RETRACT: Expressive Designated Verifier Anonymous Credentials

Anonymous credentials (ACs) are secure digital versions of credentials that allow selective proof of possession of encoded attributes without revealing additional information. Attributes can include basic personal details (e.g., passport, medical records) and also claims about existing attributes (e.g., age > 18), which can be revealed without disclosing any concrete information. However, embedding all possible claims in a credential is impractical. To address this, we propose verifiers defining policies as high-level programs executed by holders on their credentials. We also propose making the proofs designated verifier to prevent the misuse or leakage of sensitive information by dishonest verifiers to any unwanted third party.