Re: [saag] Liking Linkability

[Ben Laurie <[e-mail]>]

On 18 October 2012 17:52, Kingsley Idehen <[e-mail]> wrote:
> On 10/18/12 12:06 PM, Ben Laurie wrote:
>>
>> On 18 October 2012 16:41, Kingsley Idehen <[e-mail]> wrote:
>>>
>>> On 10/18/12 11:34 AM, Ben Laurie wrote:
>>>>
>>>> On 9 October 2012 14:19, Henry Story <[e-mail]> 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.
>>>>
>>>>
>>>>
>>>>
>>> Do you have example of what you describe? By that question I mean:
>>> implicit
>>> anonymity as a functional substrate of some realm that we experience
>>> today?
>>
>> That's what selective disclosure systems like U-Prove and the PRIME
>> project are all about.
>>
>>
>>
> Ben,
>
> How is the following incongruent with the fundamental points we've been
> trying to make about the combined effects of URIs, Linked Data, and Logic en
> route to controlling privacy at Web-scale?
>
> Excerpt from Microsoft page [1]:
>
> A U-Prove token is a new type of credential similar to a PKI certificate
> that can encode attributes of any type, but with two important differences:
>
> 1) The issuance and presentation of a token is unlinkable due to the special
> type of public key and signature encoded in the token; the cryptographic
> “wrapping” of the attributes contain no correlation handles. This prevents
> unwanted tracking of users when they use their U-Prove tokens, even by
> colluding insiders.
>
> 2) Users can minimally disclose information about what attributes are
> encoded in a token in response to dynamic verifier policies. As an example,
> a user may choose to only disclose a subset of the encoded attributes, prove
> that her undisclosed name does not appear on a blacklist, or prove that she
> is of age without disclosing her actual birthdate.
>
>
> Why are you assuming that a hyperlink based pointer (de-referencable URI)
> placed in the SAN of minimalist X.509 certificate (i.e., one that has now
> personally identifiable information) can't deliver the above and more?

Because it contains "correlation handles" to use the terminology of the quote.

> Please note, WebID is a piece of the picture. Linked Data, Entity
> Relationship Semantics and Logic are other critical parts. That's why there
> isn't a golden ontology for resource access policies, the resource publisher
> can construct a plethora of resource access policies en route to leveraging
> the power of machine discernible entity relationship semantics and
> first-order logic.
>
> In a most basic super paranoid scenario, if I want to constrain access to a
> resource to nebulous entity "You" I would share a PKCS#12 document with that
> entity. I would also have an access policy in place based on the data in
> said document. I would also call "You" by phone to give you the password of
> that PKCS#12 document. Once that's all sorted, you can open the document,
> get your crytpo data installed in your local keystore and then visit the
> resource I've published :-)
>
> Links:
>
> 1. http://research.microsoft.com/en-us/projects/u-prove/
> 2. http://en.wikipedia.org/wiki/Zero-knowledge_proof -- I don't see anything
> about that being incompatible with what the combined use of de-referencable
> URIs based names, Linked Data, Entity Relationship Semantics, Reasoning, and
> existing PKI deliver.
>
>
> --
>
> Regards,
>
> Kingsley Idehen
> Founder & CEO
> OpenLink Software
> Company Web: http://www.openlinksw.com
> Personal Weblog: http://www.openlinksw.com/blog/~kidehen
> Twitter/Identi.ca handle: @kidehen
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> LinkedIn Profile: http://www.linkedin.com/in/kidehen
>
>
>
>
>