Metamask: How is a Metamask signature verified on the server side?

Here is an article on how to verify Metamask signature on the server side:

Metamask Signature Verification on the Server Side

As a developer building decentralized applications (dApps) that interact with external services like MetaMask, it is important to provide secure authentication and authorization. One of the key aspects is verifying user signatures on the server side using Metamask. In this article, we will discuss how to do it.

Why Verify Metamask Signature?

Before we get into the process, let’s briefly discuss why Metamask signature verification is so important:

• Prevents unauthorized access: Without proper authentication, an attacker could use a compromised wallet address.

• Ensures data integrity: Verifying user signatures ensures that only authorized users can access sensitive data or perform transactions on the server.

Using web3.js and web3.py to verify

To verify a Metamask signature, you need to:

• Load the Web3.js library

  : Include web3.js in your HTML file and load it using a CDN (e.g.

• Load the private key: Load the user's private key using theeth.ethers.get()method.

// Load the Web3.js library
const web3 = require('web3');
// Set up an Ethereum provider (replace with your own)
const providerUrl = '
const web3Provider = new web3.providers.HttpProvider(providerUrl);
// Get the private key using eth.ethers.get()
async function getPrivateKey() {
const account = await web3.eth.ethers.get('0xYourAccountAddress');
return account.privateKey;
}
// Verify Metamask signature
async function verifySignature(privateKey, signature) {
try {
// Load Web3 instance with private key
const web3Instance = new web3(web3Provider);
// Sign transaction with private key and signature
const signedTransaction = await web3Instance.eth.accounts.signTransaction({
from: '0xYourAccountAddress',
to: '0xRecipientAddress',
data: // Your transaction data here
});
// Verify signature
const verifiedTransaction = await web3Instance.eth.accounts.recover(signedTransaction.rawTransaction, privateKey);
return verifiedTransaction;
} catch (error) {
console.error(error);
throw error;
}
}

In front-end code you can call verifySignature` function to verify user signature:

const web3 = require('web3');
// Load Web3 library
const web3 = new web3();
// Get private key from Metamask
async function getPrivateKey() {
const account = await web3.eth.ethers.get('0xYourAccountAddress');
return account.privateKey;
}
// Verify user signature
function verifyUserSignature() {
const privateKey = await getPrivateKey();
const signature = '0xYourSignature';
// Get transaction data from the front-end
async function getTransactionData() {
const txId = '0xYourTxId';
const receiverAddress = '0xYourRecipientAddress';
try {
const response = await web3.eth.getTransactionReceipt(txId);
const txData = response.transaction.data;
//Verify the signature with Web3.js
const verifiedTransaction = await verifySignature(privateKey, signature);
return verifiedTransaction;
} catch (error) {
console.error(error);
throw error;
}
}
getTransactionData();
}

By following these steps and examples, you will be able to securely authenticate users based on their Metamask signatures on the server side using Web3.js.