Re: [TLS] WGLC for "Deprecating TLSv1.0 and TLSv1.1"

Peter Gutmann <pgut001@cs.auckland.ac.nz> Fri, 03 May 2019 17:30 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Benjamin Kaduk <bkaduk@akamai.com>
CC: Hubert Kario <hkario@redhat.com>, "tls@ietf.org" <tls@ietf.org>, "mrex@sap.com" <mrex@sap.com>
Thread-Topic: [TLS] WGLC for "Deprecating TLSv1.0 and TLSv1.1"
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Date: Fri, 3 May 2019 17:30:38 +0000
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Subject: Re: [TLS] WGLC for "Deprecating TLSv1.0 and TLSv1.1"
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Benjamin Kaduk <bkaduk@akamai.com> writes:

>I'll make the obligatory note that SHA-2 is fine

Sure, and that was the really strange thing with TLS 1.2, why not just say
SHA-2 or better only, rather than adding mechanisms that were much, much
weaker than its predecessors?  So the simple fix is just to use SHA-2 only for
TLS 1.2.

>if someone does change their system, are really going to recommend they go to
>TLS 1.0 with MD5||SHA1 rather than TLS 1.2 with SHA2?

That would be one argument for an RFC, MUST SHA-2 only or MUST NOT MD5 and
SHA-1 in 1.2.  Which is pretty much what TLS-LTS says.  Or at least it takes
the SHA-2-suites-mandatory path which implies no MD5 or SHA-1, I guess I
should also add an explicit MUST NOT MD5 and SHA-1.

Having said that, given an RFC saying MUST NOT 1.0 and 1.1 which is what the
original discussion was about, why not also add MUST NOT MD5 and SHA1 in TLS
1.2 to the text?

Peter.