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Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00

Florian Weimer <fweimer@redhat.com> Thu, 16 October 2014 13:41 UTC

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Date: Thu, 16 Oct 2014 15:41:01 +0200
From: Florian Weimer <fweimer@redhat.com>
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To: Manuel Pégourié-Gonnard <mpg@polarssl.org>, Martin Thomson <martin.thomson@gmail.com>, Bodo Moeller <bmoeller@acm.org>
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Subject: Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00
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On 10/16/2014 12:40 PM, Manuel Pégourié-Gonnard wrote:
> On 16/10/2014 12:06, Florian Weimer wrote:
>> Interesting things will start to happen once there is TLS 1.3.
>> TLS_FALLBACK_SCSV could really complicate its deployment.
>>
> I'm afraid I don't understand which interesting things you're referring to.
> Could you please elaborate on that?
>
> I can think of the following scenarios (assuming the client supports 1.3 and
> FALLBACK_SCSV):

A widely-deployed client might use TLS 1.2 with FALLBACK_SCSV 
unconditionally.  This client would break once servers start supporting 
TLS 1.3.  That's just one example of what could go wrong which could not 
go wrong before.

-- 
Florian Weimer / Red Hat Product Security

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