⛓️ Smart contract development

This smart contract is already deployed on Ethereum Sepolia test net. You can check it out using etherscan. The contract address is: 0xd078377970eA26c29FeFa1410018A84ed861cc21

Usage

LogLock serves to make data usage transparent. This contract has two methods:

1. verify: to verify whether a log item is already notarized by contract owner. Anyone could access to this contract function. The returned result is either true or false.
2. notarize: only the contract owner can notarize a log item.

Test the deployed smart contract

In scripts/interact.js:

import { ethers } from "ethers"

// Get environment variables
require("dotenv").config()
const address = process.env.CONTRACT_ADDRESS
const abi = require("../artifacts/contracts/LogLock.sol/LogLock.json").abi
const privateKey = process.env.PRIVATE_KEY
const apiUrl = process.env.ALCHEMY_API_URL

// 1. Provider
const alchemyProvider = new ethers.providers.JsonRpcProvider(apiUrl)

// 2. Signer
const signer = new ethers.Wallet(privateKey, alchemyProvider)

// 3. Contract
const contract = new ethers.Contract(address, abi, signer)

const main = async () => {
	const { hash } = await contract.notarize("genesis log")

	// Look transaction on Etherscan
	console.log("Transaction URL: ", `https://sepolia.etherscan.io/address/${hash}`)

	// false
	console.log(await contract.verify("random log"))

	// true
	console.log(await contract.verify("genesis log"))
}

main()

1. This script is not going to be called by hardhat, we put it here only for easier file organization.
2. We need to import ethers, and also call require("dotenv").config() before accessing environment variables.
3. ⚠️ Important: Use JsonRpcProvider to connect to a sepolia testnet. AlchemyProvider in ethers v5 doesn't support sepolia.
4. In the main() function, we have tried to call the notarize function to notarize a genesis log and also test it with verify function.

Developer notes

Preparation

1. Get Alchemy API key: visit Alchemy dashboard, need registration before creating a free API key.
2. Get a crypto wallet: visit metamask or other trusted wallets.
3. Get Sepolia ETH from a faucet: visit infura faucet

Now we have a wallet that already got some ETHs for deploying and testing smart contract on the Sepolia test net. We also have a functional RPC url will be used later.

Hardhat

Install hardhat globally:

npm install -g hardhat

Install other dependencies:

npm install --save-dev @nomiclabs/hardhat-ethers "ethers@^5.7.2"

Initiate a new hardhat project:

npx hardhat

Notice: hardhat is dependent on ethers v5, so stick with the most popular version: ethers v5.7.2

Configuration

The .env file looks like this:

PRIVATE_KEY='xxxxxxxxxxxxx'
WALLET_ADDRESS='xxxxxxxxxxxxx'
ALCHEMY_API_KEY='xxxxxxxxxxxxx'
ALCHEMY_API_URL='xxxxxxxxxxxxx'
CONTRACT_ADDRESS='xxxxxxxxxxxxx'

Replace those xxxxxx with right stuff.

The hardhat.config.cjs looks like this:

// import dependencies
require("dotenv").config()
require("@nomiclabs/hardhat-ethers")

const { ALCHEMY_API_URL, PRIVATE_KEY } = process.env

module.exports = {
  // Solidity version should match with your contract file's declaration
	solidity: "0.8.9",
  // We're using Sepolia here
	defaultNetwork: "sepolia",
	networks: {
		hardhat: {},
		sepolia: {
			url: ALCHEMY_API_URL,
			accounts: [PRIVATE_KEY]
		}
	}
}

Compilation

After defining the smart contract under contracts/ folder, we can complie it using:

npx hardhat compile

This will generate an artifacts/ folder in the root.

Deployment

In ./deployments/deploy.js:

async function main() {
	const contract = await ethers.getContractFactory("LogLock")
	const deployed = await contract.deploy()
	console.log("Contract Deployed to Address:", deployed.address)
}
main()
	.then(() => process.exit(0))
	.catch(error => {
		console.error(error)
		process.exit(1)
	})

1. While running with hardhat, ethers is automatically exposed to the context, so we don't need to manually import ethers.
2. ethers.getContractFactory() can automatically locate the contract abi under artifacts folder according to the given name.

Run this depolyment script with:

npx hardhat run deployments/deploy.js --network sepolia

1. We are using Sepolia test net. Goerli is going to be discarded by the end of 2023.
2. The seplolia parameter points to our previously configured hardhat.config.cjs file.
3. All we needed when deploying a smart contract is ALCHEMY_API_URL & PRIVATE_KEY.