Re: [Cfrg] Security proofs v DH backdoors

Peter Gutmann <pgut001@cs.auckland.ac.nz> Wed, 26 October 2016 04:32 UTC

Return-Path: <pgut001@cs.auckland.ac.nz>
X-Original-To: cfrg@ietfa.amsl.com
Delivered-To: cfrg@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id B0CBF12950A for <cfrg@ietfa.amsl.com>; Tue, 25 Oct 2016 21:32:56 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.631
X-Spam-Level:
X-Spam-Status: No, score=-4.631 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_MED=-2.3, RP_MATCHES_RCVD=-0.431] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=auckland.ac.nz
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id e2YzhmPg084S for <cfrg@ietfa.amsl.com>; Tue, 25 Oct 2016 21:32:53 -0700 (PDT)
Received: from mx4.auckland.ac.nz (mx4.auckland.ac.nz [130.216.125.248]) (using TLSv1.2 with cipher RC4-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 545291294F2 for <cfrg@irtf.org>; Tue, 25 Oct 2016 21:32:52 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=auckland.ac.nz; i=@auckland.ac.nz; q=dns/txt; s=mail; t=1477456373; x=1508992373; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=ZzeHYyp5zriUvRg+Fbv4Xl7d0HA2vLlJtUXkdqesQlo=; b=mOCOz2qHOlg2C4IOAcG1AZboUrc88dLThxAkJhmv7EPs1I0nm3AVqmKd TxrUHrD8bCnxfrsmJZEL9UfzrFYo8mRFDRfC1iFSw94OmqfuQAqna8CLR Usi4u8D1Ct3A/PB08Q1VjXz7yP3w7QQxm/4UxLPc+9MwUtEQk4VOVFtX3 HLHo+vM1glsIt7jv94ZHYXv5bslWKxKles3aC8BweVvPEasCThHgpQU/V Wf++CGiUy82YNgNe48M8ktmeG8FGvHIeQt4RpURdJqvuREfwwhvayq0yx wk1/Eb11LZg3xwW0mVR751hfIbsJnnFjKwEzuVqtd9FRAPFb4uiQHJrGP w==;
X-IronPort-AV: E=Sophos;i="5.31,548,1473076800"; d="scan'208";a="112055309"
X-Ironport-HAT: MAIL-SERVERS - $RELAYED
X-Ironport-Source: 10.6.2.2 - Outgoing - Outgoing
Received: from smtp.uoa.auckland.ac.nz (HELO uxcn13-ogg-a.UoA.auckland.ac.nz) ([10.6.2.2]) by mx4-int.auckland.ac.nz with ESMTP/TLS/AES256-SHA; 26 Oct 2016 17:32:51 +1300
Received: from uxcn13-ogg-d.UoA.auckland.ac.nz (10.6.2.5) by uxcn13-ogg-a.UoA.auckland.ac.nz (10.6.2.2) with Microsoft SMTP Server (TLS) id 15.0.1178.4; Wed, 26 Oct 2016 17:32:51 +1300
Received: from uxcn13-ogg-d.UoA.auckland.ac.nz ([10.6.2.25]) by uxcn13-ogg-d.UoA.auckland.ac.nz ([10.6.2.25]) with mapi id 15.00.1178.000; Wed, 26 Oct 2016 17:32:51 +1300
From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Ilari Liusvaara <ilariliusvaara@welho.com>, Dan Brown <danibrown@blackberry.com>
Thread-Topic: [Cfrg] Security proofs v DH backdoors
Thread-Index: AdIuwSDNwRWUIafTQyeYSwlwLZEKKf//K6mAgAHV3UU=
Date: Wed, 26 Oct 2016 04:32:49 +0000
Message-ID: <1477456366629.49872@cs.auckland.ac.nz>
References: <20161025131014.5709905.2866.6563@blackberry.com>, <20161025133016.GA9081@LK-Perkele-V2.elisa-laajakaista.fi>
In-Reply-To: <20161025133016.GA9081@LK-Perkele-V2.elisa-laajakaista.fi>
Accept-Language: en-NZ, en-GB, en-US
Content-Language: en-NZ
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: [130.216.158.4]
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Archived-At: <https://mailarchive.ietf.org/arch/msg/cfrg/4PotkJgAw0gootJdmvZWz1vSvFc>
Cc: CFRG <cfrg@irtf.org>
Subject: Re: [Cfrg] Security proofs v DH backdoors
X-BeenThere: cfrg@irtf.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: Crypto Forum Research Group <cfrg.irtf.org>
List-Unsubscribe: <https://www.irtf.org/mailman/options/cfrg>, <mailto:cfrg-request@irtf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/cfrg/>
List-Post: <mailto:cfrg@irtf.org>
List-Help: <mailto:cfrg-request@irtf.org?subject=help>
List-Subscribe: <https://www.irtf.org/mailman/listinfo/cfrg>, <mailto:cfrg-request@irtf.org?subject=subscribe>
X-List-Received-Date: Wed, 26 Oct 2016 04:32:57 -0000

Ilari Liusvaara <ilariliusvaara@welho.com> writes:

>I think there was one TLS implementation that tries to verify the groups sent
>(of course, not all can be verified, even if those aren't maliscously
>constructed).

Mark Bauschke mentioned they do checking on the OpenSSH list, taking (i.e.
assuming) that q = ( p - 1 ) / 2.  I don't recall any TLS implementation doing
this.  However, with TLS-LTS there are one or more implementations now that do
check.

(Hey, I've got to get the maximum mileage out of this one :-).  LTS has
already foiled attacks that postdate its publication, so you know it's a good
thing).

Peter.