JWT-VC

A JWT-VC (JSON Web Token Verifiable Credential) is a W3C-compliant format for representing a digitally-signed credential, such as a diploma or driver's license, as a compact, URL-safe JSON Web Token. It packages the credential's claims (e.g., name, issuance date), metadata, and a cryptographic proof into a single, self-contained token string, often using JWS (JSON Web Signature) for integrity and authenticity. This format is a core profile within the broader Verifiable Credentials Data Model, providing a widely-supported, interoperable method for decentralized identity.

The structure of a JWT-VC is defined by specific JWT claims. The vc claim contains the credential payload as a JSON object, including its @context, type, issuer, issuanceDate, and the credential subject's data. The sub claim typically holds the subject identifier (e.g., a DID). The token is then signed by the issuer's private key, binding the credential data to the issuer's public key or DID. This allows any verifier with the corresponding public key to cryptographically confirm the credential's origin and that it has not been altered.

A key advantage of the JWT-VC format is its compatibility with existing web infrastructure. JWTs are natively supported by countless libraries and are the standard for API authentication and authorization (e.g., OAuth 2.0). This makes JWT-VCs relatively easy to implement for developers familiar with web security. They are particularly well-suited for holder-presented scenarios, where an individual (the holder) presents a credential directly to a verifier, such as logging into a website by sharing a verifiable email credential.

However, JWT-VCs differ from other formats like JSON-LD Signatures or Data Integrity Proofs. While JWT-VCs offer simplicity and tooling maturity, they are not inherently designed for selective disclosure or zero-knowledge proofs without extensions. The verification process is typically signature-centric, focusing on the validity of the JWS rather than complex linked data proofs. This makes them a pragmatic choice for many use cases but may be less flexible for advanced privacy-preserving applications compared to other VC formats.

In practice, JWT-VCs are issued by an issuer (e.g., a university), stored by a holder (e.g., a graduate in a digital wallet), and presented to a verifier (e.g., an employer). The verifier decodes the JWT, validates its signature against the issuer's published public key or DID Document, and checks the credential's status and expiration. This creates a trust triangle enabling portable, user-controlled credentials without relying on a central database, forming a foundational component of Self-Sovereign Identity (SSI) ecosystems.

A JWT-VC is a JSON Web Token whose payload conforms to the data model of a W3C Verifiable Credential. The core innovation is the encapsulation of credential metadata, claims, and proof within the established JWT standard (JWS or JWE). The JWT's header specifies the token type as JWT and the proof mechanism (e.g., alg: ES256K), while the payload contains the mandatory Verifiable Credential fields: @context, type, issuer, issuanceDate, credentialSubject, and optionally credentialStatus. This structure allows existing, widely deployed JWT libraries to process Verifiable Credentials with minimal adaptation.

The verification process relies on the JWT's built-in cryptographic proof, typically a JSON Web Signature (JWS). The issuer signs the JWT's header and payload, creating a detached proof that is bundled with the credential. A verifier checks the signature against the issuer's public key, which is often resolved via a Decentralized Identifier (DID) document referenced in the issuer field. This process cryptographically verifies the credential's integrity (it hasn't been altered) and authenticates its origin (it was issued by the claimed entity), fulfilling the core guarantees of a Verifiable Credential.

Selective disclosure is a critical feature enabled by the JWT-VC format through mechanisms like SD-JWT (Selective Disclosure JWT). Instead of presenting the entire signed JWT, the holder can generate a derived presentation that reveals only specific claims. This is achieved by issuing the credential with certain claim values replaced with cryptographic digests. During presentation, the holder discloses the plaintext values along with the corresponding digests, allowing the verifier to recompute the hashes and confirm they match the signed values without seeing the undisclosed data, thereby preserving privacy.

Interoperability is a primary advantage of the JWT-VC format. By building on IETF standards like RFC 7519 (JWT) and RFC 7515 (JWS), it leverages a vast ecosystem of tools, libraries, and infrastructure. This contrasts with other proof formats like Linked Data Proofs, which require specialized RDF canonicalization and graph-based signature algorithms. The trade-off is that JWT-VC is optimized for JSON-native environments and may not natively support the graph-based data integrity features of the full Linked Data ecosystem, though profiles exist to bridge these worlds.

A JWT-VC (JSON Web Token Verifiable Credential) is a Verifiable Credential (VC) encoded as a JSON Web Token (JWT), a compact, URL-safe token format defined in RFC 7519. This structure packages the credential's claims, metadata, and a cryptographic proof into a single, self-contained token string, typically formatted as a three-part sequence: a Header, a Payload, and a Signature, each encoded in Base64Url. The JWT-VC format is a core profile specified by the W3C Verifiable Credentials Data Model, enabling interoperability across systems that support JWT-based authentication and authorization.

The token's Header specifies the token type (JWT) and the cryptographic algorithm used for the signature, such as EdDSA or ES256K. The Payload contains the core credential data within a vc claim, which is a JSON object conforming to the W3C VC data model—including the @context, type, issuer, issuanceDate, credentialSubject, and optional fields like expirationDate. The payload also includes standard JWT claims like iss (issuer), sub (subject), and jti (unique identifier). The Signature is generated by signing the encoded header and payload, providing integrity and authenticity, and enabling verification without requiring a separate data fetch.

A key advantage of the JWT-VC structure is its compactness and widespread library support. Because JWTs are a standard in web security, developers can leverage existing tools and infrastructure for signing, parsing, and validation. The structure is particularly well-suited for stateless, bearer-token-based scenarios such as API access, where the credential can be presented directly in an HTTP Authorization header. However, its self-contained nature means all data must be included in the token itself, which can lead to larger payloads compared to other formats like JSON-LD Signatures or Data Integrity Proofs that can reference external contexts.

When a JWT-VC is presented for verification, the verifier decodes the token, validates the JWT signature using the issuer's public key (often resolved via a Decentralized Identifier (DID)), and then processes the contained vc claim according to Verifiable Credential rules. This includes checking the credential status, expiration, and whether the claims satisfy the required presentation policies. The JWT-VC structure is foundational for implementing Selective Disclosure through mechanisms like SD-JWT (Selective Disclosure JWT), which allows a holder to reveal only specific claims from the original credential while still providing a valid cryptographic proof.