🚩 Challenge #5 : ZKP - Age Verifier

⚠️ Important: Please complete Challenge #4 first if you haven't already, as it contains essential instructions related to all upcoming challenges.

🎫 Build an Age Verifier using Zero-Knowledge Proofs (ZKP) on Arbitrum Stylus:

👷‍♀️ In this challenge, you'll build and deploy a smart contract that utilizes Zero-Knowledge Proofs for private age verification. You'll work with ZKP circuits, deploy them to an Arbitrum Stylus dev node, and create a frontend that allows users to generate and verify proofs! 🚀

🌟 The final deliverable is a full-stack application featuring age verification. Deploy your contract to a testnet, then build and upload your app to a public web server.

How ZKP Integration Works

This project leverages Zero-Knowledge Proofs (ZKPs) to enable private verification of age on Arbitrum Stylus. Here's the workflow:

Circuit Design: The ZKP logic is defined in .circom files (e.g., AgeVerifier.circom) using the Circom language. These circuits encode the rules for verification (e.g., "is age ≥ 18?") without revealing the inputs.
Proof System Setup: We use the snarkjs library with the Groth16 proving system to generate proving and verification keys. The trusted setup is simulated using a pre-existing pot12_final.ptau file.
Contract Generation: The verification key is exported to a Solidity contract (e.g., AgeVerifier.sol) that runs on Arbitrum Stylus, allowing on-chain verification of zk-proofs.
Frontend Interaction: The Next.js frontend uses WebAssembly (.wasm) outputs from Circom to generate proofs locally, which are then submitted to the deployed contract for verification.
Arbitrum Stylus Advantage: Stylus' Rust-based environment enables efficient execution of the verifier contract, reducing gas costs compared to traditional EVM-based ZKP verification.

This integration ensures privacy (inputs remain off-chain) and scalability (proof verification is lightweight on-chain).

Checkpoint 0: 📦 Environment Setup 📚

Before starting, ensure you have the following installed:

Install Rust and Cargo

Install Rust using rustup, which is the recommended way to install Rust:
```
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
```
Follow the on-screen instructions to complete the installation.
After installation, ensure that the Cargo and Rust binaries are in your PATH. You can do this by adding the following line to your shell configuration file (e.g., ~/.bashrc or ~/.zshrc):
```
export PATH="$HOME/.cargo/bin:$PATH"
```
Then, run:
```
source ~/.bashrc  # or source ~/.zshrc
```

Install Circom

Install circom globally using npm:
```
npm install -g circom
```
Verify the installation by checking the version:
```
circom --version
```

Clone the Repository

git clone -b stylus-zkp-age-verifier https://github.com/abhi152003/speedrun_stylus.git
cd speedrun_stylus

Install Dependencies

Run the following command to install all necessary dependencies:

yarn install

Checkpoint 1: 🚀 Start Your Dev Environment

Step 1: Start the Nitro Dev Node

Ensure Docker is running on your machine. You can start Docker Desktop if it's not already running.
Navigate to the cargo-stylus folder:
```
cd packages/cargo-stylus
```
Run the run-dev-node.sh script:
```
bash run-dev-node.sh
```
This script:
- Spins up an Arbitrum Stylus Nitro dev node in Docker.
- Deploys the AgeVerifier.sol contract.
- Generates the ABI for interacting with the contract.

The dev node will be accessible at http://localhost:8547.

Step 2: Start the Frontend

Open a new terminal window to keep the dev node running.
Navigate to the nextjs folder:
```
cd packages/nextjs
```
Start the development server:
```
yarn dev
```

The app will be available at http://localhost:3000/ageVerifier.

Checkpoint 2: 💫 Explore the Features

Age Verifier

Purpose: Prove that a user's age meets a threshold (e.g., ≥ 18) without disclosing their birthdate.
Circuit Logic: The AgeVerifier.circom circuit takes a private input (birthdate) and a public input (threshold year). It computes the age and outputs a proof if the condition is met.
On-Chain Verification: The generated proof is submitted to AgeVerifier.sol on the Stylus dev node, which uses the verification key to confirm validity.

Age Verifier Interface Age verification interface and process flow

Navigate to the "Debug Contracts" tab in the frontend.
This feature interacts with the Age Verifier contract, which was generated from the AgeVerifier.circom circuit located in packages/circuits.

Circuit generation commands:

circom AgeVerifier.circom --r1cs --wasm --sym
npx snarkjs groth16 setup AgeVerifier.r1cs pot12_final.ptau AgeVerifier_0000.zkey
npx snarkjs zkey contribute AgeVerifier_0000.zkey AgeVerifier_final.zkey --name="Contributor" -v
npx snarkjs zkey export verificationkey AgeVerifier_final.zkey verification_key.json
npx snarkjs zkey export solidityverifier AgeVerifier_final.zkey AgeVerifier.sol

Choose a birthdate in the frontend to generate a zk-proof, which will be verified on-chain using the deployed AgeVerifier.sol contract.

Checkpoint 3: 🛠 Modify and Deploy Contracts

You can tinker with circuit logic by modifying files in the packages/circuits folder. After making changes, regenerate contracts using these commands:

circom AgeVerifier.circom --r1cs --wasm --sym
npx snarkjs groth16 setup AgeVerifier.r1cs pot12_final.ptau AgeVerifier_0000.zkey
npx snarkjs zkey contribute AgeVerifier_0000.zkey AgeVerifier_final.zkey --name="Contributor" -v
npx snarkjs zkey export verificationkey AgeVerifier_final.zkey verification_key.json
npx snarkjs zkey export solidityverifier AgeVerifier_final.zkey AgeVerifier.sol

Deploy new contracts by placing them in packages/cargo-stylus/contracts and running:

bash run-dev-node.sh

🛠️ Debugging Tips

Fixing Line Endings for Shell Scripts on Windows (CRLF Issue)

If you encounter errors like Command not found, convert line endings to LF:

sudo apt install dos2unix
dos2unix run-dev-node.sh
chmod +x run-dev-node.sh

Run the script again:

bash run-dev-node.sh

Checkpoint 4: 🚢 Ship your frontend! 🚁

To deploy your app to Vercel:

vercel

Follow Vercel's instructions to get a public URL.

For production deployment:

vercel --prod

Checkpoint 5: 📜 Contract Verification

You can verify your deployed smart contract using:

cargo stylus verify -e http://127.0.0.1:8547 --deployment-tx "$deployment_tx"

Replace $deployment_tx with your deployment transaction hash.

🏁 Next Steps

Explore more challenges or contribute to this project!

🏃 Head to your next challenge here.