Network Working Group Sean Turner
Internet Draft IECA
Intended Status: Standards Track April 18, 2013
Expires: October 20, 2013
Algorithms for Cryptographic Message Syntax (CMS)
Key Package Receipt and Error Content Types
draft-turner-ct-keypackage-receipt-n-error-algs-00.txt
Abstract
This document describes the conventions for using several
cryptographic algorithms with the Cryptographic Message Syntax (CMS)
key package receipt and error content types. Specifically, it
includes conventions necessary to implement SignedData,
EnvelopedData, EncryptedData, and AuthEnvelopedData.
Status of this Memo
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described in the Simplified BSD License.
1. Introduction
This document describes the conventions for using several
cryptographic algorithms with the Cryptographic Message Syntax (CMS)
key package receipt and error content types [ID.housley-keypackage-
receipt-n-error]. Specifically, it includes conventions necessary to
implement SignedData [RFC5652], EnvelopedData [RFC5652],
EncryptedData [RFC5652], and AuthEnvelopedData [RFC6083].
This document does not define any new algorithms; instead, it refers
to previously defined algorithms. In fact, the algorithm
requirements in this document are the same as those in
[RFC5959][RFC6162], [RFC6033][RFC6161], and [RFC6160] with the
following exceptions: the content-encryption algorithm is AES in CBC
mode as opposed to AES Key Wrap with MLI and the key-wrap algorithm
is AES Key Wrap as opposed to AES Key Wrap with Message Length
Indicator (MLI). The rationale for the difference is that the receipt
and error content types are not keys therefore AES Key Wrap with MLI
is not appropriate for the content-encryption algorithm and if an
implementation isn't using AES Key Wrap with MLI as the content-
encryption algorithm then there's no need to keep the key-wrap
algorithm the same as he content encryption algorithm.
NOTE: [ID.housley-keypackage-receipt-n-error] only requires that the
key package receipt be signed.
1.1 Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "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 RSA Probabilistic Signature Scheme (RSASSA-PSS) [RFC4056] and
Digital Signature Algorithm (DSA) [RFC3370]. Additionally,
implementations MUST support the hash function SHA-256 [RFC5754] in
concert with these signature schemes, and they SHOULD support the
hash function SHA-1 [RFC3370]. If an implementation supports
SignedData, then it MAY support Elliptic Curve Digital Signature
Algorithm (ECDSA) [RFC6090][RFC5753].
3. EnvelopedData
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If an implementation supports EnvelopedData, then it MUST implement
key transport, and it MAY implement key agreement.
When key transport is used, RSA encryption [RFC3370] MUST be
supported, and RSA Encryption Scheme - Optimal Asymmetric Encryption
Padding (RSAES-OAEP) [RFC3560] SHOULD be supported.
When key agreement is used, Diffie-Hellman (DH) ephemeral-static
[RFC3370] MUST be supported. When key agreement is used, Elliptic
Curve Diffie-Hellman (ECDH) [RFC6090][RFC5753] MAY be supported.
Regardless of the key management technique choice, implementations
MUST support AES-128 in CBC mode [AES] as the content-encryption
algorithm. Implementations SHOULD support AES-256 in CBC mode [AES]
as the content-encryption algorithm.
When key agreement is used, the same key-wrap algorithm MUST be used
for both key and content encryption. If the content-encryption
algorithm is AES-128 in CBC mode, then the key-wrap algorithm MUST be
AES-128 Key Wrap with Padding [RFC3394]. If the content-encryption
algorithm is AES-256 in CBC mode, then the key-wrap algorithm MUST be
AES-256 Key Wrap [RFC3394].
3. EncryptedData
If an implementation supports EncryptedData, then it MUST implement
AES-128 in CBC mode [AES] and SHOULD implement AES-256 in CBC mode
[AES].
NOTE: EncryptedData requires that keys be managed by other means;
therefore, the only algorithm specified is the content-encryption
algorithm.
4. 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 AES-CCM
[RFC5084].
5. 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 Diffie-
Hellman, then it MUST support key lengths from 1024-bit to 2048-bit,
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inclusive. If an implementation supports ECDSA or ECDH, then it MUST
support keys on P-256 [RFC6090].
6. IANA Considerations
None.
7. Security Considerations
The security considerations from [RFC3370], [RFC3394], [RFC3560],
[RFC4056], [RFC5083], [RFC5084], [RFC5652], [RFC5753], and [RFC5754]
apply.
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. Acknowledgements
I'd like to that Russ Housley for his early feedback on this
document.
9. References
9.1. Normative References
[AES] National Institute of Standards and Technology, FIPS Pub
197: Advanced Encryption Standard (AES), 26 November 2001.
[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] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, September 2002.
[RFC3560] Housley, R., "Use of the RSAES-OAEP Key Transport
Algorithm in Cryptographic Message Syntax (CMS)",
RFC 3560, July 2003.
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[RFC4056] Schaad, J., "Use of the 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.
[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.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
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.
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Transport Layer Security (DTLS) for Stream Control
Transmission Protocol (SCTP)", RFC 6083, January 2011.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090, February 2011.
[ID.housley-keypackage-receipt-n-error] Housley, R., "Cryptographic
Message Syntax (CMS) Key Package Receipt and Error Content
Types", draft-housley-ct-keypackage-receipt-n-error, April
2013.
9.2. Informative References
[RFC5959] Turner, S., "Algorithms for Asymmetric Key Package Content
Type", RFC 5959, August 2010.
[RFC6033] Turner, S., "Algorithms for Cryptographic Message Syntax
(CMS) Encrypted Key Package Content Type", RFC 6033,
December 2010.
[RFC6160] Turner, S., "Algorithms for Cryptographic Message Syntax
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(CMS) Protection of Symmetric Key Package Content Types",
RFC 6160, April 2011.
[RFC6161] Turner, S., "Elliptic Curve Algorithms for Cryptographic
Message Syntax (CMS) Encrypted Key Package Content Type",
RFC 6161, April 2011.
[RFC6162] Turner, S., "Elliptic Curve Algorithms for Cryptographic
Message Syntax (CMS) Asymmetric Key Package Content Type",
RFC 6162, April 2011.
[SP800-57] National Institute of Standards and Technology (NIST),
Special Publication 800-57: Recommendation for Key
Management - Part 1 (Revised), March 2007.
Author's Address
Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA
Email: turners@ieca.com
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