While selective disclosure can enhance a user's privacy by only revealing necessary claims, there are use cases that need certain conditions on the properties to be true (e.g. claim-based binding, age verification, set inclusion).

With the default hash algorithm identifiers defined in RFC-9901 e.g. SHA-256, there is no easy way to do zero knowledge proofs and as such, the relevant claims must always be disclosed. In our extension of RFC-9901, we standardise how to provide commitments on attributes using them as an alternative family of "hash"-like functions. Further extensions in the key binding JWT propose a way to define sigma protocols to provide efficient zero knowledge proofs for linear conditions on attributes - especially equality and range proofs.

Using our proposal, we can achieve device binding for only claim-based bound credentials using the transitivity property and linking e.g. a diploma with an ID card, without revealing more information than necessary.

With this proposal in mind, we are looking for inputs on how to include further ZKP schemes (e.g. lattice-based/hash-based schemes), and how to generalise definitions of proof systems.