Re: [saag] Liking Linkability

Robin Wilton <wilton@isoc.org> Wed, 24 October 2012 11:28 UTC

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From: Robin Wilton <wilton@isoc.org>
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Date: Wed, 24 Oct 2012 12:26:58 +0100
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References: <CCA5E789.2083A%Josh.Howlett@ja.net> <tslzk3jsjv8.fsf@mit.edu> <201210181904.PAA07773@Sparkle.Rodents-Montreal.ORG> <FB9E461D-CA62-4806-9599-054DF24C3FD9@bblfish.net> <CAG5KPzxGz+4MywjP4knfbDr2gyvqUZc1HEBXgtaDfYT+DPg5yg@mail.gmail.com> <8AB0C205-87AE-4F76-AA67-BC328E34AF5E@bblfish.net> <CABrd9SQghpi6_rVQKxYXZDtM5HwvE7Kq7SUw5zi41ZRd3y2h9A@mail.gmail.com> <4324B524-7140-49C0-8165-34830DD0F13B@bblfish.net> <CABrd9SQU1uYVaVPedokHxeYkT=759rkPFfimWK1Z8ATzo3yNFA@mail.gmail.com> <5083CCCF.2060407@webr3.org> <50842789.3080301@openlinksw.com> <50845268.4010509@webr3.org> <5084AC77.8030600@openlinksw.com> <50851512.9090803@webr3.org> <CABrd9SRNVLbWxifQAQ6iuX4qMeFmZVD6rO_q=L348G1UZzr9tg@mail.gmail.com> <50852726.9030102@openlinksw.com> <CABrd9SQ3KTqHq1hOfbLAU5hfgNyqCPK4u+ToEda+VtQ5S0utwA@mail.gmail.com> <5085360E.3080008@openlinksw.com> <50853CD8.8020005@w3.org> <5FB468E4-BDD3-4635-ACD0-A23540C08751@bblfish.net> <508562C2.1060905@w3.org> <CAG5KPzx673VKqg4=26-cvfeXZrBfK-XbURFj 8eYx_mXVkko41A@mail.gmail.com> <3EF3A430-A6C5-4ADE-92B5-0744DFFD326B@isoc.org> <CABrd9SQxy3GjKekrrCPikqRBt4z2PdzbOhzZUsDC6asZNSiu0A@mail.gmail.com>
To: Ben Laurie <benl@google.com>
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Cc: Halpin Harry <H.halplin@ed.ac.uk>, public-identity@w3.org, saag@ietf.org, "public-privacy@w3.org list" <public-privacy@w3.org>, public-webid@w3.org
Subject: Re: [saag] Liking Linkability
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Robin Wilton
Technical Outreach Director - Identity and Privacy
Internet Society

email: wilton@isoc.org
Phone: +44 705 005 2931
Twitter: @futureidentity




On 24 Oct 2012, at 10:30, Ben Laurie wrote:

> On 23 October 2012 10:58, Robin Wilton <wilton@isoc.org> wrote:
>> 
>> 
>> On 23 Oct 2012, at 09:44, Ben Laurie wrote:
>> 
>> <snip>
>> 
>> 
>> Not disagreeing with any of the above, but observing that:
>> 
>> a) There's no particular reason you could not have an email per site
>> as well as a key per site.
>> 
>> b) Linkability it not, as you say, inherently bad. The problem occurs
>> when you have (effectively) no choice about linkability.
>> 
>> 
>> 
>> But it's very hard to use either of those mechanisms (separation through
>> emails or keys) without giving some third party the ability to achieve total
>> linkability. (In other words, both options remove effective choice).
> 
> I agree that emails are a problem, but not at all sure why keys are?
> In the case of appropriate selective disclosure mechanisms, even if
> there were a third party involved, they would not be able to link uses
> of the keys. Also, if you insist on using linkable keys, then per-site
> keys do not involve third parties.
> 

It may just be that I'm not getting a clear mental picture of your architecture. But here was my thinking: 

- If you use symmetric keys, you get a system which can't scale unless you opt for Schneier's idea of a key server… but then the key server becomes a point of potential panopticality.

- If you use PKI, *and* you want your communicating parties to be able to validate the certs they're relying on, then you have to design a CRL- or OCSP-like mechanism into the architecture, and again you end up with a component which is potentially panoptical. (Plus, you have to address the 20-year-old problem of how to make PKI usable by human beings, when recent history suggests that PKI only takes off where human beings are kept well away from it).

R



> On email, this is a soluble problem, but not without using a
> completely different delivery mechanism.



> 
>> 
>> Yrs.,
>> Robin
>> 
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