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Re: Centralization dangers of applying OpenID Connect to wallets protocols (was: Re: 2022-2026 Verifiable Data Standards Roadmap [DRAFT])

From: Tobias Looker <tobias.looker@mattr.global>
Date: Mon, 21 Mar 2022 23:33:16 +0000
To: Nikos Fotiou <fotiou@aueb.gr>, 'Manu Sporny' <msporny@digitalbazaar.com>, "public-credentials@w3.org" <public-credentials@w3.org>
Message-ID: <SY4P282MB1274D9AB96B3059615FF47859D169@SY4P282MB1274.AUSP282.PROD.OUTLOOK.COM>
I want to underscore a point made by Nikos here in his latest email around the purpose of client registration before I respond separately to your other points raised Manu.

Essentially as Nikos pointed out the primary intent of client registration, whether it be accomplished dynamically or via other means is for the provider to understand certain things about it, that are core from a security and interoperability perspective.

Suffice to say even in a model that uses CHAPI + VC API, most of the exact same information will have to be shared in order for exchange to be conducted securely, for instance lets break down some of the information typically captured in a client registration:

- Redirect URIs, required so the provider knows where to send the authorization code in response, fundamentally if you want a protocol that involves the issuer interacting with the End-User, you will not be able to escape the usage of redirect and therefore the necessity of this parameter being featured somewhere in the protocol.
- response types, what the wallet supports as a response type, required for interoperability, there is no point the provider producing a response the wallet is fundamentally un-able to receive, also note it is optional in registration.
- grant types, again very much like the above but it is the client describing which possible grants it may request, also note it is optional in registration.
- application_type, client describing its nature e.g is it web or native again important around how the provider might enforce certain policies associated to the redirect uri used which can be critical to the security of the flow.

I can go on, but the point is all of the information captured during registration has a purpose in the protocol either to mitigate certain security threats OR promote interoperability between the client and provider. Just because CHAPI + VC API flow hasn't got to tackling this particular problem yet, around how these two parties will communicate certain things about each other, does not mean the end-state solution will be any different.

For example here is a concrete case with CHAPI + VC API flows today where this issue manifests clearly, say I'm on a relying parties website that support validating VP's signed with an ECDSA signature and only did:key as the did method. But when the End-User clicks "login" or "authenticate with VCs", the End-Users selects a wallet via CHAPI that only supports EdDSA and did:ion. What is going to happen is a VP is going to be generated and sent back to the relying party, which the relying party is going to have no ability to rely upon due to their in-ability to resolve the did method use OR validate the signature on the VP.


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Tobias Looker


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From: Nikos Fotiou <fotiou@aueb.gr>
Sent: 22 March 2022 10:50
To: 'Manu Sporny' <msporny@digitalbazaar.com>; public-credentials@w3.org <public-credentials@w3.org>
Subject: RE: Centralization dangers of applying OpenID Connect to wallets protocols (was: Re: 2022-2026 Verifiable Data Standards Roadmap [DRAFT])

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Received on Monday, 21 March 2022 23:33:36 UTC

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