# Cloister Protocol — Documentation

> A compliant privacy layer for stablecoin payments on any EVM chain.
> Cloister is a shielded payment pool: it hides the payer's address, amount and the
> payer-recipient link, while proving in zero knowledge that funds are clean (KYC-screened,
> association-set membership) and allowing selective audit via viewing keys. It is privacy WITH
> compliance — not an anonymous mixer. Status: Proof of Concept (pre-audit, test funds only).
> Available in English (root) and German (/de/).

## Documentation

### Overview
- [Introduction](https://docs.cloister-protocol.com/)
- [How it works](https://docs.cloister-protocol.com/how-it-works.html)
- [Why Cloister](https://docs.cloister-protocol.com/why-cloister.html)

### Core concepts
- [The shielded pool](https://docs.cloister-protocol.com/concept-pool.html)
- [Shielding funds](https://docs.cloister-protocol.com/concept-shield.html)
- [Private payments](https://docs.cloister-protocol.com/concept-pay.html)
- [Association sets & compliance](https://docs.cloister-protocol.com/concept-association.html)
- [Viewing keys & disclosure](https://docs.cloister-protocol.com/concept-viewing-keys.html)
- [Keys & recovery](https://docs.cloister-protocol.com/concept-keys.html)

### Protocol
- [Architecture](https://docs.cloister-protocol.com/architecture.html)
- [Circuit specification](https://docs.cloister-protocol.com/circuit.html)
- [Privacy model](https://docs.cloister-protocol.com/privacy.html)
- [Security](https://docs.cloister-protocol.com/security.html)
- [Fallbacks & resilience](https://docs.cloister-protocol.com/fallbacks.html)

### Build
- [Integration](https://docs.cloister-protocol.com/integration.html)
- [Smart contracts](https://docs.cloister-protocol.com/smart-contracts.html)
- [Deployment](https://docs.cloister-protocol.com/deployment.html)
- [Validation](https://docs.cloister-protocol.com/validation.html)

### Resources
- [FAQ](https://docs.cloister-protocol.com/faq.html)
- [Glossary](https://docs.cloister-protocol.com/glossary.html)

### Legal
- [Disclaimer](https://docs.cloister-protocol.com/disclaimer.html)
- [Privacy policy](https://docs.cloister-protocol.com/privacy-policy.html)
- [Imprint](https://docs.cloister-protocol.com/imprint.html)

## Dokumentation (Deutsch)

### Überblick
- [Einführung](https://docs.cloister-protocol.com/de/)
- [So funktioniert es](https://docs.cloister-protocol.com/de/how-it-works.html)
- [Warum Cloister](https://docs.cloister-protocol.com/de/why-cloister.html)

### Kernkonzepte
- [Der abgeschirmte Pool](https://docs.cloister-protocol.com/de/concept-pool.html)
- [Mittel abschirmen](https://docs.cloister-protocol.com/de/concept-shield.html)
- [Private Zahlungen](https://docs.cloister-protocol.com/de/concept-pay.html)
- [Association-Sets & Compliance](https://docs.cloister-protocol.com/de/concept-association.html)
- [Viewing-Keys & Offenlegung](https://docs.cloister-protocol.com/de/concept-viewing-keys.html)
- [Schlüssel & Wiederherstellung](https://docs.cloister-protocol.com/de/concept-keys.html)

### Protokoll
- [Architektur](https://docs.cloister-protocol.com/de/architecture.html)
- [Circuit-Spezifikation](https://docs.cloister-protocol.com/de/circuit.html)
- [Privatsphäre-Modell](https://docs.cloister-protocol.com/de/privacy.html)
- [Sicherheit](https://docs.cloister-protocol.com/de/security.html)
- [Fallbacks & Resilienz](https://docs.cloister-protocol.com/de/fallbacks.html)

### Entwickeln
- [Integration](https://docs.cloister-protocol.com/de/integration.html)
- [Smart Contracts](https://docs.cloister-protocol.com/de/smart-contracts.html)
- [Deployment](https://docs.cloister-protocol.com/de/deployment.html)
- [Validierung](https://docs.cloister-protocol.com/de/validation.html)

### Ressourcen
- [FAQ](https://docs.cloister-protocol.com/de/faq.html)
- [Glossar](https://docs.cloister-protocol.com/de/glossary.html)

### Rechtliches
- [Haftungsausschluss](https://docs.cloister-protocol.com/de/disclaimer.html)
- [Datenschutz](https://docs.cloister-protocol.com/de/privacy-policy.html)
- [Impressum](https://docs.cloister-protocol.com/de/imprint.html)

## Key facts

- First integration: OpenCryptoPay (protocol is rail-agnostic).
- ZK layer: gnark / Groth16 over BN254, Poseidon2 hashing, curve-free keys (pubKey = H(privKey)), 50,481-constraint circuit.
- ~350k gas per shielded payment (~5x cheaper) via off-chain Merkle insertion proven in-circuit.
- Self-custodial: on-device proving; the witness never leaves the device.
- Compliance: KYC-gated entry + association-set ("good-set") membership proofs + viewing-key disclosure.
- Any EVM L2 (reference: Base, Polygon, Arbitrum). Open HTTP API + SDK; additive, no lock-in.

## Links

- Website: https://cloister-protocol.com
- App: https://app.cloister-protocol.com
- Source: https://github.com/joshuakrueger-dfx/cloister-protocol