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

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 
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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 
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   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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