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

Hubert Kario <hkario@redhat.com> Tue, 07 May 2019 11:12 UTC

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From: Hubert Kario <hkario@redhat.com>
To: mrex@sap.com
Cc: tls@ietf.org, Martin Thomson <mt@lowentropy.net>
Date: Tue, 07 May 2019 13:12:21 +0200
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Subject: Re: [TLS] WGLC for "Deprecating TLSv1.0 and TLSv1.1"
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On Tuesday, 7 May 2019 01:57:30 CEST Martin Rex wrote:
> Hubert Kario <hkario@redhat.com> wrote:
> > On Friday, 3 May 2019 16:56:54 CEST Martin Rex wrote:
> >> Hubert Kario <hkario@redhat.com> wrote:
> >> > We've been over this Martin, the theoretical research shows that for
> >> > Merkle- Damgård functions, combining them doesn't increase their
> >> > security
> >> > significantly.
> >> 
> >> You are completely misunderstanding the results.
> >> 
> >> The security is greatly increased!
> > 
> > like I said, that were the follow up papers
> > 
> > the original is still Joux:
> > https://www.iacr.org/archive/crypto2004/31520306/multicollisions.pdf
> 
> Thanks to Peter Gutmann for the summary:
> 
>     https://mailarchive.ietf.org/arch/msg/tls/g0MDCdZcHsvZefv4V8fssXMeEHs
> 
> which you may have missed.

yes, Joux paper also shows that attacking MD5||SHA1 is harder than attacking  
SHA1 alone

but that doesn't matter, what matters is _how much harder it is_ and Joux 
paper says that it's less than a work factor of two, something also knows as a 
"rounding error" for cryptographic attacks

-- 
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

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