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Re: [TLS] PR #699: Simplify traffic key expansion

Martin Thomson <martin.thomson@gmail.com> Thu, 20 October 2016 23:05 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Fri, 21 Oct 2016 10:05:19 +1100
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To: Kazuho Oku <kazuhooku@gmail.com>
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Subject: Re: [TLS] PR #699: Simplify traffic key expansion
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On 21 October 2016 at 06:52, Kazuho Oku <kazuhooku@gmail.com> wrote:
> Is there any need to expand resumption_psk from resumption_secret?
>
> To me, it is unclear why resumption_secret cannot be used directly as
> a psk, since the two values have the same lengths and since the secret
> is only used for deriving the psk.
>
> Maybe is this something we could also simplify?

draft-17 makes a simplification along the lines you suggested.  Note
that this wasn't as easy to get right as you might have imagined for a
bunch of reasons.

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