Key terms

VC (Verifiable Credential), a tamper-proof, issuer-signed credential (W3C data model). In Zetrix it is dual-signed by the issuer with Ed25519 and BBS+ keys, which enables selective disclosure later.

VP (Verifiable Presentation), the object the holder presents to a verifier, wrapping one or more VCs plus proofs bound to the verifier's challenge.

DID / ZID, a Decentralised Identifier; the Zetrix variant (did:zid:…) resolves to a DID document on-chain that carries the subject's public keys.

DCQL (Digital Credentials Query Language), the JSON query a verifier uses to state which credential and which claims/constraints it needs. This is where a proof's required conditions are defined.

BBS+ selective disclosure, reveals only chosen claims from a VC while keeping the issuer signature verifiable. Producing it is a public-key re-randomisation of the issuer's signature, it needs no holder secret.

Bulletproof range proof (BulletproofRangeProof2021), proves a numeric claim lies in a range (e.g. age ≥ 18) without revealing the value.

Holder binding, an Ed25519Signature2020 over the verifier's nonce, signed inside the HSM, proving the presenter controls the holder key. This is the only private-key operation the wallet performs during a proof.

HSM (softHSM for the POC), PKCS#11 security module holding the holder key; interface-compatible with the future ms-zetrix hardware HSM (cutover is config-only).