An Escrow Smart Contract

Part 1: Setting Up the Development Environment

Step 1: Install Node.js

1. Download and Install Node.js
   • Go to the Node.js website.
   • Download the LTS version for your OS (Windows, macOS, Linux).
   • Follow the installer instructions.
2. Verify the Installation

   Copynode -v
   npm -v

   You should see version numbers for both.

Step 2: Install Truffle

1. Install globally:

   Copynpm install -g truffle

2. Verify:

   Copytruffle version

Step 3: Install Ganache

1. Download and install from the Ganache website.
2. Start Ganache → Quickstart Ethereum to launch a local blockchain.

Step 4: Set Up a New Truffle Project

1. Create the project directory:

   Copymkdir Escrow
   cd Escrow

2. Initialize Truffle:

   Copytruffle init

3. Configure truffle-config.js to connect to Ganache:

   Copymodule.exports = {
     networks: {
       development: {
         host: "127.0.0.1", // Localhost
         port: 7545,        // Ganache port
         network_id: "*",   // Match any network id
       },
     },
     compilers: {
       solc: {
         version: "0.8.0", // Compiler version
       },
     },
   };

Part 2: Creating the Escrow Smart Contract

Step 1: Create the Smart Contract

1. In contracts, create Escrow.sol.
2. Paste the following code:

Copy// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Escrow {
    address public buyer;
    address public seller;
    uint public deposit;
    uint public timeToExpiry;
    uint public startTime;

    // Buyer sets up the escrow contract and pays the deposit
    constructor(address _seller, uint _timeToExpiry) payable {
        require(msg.value > 0, "Deposit must be greater than zero");
        buyer = msg.sender;
        seller = _seller;
        deposit = msg.value;
        timeToExpiry = _timeToExpiry;
        startTime = block.timestamp;
    }

    // Buyer releases deposit to seller
    function releaseToSeller() public {
        require(msg.sender == buyer, "Only buyer can release funds");
        require(!isExpired(), "Escrow is expired");
        payable(seller).transfer(deposit);
        deposit = 0; // Set deposit to zero to prevent re-entry
    }

    // Buyer can withdraw deposit if escrow is expired
    function withdraw() public {
        require(isExpired(), "Escrow is not expired yet");
        require(msg.sender == buyer, "Only buyer can withdraw funds");
        uint amount = deposit;
        deposit = 0; // Set deposit to zero to prevent re-entry
        payable(buyer).transfer(amount);
    }

    // Seller can cancel escrow and return all funds to buyer
    function cancel() public {
        require(msg.sender == seller, "Only seller can cancel the escrow");
        uint amount = deposit;
        deposit = 0; // Set deposit to zero to prevent re-entry
        payable(buyer).transfer(amount);
    }

    // Check if the escrow is expired
    function isExpired() public view returns (bool) {
        return block.timestamp > startTime + timeToExpiry;
    }
}

Step 2: Compile

Copytruffle compile

Step 2: Write a Migration Script

Create migrations/2_deploy_contracts.js

Copyconst Escrow = artifacts.require("Escrow");

module.exports = function (deployer, network, accounts) {
  const sellerAddress = accounts[1]; // Example seller address
  const timeToExpiry = 3600; // 1 hour in seconds
  deployer.deploy(Escrow, sellerAddress, timeToExpiry, {
    value: web3.utils.toWei("1", "ether"), // 1 ETH deposit
    from: accounts[0], // Example buyer address
  });
};

Deploy the Contract

Copytruffle migrate --reset

Part 3: Interacting with the Escrow Contract

Step 1: Start the Truffle Console

Copytruffle console

Step 2: Interact with the Contract

1. Get the deployed instance:

Copyconst escrowInstance = await Escrow.deployed();

2. Check initial state:

Copyconst buyer = await escrowInstance.buyer();
const seller = await escrowInstance.seller();
const deposit = await escrowInstance.deposit();
const timeToExpiry = await escrowInstance.timeToExpiry();
const startTime = await escrowInstance.startTime();

console.log("Buyer:", buyer);
console.log("Seller:", seller);
console.log("Deposit (in wei):", deposit.toString());
console.log("Time to Expiry (seconds):", timeToExpiry.toString());
console.log("Start Time (timestamp):", startTime.toString());

3. Call functions:

Copy// Release Funds to Seller
await escrowInstance.releaseToSeller({ from: buyer });
// Withdraw Funds (if expired)
await escrowInstance.withdraw({ from: buyer });
// Cancel Escrow (seller returns funds)
await escrowInstance.cancel({ from: seller });
// Check expiry
const expired = await escrowInstance.isExpired();
console.log("Is the escrow expired?", expired);

Step 4: Testing with Different Accounts

Copyconst accounts = await web3.eth.getAccounts();

// As the buyer (account[0])
await escrowInstance.releaseToSeller({ from: accounts[0] });

// As the seller (account[1])
await escrowInstance.cancel({ from: accounts[1] });

Monitoring Transactions in Ganache

While interacting with the contract, watch the Ganache UI for transaction hashes, gas used, and which accounts were affected.