Re: [saag] Liking Linkability

Henry Story <henry.story@bblfish.net> Fri, 19 October 2012 12:01 UTC

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From: Henry Story <henry.story@bblfish.net>
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Date: Fri, 19 Oct 2012 14:01:04 +0200
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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>
To: Ben Laurie <ben@links.org>
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Subject: Re: [saag] Liking Linkability
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On 18 Oct 2012, at 21:29, Ben Laurie <ben@links.org> wrote:

> On Thu, Oct 18, 2012 at 8:20 PM, Henry Story <henry.story@bblfish.net> wrote:
>> 
>> On 18 Oct 2012, at 21:04, Mouse <mouse@Rodents-Montreal.ORG> wrote:
>> 
>>>> [...]
>>>> Unfortunately, I think that's too high of a price to pay for
>>>> unlinkability.
>>>> So I've come to the conclusion that anonymity will depend on
>>>> protocols like TOR specifically designed for it.
>>> 
>>> Is it my imagination, or is this stuff confusing anonymity with
>>> pseudonymity?  I feel reasonably sure I've missed some of the thread,
>>> but what I have seem does seem to be confusing the two.
>>> 
>>> This whole thing about linking, for example, seems to be based on
>>> linking identities of some sort, implying that the systems in question
>>> *have* identities, in which case they are (at best) pseudonymous, not
>>> anonymous.
>> 
>> With WebID ( http://webid.info/ ) you have a pseudonymous global identifier,
>> that is tied to a document on the Web that need only reveal your public key.
>> That WebID can then link to further information that is access controlled,
>> so that only your friends would be able to see it.
>> 
>> The first diagram in the spec shows this well
>> 
>>  http://webid.info/spec/#publishing-the-webid-profile-document
>> 
>> If you put WebID behind TOR and only have .onion WebIDs - something that
>> should be possible to do - then nobody would know WHERE the box hosting your
>> profile is, so they would not be able to just find your home location
>> from your ip-address. But you would still be able to link up in an access
>> controlled manner to your friends ( who may or may not be serving their pages
>> behind Tor ).
>> 
>> You would then be unlinkable in the sense of
>> http://tools.ietf.org/html/draft-iab-privacy-considerations-03
>> 
>> [[
>>      Within a particular set of information, the
>>      inability of an observer or attacker to distinguish whether two
>>      items of interest are related or not (with a high enough degree of
>>      probability to be useful to the observer or attacker).
>> ]]
>> 
>> from any person that was not able to access the resources. But you would
>> be linkable by your friends. I think you want both. Linkability by those
>> authorized, unlinkability for those unauthorized. Hence linkability is not
>> just a negative.
> 
> I really feel like I am beating a dead horse at this point, but
> perhaps you'll eventually admit it. Your public key links you.

The question is to whom? What is the scenario you are imagining, and who is
the attacker there?

> Access
> control on the rest of the information is irrelevant. Indeed, access
> control on the public key is irrelevant, since you must reveal it when
> you use the client cert.

You are imagining that the server I am connecting to, and that I have
decided to identify myself to, is the one that is attacking me? Right?
Because otherwise I cannot understand your issue. 

But then I still do not understand your issue, since I deliberately
did connect to that site in an identifiable manner with a global id.
I could have created a locally valid ID only, had I wanted to not 
connect with a globally valid one.

So your issue boils down to this: if I connect to a web site deliberately
with a global identifier, then I am globally identified by that web site.
Which is what I wanted.

So perhaps it is up to you to answer: why should I not want that? 

> Incidentally, to observers as well as the
> server you connect to.

Not when you re-negotiation I think. 
And certainly not if you use Tor, right?


Social Web Architect
http://bblfish.net/