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.... 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
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Adrian Gropper MD
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