> For the complete documentation index, see [llms.txt](https://whitepaper.lacunalabs.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://whitepaper.lacunalabs.io/how-lacuna-works/zk-circuits.md).

# Zero-Knowledge Circuits

Lacuna uses zero-knowledge proofs to verify actions without revealing the underlying data. Proofs are produced by arithmetic circuits and verified on-chain by Groth16 verifier contracts.

## What The Circuits Prove

* **Shield** — a valid deposit creates a valid note.
* **Transfer** — the spender owns enough shielded value, without revealing the amount or identity.
* **Unshield** — a valid note is being withdrawn, with a nullifier to prevent double-spends.

## Verified On-Chain

Each proof is checked by a deployed Groth16 verifier. If the proof is valid, the contract accepts the action; the private inputs are never revealed.

```
witness (private)       ->  circuit  ->  proof
proof + public inputs   ->  on-chain Groth16 verifier  ->  accept / reject
```

> **Roadmap:** Moving proof generation fully on-device — so no secret material ever leaves your phone — is tracked on the [Roadmap](/resources/roadmap.md).


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