Solana to Ethereum ZK Bridge

A production-ready cross-chain bridge that enables secure token transfers from Solana (using Light Protocol) to Ethereum using zero-knowledge proofs.

Architecture Overview

Solana (Light Protocol) → ZK Circuit → Ethereum Bridge Contract
                ↓           ↓              ↓
    Compressed Account → SNARK Proof → Token Transfer

Components

1. Circom Circuit (circom/solDepositProof.circom)

• Verifies Light Protocol compressed account inclusion
• Generates unique nullifiers to prevent double spending
• Creates commitments binding all transaction parameters
• Outputs ZK-SNARK proof for Ethereum verification

2. Solidity Verifier (evm-bridge/contracts/SolDepositVerifier.sol)

• Generated from Circom circuit using snarkjs
• Verifies Groth16 proofs on-chain
• BN254 elliptic curve pairing verification

3. Bridge Contract (evm-bridge/contracts/evm-bridge.sol)

• Main contract for processing withdrawals
• Validates deposit records against ZK proofs
• Prevents replay attacks using nullifiers
• Transfers ERC20 tokens to recipients

Security Features

✅ Replay Protection - Unique nullifiers prevent double spending
✅ Amount Binding - ZK circuit ensures exact amount matching
✅ State Verification - Only valid Solana deposits can be processed
✅ Privacy - Sensitive data remains hidden in ZK proof
✅ Fail-Safe - Multiple validation layers with emergency controls

Usage

Prerequisites

# Install dependencies
cd evm-bridge && npm install
cd ../circom && npm install

# Install Circom
npm install -g circom

Step 1: Generate Circuit Input

From your Light Protocol deposit data:

cd circom/scripts
npx ts-node generateInput.ts

This creates input.json from your proof.json, account.json, and record.json.

Step 2: Generate ZK Proof

cd circom

# Compile circuit
circom solDepositProof.circom --r1cs --wasm --sym

# Generate witness
node solDepositProof_js/generate_witness.js solDepositProof_js/solDepositProof.wasm input.json witness.wtns

# Setup ceremony (development only)
snarkjs powersoftau new bn128 12 pot12_0000.ptau -v
snarkjs powersoftau contribute pot12_0000.ptau pot12_0001.ptau --name="First contribution" -v
snarkjs powersoftau prepare phase2 pot12_0001.ptau pot12_final.ptau -v

# Generate proving/verification keys
snarkjs groth16 setup solDepositProof.r1cs pot12_final.ptau circuit_0000.zkey
snarkjs zkey contribute circuit_0000.zkey circuit_final.zkey --name="1st Contributor" -v

# Generate proof
snarkjs groth16 prove circuit_final.zkey witness.wtns proof.json public.json

# Export Solidity verifier
snarkjs zkey export solidityverifier circuit_final.zkey verifier.sol

Step 3: Deploy Contracts

cd evm-bridge

# Deploy verifier and bridge
npx hardhat run scripts/deploy.ts --network <your-network>

Step 4: Process Withdrawal

# Set contract addresses
export BRIDGE_CONTRACT_ADDRESS="0x..."
export VERIFIER_CONTRACT_ADDRESS="0x..."

# Process withdrawal
npx hardhat run scripts/processWithdrawal.ts --network <your-network>

Example: Using Your Record Data

Your record.json:

{
  "owner": "Ea9KnXpSXdRKfJAUhrqqWhuBMK3RKPWGQGFto6gvhVco",
  "source_chain_id": 1,
  "dest_chain_id": 41312,
  "dest_chain_addr": "2Uk4AtEZ3mbEVqZQ7En7c4cLuc4Q",
  "dest_chain_mint_addr": "",
  "mint": "svCXW2ivW3L7yBuFLapYKqdeKCcdAEnFQEXpZEF9CUw",
  "amount": "64",
  "timestamp": "6852bbce",
  "deposit_id": "01"
}

Setup Required:

1. Map destination address to Ethereum address:

bridge.mapAddress("2Uk4AtEZ3mbEVqZQ7En7c4cLuc4Q", "0xYourEthereumAddress");

2. Set ERC20 token contract address in dest_chain_mint_addr

3. Deposit tokens to bridge for liquidity:

bridge.depositTokens("0xTokenContract", "64");

4. Update state root with Light Protocol root:

bridge.updateStateRoot("0xStateRoot", blockHeight);

Contract Interactions

Bridge Contract Methods

// Process withdrawal with ZK proof
function processWithdrawal(DepositRecord record, ZKProof proof)

// Admin functions
function mapAddress(string base58Addr, address ethAddr)
function updateStateRoot(uint256 stateRoot, uint256 blockHeight)
function depositTokens(address tokenContract, uint256 amount)

// View functions
function isNullifierUsed(uint256 nullifier) → bool
function getTokenBalance(address tokenContract) → uint256

Development

Testing Circuit

cd circom
circom solDepositProof.circom --r1cs --wasm --sym
# Check circuit info
snarkjs r1cs info solDepositProof.r1cs

Testing Contracts

cd evm-bridge
npx hardhat test
npx hardhat coverage

Production Deployment

Security Checklist

• Use production ceremony for trusted setup
• Audit ZK circuit and contracts
• Set up multi-sig for admin functions
• Configure proper state root oracle
• Set withdrawal limits and rate limiting
• Monitor for unusual activity
• Prepare emergency pause mechanisms

Mainnet Deployment

1. Generate production trusted setup
2. Deploy contracts with proper access controls
3. Set up relayer infrastructure
4. Configure monitoring and alerting
5. Coordinate with Light Protocol team for state root sync

Troubleshooting

Circuit compilation fails:

• Ensure circom 2.1.8+ is installed
• Check circomlib is in node_modules

Proof verification fails:

• Verify circuit inputs match expected format
• Check public signals order matches contract
• Ensure verifying key matches proving key

Transaction reverts:

• Check nullifier not already used
• Verify state root is valid
• Ensure sufficient bridge token balance
• Confirm address mapping is set

Contributing

1. Fork the repository
2. Create feature branch
3. Add tests for new functionality
4. Submit pull request

License

MIT License - see LICENSE file for details.

Security

For security issues, please email [email protected]

Do not create public GitHub issues for security vulnerabilities.