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Found 'SHOULD not' in this paragraph: Applications using the S/MIME Capabilities extension SHOULD not use information provided in this certificate extension if more recent S/MIME capabilities information is available from signed messages from the certified subject. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (February 2005) is 7010 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC 2119' is defined on line 140, but no explicit reference was found in the text == Unused Reference: 'RFC 3280' is defined on line 143, but no explicit reference was found in the text == Unused Reference: 'RFC 3851' is defined on line 148, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3280 (Obsoleted by RFC 5280) ** Obsolete normative reference: RFC 3851 (Obsoleted by RFC 5751) Summary: 5 errors (**), 0 flaws (~~), 7 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 S/MIME Working Group S. Santesson (Microsoft) 3 INTERNET-DRAFT Expires February 2005 4 August 2004 6 S/MIME Capabilities in X.509 certificates 7 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that other 16 groups may also distribute working documents as Internet-Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six months 19 and may be updated, replaced, or obsoleted by other documents at any 20 time. It is inappropriate to use Internet-Drafts as reference 21 material or to cite them other than as "work in progress." 23 The list of current Internet-Drafts can be accessed at 24 http://www.ietf.org/ietf/1id-abstracts.txt 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 Copyright (C) The Internet Society (2002). All Rights Reserved. 31 Abstract 33 This document defines a certificate extension for inclusion of S/MIME 34 capabilities in public key certificates as defined by RFC 3280. 36 S/MIME Capabilities provides a method of broadcasting the 37 cryptographic S/MIME capabilities of the certified subject as a 38 complement to use of S/MIME Capabilities signed attributes as defined 39 in RFC 3851. 41 Table of Contents 43 1 Introduction ................................................ 2 44 2 S/MIME Capabilities Extension ............................... 3 45 3 Use in applications ......................................... 3 46 4 Security Considerations ..................................... 3 47 5 References .................................................. 4 48 6 Intellectual Property Rights ................................ 4 49 A ASN.1 definitions ........................................... 6 50 Authors' Addresses ............................................. 6 51 Full Copyright Statement ....................................... 7 53 1. Introduction 55 S/MIME defines in RFC 3851 the S/MIME Capabilities attribute as a 56 means to communicate the cryptographic capabilities of a sender of a 57 signed S/MIME message. This information can then be used by the 58 recipient in subsequent S/MIME secured exchanges with the sender to 59 select appropriate cryptographic properties for the exchange. 61 However, the use of S/MIME in electronic mail also introduces the 62 scenario where a sender of an encrypted e-mail has no prior 63 established knowledge of the recipient's cryptographic capabilities 64 through recent S/MIME exchanges. 66 In this case the sender has no other option but to fall back to a 67 default assumption of the recipient which may be incompatible with 68 the recipient's capabilities and/or security policy. 70 Sending an encrypted e-mail does however require possession of the 71 recipient's public key certificate which in turn contains information 72 about the recipient's public key cryptographic capabilities but not 73 its symmetric cryptographic capabilities needed for S/MIME. 75 The approach of this document to minimize the need to revert to 76 default cryptographic settings due to lack of knowledge, is enable 77 the capacity to include S/MIME Capabilities also in public key 78 certificates. 80 2. S/MIME Capabilities Extension 82 Data objects and their syntax and semantics needed to communicate 83 S/MIME capabilities have already been defined in RFC 3633 through the 84 sMIMECapabilities attribute and there is no need to re-invent this 85 structure. 87 The S/MIME Capabilities extension does therefore reuse the data 88 structure of the sMIMECapabilities attribute as well as the defined 89 object identifier for this structure. 91 The S/MIME Capabilities extension MUST have the following definition: 93 smimeCapabilities OBJECT IDENTIFIER ::= 94 {iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 95 pkcs-9(9) 15} 97 sMIMECapabilitiesExt EXTENSION ::= { 98 SYNTAX SMIMECapabilities 99 IDENTIFIED BY smimeCapabilities } 101 SMIMECapabilities ::= SEQUENCE OF SMIMECapability 103 SMIMECapability ::= SEQUENCE { 104 capabilityID OBJECT IDENTIFIER, 105 parameters ANY DEFINED BY capabilityID OPTIONAL } 107 Algorithms should be ordered by preference 109 3. Use in applications 111 Applications using the S/MIME Capabilities extension SHOULD not use 112 information provided in this certificate extension if more recent 113 S/MIME capabilities information is available from signed messages 114 from the certified subject. 116 In this case the information in the S/MIME capabilities extension 117 SHOULD be ignored. 119 4 Security Considerations 121 Implementers should be aware that the S/MIME capabilities extension 122 contains a statement about the subject's capabilities at the time of 123 certificate issuance, which may change over the lifetime of the 124 certificate. 126 Certification Authorities should therefore renew a certificate 127 including S/MIME Capabilities, if the subjects cryptographic 128 capabilities changes in a way that is no longer compatible with the 129 current certificate. 131 It is however, despite any available information about the 132 recipient's cryptographic capabilities, still the responsibility of 133 the sender to always choose sufficiently strong encryption for its 134 information disclosure and the responsibility of the recipient to 135 only accept data that has been protected according to the recipient's 136 security policy. 138 5 References 140 [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate 141 Requirement Levels", BCP 14, RFC 2119, March 1997. 143 [RFC 3280] R. Housley, W. Polk, W. Ford, and D. Solo, "Internet 144 X.509 Public Key Infrastructure: Certificate and 145 Certificate Revocation List (CRL) Profile", RFC 3280, 146 April 2002. 148 [RFC 3851] B. Ramsdell, "Secure/Multipurpose Internet Mail 149 Extensions (S/MIME) Version 3.1 Message Specification", 150 RFC 3851, July 2004 152 6 Intellectual Property Rights 154 The IETF takes no position regarding the validity or scope of any 155 intellectual property or other rights that might be claimed to 156 pertain to the implementation or use of the technology described in 157 this document or the extent to which any license under such rights 158 might or might not be available; neither does it represent that it 159 has made any effort to identify any such rights. Information on the 160 IETF's procedures with respect to rights in standards-track and 161 standards related documentation can be found in BCP-11. Copies of 162 claims of rights made available for publication and any assurances of 163 licenses to be made available, or the result of an attempt made to 164 obtain a general license or permission for the use of such 165 proprietary rights by implementors or users of this specification can 166 be obtained from the IETF Secretariat. 168 The IETF invites any interested party to bring to its attention any 169 copyrights, patents or patent applications, or other proprietary 170 rights which may cover technology that may be required to practice 171 this standard. Please address the information to the IETF Executive 172 Director. 174 A. ASN.1 definitions 176 TBD 178 Authors' Addresses 180 Stefan Santesson 181 Microsoft 182 Tuborg Boulevard 12 183 2900 Hellerup 184 Denmark 186 EMail: stefans@microsoft.com 188 Full Copyright Statement 190 Copyright (C) The Internet Society (2004). All Rights Reserved. 192 This document and translations of it may be copied and furnished to 193 others, and derivative works that comment on or otherwise explain it 194 or assist in its implementation may be prepared, copied, published 195 and distributed, in whole or in part, without restriction of any 196 kind, provided that the above copyright notice and this paragraph are 197 included on all such copies and derivative works. In addition, the 198 ASN.1 modules presented in Appendices A and B may be used in whole or 199 in part without inclusion of the copyright notice. However, this 200 document itself may not be modified in any way, such as by removing 201 the copyright notice or references to the Internet Society or other 202 Internet organizations, except as needed for the purpose of 203 developing Internet standards in which case the procedures for 204 copyrights defined in the Internet Standards process shall be 205 followed, or as required to translate it into languages other than 206 English. 208 The limited permissions granted above are perpetual and will not be 209 revoked by the Internet Society or its successors or assigns. This 210 document and the information contained herein is provided on an "AS 211 IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK 212 FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT 213 LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL 214 NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY 215 OR FITNESS FOR A PARTICULAR PURPOSE.