Re: Selective Disclosure of lists

David,

The conclusion I draw is that the verifier should avoid infering properties
of the VC from document metadata, such as node counts, or counts of items
in a list. On the other hand, the issuer should add properties explicitly
to the document (e.g. numDirectors=2). Trying to calculate any property of
the VC by implication seems to produce errors.

Is this really a problem of selective disclosure. If an issuer creates a VC
containing a list of directors, without stating whether it is a complete
list, the document signature won't encapsulate such information so such a
claim cannot be verified. Is surely does not matter if the document is
subsequently redacted or not?

This kind of problem seems to spring up elsewhere. Could the issuer infer
that a list is up to date as of  this year if the VC's issuance date is
recent for example? It feels like only applications can decide this. To
that end, perhaps a 'numDirectors=6' approach would be the simpest and most
reliable.

Did you have something more cunning in mind?

Regards,
Jeremy



On Tue, 8 Jun 2021 at 13:47, David Chadwick <
d.w.chadwick@verifiablecredentials.info> wrote:

> One example is the list of directors and list of secretaries of a company.
> A list might be empty (allowed), or the holder might wish to remove
> specific names before disclosing the list to the verifier. The issue is how
> can the verifier tell the difference between a culled long list and a
> complete small list.
>
> Kind regards
>
> David
>
>
> On 08/06/2021 13:01, Jeremy Townson wrote:
>
> Could you give an example, David, I had thought the point of selective
> disclosure was that the verifier could make only a binary (not)valid
> decision about validity and was not able to infer other properties of the
> undisclosed data, such as properties of lists.
>
> On Tue, 8 Jun 2021 at 12:10, David Chadwick <
> d.w.chadwick@verifiablecredentials.info> wrote:
>
>> I dont know if anyone has discussed the selective disclosure of lists but
>> here are at least some of the issues:
>>
>> The user's VC has a property with a list of values (e.g. names of role
>> holders). The user only wants to disclose n of m of this list to the
>> verifier.
>>
>> How can the verifier determine the difference between
>>
>> i) a list with only n entries
>>
>> ii) a list that has more than n entries but the user has withheld some of
>> them.
>>
>> Then we have the case where
>>
>> iii) the list is genuinely empty because e.g. the role, has not been
>> assigned to anyone yet, and
>>
>> iv) the user does not want to tell the verifier any of the list values.
>>
>> As far as I am aware the current data model does not have any way of
>> differentiating between any of the above in a selectively disclosed VC.
>>
>> Kind regards
>>
>> David
>>
>