Re: RqP presenting W3C Verifiable Credentials to an UMA Authorization Server

Hi Adrian

in the VC work the verifier trusts the issuer(s) of the VCs, not the
holder.

Translating the VC model into UMA language, the VC verifier is the UMA
requesting party, the UMA protected resource would be the VC holder's
wallet holding his/her VCs. The UMA resource owner is the VC holder. The
VC issuer is not in the UMA diagram in Figure 1: Federated Authorization
Enhancements to UMA Grant Flow.

If you add this missing entity(ies), namely the VC issuer(s) into your
diagram, and indicate that the requesting party trusts the VC issuer(s),
then the requesting party can determine whether the resource owner can
be trusted or not after validating the VCs.

Note that VCs do not generally use bearer tokens, and the holder has to
prove that he/she is the genuine holder of the issued VCs. This PoP
might mean you need an enhancement to the UMA protocol (I dont know the
UMA protocol in detail. You may already have PoP). One way is for the AS
or RS to hold the RO's private keys and to sign the response message to
the requesting party.

regards

David

On 19/10/2018 19:20, Adrian Gropper wrote:
> I'm cross posting this for the obvious reason and will try to act as
> relay if a discussion ensues. 
> 
> On today’s UMA standards call, the following came up:
> 
> 
>         180 degrees use case / decoupled use case discussion
> 
> Nancy has written up some "180 degrees" use cases, which she'll share
> more widely soon. These got Eve thinking.
> 
> We briefly discussed use cases where the requesting party needs to trust
> the resource owner before taking some action (potentially against
> resources shared), e.g. a loan officer needing to trust that the
> putative resource owner is who they say they are so that the (e.g.)
> personal attributes (resource) shared can be trusted to be associated
> with that resource owner "bearer". This way, the loan officer can
> approve a loan (which might be a second resource that the same resource
> owner could later share with others).
> 
> The current UMA model allows the RO and their AS to match RqP claims
> (not just a plain authenticated identity) against policy, and the RO can
> be decoupled (asynchronous) from that process. The client that the RqP
> uses is explicitly accounted for in the protocol, and UMA has a
> framework for this matching and for the RO's delegation / access
> granting to the RqP. But it only accounts for the client that the RO
> uses to interact with the RS and AS through the OAuth authorization
> endpoint (resulting in a PAT), and otherwise the client handling on the
> RO side is implicit.
> 
> The notion of the RqP needing to trust the RO and the RO needing to
> grant resource access to the RqP seems similar to the "decoupled" use
> cases, where a CSR or bank teller needs to know that Alice is really
> Alice before getting access to her account. 
> 
> What would make sense for ensuring that the RqP could come to trust the
> RO "binding"? Alec will describe some work they've done along these
> lines in our next meeting.
> 
> 
> For the UMA folks, check out Figure 2 at
> https://www.w3.org/TR/verifiable-claims-data-model/ to get oriented. For
> the VC folks, check out 
> https://docs.kantarainitiative.org/uma/wg/rec-oauth-uma-federated-authz-2.0.html
> by way of orientation.
> 
> Our HIE of One Trustee implementation would not be practical without
> _both_ UMA authorization and self-sovereign identifier standards.
> Federation in healthcare is not deployed widely enough to serve a
> patient-centric health record application. I hope this email inspires
> our group’s to harmonize or at least to produce a brief paper describing
> why or why not.
> 
> Adrian
> 
> 
> 
> -- 
> 
> Adrian Gropper MD
> 
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Received on Friday, 19 October 2018 21:22:43 UTC