sdjwt_oid4vc 0.1.3

SD-JWT VC + OpenID4VCI/OpenID4VP protocol library for Dart wallets (holder role). Key- and HTTP-agnostic, pure logic, fully testable without hardware.

sdjwt_oid4vc

SD-JWT VC + OpenID4VCI/OpenID4VP protocol library for Dart wallets — the holder role only. It is the piece a wallet app needs to import an EUDI-style credential and present it to a verifier, with selective disclosure and key binding.

There is no comprehensive Dart package for this on pub.dev (only classic OIDC login clients and partial JOSE libraries), so this is a thin, reusable one, deliberately scoped to what a wallet does.

Design in one breath

• Holder only. No issuer/verifier server helpers.
• Key-agnostic. You inject an [Es256Signer]; the library never imports a key backend. Hardware (attested_secure_keys) is an adaptor; tests use an in-memory signer.
• HTTP-agnostic. You inject an Oid4vcHttp (default: DefaultOid4vcHttp over package:http). Testable with no network.
• Layered. Transport (oid4vci, oid4vp) is separate from format (sdjwt), so a future mdoc codec drops onto the same transport.
• Pure. No hidden I/O, no ambient clock — time and randomness are injected, so every signing path is deterministic under test.

Install

dependencies:
  sdjwt_oid4vc:
    git: https://github.com/exilonX/sdjwt_oid4vc

The two seams you provide

Everything below takes the same two injected objects:

Seam	Interface	Do you implement it?
Holder key	Es256Signer	Yes — there is no default; only you can reach your key.
HTTP transport	Oid4vcHttp	No, usually — pass DefaultOid4vcHttp().

Es256Signer is the one required adaptor. In production it wraps a hardware-backed key (see example/README.md for the real attested_secure_keys adaptor); in tests use the bundled SoftwareEs256Signer. It is three methods: publicJwk(), signEs256(signingInput) (return raw R‖S base64url), and an optional attest(nonce).

Oid4vcHttp is just GET / form-POST / JSON-POST plumbing — not your API logic. The OpenID4VCI/OpenID4VP endpoint choreography (which endpoints, what bodies) already lives in Oid4vciClient / Oid4vpClient. Use the default DefaultOid4vcHttp (over package:http) unless you want Dio, interceptors, logging, certificate pinning, or a fake for tests — then implement the three methods over your client of choice.

Receive a credential (OpenID4VCI)

final signer = /* your Es256Signer, e.g. hardware-backed */;
final vci = Oid4vciClient(DefaultOid4vcHttp());

final compact = await vci.redeemOffer(
  offerUriOrJson: deepLink, // openid-credential-offer://...
  txCode: codeFromEmail,    // the one-time activation code
  signer: signer,
);

final credential = SdJwt.parse(compact);
if (!await credential.verifyIssuer(IssuerTrust.signatureOnly())) {
  throw StateError('issuer signature did not verify');
}
// Store `compact`; show credential.resolveClaims() to the user.

Present a credential (OpenID4VP)

final vp = Oid4vpClient(DefaultOid4vcHttp());

final request = await vp.fetchRequest(authorizationRequest); // QR / deep link
final match = vp.match(request, heldCredentials);
if (match == null) return; // nothing satisfies the query

final vpToken = await vp.buildVpToken(
  credential: match.credential,
  revealClaims: match.requestedClaims, // disclose only what was asked
  req: request,
  signer: signer, // signs the KB-JWT → proof of possession
);
await vp.submit(req: request, vpToken: vpToken);

See example/ for a runnable end-to-end walk-through and the hardware-key adaptor.

Testing

package:sdjwt_oid4vc/testing.dart exposes SoftwareEs256Signer, a real P-256 key in memory. With it (and a fake Oid4vcHttp) the whole flow runs without hardware or network. The suite has 100% line coverage.

dart test

Scope

In: SD-JWT VC (dc+sd-jwt) parse/resolve/verify/present (including nested and array claims by DCQL path), OpenID4VCI pre-authorized-code issuance, OpenID4VP presentation with DCQL (single and multi-credential credential_sets), KB-JWT, issuer trust via x5c signature, x5c chain validation to caller-supplied anchors, or jwt-vc-issuer metadata, revocation via the IETF Token Status List, and the request-object signature exposed so the wallet can authenticate the verifier.

Out (for now): mdoc/ISO 18013, W3C JSON-LD VC, OIDC login, issuer/verifier server roles, and credential storage. The library does the mechanism but leaves the governance data to the app: it validates an issuer x5c chain against trust anchors you provide (fetching/parsing the EU Trusted List is yours), it verifies a Relying-Party's request signature on demand but you decide whether to trust the certificate, and certificate revocation (CRL/OCSP) is out of scope.

Context

Built for an EUDI wallet (holder role). Design rationale: docs/SDJWT_OID4VC_LIB.md, engineering notes for contributors: CONTEXT.md.