Re: [TLS] Pull Request: Removing the AEAD explicit IV

Eric Rescorla <ekr@rtfm.com> Sat, 21 March 2015 20:04 UTC

Return-Path: <ekr@rtfm.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 567741A8A95 for <tls@ietfa.amsl.com>; Sat, 21 Mar 2015 13:04:46 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -0.977
X-Spam-Level:
X-Spam-Status: No, score=-0.977 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, FM_FORGED_GMAIL=0.622, HTML_MESSAGE=0.001, J_BACKHAIR_51=1, RCVD_IN_DNSWL_LOW=-0.7] 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 LpJ90qR0F8Rg for <tls@ietfa.amsl.com>; Sat, 21 Mar 2015 13:04:45 -0700 (PDT)
Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) (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 142621A8782 for <tls@ietf.org>; Sat, 21 Mar 2015 13:04:45 -0700 (PDT)
Received: by wibgn9 with SMTP id gn9so20446322wib.1 for <tls@ietf.org>; Sat, 21 Mar 2015 13:04:43 -0700 (PDT)
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=6ZvyQaN08b8tMByXeozlUFxCRCDOLh7HIS+d0wgAx+o=; b=NY1ufl24tBGzsA2ESKTiNVEIzYbn0Us/2knexiTAGikA2+3ycwPqca2WKQZLmS1Rtj velUNG+9VEW2lEkAVcwVfUTjCz3ZDJXGDkQgI1f2m60ScQ89cr6M+espCdIFR3x4MbzW KTOg9kdFQ98WKU+OnopF3tzxRavhju2lc2N+c4P9CrV2GvHiKWOt4l0AlEiy8U/UaHDL 0DRX3+U0WVbOtVlYfTUiVd5Dn5xbQ4ZiW1k1JSOFUcTYvVFG1d8L9d7t/nefm1OVc8AF ZUz10XLsCdiu6uH6fPgAnpae1G4GGUDJnZNSBZnUfIp9ZQBP6AqJhca9ZPKIdiFtMa5j 9ljg==
X-Gm-Message-State: ALoCoQnvkpcnCMeug9D9O5EkGL1G3GZidzlySli94GAE0i1zxTHpPZTMTQpW/rIc7eYiO20I7pm5
X-Received: by 10.194.235.71 with SMTP id uk7mr173445773wjc.13.1426968283816; Sat, 21 Mar 2015 13:04:43 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.27.205.198 with HTTP; Sat, 21 Mar 2015 13:04:03 -0700 (PDT)
In-Reply-To: <20150321195356.GA5190@LK-Perkele-VII>
References: <CABcZeBPfasM5HmJaATLUHQKRgiSGCreJt1T=UoDBGCbcuzyW8Q@mail.gmail.com> <CAFewVt7_+oqy0EczdaxVpgS9gkzp8EMjLCgjXj+DE7S-e94Q7A@mail.gmail.com> <CABcZeBMN=0GUsqDMnLM5eTg54t6Sn0ME9213ts75OXLKZxr9+w@mail.gmail.com> <CAMfhd9Xckw9s=5OxC_Cv7YSoZ4bxu4Xe59ZhmkUFuYcJNawEiA@mail.gmail.com> <CABcZeBNpV7qQSpUESEn64xr8_RjDboPsS9CHupkP5OAQfPkD-A@mail.gmail.com> <CAMfhd9UN6ZjCpg5LhWh+zMd5m55N-MiP9-qcVviSJKOr--tZaw@mail.gmail.com> <CABcZeBNYKuvg5VVQK9TLUKqhoiz2+bupuQfFBfGS08oHrYoc1w@mail.gmail.com> <20150321195356.GA5190@LK-Perkele-VII>
From: Eric Rescorla <ekr@rtfm.com>
Date: Sat, 21 Mar 2015 13:04:03 -0700
Message-ID: <CABcZeBO99graWLdsQ=3yVJT3kBBBuPT82DY_Az5U9+Rc9j1SrA@mail.gmail.com>
To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Content-Type: multipart/alternative; boundary=089e01493afaa9bdfa0511d1f14b
Archived-At: <http://mailarchive.ietf.org/arch/msg/tls/81oZCVMVRr6vtrDGtHtiq5CQQDI>
Cc: Adam Langley <agl@imperialviolet.org>, "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Pull Request: Removing the AEAD explicit IV
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <tls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tls>, <mailto:tls-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/tls/>
List-Post: <mailto:tls@ietf.org>
List-Help: <mailto:tls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sat, 21 Mar 2015 20:04:46 -0000

On Sat, Mar 21, 2015 at 12:53 PM, Ilari Liusvaara <
ilari.liusvaara@elisanet.fi>; wrote:

> On Sat, Mar 21, 2015 at 12:22:44PM -0700, Eric Rescorla wrote:
> > On Sat, Mar 21, 2015 at 12:20 PM, Adam Langley <agl@imperialviolet.org>;
> > wrote:
> >
> > > On Sat, Mar 21, 2015 at 11:58 AM, Eric Rescorla <ekr@rtfm.com>; wrote:
> > > > Adam, Brian, what would you think of XOR rather than addition?
> > > >
> > > > E.g., generate a per-connection value V and then do:
> > > >
> > > > Nonce = Seq XOR V?
> > >
> > > It's invertable so can't break uniqueness. So that would be ok too. Is
> > > V a 12-byte (or whatever) value and thus fixes the upper 4 (or
> > > whatever) bytes of the nonce?
> > >
> >
> > I was thinking that we would generate an N_MIN long V and XOR
> > it with Seq. So, yes, N_MAX - 8 bytes would be effectively fixed.
>

I meant N_MIN here, btw.



> A few thing to note:
>
> - RFC5116 allows N_MIN=0, which means the scheme can operate without
>   nonces, but there doesn't seem to be any such registered algorithms.
> - There are registred AEAD algorithms with N_MIN<8, N_MAX>8.
>

This is the one that concerns me (though the general problem is a concern
for all of these).

Perhaps instead use max(N_MIN, 8)?

-Ekr



> - Some registered algorithms have huge N_MAX.