649].

   NOTE: EncryptedData requires that keys be managed by other means;
   therefore, the only algorithm specified is the content encryption
   algorithm.

5. AuthEnvelopedData

   If an implementation supports AuthEnvelopedData, then it MUST
   implement the EnvelopedData recommendations except for the content
   encryption algorithm, which in this case MUST be AES-GCM [RFC5084];
   the 128-bit version MUST be implemented and the 256-bit version
   SHOULD be implemented.  Implementations MAY also support for AES-CCM
   [RFC5084].

6. Public Key Sizes

   The easiest way to implement SignedData, EnvelopedData, and
   AuthEnvelopedData is with public key certificates [RFC5280]. If an
   implementation supports RSA, RSASSA-PSS, DSA, RSAES-OAEP, or DH, then
   it MUST support key lengths from 1024-bit to 2048-bit, inclusive.  If
   an implementation supports ECDSA or ECDH, then it MUST support keys
   on P-256.



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7. Security Considerations

   The security considerations from [RFC3370], [RFC3560], [RFC4056],
   [RFC5083], [RFC5084], [RFC5649], [RFC5652], [RFC5753], [RFC5754], and
   [I-D.keyprov-symmetrickeyformat] apply.

   The choice of content encryption algorithms for this document was
   based on [RFC5649]: "In the design of some high assurance
   cryptographic modules, it is desirable to segregate cryptographic
   keying material from other data. The use of a specific cryptographic
   mechanism solely for the protection of cryptographic keying material
   can assist in this goal." Unfortunately, there is no AES-GCM or AES-
   CCM mode that provides the same properties.  If an AES-GCM and AES-
   CCM mode that provides the same properties is defined, then this
   document will be updated to adopt that algorithm.

   [SP800-57] provides comparable bits of security for some algorithms
   and key sizes. [SP800-57] also provides time frames during which
   certain numbers of bits of security are appropriate and some
   environments may find these time frames useful.

8. IANA Considerations

   None.  Please remove this section prior to publication as an RFC.

9. References

9.1. Normative References

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

   [RFC3370]   Housley, R., "Cryptographic Message Syntax (CMS)
               Algorithms", RFC 3370, August 2002.

   [RFC3560]   Housley, R., "Use of the RSAES-OAEP Key Transport
               Algorithm in the Cryptographic Message Syntax (CMS)", RFC
               3560, July 2003.

   [RFC4056]   Schaad, J., "Use of RSASSA-PSS Signature Algorithm in
               Cryptographic Message Syntax (CMS)", RFC 4056, June 2005.

   [RFC5083]   Housley, R., "Cryptographic Message Syntax (CMS)
               Authenticated-Enveloped-Data Content Type", RFC 5083,
               November 2007.




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   [RFC5084]   Housley, R., "Using AES-CCM and AES-GCM Authenticated
               Encryption in the Cryptographic Message Syntax (CMS)",
               RFC 5084, November 2007.

   [RFC5280]   Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
               Housley, R., and W. Polk, "Internet X.509 Public Key
               Infrastructure Certificate and Certificate Revocation
               List (CRL) Profile", RFC 5280, May 2008.

   [RFC5649]   Housley, R., and M. Dworkin, "Advanced Encryption
               Standard (AES) Key Wrap with Padding Algorithm", RFC
               5649, September 2009.

   [RFC5652]   Housley, R., "Cryptographic Message Syntax (CMS)", RFC
               5652, September 2009.

   [RFC5753]   Turner, S., and D. Brown, "Use of Elliptic Curve
               Cryptography (ECC) Algorithms in Cryptographic Message
               Syntax (CMS)", RFC 5753, January 2010.

   [RFC5754]   Turner, S., "Using SHA2 Algorithms with Cryptographic
               Message Syntax", RFC 5754, January 2010.

   [I-D.keyprov-symmetrickeyformat] Turner, S., and R. Housley,
               "Symmetric Key Package Content Type", draft-ietf-keyprov-
               symmetrickeyformat-11.txt, work-in-progress.

   [I-D.mcgrew-fundamental-ecc]  McGrew, D., Igoe, E., and M. Salter,
               "Fundamental Elliptic Curve Cryptography Algorithms",
               draft-mcgrew-fundamental-ecc-03.txt, work-in-progress.

9.2. Informative References

   [SP800-57]  National Institute of Standards and Technology (NIST),
               Special Publication 800-57: Recommendation for Key
               Management - Part 1 (Revised), March 2007.

Author's Addresses

   Sean Turner
   IECA, Inc.
   3057 Nutley Street, Suite 106
   Fairfax, VA 22031
   USA

   EMail: turners@ieca.com



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