Questions about ecdsa-sd-2023

Hi all,

As discussed privately with Manu I have a few questions about the ecdsa-sd-2023 crypto suite implementation and I thought having them on the public list could help others at least get those answered too, should they need it one day.

So I understand mandatory and selectively disclosed pointers on the technical level, but I’m confused with the vector which determines them:

  *   If the verifier asks for mandatory fields, it means that they should have quite a precise knowledge of the structure of the document, which might not always be the case, for instance in the case of a more universal verifier. Wouldn’t it make more sense to have the issuer specify what are those mandatory fields, through a property of the VC or its proof?
  *   When selecting the fields to disclose, I understand this would be the responsibility of both the holder (from the user perspective) and the wallet (for the technical action of doing so). There is an example of what the verifier might ask to disclose to the holder, but contrary to the BBS+ suite where the reveal document serves of some kind of binding contract to the disclosed data, here it seems entirely up to the holder to choose which properties to disclose. So, at that point, how can we “automate” the verification, to make sure the actual requested data is disclosed without human intervention (which would imply reading a JSON file basically)?
  *   Why isn’t it possible to verify the initially signed full VC when signed with @digitalbazaar/ecdsa-sd-2023-cryptosuite?
  *   Is support for predicates envisioned for this spec?
  *   I didn’t quite understand the reasoning behind the blank node ids? Looking at this example https://w3c.github.io/vc-di-ecdsa/#example-canonical-hmac-document, is the goal just to obfuscate the _c14n indexes so one wouldn’t be able to guess the structure of the original document?

Otherwise thanks as always to the Digital Bazaar team for the spec and open sourcing of the solution.

--

Julien Fraichot
Developer – Hyland Credentials

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