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

Tony Arcieri <bascule@gmail.com> Thu, 13 August 2015 19:17 UTC

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References: <20150811085205.bbcd37b3b0bb0482f6522b1a@andrewayer.name> <CAL02cgRf2M0Gkqymif-=rmNG0v9hhaMC2SBiXf-n5aYiRKBnmQ@mail.gmail.com> <20150812160405.b824b673ad9b139a4fd9446f@andrewayer.name> <CAL02cgReCTMZ+ECiZVtv2=sNDng3mvEmGv4w6V_REbZ6xf75dw@mail.gmail.com> <55CC6BEC.6050706@cs.tcd.ie> <CAMm+Lwi4Y5J2w2TB=n78KQnRvS7f171k8rUjcD3RRu5PMNPPMQ@mail.gmail.com> <20150813145155.GA7501@LK-Perkele-VII> <CAMm+LwgfD6bJYsNOKgwAG368zHU3b2_WLej0--5QCfCjW6NVAw@mail.gmail.com> <87si7n8abu.fsf@latte.josefsson.org>
From: Tony Arcieri <bascule@gmail.com>
Date: Thu, 13 Aug 2015 12:17:11 -0700
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To: Simon Josefsson <simon@josefsson.org>
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Cc: Phillip Hallam-Baker <phill@hallambaker.com>, Richard Barnes <rlb@ipv.sx>, "acme@ietf.org" <acme@ietf.org>, Ilari Liusvaara <ilari.liusvaara@elisanet.fi>, Andrew Ayer <agwa@andrewayer.name>, Stephen Farrell <stephen.farrell@cs.tcd.ie>
Subject: Re: [Acme] Signature misuse vulnerability in draft-barnes-acme-04
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On Thu, Aug 13, 2015 at 8:41 AM, Simon Josefsson <simon@josefsson.org>
wrote:

> This is not a good discriminator of the CFRG options -- this problem is
> a weakness in this protocol, and should be addressed here.


I'd agree, this is a conceptual misuse of digital signatures. While
creating a signature algorithm resistant to this is a "neat trick" much
like nonce reuse resistant AEAD schemes, you shouldn't design protocols
that rely on that resistance in either case.

-- 
Tony Arcieri

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