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Re: [TLS] Adding an additional step to exporters

Martin Thomson <martin.thomson@gmail.com> Fri, 24 February 2017 05:40 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Fri, 24 Feb 2017 16:40:19 +1100
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To: Felix Günther <guenther@cs.tu-darmstadt.de>
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Subject: Re: [TLS] Adding an additional step to exporters
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On 24 February 2017 at 16:01, Sean Turner <sean@sn3rd.com> wrote:
> So this isn’t entirely novel right I mean we did something similar wrt other key schedules?

I certainly hope it isn't novel.  I'm just applying the same
technique: keep independent keys independent.

On 24 February 2017 at 16:09, Felix Günther <guenther@cs.tu-darmstadt.de> wrote:
> just to clarify: you add an additional HKDF.Expand step, not
> HKDF.Extract, right?

Yes, you are right, I should have said expand.  You need to use expand
to get the label-based separation on type.

I don't know how I got confused about that.  If we need to maintain
extract and expand in pairs (as we have already been burned by), then
I will defer to cryptographers on that.

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