Internet DRAFT - draft-turner-cms-symmetrickeypackage-algs
draft-turner-cms-symmetrickeypackage-algs
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
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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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Internet-Draft Algorithms for Symmetric Key Packages Sept 2010
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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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