Re: [saag] Liking Linkability

David Chadwick <d.w.chadwick@kent.ac.uk> Thu, 18 October 2012 19:18 UTC

Return-Path: <d.w.chadwick@kent.ac.uk>
X-Original-To: saag@ietfa.amsl.com
Delivered-To: saag@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 705CD21F81FF for <saag@ietfa.amsl.com>; Thu, 18 Oct 2012 12:18:54 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -6.599
X-Spam-Level:
X-Spam-Status: No, score=-6.599 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, RCVD_IN_DNSWL_MED=-4]
Received: from mail.ietf.org ([64.170.98.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Ncd6HhHILju7 for <saag@ietfa.amsl.com>; Thu, 18 Oct 2012 12:18:53 -0700 (PDT)
Received: from mx1.kent.ac.uk (mx1.kent.ac.uk [129.12.21.39]) by ietfa.amsl.com (Postfix) with ESMTP id CBC6B21F86F3 for <saag@ietf.org>; Thu, 18 Oct 2012 12:18:53 -0700 (PDT)
Received: from mx0.kent.ac.uk ([129.12.21.32]) by mx1.kent.ac.uk with esmtps (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from <d.w.chadwick@kent.ac.uk>) id 1TOvcE-00085z-TZ; Thu, 18 Oct 2012 20:18:46 +0100
Received: from [63.133.198.91] (helo=[172.16.13.114]) by mx0.kent.ac.uk with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from <d.w.chadwick@kent.ac.uk>) id 1TOvcD-00052p-LT; Thu, 18 Oct 2012 20:18:46 +0100
Message-ID: <50805611.2000904@kent.ac.uk>
Date: Thu, 18 Oct 2012 20:18:41 +0100
From: David Chadwick <d.w.chadwick@kent.ac.uk>
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20121010 Thunderbird/16.0.1
MIME-Version: 1.0
To: Ben Laurie <benl@google.com>
References: <88F98DFD-EF7D-4444-A9C2-FB8E15F5DA89@bblfish.net> <3757D928-C3AE-4630-98E7-E30B5CC604B0@cisco.com> <C8B17065-FD7A-4E4C-B423-4FAB02A48A6D@bblfish.net> <7E1636E02F313F4BA69A428B314B77C708217189@xmb-aln-x12.cisco.com> <7ABCD095-4B09-40DD-A084-1BBE761CA72F@bblfish.net> <CABrd9SRqZN5Bm6rHmduUxXW4ED0yPTxU148Y3txLPjPhbA=hpQ@mail.gmail.com>
In-Reply-To: <CABrd9SRqZN5Bm6rHmduUxXW4ED0yPTxU148Y3txLPjPhbA=hpQ@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Mailman-Approved-At: Mon, 22 Oct 2012 08:25:26 -0700
Cc: "public-philoweb@w3.org" <public-philoweb@w3.org>, "public-identity@w3.org" <public-identity@w3.org>, "saag@ietf.org" <saag@ietf.org>, "public-privacy@w3.org" <public-privacy@w3.org>, "Klaas Wierenga \(kwiereng\)" <kwiereng@cisco.com>, "public-webid@w3.org" <public-webid@w3.org>
Subject: Re: [saag] Liking Linkability
X-BeenThere: saag@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Security Area Advisory Group <saag.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/saag>, <mailto:saag-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/saag>
List-Post: <mailto:saag@ietf.org>
List-Help: <mailto:saag-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/saag>, <mailto:saag-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 18 Oct 2012 19:18:54 -0000

Hi Ben

I disagree. It depends upon your risk assessment. Your stand is like 
saying TLS should be the substrate, not http. There are two alternative 
viewpoints. You can either start with the lowest security/privacy and 
add to it, or make the highest security/privacy the default and then 
take from it. So you should not necessarily mandate that U-Prove/Idemix 
are the default tokens, but rather only require them if your risk 
assessment says privacy protection is essential

regards

David

On 18/10/2012 16:34, Ben Laurie wrote:
> On 9 October 2012 14:19, Henry Story <henry.story@bblfish.net> wrote:
>> Still in my conversations I have found that many people in security spaces
>> just don't seem to be  able to put the issues in context, and can get sidetracked
>> into not wanting any linkability at all. Not sure how to fix that.
>
> You persist in missing the point, which is why you can't fix it. The
> point is that we want unlinkability to be possible. Protocols that do
> not permit it or make it difficult are problematic. I have certainly
> never said that you should always be unlinked, that would be stupid
> (in fact, I once wrote a paper about how unpleasant it would be).
>
> As I once wrote, anonymity should be the substrate. Once you have
> that, you can the build on it to be linked when you choose to be, and
> not linked when you choose not to be. If it is not the substrate, then
> you do not have this choice.
>