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Re: [TLS] Adding an additional step to exporters

Sean Turner <sean@sn3rd.com> Fri, 24 February 2017 05:01 UTC

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From: Sean Turner <sean@sn3rd.com>
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Date: Fri, 24 Feb 2017 00:01:37 -0500
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To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: [TLS] Adding an additional step to exporters
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So this isn’t entirely novel right I mean we did something similar wrt other key schedules?

spt

> On Feb 23, 2017, at 23:30, Martin Thomson <martin.thomson@gmail.com> wrote:
> 
> https://github.com/tlswg/tls13-spec/pull/882 contains the longer description.
> 
> In short, the existence of an exporter secret threatens the forward
> secrecy of any exported secret.  This is a problem for QUIC and is
> likely to be a more general problem.
> 
> The proposed fix is small: separate exporters into two steps
> (extract+expand) where the first step allows for separation based on
> exporter type and the second on context.  That allows an endpoint to
> keep separate secrets for each exporter type and discard those that it
> no longer needs, thus gaining forward secrecy if it likes.
> 
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