Zero-Knowledge Proofs (Midnight)

This shows how the Fairway Cloud Agent transforms off-chain KYC data into a Midnight ZK-proof, records it on Midnight, and enables cross-chain eligibility checks on Cardano and EVM.

Flow

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What’s Proven in the Circuit

• The user’s KYC data satisfies required rules (e.g., KYC2_OK, jurisdiction).

• The proof is bound to a specific wallet address.

• The proof is linked to a timestamp of KYC verification (kyc_verified_at).

• The proof is anchored on Midnight as an immutable reference (midnight_ref).

• Cross-chain (Cardano/EVM) contracts only verify Merkle membership, Fairway sig, sanctions_epoch, and KYC recency — no raw PII.

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Verifier Checklist (Cardano/EVM)

• ✅ Verify Merkle membership for address.

• ✅ Verify Fairway signature over (root, sanctions_epoch, midnight_ref).

• ✅ Enforce KYC recency → now - kyc_verified_at ≤ max_age.

• ✅ Enforce sanctions freshness → sanctions_epoch == latestEpochRoot.

• ⬜ Optional audit: resolve midnight_ref on Midnight for regulator review.

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Notes on Keys & Curves

• Fairway signature uses chain-appropriate keys:

  • secp256k1 for EVM chains.

  • Cardano-compatible key for UTXO scripts.

• Midnight Compact supports Schnorr signatures inside circuits.

• On-chain verifiers don’t recompute the ZK — they only check Fairway’s signature + Merkle inclusion.

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Next Steps

• See Build on Cardano → validator checks for Merkle, timestamp, and sanctions epoch.

• See Build on EVM → attestation schema with kyc_verified_at + sanctions_epoch.

• Review Revocation Epochs & Freshness → how long-term KYC vs short-term sanctions are combined.