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

Ilari Liusvaara <ilariliusvaara@welho.com> Wed, 30 December 2015 11:16 UTC

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Date: Wed, 30 Dec 2015 13:16:31 +0200
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Kurt Roeckx <kurt@roeckx.be>
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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 11:52:07AM +0100, Kurt Roeckx wrote:
> On Tue, Dec 29, 2015 at 10:10:47PM +0200, Karthikeyan Bhargavan wrote:
> > As mentioned before, validating Curve25519 public values is necessary in TLS 1.2 without session hash.
> > Otherwise, as we pointed out in [1], the triple handshake attack returns.
> 
> Would it make sense to have session hash as a requirement in TLS
> 1.2 when you want to use Curve25519?

I don't think that is reasonable.

The RFC4492bis document could point out the consequences of omitting
the zero check (which is already REQUIRED) in the security
considerations tho.


-Ilari