What is Cloak?
Cloak is a privacy-preserving exit router for Solana. It combines zero-knowledge proofs, on-chain verification, and off-chain services to let users deposit SOL privately and withdraw later without linking the two actions.
System Goals
- Privacy-first withdrawals: Users deposit into a shared shield pool and later withdraw without revealing which deposit they own.
- Programmable guarantees: The withdraw circuit enforces nullifier uniqueness, Merkle inclusion, and amount conservation.
- Economic sustainability: Miners earn fees by supplying proof-of-work (PoW) wildcard claims that unblock congested withdraws.
- Operational clarity: Indexer, relay, web app, tooling, and runbooks are all contained in this repository with a consistent Rust + TypeScript stack.
Major Components
- Zero-Knowledge Layer – SP1 guest and host programs, verification key generation, proof extraction utilities.
- On-Chain Programs – Shield Pool (privacy pool), Scramble Registry (wildcard claims).
- Off-Chain Services – Indexer (Merkle tree management), Relay (transaction submission).
- Wildcard Miner – Proof-of-work claim generation for prioritized withdrawals.
- Tooling & Tests – Integration test suite for localnet and testnet validation.
Repository Layout
| Path | Description |
|---|---|
docs/ | Design notes, architecture diagrams, ZK specs, and this Docusaurus content. |
packages/ | Rust crates for miners, ZK tooling, and SP1 guest/host code. |
programs/ | Solana BPF programs (Pinocchio) for shield pool and scramble registry. |
services/ | Rust indexer, Rust relay, and Next.js web interface. |
tooling/ | Shared testing utilities for localnet/testnet validation. |
compose.yml | Docker services for Postgres, and local dependencies. |
Feature Pillars
- Privacy-Preserving Withdrawals – Zero-knowledge proofs enable unlinkable withdrawals to arbitrary recipients with cryptographically enforced fee policies.
- Wildcard Mining System – Economic incentives through BLAKE3 proof-of-work claims enable prioritized transaction processing.
- On-Chain ZK Verification – SP1 Groth16 proofs verified on-chain via
sp1-solana, ensuring trustless privacy guarantees. - Production Infrastructure – Comprehensive testing, metrics, and operational tooling for reliable deployment.
Next Steps
- Continue with the Quickstart to set up a local environment.
- Review the System Architecture for a component-level map.
- Dive into the Zero-Knowledge Layer for protocol internals.