Deprecating MD5 and SHA-1 signature hashes in TLS 1.2
draft-ietf-tls-md5-sha1-deprecate-00

Document Type Active Internet-Draft (tls WG)
Last updated 2019-10-16 (latest revision 2019-09-02)
Replaces draft-lvelvindron-tls-md5-sha1-deprecate
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Internet Engineering Task Force                            L. Velvindron
Internet-Draft                                             cyberstorm.mu
Updates: 5246 7525 (if approved)                             K. Moriarty
Intended status: Standards Track                                Dell EMC
Expires: March 5, 2020                                        A. Ghedini
                                                         Cloudflare Inc.
                                                       September 2, 2019

         Deprecating MD5 and SHA-1 signature hashes in TLS 1.2
                  draft-ietf-tls-md5-sha1-deprecate-00

Abstract

   The MD5 and SHA-1 hashing algorithms are steadily weakening in
   strength and their deprecation process should begin for their use in
   TLS 1.2 digital signatures.  However, this document does not
   deprecate SHA-1 in HMAC for record protection.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on March 5, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Signature Algorithms  . . . . . . . . . . . . . . . . . . . .   2
   3.  Certificate Request . . . . . . . . . . . . . . . . . . . . .   3
   4.  Server Key Exchange . . . . . . . . . . . . . . . . . . . . .   3
   5.  Certificate Verify  . . . . . . . . . . . . . . . . . . . . .   3
   6.  Updates to RFC5246  . . . . . . . . . . . . . . . . . . . . .   3
   7.  Updates to RFC7525  . . . . . . . . . . . . . . . . . . . . .   3
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   4
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   4
     10.2.  Informative References . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The usage of MD5 and SHA-1 for signature hashing in TLS 1.2 is
   specified in RFC 5246 [RFC5246].  MD5 and SHA-1 have been proven to
   be insecure, subject to collision attacks.  RFC 6151 [RFC6151]
   details the security considerations, including collision attacks for
   MD5, published in 2011.  NIST formally deprecated use of SHA-1 in
   2011 [NISTSP800-131A-R2] and disallowed its use for digital
   signatures at the end of 2013, based on both the Wang, et. al, attack
   and the potential for brute-force attack.  Further, in 2017,
   researchers from Google and CWI Amsterdam [SHA-1-Collision] proved
   SHA-1 collision attacks were practical.  This document updates
   RFC 5246 [RFC5246] and RFC7525 [RFC7525] in such as way that MD5 and
   SHA1 MUST NOT be used for digital signatures.  However, this document
   does not deprecate SHA-1 in HMAC for record protection.

1.1.  Requirements Language

   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 RFC 2119 [RFC2119].

2.  Signature Algorithms

   Clients SHOULD NOT include MD5 and SHA-1 in signature_algorithms
   extension.  If a client does not send a signature_algorithms
   extension, then the server MUST abort the handshake and send a
   handshake_failure alert.

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