Re: [Cfrg] ChaCha20

Yoav Nir <ynir.ietf@gmail.com> Fri, 08 August 2014 21:38 UTC

Return-Path: <ynir.ietf@gmail.com>
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 7D0391A0AE8 for <cfrg@ietfa.amsl.com>; Fri, 8 Aug 2014 14:38:32 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Level:
X-Spam-Status: No, score=-2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, SPF_PASS=-0.001] autolearn=ham
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 l5gRa0pZuoUl for <cfrg@ietfa.amsl.com>; Fri, 8 Aug 2014 14:38:30 -0700 (PDT)
Received: from mail-wg0-x233.google.com (mail-wg0-x233.google.com [IPv6:2a00:1450:400c:c00::233]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id C0FD51A00E2 for <cfrg@irtf.org>; Fri, 8 Aug 2014 14:38:29 -0700 (PDT)
Received: by mail-wg0-f51.google.com with SMTP id b13so6117780wgh.10 for <cfrg@irtf.org>; Fri, 08 Aug 2014 14:38:28 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=8hOveBR7oKmu1LUnhz47BKYMuNZxJYV6Be+r/54RBJI=; b=M1Pb9KicuLpyr6FWzleJwdOrgSDjXl6+pmnsO5naVWHJZ0sYZ4zE4KoS5sI8SNcISv sNF1bNAHJliH2C1THIU64HdjmizH5h+NTzm5vxVafMmogzQ46J526gSUYiukhHTujTA9 ep3/FeK4x/XQQK+cG8avknxBusIGN6j5y7iMBEdKiLonKzJtPJ9VfhFCSWTabvlycAvi sKau4FZ0VmxY5m71T9g/fJx8nO8W7NCGuoZfIqqiyEcqCRMJIKQF8VZ7F+0fa0/bV0sh iarUVFouHsh/T0tx1+zfKrwQeRGXZa4qF11CP2O+JLun3D2IkNoANT4RJzZlSpu2ibIG PKTw==
X-Received: by 10.194.219.225 with SMTP id pr1mr35704199wjc.34.1407533908469; Fri, 08 Aug 2014 14:38:28 -0700 (PDT)
Received: from [192.168.1.100] (bzq-84-109-50-18.red.bezeqint.net. [84.109.50.18]) by mx.google.com with ESMTPSA id w6sm20018579wjq.39.2014.08.08.14.38.27 for <multiple recipients> (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 08 Aug 2014 14:38:28 -0700 (PDT)
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\))
From: Yoav Nir <ynir.ietf@gmail.com>
In-Reply-To: <20140808133614.GA24182@LK-Perkele-VII>
Date: Sat, 9 Aug 2014 00:38:27 +0300
Content-Transfer-Encoding: quoted-printable
Message-Id: <026EAED2-09A4-48E8-9DA9-DC533151720D@gmail.com>
References: <CACsn0cmUg1A1wxgOuubfPNg2XJGVq6BNFkARkv_eCSYqvqWRCA@mail.gmail.com> <20140808133614.GA24182@LK-Perkele-VII>
To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
X-Mailer: Apple Mail (2.1878.6)
Archived-At: http://mailarchive.ietf.org/arch/msg/cfrg/XQ7StOedAMHFCOvuDL9wiM5HnK0
Cc: "cfrg@irtf.org" <cfrg@irtf.org>
Subject: Re: [Cfrg] ChaCha20
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: Fri, 08 Aug 2014 21:38:32 -0000

On Aug 8, 2014, at 4:36 PM, Ilari Liusvaara <ilari.liusvaara@elisanet.fi> wrote:

> On Thu, Aug 07, 2014 at 06:23:05PM -0700, Watson Ladd wrote:
>> Dear all,
>> In the past 6 years only one cryptanalysis result has been published
>> against ChaCha, and that was against a variant before the final
>> version was announced. While Salsa20 was an eStream finalist, ChaCha
>> wasn't.
>> 
>> I'd like to see some more cryptanalytic attention on ChaCha: in
>> particular are the differentials from "Latin Dances" still valid for
>> the published version of ChaCha? What are the best differential
>> characteristics? And can we figure this out quickly?
> 
> Trying to find paper about "Latin Dances", I ran into these:
> 
> https://eprint.iacr.org/2007/472
> https://eprint.iacr.org/2012/065
> 
> Both seem to analyze final version of Chacha, and seemingly make
> worse job than on Salsa (e.g. the first "breaks" Salsa8, but not
> Chacha8).

Thanks, Ilari

The second of those is not (yet) referenced in the draft. I will add this to the next revision.

Yoav