Re: [TLS] Proposal to deprecate sha1 and md5 for digital signatures in TLS 1.2

Loganaden Velvindron <loganaden@gmail.com> Wed, 29 May 2019 19:51 UTC

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From: Loganaden Velvindron <loganaden@gmail.com>
Date: Wed, 29 May 2019 23:51:24 +0400
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To: Hubert Kario <hkario@redhat.com>
Cc: "<tls@ietf.org>" <tls@ietf.org>, Martin Thomson <mt@lowentropy.net>
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Subject: Re: [TLS] Proposal to deprecate sha1 and md5 for digital signatures in TLS 1.2
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On Tue, May 14, 2019 at 10:57 PM Hubert Kario <hkario@redhat.com> wrote:

> On Tuesday, 14 May 2019 20:16:17 CEST Loganaden Velvindron wrote:
> > On Tue, May 14, 2019 at 3:24 PM Hubert Kario <hkario@redhat.com> wrote:
> > > On Tuesday, 14 May 2019 08:34:38 CEST Loganaden Velvindron wrote:
> > > > Latest draft is here:
> > > >
> https://www.ietf.org/id/draft-lvelvindron-tls-md5-sha1-deprecate-04.txt
> > >
> > > why did you drop SHA-1 from Section 4 and 5?
> >
> > It was done following this comment from David Cooper.
> >
> > "
> > [..] While they may be subject to collision attacks, SHA-1 is still
> > considered secure in cases in which collision resistance is not required,
> > and I do not believe that collision resistance is required when SHA-1 is
> > used to create the "signatures" in the ServerKeyExchange and
> > CertificateVerify messages.
> > "
>
> SLOTH paper disagrees on that as far as CertificateVerify message is
> concerned
>
> SP 800-52 rev-2 does not provide much in terms of justification why SLOTH
> paper would be wrong and allows for SHA-1 signatures only in TLS 1.0 and
> TLS
> 1.1, it does not explicitly state that SHA-1 signatures in TLS 1.2 are
> allowed...
>

Hello All,

We've updated the document based on the feedback we've got:

We've re-added deprecating sha-1 in ServerKeyExchange and CertificateVerify:
https://tools.ietf.org/html/draft-lvelvindron-tls-md5-sha1-deprecate-05

-- 
> Regards,
> Hubert Kario
> Senior Quality Engineer, QE BaseOS Security team
> Web: www.cz.redhat.com
> Red Hat Czech s.r.o., Purkyňova 115, 612 00  Brno, Czech Republic