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Internet Engineering Task Force (IETF)                         S. TurnerRequest for Comments: 7192                                          IECACategory: Standards Track                                     April 2014ISSN: 2070-1721Algorithms for Cryptographic Message Syntax (CMS)Key Package Receipt and Error Content TypesAbstract   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   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7192.Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Turner                       Standards Track                    [Page 1]

RFC 7192       Algs for CMS Key Package Rcpt Content Type     April 20141.  Introduction   This document describes the conventions for using several   cryptographic algorithms with the Cryptographic Message Syntax (CMS)   key package receipt and error content types [RFC7191].  Specifically,   it includes conventions necessary to implement SignedData [RFC5652],   EnvelopedData [RFC5652], EncryptedData [RFC5652], and   AuthEnvelopedData [RFC5083].   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],   [RFC6033], [RFC6160], [RFC6161], and [RFC6162] with the following   exceptions: the content-encryption algorithm is AES in Cipher Block   Chaining (CBC) mode as opposed to AES Key Wrap with Message Length   Indicator (MLI) and the key-wrap algorithm is AES Key Wrap as opposed   to AES Key Wrap with 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.  If an implementation is not 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 the content encryption algorithm.   NOTE: [RFC7191] 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].  Implementations can also choose the   to support Elliptic Curve Digital Signature Algorithm (ECDSA)   [RFC5753] and [RFC6090].Turner                       Standards Track                    [Page 2]

RFC 7192       Algs for CMS Key Package Rcpt Content Type     April 20143.  EnvelopedData   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) [RFC5753] [RFC6090] 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 length for the underlying block   algorithm MUST be used.  If the content-encryption algorithm is   AES-128 in CBC mode, then the key-wrap algorithm MUST be AES-128 Key   Wrap [RFC3394].  If the content-encryption algorithm is AES-256 in   CBC mode, then the key-wrap algorithm MUST be AES-256 Key Wrap   [RFC3394].4.  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.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 AES-CCM   [RFC5084].Turner                       Standards Track                    [Page 3]

RFC 7192       Algs for CMS Key Package Rcpt Content Type     April 20146.  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,   inclusive.  If an implementation supports ECDSA or ECDH, then it MUST   support keys on the P-256 curve [RFC6090].7.  Security Considerations   The security considerations from [RFC3370], [RFC3394], [RFC3560],   [RFC4056], [RFC5084], [RFC5652], [RFC5753], and [RFC5754] apply.   [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 thank Russ Housley for his early feedback on this   document.9.  References9.1.  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)",RFC3560, July 2003.   [RFC4056]  Schaad, J., "Use of the RSASSA-PSS Signature Algorithm in              Cryptographic Message Syntax (CMS)",RFC 4056, June 2005.Turner                       Standards Track                    [Page 4]

RFC 7192       Algs for CMS Key Package Rcpt Content Type     April 2014   [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)",RFC5084, 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.   [RFC6090]  McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic              Curve Cryptography Algorithms",RFC 6090, February 2011.   [RFC7191]  Housley, R., "Cryptographic Message Syntax (CMS) Key              Package Receipt and Error Content Types",RFC 7191, April              2014.9.   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              (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.Turner                       Standards Track                    [Page 5]

RFC 7192       Algs for CMS Key Package Rcpt Content Type     April 2014   [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.comTurner                       Standards Track                    [Page 6]