Re: [TLS] Security review of TLS1.3 0-RTT

Eric Rescorla <ekr@rtfm.com> Tue, 02 May 2017 23:44 UTC

Return-Path: <ekr@rtfm.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id D56551274D0 for <tls@ietfa.amsl.com>; Tue, 2 May 2017 16:44:02 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.599
X-Spam-Level:
X-Spam-Status: No, score=-2.599 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_LOW=-0.7] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=rtfm-com.20150623.gappssmtp.com
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 o3Atd6RkZLeP for <tls@ietfa.amsl.com>; Tue, 2 May 2017 16:44:01 -0700 (PDT)
Received: from mail-yw0-x236.google.com (mail-yw0-x236.google.com [IPv6:2607:f8b0:4002:c05::236]) (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 CF5931292F5 for <tls@ietf.org>; Tue, 2 May 2017 16:42:33 -0700 (PDT)
Received: by mail-yw0-x236.google.com with SMTP id 203so77469638ywe.0 for <tls@ietf.org>; Tue, 02 May 2017 16:42:33 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rtfm-com.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=zrmL966KZBflwwLhI/xjs/agJn931HGw2Xa6nJFBXvU=; b=qExfhiLKXgel03NSAyreiHEyNTQnycHTQmqi6jUad1k0WXhJv4H/Ynn/bfECQfgsbk 6DjL0CgU98dlfYluJosI461WJWkeQNJhkD3bLXiNF9bSiMZXaKtolmzHll6kA3squ/27 UGeEHdx2pcv71JJATTjaTntooV6WYgRFKq+5VM0gbolEwZzAm7GIl0EvfmShPEZTZI9y rps2wL7ybgUC3iOp5vqICP1mgD91ngcxoh3VSzV6o2O6MGBB5FOgPbB/iE8gRQsUo+Mz vVcNyLpXRA5HGU8fejuLhpGET8mHgH20E1weALC3aR3jT7ymtSdRHoWOEGAADL5DDF6m LvzQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=zrmL966KZBflwwLhI/xjs/agJn931HGw2Xa6nJFBXvU=; b=XC+R9HbWbt3z8AhxHxgItakjaV4uo7AJPhxv/Z1LVBsxrl5QmGZQrlXFtnmglfmgpv ChFR4+7nyctkNAcOlfLYLPK1o2GffuLlCwiDTztmh5l+rYLWsR461eNIGbR/pQEa4iW8 mTs/E3JcS06L5E0K05k3AKKxnM1NOVvikq0yVnAAjV2zH8smClh2nTSdGr5fzphSHsM2 sUNCgodrjTKGntvu6jHuYqaHkQfCl7N4XRkLUY/kIdb/Yl2/++tLFkn2ypCnVE+ymjBP kz81uGQyg5TmRe6t4nD3EQG4z9ggR+0kC9eOM9xsd+036W0u9dfP1U00zyRoFiyZeOkC Vixw==
X-Gm-Message-State: AN3rC/7CwBXfo+pUVE9hOGu7gGULdFxaJ682Mk7adHLF7zylkhd1LTUQ s3VEaORSEJE7RaUYTIXf4uKf2wQedhhY
X-Received: by 10.129.52.141 with SMTP id b135mr26916251ywa.85.1493768553125; Tue, 02 May 2017 16:42:33 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.129.113.7 with HTTP; Tue, 2 May 2017 16:41:52 -0700 (PDT)
In-Reply-To: <20170502230258.GL10188@localhost>
References: <20170502182529.GG10188@localhost> <466fad64-5acd-d888-1574-10f95b2ab7bc@akamai.com> <20170502192003.GH10188@localhost> <e313032d-2ac8-cc4e-0aa7-de869007e397@akamai.com> <20170502193145.GI10188@localhost> <42522b3c-8987-ea2a-2173-bcadaf6ff326@akamai.com> <20170502195753.GJ10188@localhost> <87a86vrnge.fsf@fifthhorseman.net> <20170502212953.GK10188@localhost> <CABcZeBNvFAe+otDgE6rMG0wGaBA=Z3bDBRRvirxPFJFuc+KbeQ@mail.gmail.com> <20170502230258.GL10188@localhost>
From: Eric Rescorla <ekr@rtfm.com>
Date: Tue, 02 May 2017 16:41:52 -0700
Message-ID: <CABcZeBMHPi3dJQRuxU_y5E=NPYpYEwikBxjXPUVw4m2WSjWrWw@mail.gmail.com>
To: Nico Williams <nico@cryptonector.com>
Cc: Daniel Kahn Gillmor <dkg@fifthhorseman.net>, TLS WG <tls@ietf.org>
Content-Type: multipart/alternative; boundary="001a11408984fc74a8054e9317ac"
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/Z238vs8s9lPIvPzdI6SfYnv4eAM>
Subject: Re: [TLS] Security review of TLS1.3 0-RTT
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.22
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: <https://mailarchive.ietf.org/arch/browse/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: Tue, 02 May 2017 23:44:03 -0000

On Tue, May 2, 2017 at 4:02 PM, Nico Williams <nico@cryptonector.com> wrote:

> On Tue, May 02, 2017 at 03:53:48PM -0700, Eric Rescorla wrote:
> > It's not XOR. It's addition mod 2^32. That's important because the
> > *difference*
> > between the ticket replay times is directly observable anyway.
>
> Computationally there's no real difference between that and XOR.
>

What information do you believe you are gathering here?

As I stated, when the ticket is replayed, you already know the absolute time
difference between those replays.

-Ekr