midnight-nft

This project is built on the Midnight Network.

Privacy-preserving (shielded) NFT and credential primitives for Midnight, written in Compact. Two of the three contracts contain original contract logic built well beyond any example: a zero-leakage shielded NFT and a soulbound credential primitive that has been submitted as a Midnight Improvement Proposal.

Toolchain	compactc 0.31.0, compact-runtime 0.16, ledger v8, midnight-js 4.0.4, Node 24.11.1, yarn
Build	yarn install && yarn compact (compiles 25 circuits across 3 contracts)
Test	yarn test — 65 tests, all passing (in-process vitest, no Docker)

What's original here

This is not a renamed template. The repo vendors the Apache-2.0 midnightntwrk/example-nft-contracts as a starting point (attributed in NOTICE), then adds substantial original contract logic on top:

contracts/credential-zk — Soulbound Credential Primitive (new, original)

A non-transferable shielded credential contract, written from scratch. It is the reference implementation for MIP-A, submitted to midnightntwrk/midnight-improvement-proposals as PR #214 (co-authored). Full spec lives at contracts/credential-zk/MIP-A-soulbound-credential-primitive.md.

• Commitment-bound holder — no plaintext owner field on-chain; the holder builds a hiding commitment off-chain.
• Secret-derived issuer authority — store H([tag, sk]) and prove knowledge of sk per call, instead of the forgeable ownPublicKey() auth pattern.
• Private non-revocation via an Indexed Merkle Tree — prove a credential is not revoked without revealing the handle or which gap it occupies.
• Non-revealing membership via a HistoricMerkleTree — prove a credential is issued against any historic root, so in-flight proofs survive later issuance.
• One provePresentation(verifierChallenge) circuit binds membership + non-revocation + holder-key-control over a single opening, returning a challenge-bound nullifier for replay protection.
• Per-deployment namespace via a deploymentSalt constructor param (kernel.self() is unavailable in-constructor on Midnight).
• 28 tests; cleared an internal adversarial security review and an external audit pass.

contracts/nft-zk — zero-leakage shielded NFT (substantially reworked)

The vendored example shipped a single global shared_secret for transfers, which anyone holding it can de-anonymise. That was removed and replaced with original logic:

• Ownership is a per-token commitment persistentHash(["nftzk:owner:v1", pubKey, local_secret, tokenId]). Your public key never lands on-chain, and folding in tokenId makes your holdings unlinkable across tokens.
• Transfers are a zero-leakage release → claim. The sender releases to an off-chain claim_commitment; the recipient claims by proving persistentHash(["nftzk:claim:v1", ownPublicKey(), salt]) == it. No recipient named on-chain, no wallet-scanning, no stranger front-run.
• Secret-derived admin key (replaced a forgeable ownPublicKey() check).
• On-chain per-token metadata (tokenUri), set at mint and preserved across transfer.
• 16 tests, plus a runnable real-chain demo in harness/midnight (deploy → mint → claim → burn, each landing on-chain with real ZK proofs).

contracts/nft — transparent ERC-721-style reference

The transparent control contract from the base, kept for comparison, with admin auth hardened to the same secret-derived pattern. 21 tests.

Layout

contracts/<name>/src/*.compact        the contracts
contracts/<name>/src/test/*.test.ts   simulator tests
contracts/managed/<name>/             compiled output (circuits, keys, zkir)
harness/midnight/                     runnable demo: deploy nft-zk to a local chain, mint/claim/burn with real proofs

Quick start

# compactc 0.31.0 on PATH (compact update 0.31.0), Node 24.11.1
yarn install
yarn compact        # compile all three contracts
yarn test           # 65 tests

Attribution

Starting point: midnightntwrk/example-nft-contracts @ f386411 (Apache-2.0). See NOTICE. All modifications remain Apache-2.0.