Write privacy-preserving smart contracts in Compact (Minokawa) for Midnight Network. Use when creating contracts, defining types, using standard library functions, or implementing ZK patterns. Triggers on Compact language, circuits, ledger state, hashing, or zero-knowledge contract questions.
Compact (being renamed to Minokawa) is Midnight's domain-specific language for privacy-preserving smart contracts. Contracts compile to ZK-SNARKs, enabling selective disclosure of data.
Note: As of compiler v0.26.0, the language is being renamed from "Compact" to "Minokawa" under the Linux Foundation Decentralized Trust. The toolchain commands still use
compact.
pragma language_version 0.18;
export ledger message: Opaque<"string">;
export circuit setMessage(input: Opaque<"string">): [] {
message = disclose(input); // Makes private input public
}
Every Compact contract has three parts:
pragma language_version 0.18;)| Level | Syntax | Visibility |
|---|---|---|
| Private | const x = input; | Only prover |
| Disclosed | disclose(value) | Allowed to become public |
| Proven | disclose(a >= b) | Public boolean only |
| Witness | witness f(...): T; | Private, DApp-provided |
Notes:
disclose(...) is a compiler acknowledgement: it does not itself publish anything, it just permits
an expression to flow into public outputs (ledger writes / exported circuit returns / cross-contract comms).Opaque<"string"> and Opaque<"Uint8Array"> are currently supported.ledger counter: Counter; // Auto-incrementing
ledger balances: Map<Bytes<32>, Uint<64>>; // Key-value
ledger members: Set<Field>; // Membership tracking
ledger tree: MerkleTree<20, Field>; // Cryptographic proofs
| Topic | Resource |
|---|---|
| Type System | references/types.md - Full type reference |
| Standard Library | references/stdlib.md - Hashing, coins, EC ops |
| VS Code extension | references/vscode-extension.md - Editor setup and tasks |
| Ledger Patterns | references/ledger-patterns.md - State management |
| Advanced Patterns | references/advanced-patterns.md - Access control, state machines |
| Detailed API Patterns | references/detailed-api-patterns.md - API, code |
| Template | Description |
|---|---|
| assets/basic-contract.compact | Simple ledger + circuit |
| assets/token-contract.compact | Token with transfers |
| assets/private-voting.compact | Anonymous voting |
| assets/commitment-reveal.compact | Commit-reveal pattern |
# Compile contract
compact compile contracts/my-contract.compact contracts/managed/my-contract
# Output structure
contracts/managed/my-contract/
├── contract/ # JSON artifacts
├── keys/ # ZK proving/verifying keys
└── zkir/ # ZK Intermediate Representation
| Error | Cause | Fix |
|---|---|---|
Type mismatch | Wrong bit width | Use correct Uint<N> size |
Cannot assign private to public | Missing disclose | Add disclose() wrapper |
Undefined symbol | Import missing | Check pragma and imports |
pragma language_version 0.18;witness for private inputs that need proofsUint<N> that fits your datapersistentHash for on-chain data, transientHash for tempdisclose() unnecessarily