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

Ilari Liusvaara <ilariliusvaara@welho.com> Fri, 01 January 2016 18:22 UTC

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Date: Fri, 1 Jan 2016 20:22:40 +0200
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: tls@ietf.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 Thu, Dec 31, 2015 at 08:16:35PM +0000, Blumenthal, Uri - 0553 - MITLL wrote:
> I think Watson made a good point about "omittable checks". ‎If an
> implementation A "omits" this mechanism, it should fail session
> establishment.

Well, here is one scheme that I can't break myself and has no checks one
can just "omit":

PMS = SHA-512(A|B|DHF(a,B)) = SHA-512(A|B|DHF(b,A))

Where a and b are the private keys and A and B are the public keys
and DHF is X25519 or X448.



-Ilari