How To Build A Layer 2 Blockchain with ZK Proofs

In this guide, you'll learn how to create and operate your own ZK-Validium, a Layer 2 blockchain that leverages zero-knowledge proofs (ZKPs) to validate transaction batches. This solution combines scalability with security by offloading computation while maintaining cryptographic integrity.

What You’ll Build

By the end, you’ll have a fully functional chain featuring:

• A faucet for test funds
• A block explorer to monitor transactions
• An RPC endpoint for network interactions
• A bridge for asset transfers between layers
• Smart contract deployment capabilities

Powered by Polygon CDK, this setup ensures EVM compatibility, enabling familiar tools like Hardhat and MetaMask.

Understanding Polygon CDK

Polygon Chain Development Kit (CDK) simplifies the creation of ZK-powered L2 chains. Key features:

• Custom app chains: Tailor-made for specific use cases (e.g., gaming, DeFi).
• Interoperability: Native connectivity with other CDK chains via Polygon’s interop layer.
• Proven infrastructure: Used by projects like Immutable, Canto, and Astar.

👉 Explore Polygon CDK’s architecture

Step-by-Step Deployment

1. Configuring Your Chain

Use an implementation provider like Presto (a Rollup-as-a-Service platform) to streamline deployment:

• Select Private zk-Validium as your chain type.
• Choose pre-configured AWS regions (e.g., "Stockholm") for automated infrastructure setup.

Deployment Time: ~2–4 hours (background AWS resource provisioning).

2. Accessing Developer Tools

Post-deployment, Presto provides:

• RPC URL and chain ID for wallet integration.
• Block explorer links to verify transactions.
• Faucet to fund test wallets.

Deploying a Smart Contract

1. Project Setup

Create a Solidity project with thirdweb and Hardhat:

npx thirdweb@latest create contract

Select Hardhat and configure a simple Greeter.sol contract:

contract Greeter {
  string private greeting;
  constructor(string memory _greeting) { greeting = _greeting; }
  function greet() public view returns (string memory) { return greeting; }
  function setGreeting(string memory _greeting) public { greeting = _greeting; }
}

2. Deployment

• Use npx thirdweb@latest deploy to push the contract.
• Add your validium’s RPC to thirdweb’s dashboard.
• Fund your wallet via the faucet to cover gas fees.

Verify Deployment: Check your block explorer for the contract address.

Building a dApp

1. Initialize a Frontend

Create a React app with thirdweb’s SDK:

npx thirdweb@latest create app

2. Connect to Your Chain

Update _app.tsx with your custom network details:

const activeChain = {
  chainId: 1571747963, // From Presto
  rpc: ["https://your-rpc-url.here"],
  nativeCurrency: { name: "ETH", symbol: "ETH", decimals: 18 },
  testnet: true,
  explorers: [{ url: "https://your-block-explorer.here", name: "blockscout" }]
};

3. Interact with Your Contract

Demo code for reading/writing data:

const { contract } = useContract("0xYOUR_CONTRACT_ADDRESS");
const { data } = useContractRead(contract, "greet");

return (
  <div>
    <p>{data}</p>
    <Web3Button
      contractAddress="0xYOUR_CONTRACT_ADDRESS"
      action={() => contract.call("setGreeting", ["Hello World!"])}
    >
      Update Greeting
    </Web3Button>
  </div>
);

👉 View full demo code on GitHub

FAQ

Q1: What’s the difference between a zk-Validium and a zkEVM Rollup?

A: Validiums use off-chain data availability for higher throughput, while zkEVM rollups post data to Ethereum, enhancing security but with higher costs.

Q2: Can I migrate my existing dApp to a CDK chain?

A: Yes! CDK chains are EVM-compatible, so tools like Hardhat and MetaMask work seamlessly.

Q3: How much does it cost to deploy a chain?

A: Costs vary by implementation provider. Presto offers free testnet deployments; mainnet costs depend on AWS resource usage.

Key Takeaways

1. Polygon CDK democratizes L2 chain creation with ZK proofs.
2. Validiums balance scalability and security for app-specific needs.
3. EVM compatibility ensures developer-friendly tooling.

Next Steps:

• Experiment with cross-chain bridges.
• Explore custom tokenomics for your chain.
• Join the Polygon CDK community for support.