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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Sean Turner 2 Internet Draft IECA 3 Intended Status: Standard Track September 23, 2010 4 Expires: March 23, 2010 6 Algorithms for Cryptographic Message Syntax (CMS) 7 Protection of Symmetric Key Package Content Types 8 draft-turner-cms-symmetrickeypackage-algs-00.txt 10 Abstract 12 This document describes the conventions for using several 13 cryptographic algorithms with the Cryptographic Message Syntax (CMS) 14 to protect the symmetric key package content type. Specifically, it 15 includes conventions necessary to implement SignedData, 16 EnvelopedData, EncryptedData, and AuthEnvelopedData. 18 Status of this Memo 20 This Internet-Draft is submitted to IETF in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF), its areas, and its working groups. Note that 25 other groups may also distribute working documents as Internet- 26 Drafts. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 The list of current Internet-Drafts can be accessed at 34 http://www.ietf.org/ietf/1id-abstracts.txt 36 The list of Internet-Draft Shadow Directories can be accessed at 37 http://www.ietf.org/shadow.html 39 This Internet-Draft will expire on March 23, 2011. 41 Copyright Notice 43 Copyright (c) 2010 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 1. Introduction 58 This document describes the conventions for using several 59 cryptographic algorithms with the Cryptographic Message Syntax (CMS) 60 [RFC5652] to protect the symmetric key package content type defined 61 in [I-D.keyprov-symmetrickeyformat]. Specifically, it includes 62 conventions necessary to implement the following CMS content types: 63 SignedData [RFC5652], EnvelopedData [RFC5652], EncryptedData 64 [RFC5652], and AuthEnvelopedData [RFC5083]. Familiarity with 65 [RFC5083], [RFC5652], [RFC5753], and [I-D.keyprov-symmetrickeyformat] 66 is assumed. 68 This document does not define any new algorithms; instead it refers 69 to previously defined algorithms. 71 1.1. Terminology 73 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 74 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 75 document are to be interpreted as described in [RFC2119]. 77 2. SignedData 79 If an implementation supports SignedData, then it MUST support the 80 signature scheme RSA [RFC3370] and SHOULD support the signature 81 schemes RSASSA-PSS [RFC4056] and DSA [RFC3370]. Additionally, 82 implementations MUST support in concert with these signature schemes 83 the hash function SHA-256 [RFC5754] and they SHOULD support the hash 84 function SHA-1 [RFC3370]. If an implementation supports SignedData, 85 then it MAY support ECDSA [I-D.mcgrew-fundamental-ecc][RFC5753]. 87 3. EnvelopedData 89 If an implementation supports EnvelopedData, then it MUST implement 90 key transport and it MAY implement key agreement. 92 When key transport is used, RSA encryption [RFC3370] MUST be 93 supported and RSAES-OAEP [RFC3560] SHOULD be supported. 95 When key agreement is used, Diffie-Hellman ephemeral-static [RFC3370] 96 MUST be supported. When key agreement is used, ECDH 97 [I-D.mcgrew-fundamental-ecc][RFC5753] MAY be supported. 99 Regardless of the key management technique choice, implementations 100 MUST support AES-128 Key Wrap with Padding [RFC5649] as the content 101 encryption algorithm. Implementations SHOULD support AES-256 Key 102 Wrap with Padding [RFC5649] as the content encryption algorithm. 104 When key agreement is used, a key wrap algorithm is also specified to 105 wrap the content encryption key. If the content encryption algorithm 106 is AES-128 Key Wrap with Padding, then the key wrap algorithm MUST be 107 AES-128 Key Wrap with Padding [RFC5649]. If the content encryption 108 algorithm is AES-256 Key Wrap with Padding, then the key wrap 109 algorithm MUST be AES-256 Key Wrap with Padding [RFC5649]. 111 4. EncryptedData 113 If an implementation supports EncryptedData, then it MUST implement 114 AES-128 Key Wrap with Padding [RFC5649] and SHOULD implement AES-256 115 Key Wrap with Padding [RFC5649]. 117 NOTE: EncryptedData requires that keys be managed by other means; 118 therefore, the only algorithm specified is the content encryption 119 algorithm. 121 5. AuthEnvelopedData 123 If an implementation supports AuthEnvelopedData, then it MUST 124 implement the EnvelopedData recommendations except for the content 125 encryption algorithm, which in this case MUST be AES-GCM [RFC5084]; 126 the 128-bit version MUST be implemented and the 256-bit version 127 SHOULD be implemented. Implementations MAY also support for AES-CCM 128 [RFC5084]. 130 6. Public Key Sizes 132 The easiest way to implement SignedData, EnvelopedData, and 133 AuthEnvelopedData is with public key certificates [RFC5280]. If an 134 implementation supports RSA, RSASSA-PSS, DSA, RSAES-OAEP, or DH, then 135 it MUST support key lengths from 1024-bit to 2048-bit, inclusive. If 136 an implementation supports ECDSA or ECDH, then it MUST support keys 137 on P-256. 139 7. Security Considerations 141 The security considerations from [RFC3370], [RFC3560], [RFC4056], 142 [RFC5083], [RFC5084], [RFC5649], [RFC5652], [RFC5753], [RFC5754], and 143 [I-D.keyprov-symmetrickeyformat] apply. 145 The choice of content encryption algorithms for this document was 146 based on [RFC5649]: "In the design of some high assurance 147 cryptographic modules, it is desirable to segregate cryptographic 148 keying material from other data. The use of a specific cryptographic 149 mechanism solely for the protection of cryptographic keying material 150 can assist in this goal." Unfortunately, there is no AES-GCM or AES- 151 CCM mode that provides the same properties. If an AES-GCM and AES- 152 CCM mode that provides the same properties is defined, then this 153 document will be updated to adopt that algorithm. 155 [SP800-57] provides comparable bits of security for some algorithms 156 and key sizes. [SP800-57] also provides time frames during which 157 certain numbers of bits of security are appropriate and some 158 environments may find these time frames useful. 160 8. IANA Considerations 162 None. Please remove this section prior to publication as an RFC. 164 9. References 166 9.1. Normative References 168 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 169 Requirement Levels", BCP 14, RFC 2119, March 1997. 171 [RFC3370] Housley, R., "Cryptographic Message Syntax (CMS) 172 Algorithms", RFC 3370, August 2002. 174 [RFC3560] Housley, R., "Use of the RSAES-OAEP Key Transport 175 Algorithm in the Cryptographic Message Syntax (CMS)", RFC 176 3560, July 2003. 178 [RFC4056] Schaad, J., "Use of RSASSA-PSS Signature Algorithm in 179 Cryptographic Message Syntax (CMS)", RFC 4056, June 2005. 181 [RFC5083] Housley, R., "Cryptographic Message Syntax (CMS) 182 Authenticated-Enveloped-Data Content Type", RFC 5083, 183 November 2007. 185 [RFC5084] Housley, R., "Using AES-CCM and AES-GCM Authenticated 186 Encryption in the Cryptographic Message Syntax (CMS)", 187 RFC 5084, November 2007. 189 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 190 Housley, R., and W. Polk, "Internet X.509 Public Key 191 Infrastructure Certificate and Certificate Revocation 192 List (CRL) Profile", RFC 5280, May 2008. 194 [RFC5649] Housley, R., and M. Dworkin, "Advanced Encryption 195 Standard (AES) Key Wrap with Padding Algorithm", RFC 196 5649, September 2009. 198 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 199 5652, September 2009. 201 [RFC5753] Turner, S., and D. Brown, "Use of Elliptic Curve 202 Cryptography (ECC) Algorithms in Cryptographic Message 203 Syntax (CMS)", RFC 5753, January 2010. 205 [RFC5754] Turner, S., "Using SHA2 Algorithms with Cryptographic 206 Message Syntax", RFC 5754, January 2010. 208 [I-D.keyprov-symmetrickeyformat] Turner, S., and R. Housley, 209 "Symmetric Key Package Content Type", draft-ietf-keyprov- 210 symmetrickeyformat-11.txt, work-in-progress. 212 [I-D.mcgrew-fundamental-ecc] McGrew, D., Igoe, E., and M. Salter, 213 "Fundamental Elliptic Curve Cryptography Algorithms", 214 draft-mcgrew-fundamental-ecc-03.txt, work-in-progress. 216 9.2. Informative References 218 [SP800-57] National Institute of Standards and Technology (NIST), 219 Special Publication 800-57: Recommendation for Key 220 Management - Part 1 (Revised), March 2007. 222 Author's Addresses 224 Sean Turner 225 IECA, Inc. 226 3057 Nutley Street, Suite 106 227 Fairfax, VA 22031 228 USA 230 EMail: turners@ieca.com