Network Working Group B. Ramsdell Internet-Draft Sendmail, Inc. Expires: April 20, 2006 October 17, 2005 Use of the SHA-256 algorithm in S/MIME draft-ramsdell-smime-sha256-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 20, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document describes the integration of the SHA-256 cryptographic digest algorithm with S/MIME. Ramsdell Expires April 20, 2006 [Page 1] Internet-Draft SHA-256 in S/MIME October 2005 Table of Contents 1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Changes to the S/MIME message specification . . . . . . . . . . 5 4. Changes to the S/MIME certificate handling specification . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . . 9 Ramsdell Expires April 20, 2006 [Page 2] Internet-Draft SHA-256 in S/MIME October 2005 1. Requirements notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Ramsdell Expires April 20, 2006 [Page 3] Internet-Draft SHA-256 in S/MIME October 2005 2. Introduction In light of recent developments with the SHA-1 algorithm, this document describes the use of SHA-256. Ramsdell Expires April 20, 2006 [Page 4] Internet-Draft SHA-256 in S/MIME October 2005 3. Changes to the S/MIME message specification The following changes are made to [RFC3851] The notation for SHOULD+ and MUST- needs to be added. The first sentence of section 2.1 is changed to read: Sending and receiving agents MUST- support SHA-1 [CMSALG] and SHOULD+ support SHA-256 [SHA256]. The following paragraph is added as the second paragraph to section 2.2: Sending and receiving agents SHOULD+ support sha256WithRSAEncryption [SHA256]. The last paragraph of section 2.2 needs some serious rework. The reference for [SHA256] needs to point to [RFC4055]. Ramsdell Expires April 20, 2006 [Page 5] Internet-Draft SHA-256 in S/MIME October 2005 4. Changes to the S/MIME certificate handling specification The following changes should be made to [RFC3850] The notation for SHOULD+ and MUST- needs to be added. Section 4.3 paragraph 2 is changed to the following: A receiving agent MUST- be capable of verifying the signatures on certificates and CRLs made with md5WithRSAEncryption and sha1WithRSAEncryption signature algorithms with key sizes from 512 bits to 2048 bits described in [CMSALG]. A receiving agent SHOULD+ be capable of verifying the signatures on certificates and CRLs made with sha256WithRSAEncryption described in [SHA256]. Rewrite of last paragraph of section 4.3 to include SHA-1 and MD5 warnings? Ramsdell Expires April 20, 2006 [Page 6] Internet-Draft SHA-256 in S/MIME October 2005 5. Security Considerations Discussion of problems with SHA-1 that caused this draft to happen. 6. References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3850] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Certificate Handling", RFC 3850, July 2004. [RFC3851] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification", RFC 3851, July 2004. [RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional Algorithms and Identifiers for RSA Cryptography for use in the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 4055, June 2005. Ramsdell Expires April 20, 2006 [Page 7] Internet-Draft SHA-256 in S/MIME October 2005 Author's Address B. Ramsdell Sendmail, Inc. Email: blake@sendmail.com URI: htp://www.sendmail.com Ramsdell Expires April 20, 2006 [Page 8] Internet-Draft SHA-256 in S/MIME October 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Ramsdell Expires April 20, 2006 [Page 9]