zk-age-verifier

zk-age-verifier is a verifier service for EU age verification, accepting Longfellow zero-knowledge proofs over mdoc through the W3C Digital Credentials API. It runs as a sidecar HTTP service beside a consumer backend. A verified verdict contains one boolean per requested check. The service has no authentication and is intended to be reachable only from the consumer backend, not the browser or internet. It is experimental and unstable.

Installation

pip install zk-age-verifier
uv add zk-age-verifier
docker pull ghcr.io/pipe23-org/zk-age-verifier:latest

Usage

The verifier needs a configured origin and at least one trust source.

[service]
expected_origin = "https://av.example"

[[trust.sources]]
pem = "/etc/zk-age-verifier/anchors"

python -m zk_age_verifier --config config.toml

POST /sessions opens a session and returns the navigator.credentials.get() argument under transports.dc.

$ curl -X POST http://127.0.0.1:8000/sessions \
    -H 'content-type: application/json' -d '{"checks": ["age_over_18"]}'
{"session_id": "tmcdOPmo7oCgd4AmmMFyYg",
 "transports": {"dc": {"digital": {"requests": [{"protocol": "org-iso-mdoc",
   "data": {"deviceRequest": "omd2ZXJzaW9u…", "encryptionInfo": "gmVkY2FwaaJ…"}}]},
   "mediation": "required"}},
 "expires_at": "2026-07-20T09:34:22.089682Z"}

The consumer backend relays the wallet response to POST /sessions/{session_id}/presentation. A verified and a failed verification both return 200.

POST /sessions/{session_id}/presentation
{"response": "<wallet response, base64url>"}

{"state": "verified", "result": {"age_over_18": true}, "verified_at": "<iso8601>"}
{"state": "failed", "reason": "decrypt-failed"}

GET /health returns {"status": "ok"} while the process is up.

GET /debug/transcript/{session_id} returns the transcript inputs stored for a session — the origin and the encryptionInfo string — with the handover hash and session-transcript bytes reconstructed from them, hex-encoded. It is a development route, unauthenticated like the rest of the service.

Configuration

Two TOML tables, [service] and [trust], passed with --config.

• expected_origin (required) — the exact scheme://host[:port] origin the presentation asserts.
• backend (default google-cpp) — the pylongfellow verifier backend, google-cpp or isrg-rust; an unknown or unbuilt name fails startup.
• session_ttl_seconds (default 300) — session lifetime.
• session_cap (default 1000) — live-session limit; POST /sessions returns 503 at the cap.
• timestamp_skew_seconds (default 300) — proofs whose timestamp differs from the current time by more than this fail stale-proof.
• cors_allowed_origins (default []) — origins for which CORS headers are emitted.
• trust.sources (required) — non-empty list; each entry sets one of pem (a PEM file or directory of issuer CA certs) or etsi_xml (an ETSI trusted-list https URL or file path).

A presented document-signer certificate must carry the keyUsage extension asserting digitalSignature; an anchor accepted as the issuer of a chained leaf must assert keyCertSign.

Configured trust sources merge into one anchor set. Any anchor in that set can vouch for a certificate that signs age credentials. The certificate layer carries no required marker restricting what an anchor's certificates may sign. ETSI TS 119 412-6 clause 6 places no type indicator on EAA signing certificates. The trust.sources list must name only anchors intended to vouch for age credentials. A mixed-purpose or broad list authorizes every CA on it as an age-credential issuer.

Environment variables ZK_AGE_VERIFIER_<SECTION>__<KEY> override scalar values; lists and nested tables come from the TOML file only. Environment variables take precedence over the TOML file, which takes precedence over the defaults.

Documentation

Full documentation: https://zk-age-verifier.readthedocs.io/

Development

uv sync
uv run pytest
uv run ruff check
uv run ruff format --check
uv run mypy

make test-live runs the suite against a running server over HTTP. make test-container runs it against the built container image.

Status

You should not rely on this code.

• No rate limiting.
• The session store is in-process.
• The proof is verified against an empty device-namespace map; the ZK response format carries no field holding the map the wallet signed.

License

Apache-2.0.