Building a Basic Ethereum Wallet with a Custom RPC Endpoint

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This guide walks you through creating a fundamental Ethereum wallet using JavaScript and a dedicated RPC endpoint. The process involves generating key pairs, checking balances, and signing transactions programmatically.

Prerequisites

Before starting, ensure you have a foundational understanding of these concepts:

What Is Ethereum?

Ethereum is a global, decentralized network of computers that collectively follow a set of rules known as the Ethereum protocol. This distributed system forms the foundation for a vast ecosystem of digital assets, decentralized applications (dApps), communities, and organizations that are open for anyone to build and use.

A core innovation of Ethereum is the ability to create an account and interact with this ecosystem without relying on a central authority that could change the rules or restrict access.

Core Technologies: JavaScript and Node.js

JavaScript is a versatile, high-level programming language essential for creating dynamic and interactive web applications. For this project, we use JavaScript on the server-side via Node.js, which allows us to execute JavaScript code outside of a web browser.

Key aspects of JavaScript include:

Project Setup and Initialization

The first step is to create the project's foundation and install the necessary tools.

1. Create a Project Directory:
Open your terminal or command line and run the following commands to create and navigate into a new folder for your project.

mkdir custom-ethereum-wallet
cd custom-ethereum-wallet

2. Initialize a Node.js Project:
Initialize a new project, which will create a package.json file to manage your dependencies.

npm init -y

3. Install Required Dependencies:
Install the crucial libraries that will handle Ethereum-specific functionality.

Implementing Wallet Functions

Create a new file named wallet.js. This file will contain the core logic for generating wallets and interacting with the blockchain.

Paste the following code into wallet.js:

const Wallet = require('ethereumjs-wallet');
const Web3 = require('web3');

// Initialize Web3 with your chosen RPC endpoint
const web3 = new Web3('Your_RPC_Endpoint_URL'); // Replace with your actual endpoint

// Function to generate a new Ethereum address and private key
function generateWallet() {
  const wallet = Wallet.generate();
  return {
    address: wallet.getAddressString(),
    privateKey: wallet.getPrivateKeyString(),
  };
}

// Function to check the Ethereum balance of an address
async function checkBalance(address) {
  try {
    const balanceWei = await web3.eth.getBalance(address);
    return web3.utils.fromWei(balanceWei, 'ether');
  } catch (error) {
    console.error(error);
    return 'Error';
  }
}

// Function to sign a transaction
async function signTransaction(privateKey, transactionData) {
  try {
    const wallet = Wallet.fromPrivateKey(Buffer.from(privateKey.substring(2), 'hex'));
    const signedTx = await wallet.signTransaction(transactionData);
    return signedTx;
  } catch (error) {
    console.error(error);
    return null;
  }
}

module.exports = { generateWallet, checkBalance, signTransaction };

Important Configuration: You must replace 'Your_RPC_Endpoint_URL' with a valid HTTP provider endpoint from your chosen RPC service. This is the gateway your application uses to communicate with the Ethereum network. You can often find this URL in your service provider's dashboard after creating an account and setting up an endpoint.

👉 Explore reliable RPC endpoint providers

Building a Simple User Interface

To interact with your wallet logic, create a basic web interface.

1. Create an index.html file:
This file provides the structure for your wallet's user interface.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Custom Ethereum Wallet</title>
</head>
<body>
    <h1>Custom Ethereum Wallet</h1>

    <button id="generateWallet">Generate Wallet</button>
    <div id="walletInfo"></div>

    <button id="checkBalance">Check Balance</button>
    <div id="balanceInfo"></div>

    <button id="signTransaction">Sign Transaction</button>
    <div id="transactionInfo"></div>

    <script src="app.js"></script>
</body>
</html>

2. Create an app.js file:
This script connects the HTML buttons to the functions in your wallet.js module.

const { generateWallet, checkBalance, signTransaction } = require('./wallet');

const generateWalletButton = document.getElementById('generateWallet');
const walletInfoDiv = document.getElementById('walletInfo');
const checkBalanceButton = document.getElementById('checkBalance');
const balanceInfoDiv = document.getElementById('balanceInfo');
const signTransactionButton = document.getElementById('signTransaction');
const transactionInfoDiv = document.getElementById('transactionInfo');

generateWalletButton.addEventListener('click', () => {
  const wallet = generateWallet();
  walletInfoDiv.innerHTML = `
    <p><strong>Address:</strong> ${wallet.address}</p>
    <p><strong>Private Key:</strong> ${wallet.privateKey}</p>
  `;
});

checkBalanceButton.addEventListener('click', async () => {
  const address = prompt('Enter an Ethereum address to check its balance:');
  if (address) {
    const balance = await checkBalance(address);
    balanceInfoDiv.textContent = `Balance: ${balance} ETH`;
  }
});

signTransactionButton.addEventListener('click', async () => {
  const privateKey = prompt('Enter your private key:');
  if (privateKey) {
    // Example transaction data - must be customized
    const transactionData = {
      to: '0xRecipientAddress', // Replace with actual recipient
      value: '1000000000000000', // 0.001 ETH in wei
      gas: '21000',
      gasPrice: '20000000000', // 20 Gwei
    };
    const signedTx = await signTransaction(privateKey, transactionData);
    if (signedTx) {
      transactionInfoDiv.textContent = `Signed Transaction: ${signedTx.rawTransaction}`;
    } else {
      transactionInfoDiv.textContent = 'Transaction signing failed.';
    }
  }
});

Testing and Next Steps

To test your custom Ethereum wallet:

  1. Run a Local Server: Use a simple local server (e.g., with live-server or http-server npm packages) to serve your index.html file.
  2. Use Test Networks: Always conduct initial testing on Ethereum testnets (like Sepolia or Goerli) using testnet ETH. This prevents the loss of real funds during development.
  3. Test Functionality: Use the interface to generate a new wallet, check its balance (it will be zero initially), and practice signing transactions.
  4. Security Warning: This is a basic educational example. Never expose your private keys in a real application, and never use this code with mainnet funds without extensive security audits and improvements.

This project provides a solid starting point for understanding the core mechanics of Ethereum wallet creation and management.

Frequently Asked Questions

What is an RPC endpoint in Ethereum?
An RPC (Remote Procedure Call) endpoint is a gateway that allows your application to communicate with an Ethereum node. It's how you send transactions, read blockchain data, and interact with smart contracts without having to run your own full node.

Is it safe to generate a wallet with this code?
This code demonstrates the process for educational purposes. For storing real value, you should use thoroughly audited, production-ready wallet libraries and never expose your private key in an unsecured web environment. Always prioritize security best practices.

What's the difference between a private key and a public address?
A private key is a secret number that allows you to spend Ether and sign transactions from your account. It must be kept secure. A public address (or public key) is derived from the private key and can be shared publicly to receive funds. You cannot derive the private key from the public address.

Why should I use a testnet first?
Testnets are parallel networks to Ethereum Mainnet that use valueless ETH. They allow developers to experiment, debug, and test their applications without incurring any real financial cost or risk.

Can I use this wallet to interact with smart contracts?
This basic version is designed for simple ETH transfers. Interacting with smart contracts requires additional logic to encode function calls and decode data, which can be implemented using the Web3.js library's contract methods.

How can I make this wallet more secure?
To enhance security, integrate secure key management solutions, avoid handling raw private keys in the front end, implement encryption for storage, and consider using hardware wallets for signing transactions in a production environment. For a more robust setup, 👉 discover advanced development tools.