DAYPASS App

EU Battery Regulation 2023/1542 Digital Battery Passport on Cardano: one CIP-25 NFT per passport plus an anchor metadata label carrying the payload hash, a Merkle content root and the public Point-1 fields. Sensitive data stays AES-encrypted off-chain; three disclosure tiers render lawful views of one backend. Threshold statements (“carbon footprint below X”) are proven in zero knowledge — with the Groth16 verification executed by the Cardano ledger itself. DAYPASS is the transparent-chain twin of NIGHTPASS (Midnight, shielded ZK).

Highlights

• CIP-25 NFT anchor: Mint under a policy bound to the producer key + anchor label 1155 with payloadHash, contentRoot, Point-1 cleartext
• Three disclosure tiers (Annex XIII): consumer / recycler / authority — enforced in the API layer; the chain carries the evidence, not the access control
• Selective disclosure: Reveal ONE field value with a Merkle inclusion proof against the anchored content root — any Cardano API can re-verify it
• On-chain ZK predicates: provePassportPredicate mints a predicate token whose mint redeemer IS the Groth16 proof; the Plutus V3 validator runs the full pairing check
• Re-attest chain: Metadata txs with new payload versions, chained via prev; burn nets supply to zero on revocation
• Catena-X export: CX-0143 BatteryPass aspect JSON + W3C-VC Predicate Attestation Credential (PAC) verifiable portably against Cardano

Stack

Metadata Labels

Label 721  (CIP-25)   display: name "DPP <passportId>", model, QR image
Label 1155 (anchor)   evidence: op (mint|reattest|grant|revoke),
                      payloadHash, contentRoot, poseidonRoot,
                      version + prev tx hash, Point-1 cleartext

The mint tx carries both labels; re-attest and audit anchors are plain metadata txs with only the 1155 label. Grant/revoke anchors are pseudonymous: the grantee is sha256(did), never PII.

Zero-Knowledge Predicates

1. Anchor commits a Poseidon Merkle root over the 9 provable fields
2. Prover sidecar (@odatano/dayzero) builds the Groth16 proof
3. provePassportPredicate mints a token: redeemer = proof
4. Validator verifies the pairing on-chain; asset name commits
   to the public inputs (blake2b-224 over the serialised datum)

Live on Preview: mint + anchor tx ae0d4c2d…05af8f, zk predicate tx 5a5c0a64…57d52c proving carbonFootprint lessOrEqual threshold.

Quick Start

git clone https://github.com/ODATANO/DAYPASS && cd DAYPASS
npm install
cp .env.example .env                  # fill in BLOCKFROST_API_KEY (preview)
npm run deploy                        # creates db/daypass.db + demo seeds
docker compose up -d daypass-prover   # ZK prover sidecar on :8799
npm start                             # http://localhost:4004

• Producer cockpit: /producer/webapp/index.html (producer/producer)
• Consumer viewer: /passport/webapp/index.html (recycler/recycler, authority/authority)
• QR landing /p/<passportId>, public verification JSON /verify/<passportId>

Sourcecode

github.com/ODATANO/DAYPASS