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Re: [TLS] Labels in HKDF-Expand-Label

Eric Rescorla <ekr@rtfm.com> Wed, 23 November 2016 05:27 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Tue, 22 Nov 2016 21:27:07 -0800
Message-ID: <CABcZeBMeXg5yLY8mp9=Cw8haLbpmJFaEQdicj4MLM0Pv5CONmA@mail.gmail.com>
To: Martin Thomson <martin.thomson@gmail.com>
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Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Labels in HKDF-Expand-Label
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Actually all future EXPORTERs need to start with EXPORTER-. But this does
seem like a reasonable change so I have merged it

-Ekr


On Tue, Nov 22, 2016 at 9:25 PM, Martin Thomson <martin.thomson@gmail.com>
wrote:

> The grammar for the label permits the label to be 9 octets long.
> That's the exact length of the prefix.
>
> That means that it is valid to use an exporter with an empty label
> string.  That seems dangerous.  I propose that we require at least one
> octet:
>
> https://github.com/tlswg/tls13-spec/pull/774
>
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