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Re: [Acme] Signature misuse vulnerability in draft-barnes-acme-04

Phillip Hallam-Baker <phill@hallambaker.com> Thu, 13 August 2015 14:27 UTC

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Date: Thu, 13 Aug 2015 10:27:09 -0400
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From: Phillip Hallam-Baker <phill@hallambaker.com>
To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Cc: Richard Barnes <rlb@ipv.sx>, "acme@ietf.org" <acme@ietf.org>, Andrew Ayer <agwa@andrewayer.name>
Subject: Re: [Acme] Signature misuse vulnerability in draft-barnes-acme-04
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+1

I would much rather block the entire class of attacks rather than spend any
time working out if there is a way to do this with ECC based keys.

On Thu, Aug 13, 2015 at 6:05 AM, Stephen Farrell <stephen.farrell@cs.tcd.ie>
wrote:

>
>
> On 13/08/15 06:21, Richard Barnes wrote:
> > I would note, though that in practice, e=65537 pretty much always, and
> > the attack would almost never produce that value.  So this could still
> > be prevented by checks on account public keys.
>
> I know you're not suggesting we do, but depending on special values
> or patterns for keys would be risky. I think it has often turned out
> that application developers are unaware of the details of what their
> crypto libraries do or do not support at that level. So it could be
> quite easy to recommend something that'd fall between the cracks.
>
> Cheers,
> S.
>
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