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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Sean Turner, IECA 2 Internet Draft May 7, 2010 3 Intended Status: Standard Track 4 Expires: November 7, 2010 6 Algorithms for Cryptographic Message Syntax (CMS) 7 Encrypted Key Package Content Type 8 draft-turner-encryptedkeypackagecontenttype-algs-02.txt 10 Abstract 12 This document describes the conventions for using several 13 cryptographic algorithms with the Cryptographic Message Syntax (CMS) 14 encrypted key package content type. Specifically, it includes 15 conventions necessary to implement EnvelopedData, EncryptedData, and 16 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 November 7, 2010. 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 encrypted key package content type [RFCTBD]. Specifically, it 61 includes conventions necessary to implement the following CMS content 62 types: EnvelopedData [RFC5652], EncryptedData [RFC5652], and 63 AuthEnvelopedData [RFC5083]. 65 This document does not define any new algorithms; instead it refers 66 to previously defined algorithms. 68 1.1. Terminology 70 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 71 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 72 document are to be interpreted as described in [RFC2119]. 74 2. EnvelopedData 76 EnvelopedData [RFC5652] supports a number of key management 77 techniques. Implementations that claim conformance to this document 78 MUST support the key transport mechanisms and SHOULD support the key 79 agreement mechanisms as defined below. Other techniques MAY be 80 supported. 82 When key transport is used, RSA encryption [RFC3370] MUST be 83 supported and RSA-OAEP [RFC3560] SHOULD be supported. 85 When key agreement is used, Diffie-Hellman ephemeral-static [RFC3370] 86 MUST be supported. 88 Regardless of the key management technique choice, implementations 89 MUST support AES-128 Key Wrap with Padding [RFC5649]. 90 Implementations SHOULD support AES-256 Key Wrap with Padding 91 [RFC5649]. 93 When key agreement is used, a key wrap algorithm is also specified to 94 wrap the content encryption key. If the content encryption algorithm 95 is AES-128 Key Wrap with Padding, then the key wrap algorithm MUST be 96 AES-128 Key Wrap with Padding [RFC5649]. If the content encryption 97 algorithm is AES-256 Key Wrap with Padding, then the key wrap 98 algorithm MUST be AES-256 Key Wrap with Padding [RFC5649]. 100 3. EncryptedData 102 EncryptedData [RFC5652] requires that keys be managed by other means; 103 therefore, the only algorithm specified is the content encryption 104 algorithm. Implementations MUST support AES-128 Key Wrap with Padding 105 [RFC5649]. Implementations SHOULD support AES-256 Key Wrap with 106 Padding [RFC5649]. 108 4. AuthEnvelopedData 110 AuthEnvelopedData [RFC5083], like EnvelopedData, supports a number of 111 key management techniques. The key management requirements for 112 AuthEnvelopedData are the same as for EnvelopedData. The difference 113 is the content encryption algorithm. Implementations MUST support 114 128-bit AES-GCM [RFC5084] and SHOULD support 256-bit AES-GCM 115 [RFC5084]. Implementations MAY also support AES-CCM [RFC5084]. 117 5. Public Key Sizes 119 The easiest way to implement the key transport requirement for 120 EnvelopedData and AuthEnvelopedData is with public key certificates 121 [RFC5280]. If an implementation supports RSA, RSAES-OAEP, or DH, 122 then it MUST support key lengths from 1024-bit to 2048-bit, 123 inclusive. 125 6. Security Considerations 127 The security considerations from [RFC3370], [RFC3560], [RFC5083], 128 [RFC5084], [RFC5649], [RFC5652], and [RFCTBD] apply. 130 The choice of content encryption algorithms for this document was 131 based on [RFC5649]: "In the design of some high assurance 132 cryptographic modules, it is desirable to segregate cryptographic 133 keying material from other data. The use of a specific cryptographic 134 mechanism solely for the protection of cryptographic keying material 135 can assist in this goal." Unfortunately, there is no AES-GCM or AES- 136 CCM mode that provides the same properties. If an AES-GCM and AES- 137 CCM mode that provides the same properties is defined, then this 138 document will be updated to adopt that algorithm. 140 [SP800-57] provides comparable bits of security for some algorithms 141 and key sizes. [SP800-57] also provides time frames during which 142 certain numbers of bits of security are appropriate and some 143 environments may find these time frames useful. 145 7. IANA Considerations 147 None. Please remove this section prior to publication as an RFC. 149 8. References 151 8.1. Normative References 153 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 154 Requirement Levels", BCP 14, RFC 2119, March 1997. 156 [RFC3370] Housley, R., "Cryptographic Message Syntax (CMS) 157 Algorithms", RFC 3370, August 2002. 159 [RFC3560] Housley, R., "Use of the RSAES-OAEP Key Transport 160 Algorithm in the Cryptographic Message Syntax (CMS)", RFC 161 3560, July 2003. 163 [RFC5083] Housley, R., "Cryptographic Message Syntax (CMS) 164 Authenticated-Enveloped-Data Content Type", RFC 5083, 165 November 2007. 167 [RFC5084] Housley, R., "Using AES-CCM and AES-GCM Authenticated 168 Encryption in the Cryptographic Message Syntax (CMS)", 169 RFC 5084, November 2007. 171 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 172 Housley, R., and W. Polk, "Internet X.509 Public Key 173 Infrastructure Certificate and Certificate Revocation 174 List (CRL) Profile", RFC 5280, May 2008. 176 [RFC5649] Housley, R., and M. Dworkin, "Advanced Encryption 177 Standard (AES) Key Wrap with Padding Algorithm", RFC 178 5649, September 2009. 180 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 181 5652, September 2009. 183 [RFCTBD] Turner, S., and R. Housley, "Cryptographic Message Syntax 184 (CMS) Encrypted Key Package Content Type", draft-turner- 185 encryptedkeypackagecontenttype-02.txt, work-in-progress. 187 /** 188 RFC Editor: Please replace "TBD" with the number of the published 189 RFC. Please do this in both the references and the text. 190 **/ 192 8.2. Informative References 194 [SP800-57] National Institute of Standards and Technology (NIST), 195 Special Publication 800-57: Recommendation for Key 196 Management - Part 1 (Revised), March 2007. 198 Authors' Addresses 200 Sean Turner 201 IECA, Inc. 202 3057 Nutley Street, Suite 106 203 Fairfax, VA 22031 204 USA 206 EMail: turners@ieca.com