Terminology and Concepts

This glossary defines the terms used throughout the Verifier documentation.

• Self-Sovereign Identity (SSI): A user-centric approach to digital identity, allowing individuals and organizations to control their identifiers and credentials without centralized authorities.

• Decentralized Identifier (DID): A unique identifier whose DID Document (public keys and service endpoints) can be resolved to establish trust. In this system, DIDs are either did:web (resolved over HTTPS at a domain) or did:key (self-contained — the public key is encoded directly in the identifier). A verifier signs its authorization requests with one of these DIDs so that wallets can verify the request originates from a known party.

• Verifiable Credential (VC): A cryptographically signed credential that attests to certain attributes of an entity. VCs follow W3C standards, ensuring integrity and authenticity.

• Verifiable Presentation (VP): A presentation of one or more VCs by a holder to a verifier. The VP proves possession and authenticity of the credentials without revealing unnecessary information.

• Credential formats: The Verifier accepts two credential formats: SD-JWT VC (dc+sd-jwt), which supports selective disclosure so a holder can reveal only the claims a verifier needs, and JWT-VC-JSON (jwt_vc_json), a JWT-based W3C credential.

• OpenID4VP (OpenID for Verifiable Presentations): The protocol the Verifier uses to request, receive, and validate presentations. You create an authorization request, the holder's wallet returns a presentation, and the Verifier validates it. Supported draft versions are v1, v1.draft21, and v1.draft24.

• Verification queries (DCQL / Presentation Exchange): The two ways to express which credentials and which fields a presentation must contain. DCQL (Digital Credentials Query Language) and DIF Presentation Exchange v2 are both supported — each authorization request carries exactly one of them. They act as structured filters, ensuring that only credentials meeting the defined criteria are accepted.

• EMPE DID method / EMPE blockchain: An on-chain DID method in the wider Empeiria EVDI ecosystem. The Verifier resolves did:web, did:key, and did:jwk directly; did:empe resolution is an ecosystem roadmap item (see Future Enhancements).