Re: [Cfrg] Elliptic Curves - curve form and coordinate systems (ends on March 12th)

Nadim Kobeissi <nadim@nadim.computer> Sun, 08 March 2015 10:13 UTC

Return-Path: <nadim@nadim.computer>
X-Original-To: cfrg@ietfa.amsl.com
Delivered-To: cfrg@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 6614A1A6F38 for <cfrg@ietfa.amsl.com>; Sun, 8 Mar 2015 03:13:38 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.378
X-Spam-Level:
X-Spam-Status: No, score=-1.378 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FM_FORGED_GMAIL=0.622, HTML_MESSAGE=0.001, SPF_PASS=-0.001] autolearn=no
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 mra3ggg6D8yM for <cfrg@ietfa.amsl.com>; Sun, 8 Mar 2015 03:13:36 -0700 (PDT)
Received: from mail-qg0-x231.google.com (mail-qg0-x231.google.com [IPv6:2607:f8b0:400d:c04::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id A528E1A1B71 for <cfrg@irtf.org>; Sun, 8 Mar 2015 03:13:36 -0700 (PDT)
Received: by qgdz60 with SMTP id z60so22455090qgd.1 for <cfrg@irtf.org>; Sun, 08 Mar 2015 03:13:36 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nadim.computer; s=mail; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type; bh=P+k11lnc0N0CPQtRkkfN1kdM4MIOPhyCOMI6pANtEGI=; b=ANS8YjUyUA0sKuVcL7YHkF2p1TIAyqqq2txOlZbrAY35io+J5zRL3BT0Q/c3p+AQGE +DvbmgrxE/gXX8OmPFpaWBsNrwo91DJ5J7LuMI7/hg0KrW2xkK2iPGzKas1GSW6FkkXU MU4ELV/DTaIVXUU/QuvnWqeprOEaBEfU9o3A8=
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-type; bh=P+k11lnc0N0CPQtRkkfN1kdM4MIOPhyCOMI6pANtEGI=; b=IMfdMuxUU2/nRFxK1XuoWl/uaz1Yyp2uKjWpABCGWsGpv6BCQGzGVOq+l0rBtAVfQs +9rFacPHKogEnM1fnbnnd5AhVxLev1V8IG3jhEgPOKzlNYG6FsZAvHHyE/wZ7c8zg/ZR kXDGW7slj40n11YkyuP+hnPZV63A+AvoSr1xXFye5GrxKMy+isYLITCRCbvv/hAvP9Rz lUr9e8y/aJDhn9kz4NyPZFSobY23+b7IPPHt+a1S+OnuweNiW+TvSxRku50r8cjedINz 76ux7uZtC9SdgDcs6vfvBmOtRPqpiWL2lf6yHlR22roKoG9W0TJcHShJj56phl4JKOqO XHPg==
X-Gm-Message-State: ALoCoQlD4LAr2Raadls3RyAWdu/+eN/6GEkbzPVCeBu4fUDBnUOz5/U7v1Elj7O2JgYfX1IhmU1x
X-Received: by 10.140.97.38 with SMTP id l35mr28587404qge.47.1425809615907; Sun, 08 Mar 2015 03:13:35 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.229.140.69 with HTTP; Sun, 8 Mar 2015 03:13:15 -0700 (PDT)
In-Reply-To: <54F9E7C6.5060107@shiftleft.org>
References: <54F8E735.2010202@isode.com> <20150306115557.GA1503@LK-Perkele-VII> <54F9E7C6.5060107@shiftleft.org>
From: Nadim Kobeissi <nadim@nadim.computer>
Date: Sun, 8 Mar 2015 11:13:15 +0100
Message-ID: <CAOZ60qD=4sy2SCmEWqYK2Q8N_VVifXOvHrcz5NE=71HCS8dBEg@mail.gmail.com>
To: Mike Hamburg <mike@shiftleft.org>
Content-Type: multipart/alternative; boundary=001a113a9ca2aca0a00510c42b1a
Archived-At: <http://mailarchive.ietf.org/arch/msg/cfrg/xnx5GHsRshyl_ibDfClAP43ctyk>
Cc: "cfrg@irtf.org" <cfrg@irtf.org>
Subject: Re: [Cfrg] Elliptic Curves - curve form and coordinate systems (ends on March 12th)
X-BeenThere: cfrg@irtf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: Crypto Forum Research Group <cfrg.irtf.org>
List-Unsubscribe: <http://www.irtf.org/mailman/options/cfrg>, <mailto:cfrg-request@irtf.org?subject=unsubscribe>
List-Archive: <http://www.irtf.org/mail-archive/web/cfrg/>
List-Post: <mailto:cfrg@irtf.org>
List-Help: <mailto:cfrg-request@irtf.org?subject=help>
List-Subscribe: <http://www.irtf.org/mailman/listinfo/cfrg>, <mailto:cfrg-request@irtf.org?subject=subscribe>
X-List-Received-Date: Sun, 08 Mar 2015 10:17:26 -0000

Since I've never commented on this list about this before, I'd like to
quickly vouch for C25519's deployability/implementability/availability in
the field. It would be a mistake to lessen its inclusion now.

On Fri, Mar 6, 2015 at 6:45 PM, Mike Hamburg <mike@shiftleft.org> wrote:

> On 03/06/2015 03:55 AM, Ilari Liusvaara wrote:
>
>> On Thu, Mar 05, 2015 at 11:31:01PM +0000, Alexey Melnikov wrote:
>>
>>> CFRG chairs are starting discussion of the next topic:
>>>
>>> Q4: draft-irtf-cfrg-curves-01 currently contains curves in both
>>> Montgomery
>>> form and Edwards form. The scalar multiplication routine is specified
>>> using
>>> Montgomery form (and is specific to Curve25519, which will need to be
>>> changed given our decision to include a higher security level curve). Its
>>> input is a scalar and the u-coordinate of a point on a Montgomery-form
>>> curve; its output is the u-coordinate of a point on a Montgomery-form
>>> curve.
>>> The DH function builds on this routine. Do we want to stay with
>>> specifying
>>> the inputs and outputs in Montgomery form for these routines? Or do we
>>> want
>>> to switch to an alternative curve form and coordinate system for defining
>>> the routines? If so, which form and coordinate system?
>>>
>> Montgomery u with infinity-to-zero-fold[1] for both.
>>
>> Basically, offers excellent combination of performance, simplicity and
>> small
>> implementation security gap.
>>
>>
>> [1] A.k.a. what Curve25519 does. The folding actually simplifies things
>> (infinity is no longer special case).
>>
>>
>> -Ilari
>>
>
> +1.  Despite my love for fancy point formats, the simplicity of Curve25519
> is very valuable.
>
> When it comes time for signatures, though, we will need at least a sign
> bit and possibly a different format.
>
> -- Mike
>
>
> _______________________________________________
> Cfrg mailing list
> Cfrg@irtf.org
> http://www.irtf.org/mailman/listinfo/cfrg
>