Internet DRAFT - draft-ramsdell-smime-sha256
draft-ramsdell-smime-sha256
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
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes the integration of the SHA-256 cryptographic
digest algorithm with S/MIME.
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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
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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].
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2. Introduction
In light of recent developments with the SHA-1 algorithm, this
document describes the use of SHA-256.
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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].
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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?
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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.
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Author's Address
B. Ramsdell
Sendmail, Inc.
Email: blake@sendmail.com
URI: htp://www.sendmail.com
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