Metamask: Verify ethers.js signature in the background with web3.py

Here is an article that explains how to verify Ethers.js signature in your backend with web3.py:

Metamask: Verify Ethers.js Signature in Backend with Web3.py

Introduction

In this guide, we will walk you through the process of verifying Ethers.js signatures in your backend using web3.py. Metamask is a popular wallet that allows users to securely store their private keys on their mobile devices. By integrating Metamask into your dapp (decentralized application), you can enable seamless login functionality for your users.

Step 1: Install the Required Libraries

Before we dive into the implementation, make sure you have the following libraries installed:

• web3.py: A JavaScript library that provides a simple and intuitive way to interact with the Ethereum blockchain.

• ethers.js: A JavaScript library that provides an interface to access Ethers.js accounts and contract functions.

You can install these libraries using npm:

npm install web3 ethers

To verify Ethers.js signatures, we need to set up a Metamask provider in the backend. You can do this by creating a new file calledmetamask-provider.jsand adding the following code:

const Web3 = require('web3');
const provider = new ethers.providers.Web3Provider(new window.ethereum.MetamaskProvider());

In this example, we use the MetamaskProvider'' instance to connect to the Metamask wallet.

To verify Ethers.js signatures, you can use theethers.signMessage()method. This method takes a signed message as input and returns an object with two properties:bytes(the actual bytes of the signed message) andsignature(the public key that verifies the signature).

const provider = new ethers.providers.Web3Provider(window.ethereum.MetamaskProvider());
const signer = provider.getSigner();
// Create a signed message
const signedMessage = '0x1234567890abcdef01234567890abcdef';
// Verify Ethers.js signature using ethers.signMessage()
const verifiedSignature = signer.signMessage(signedMessage);
console.log(Signature verified);

In this example, we create a new instance of signer’ and then sign signedMessage' withsigner’. The resulting signature is stored in the verifiedSignature variable.

Step 4: Handle User Input

Once your frontend has verified the Ethers.js signature, you’ll need to handle user input. You can do this by creating a new function that listens for changes to the user’s account or private key fields. Here’s an example implementation:

const const = window.ethereumaccounts;
const privateKeyField = document.getElementById('private-key-field');
// Add an event listener to update the private key field when the user enters it
document.addEventListener('input', (event) => {
const privateKey = event.target.value;
// Verify the Ethers.js signature using web3.py
signer.verify(privateKey);
// Handle successful verification
console.log('Signature verified:', signature verified);
});

In this example, we create a new “signer” instance and then listen for changes to the user account or private key fields. When the user enters the private key field, we verify it using the “Signature verified”.

Conclusion

By following these steps, you can easily integrate Metamask verification into your backend with web3.py. This will allow your users a seamless login functionality and provide them with an additional layer of security on top of the Ethereum blockchain.

Note: Make sure to properly handle errors and edge cases in a production environment. Additionally, this implementation assumes that the user is familiar with Ethers.js and Metamask wallets.