zk-id/README.md

# ZK-ID Program

A minimal zk id Solana program that uses zero-knowledge proofs for identity verification with compressed accounts.
Note this is an example how to verify a zk inclusion proof, not a full zk identity protocol and not production-ready.
For examples of zk identity protocols, see:
- [Iden3](https://github.com/iden3) - Full decentralized identity protocol with claims, revocation, and recovery
- [Semaphore](https://github.com/semaphore-protocol/semaphore) - Privacy-preserving group signaling with nullifiers

## Program Instructions

### 1. `create_issuer`
Creates a compressed account for an issuer entity who can credential other users, storing their pubkey and initializing their credential issuance counter.

### 2. `add_credential`
Issues a new credential by creating a compressed account that binds a user's pubkey to an issuer, incrementing the issuer's credential counter in the process.

### 3. `zk_verify_credential`
Verifies a zero-knowledge proof of credential ownership using Groth16 verification and creates an encrypted event account to store the verification result on-chain.

**Properties:**
- Credential verification is private. The credential is not exposed during zk proof verification.
  (The transaction payer is not private, for full privacy a relayer or freshly funded keypair should be used.)
- Each credential can only be used once per `verification_id`. (The event account address serves as a nullifier.)
- Only the credential owner can produce a valid proof.

## Requirements

### System Dependencies
- **Rust** (1.90.0 or later)
- **Node.js** (v22 or later) and npm
- **Solana CLI** (2.3.11 or later)
- **Light CLI**: Install with `npm install -g @lightprotocol/zk-compression-cli`

### ZK Circuit Tools
- **Circom** (v2.2.2): Zero-knowledge circuit compiler
- **SnarkJS**: JavaScript library for generating and verifying ZK proofs

To install circom and snarkjs:
```bash
# Install circom (Linux/macOS)
wget https://github.com/iden3/circom/releases/download/v2.2.2/circom-linux-amd64
chmod +x circom-linux-amd64
sudo mv circom-linux-amd64 /usr/local/bin/circom

# For macOS, replace with circom-macos-amd64

# Install snarkjs globally
npm install -g snarkjs

# Run the setup script to compile circuits and generate keys
./scripts/setup.sh

# Build the program
cargo build-sbf

# Run tests and see tx
RUST_BACKTRACE=1 cargo test-sbf -- --nocapture

zk-id/
├── circuits/                 # Circom circuit definitions
│   └── compressed_account_merkle_proof.circom
├── build/                   # Generated circuit artifacts (after setup)
│   ├── verification_key.json
│   └── *.zkey, *.wasm, etc.
├── scripts/
│   └── setup.sh            # Circuit compilation and setup script
├── src/
│   └── lib.rs             # Solana program implementation
└── tests/
    └── test.rs            # Integration tests

./scripts/clean.sh