> ## Documentation Index
> Fetch the complete documentation index at: https://docs.opaque.cash/llms.txt
> Use this file to discover all available pages before exploring further.

# Protocol overview

> CSAP, PSR, and UAB specifications and how they fit together.

Opaque Protocol is documented in the [`opaquecash/spec`](https://github.com/opaquecash/spec) repository. The SDK implements these three layers:

## CSAP: Confidential Stealth Address Protocol

[EIP-5564](https://eips.ethereum.org/EIPS/eip-5564) stealth addresses with Opaque's DKSAP key derivation (`opaque-cash-v1` HKDF).

* Meta-address registry
* Stealth address announcer
* View-tag prefilter + WASM ownership scan

**Spec:** [CSAP.md](https://github.com/opaquecash/spec/blob/main/CSAP.md)

**SDK surface:** [Stealth API](/sdk/stealth-api), [Stealth payments concept](/concepts/stealth-payments)

***

## PSR: Provable Stealth Reputation

Schema registry, attestation engine, and Groth16 reputation verifier. Attestations bind to `stealth_address_hash`, not a public EOA.

* V2 schemas with ABI-style field definitions
* Delegated issuance (up to 10 delegates)
* Discovery announcements with attestation metadata
* ZK proofs scoped by `externalNullifier`

**Spec:** [PSR.md](https://github.com/opaquecash/spec/blob/main/PSR.md)

**SDK surface:** [PSR API](/sdk/psr-api), [PSR concept](/concepts/psr)

***

## UAB: Universal Announcement Bus

Cross-chain relay of 96-byte stealth announcement payloads over Wormhole.

* `UABSender.announceWithRelay` on source chain
* `UABReceiver` re-emits on destination chain
* Off-chain relayer delivers VAAs

**Spec:** [UAB.md](https://github.com/opaquecash/spec/blob/main/UAB.md)

**SDK surface:** [Cross-chain API](/sdk/cross-chain-api), [Cross-chain concept](/concepts/cross-chain)

***

## Repositories

| Repo                                                            | Role                                                                                                                                                                   |
| --------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`opaquecash/sdk`](https://github.com/opaquecash/sdk)           | TypeScript SDK (`@opaquecash/opaque`)                                                                                                                                  |
| [`opaquecash/spec`](https://github.com/opaquecash/spec)         | Protocol specifications                                                                                                                                                |
| [`opaquecash/ethereum`](https://github.com/opaquecash/ethereum) | EVM contracts                                                                                                                                                          |
| [`opaquecash/solana`](https://github.com/opaquecash/solana)     | Solana programs                                                                                                                                                        |
| [`opaquecash/starknet`](https://github.com/opaquecash/starknet) | Starknet (Cairo) contracts                                                                                                                                             |
| [`opaquecash/relayer`](https://github.com/opaquecash/relayer)   | UAB VAA relayer                                                                                                                                                        |
| [`opaquecash/scanner`](https://github.com/opaquecash/scanner)   | Rust cryptography crate: WASM scanner for browsers, plus a universal scanner with Ethereum/Solana JSON-RPC adapters behind the `native` cargo feature for Rust wallets |