Re: Verifiable Requests?

Gabe said:

>On the surface I agree with you. My stance then is either Verifiable
Presentations should be removed from the VC spec, or Verifiable Requests be
added. If you disagree, I’d like to know how you view Verifiable
Presentations and Requests as asymmetric.

When you give testimony in court, the dynamics are asymmetric. The court
requests your testimony; you give a verifiable response. You take an oath
to tell the truth. The court does not. This asymmetry is normal. It is not
*universal* -- I can imagine a witness agreeing to testify, but only after
demanding proof that the court is legitimate, etc. But we don't fix that
corner case by modeling the process of giving testimony as a
reciprocal/symmetric process. We allow the giver-of-testimony and the
requester-of-testimony to exist in an asymmetric relationship, with
non-equivalent duties and powers -- and then we apply the asymmetric
relationship in a new direction to compensate (ask the court to prove its
legitimacy), as needed.

What I'm saying is that "Verifiable" Requests are not and need not be a
thing, because usually the burden of proof on the request doesn't justify
the "verifiable" label. A request is just like any sentence, statement, or
message. If you need to say anything on the record so it's non-repudiable,
great -- do that. We don't need a format to make it verifiable, and in
particular we don't need to standardize requests for credential material as
a format *for the purpose of verifiability.* We want to standardize
requests for a different purpose.

This does not mean I'm against a standard format for making requests for
credential material. I actually love the idea of the presentation
definition that DIF's proposing. What I'm against is the idea that such a
request needs special format properties to make it verifiable. It doesn't.
It shouldn't have the word "verifiable" in front of it. If we want our
request to be on the record, include a digital signature over its hash, or
use some other auditable authentication, or whatever. No format changes
needed. If what we want to do is check the bona fides of the party making
the request, we do that by reversing the holder and verifier roles
temporarily, and asking the verifier to prove something to us using VCs of
their own, before we honor their own request for proof. There's already a
format for that.




On Sat, Dec 19, 2020 at 10:15 AM David Chadwick <D.W.Chadwick@kent.ac.uk>
wrote:

> Hi Daniel
>
> I would revise your requirements somewhat as follow
>
> On 19/12/2020 04:06, Daniel Hardman wrote:
> > FWIW, here are the things that I think we need to standardize:
> >
> > 1. A credential and a presentation (the VC spec)
> > 2. How a credential is requested (what the new DIF spec calls a
> > "presentation definition", which is quite powerful and generally
> > useful, IMO)
>
> Rather I would say: How a set of credentials, or alternative sets of
> credentials, are requested.
>
> This request needs to be fully flexible to cater for (as near as
> possible) any conceivable requirements of the SP. In our implementation
> we use DNF and CNF as these can present any set of requirements.
>
> > 3. How a response to a request explains the way that the response maps
> > to the request ("You asked me for either a driver's license or a
> > passport, plus proof of my current address. I chose to give you the
> > passport, and to prove my current address by showing you a utility
> > bill.")\
>
> I actually don't think this is needed. The returned VP is the holder's
> answer to the request. It contains the requested VCs embedded in it. So
> it is self-explanatory. (The Holder does not need to say its a utility
> bill because the VC itself will say what type it is). It is the
> responsibility of the verifier to see if the VP does contain the set of
> VCs that meets the SP's requirements. There is little point in the
> holder giving an explanation because:
>
> a) the explanation could be acceptable but the actual VC may not be (I
> am showing you a utility bill, but the utility bill issuer is unknown to
> the verifier)
>
> b) the explanation might not be acceptable, but the VC might be (I am
> sending you my employment card (instead of passport), but this contains
> the holder's current address)
>
> c) the explanation could be false and the VC could be something entirely
> different to the explanation, so what does the verifier believe, the
> explanation or the actual VC? (I am giving you my passport but the VC is
> an employment certificate.)
>
> So I see no useful purpose for the explanation. I don't believe it is
> needed, but worse, I think it complicates the processing by the verifier.
>
> Kind regards
>
> David
>
>
>