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Versions: 00 01 02 RFC 6033

Network Working Group                                 Sean Turner, IECA
Internet Draft                                       September 08, 2009
Intended Status: Standard Track
Expires: March 08, 2010



             Algorithms for Encrypted Key Package Content Type
          draft-turner-encryptedkeypackagecontenttype-algs-00.txt


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Abstract

   This document describes the conventions for using several
   cryptographic algorithms with the encrypted key package content type.
   Specifically, it includes conventions necessary to implement
   EnvelopedData, EncryptedData, and AuthEnvelopedData.

1. Introduction

   This document describes the conventions for using several
   cryptographic algorithms with the encrypted key package content type
   [RFCTBD1].  Specifically, it includes conventions necessary to
   implement EnvelopedData [RFC3852], EncryptedData [RFC3852], and
   AuthEnvelopedData [RFC5083].

   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. EnvelopedData

   EnvelopedData supports a number of key management techniques.
   Implementations that claim conformance to this document MUST support
   the key transport mechanisms and SHOULD support the key agreement
   mechanisms.  Other techniques MAY be supported.

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

   When key agreement is used, Diffie-Hellman ephemeral-static [RFC3370]
   SHOULD be supported.

   Regardless of the key management technique choice, implementations
   MUST support AES-128 Key Wrap with Padding [RFCTBD2].
   Implementations SHOULD support AES-256 Key Wrap with Padding
   [RFCTBD2].

   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 key wrap algorithm MUST be
   AES-128 Key Wrap with Padding [RFCTBD2].  If the content encryption



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   algorithm is AES-256 Key Wrap with Padding, then the key wrap
   algorithm MUST be AES-256 Key Wrap with Padding [RFCTBD2].

3. EncryptedData

   EncryptedData requires that keys be managed by means other than
   EncryptedData; therefore, the only algorithm specified is the content
   encryption algorithm. Implementations MUST support AES-128 Key Wrap
   with Padding [RFCTBD2].  Implementations SHOULD support AES-256 Key
   Wrap with Padding [RFCTBD2].

4. AuthEnvelopedData

   AuthEnvelopedData, like EnvelopedData, supports a number of key
   management techniques.  The key management requirements for
   AuthEnvelopedData are the same as EnvelopedData.  The difference is
   the content encryption algorithm.  Implementations MUST support
   either 128-bit AES-CCM or AES-GCM [RFC5084] and SHOULD support 256-
   bit AES-CCM or AES-GCM [RFC5084].

5. Public Key Sizes

   The easiest way to implement the key transport requirement for
   EnvelopedData and AuthenticatedData 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.

6. Security Considerations

   The security considerations from [RFC3370], [RFC3394], [RFC3560],
   [RFC3852], [RFC5083], [RFC5084], [RFCTBD1], and [RFCTBD2] apply.

   The choice of content encryption algorithms for this document was
   based on [RFCTBD2]: "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-CCM or AES-
   GCM mode that provides the same properties.  If an AES-CCM and AES-
   GCM 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.


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7. IANA Considerations

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

8. References

8.1. 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.

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

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

   [RFC3852]   Housley, R., "Cryptographic Message Syntax (CMS)", RFC
               3852, July 2004.

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

   [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.

   [RFCTBD1]   Turner, S., and R. Housley, "Encrypted Key Package
               Content Type", draft-
               turner-encryptedkeypacakgecontenttype-00.txt, work-in-
               progress.

   [RFCTBD2]   Housley, R., and M. Dworkin, "Advanced Encryption
               Standard (AES) Key Wrap with Padding Algorithm", draft-
               housley-aes-key-wrap-with-pad-03.txt, work-in-progress.




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8.2. Informative References

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

Authors' Addresses

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

   EMail: turners@ieca.com


































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