Lottery Smart Contract with Age Check zkSNARKs ZoKrates

This project is a lottery smart contract that uses zkSNARKs to verify the age of participants. The age check is done using ZoKrates, a toolbox for zkSNARKs on Ethereum.

Project Structure

The project is structured as follows:

• contracts/: Contains the Solidity smart contracts for the lottery.
• deploy/: Contains the deployment scripts for the smart contracts.
• deployments/: Contains the deployment outputs for the smart contracts.
• scripts/: Contains scripts for deploying and interacting with the smart contracts.
• test/: Contains the test scripts for the smart contracts.
• ZoKrates/: Contains the ZoKrates code for the age check.

Prerequisites

• Node.js and npm installed
• Hardhat installed globally (npm install -g hardhat)

Setup

1. Clone the repository and navigate into the project directory

2. Install the project dependencies with npm install

Compile Contracts

Run npx hardhat compile to compile the Solidity contracts.

Run Tests

Run npx hardhat test to execute the test scripts.

Deploy Contracts

1. Update the hardhat.config.ts file with your network details

2. Run npx hardhat run scripts/deploy.ts --network <network_name> to deploy the contracts to the specified network.

ZoKrates Setup

1. Navigate into the ZoKrates directory with cd ZoKrates

2. Build ZoKrates with the following commands

3. Build ZoKrates

cd ZoKrates
export ZOKRATES_STDLIB=$PWD/zokrates_stdlib/stdlib
cargo +nightly build --release

4. Creates ageCheck.zok

cd target/release
mkdir code
cd code && touch ageCheck.zok

5. Configure the ageCheck.zok

def main(private field birthYear, field comparisonYear, field minimumDifference) -> bool{
    bool result = comparisonYear - birthYear >= minimumDifference;
    return result;
}

6. Execute all in /zoKrates

zokrates compile -i code/ageCheck.zok
zokrates setup
zokrates compute-witness -a 1990 2020 18
zokrates generate-proof
zokrates export-verifier

7. Deploy Lottery Smart Contract in localhost or live network

npx hardhat deploy --network <blockchain-network> --tags Lottery

8. Paste Proof and Input Generated in enterLottery()

proof.txt