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

Ilari Liusvaara <ilariliusvaara@welho.com> Thu, 31 December 2015 00:32 UTC

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Date: Thu, 31 Dec 2015 02:32:20 +0200
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Watson Ladd <watsonbladd@gmail.com>
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Cc: Karthikeyan Bhargavan <karthik.bhargavan@gmail.com>, "<tls@ietf.org>" <tls@ietf.org>
Subject: Re: [TLS] draft-ietf-tls-curve25519-01: Is public key validation necessary or helpful?
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On Wed, Dec 30, 2015 at 07:23:12PM -0500, Watson Ladd wrote:
> On Dec 30, 2015 7:08 PM, "Ilari Liusvaara" <ilariliusvaara@welho.com> wrote:
> >
> > I also think I figured out a way to truly force contributory behaviour
> > without any checks:
> >
> > It is a bit nasty hack: Throw the exchange keys into the PMS, expanding
> > it from 32/56 bytes to 96/168 bytes.
> 
> Why not hash the public values into the result of the key exchange? I don't
> want security to depend on omittable checks.

What values you think are realistically available at that point, other than
the exchange public keys?


-Ilari