Re: [TLS] draft-ietf-tls-curve25519-01: Is public key validation necessary or helpful?

Martin Thomson <martin.thomson@gmail.com> Tue, 22 December 2015 23:29 UTC

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Date: Wed, 23 Dec 2015 10:29:27 +1100
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From: Martin Thomson <martin.thomson@gmail.com>
To: Brian Smith <brian@briansmith.org>
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Subject: Re: [TLS] draft-ietf-tls-curve25519-01: Is public key validation necessary or helpful?
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On 23 December 2015 at 10:23, Brian Smith <brian@briansmith.org> wrote:
> It may be the case that TLS requires contributory behavior and point
> validation is still unnecessary. Or, it may be the case that TLS doesn't
> really require contributory behavior (though, it seems obvious to me that it
> does, at least for TLS 1.2 and earlier). Or, it may be the case that TLS
> requires contributory behavior and a check is necessary. The draft should
> make it clear which case we are dealing with, with a reference to the
> reasoning that gave us whatever conclusion is reached, but currently that is
> missing.

My understanding is that with session hash TLS 1.2 is OK, as is 1.3.
Like Watson and Thai, I think that 1.2 without session hash is not OK.

That suggests that the 25519 draft should require session hash in 1.2.