Building a Decentralized Identity (DID) System with QuickNode

Introduction

Decentralized Identity (DID) systems offer a new paradigm for managing digital identities while ensuring privacy, security, and user control. In this tutorial, we'll guide you through the process of building a simple DID system using blockchain technology and the QuickNode platform. This tutorial will cover key concepts, and development steps, and provide accurate code snippets to help you create a functional DID system.

Prerequisites

Before you begin, ensure you have the following:

Basic understanding of blockchain and Ethereum
QuickNode account for accessing the Ethereum network
Node.js and npm installed on your computer
Ethereum wallet with some Ether for transaction fees

Step 1: Smart Contract Deployment

Write a Solidity smart contract to manage the DID system's identity records.

// DIDRegistry.sol

pragma solidity ^0.8.0;

contract DIDRegistry {
    struct Identity {
        address owner;
        string publicKey;
    }

    mapping(address => Identity) public identities;

    function registerIdentity(string memory publicKey) public {
        identities[msg.sender] = Identity(msg.sender, publicKey);
    }

    function getPublicKey(address user) public view returns (string memory) {
        return identities[user].publicKey;
    }
}

Compile and deploy the smart contract using tools like Truffle or Remix.

Step 2: Integrate QuickNode API

Install the web3 package to interact with the Ethereum network.

npm install web3

Configure your QuickNode endpoint and create a web3 instance.

const Web3 = require('web3');

const quickNodeEndpoint = 'YOUR_QUICKNODE_ENDPOINT';
const web3 = new Web3(new Web3.providers.HttpProvider(quickNodeEndpoint));

Step 3: User Registration

Create a simple HTML form for users to register their public keys.

<!-- index.html -->

<!DOCTYPE html>
<html>
<head>
    <title>DID System Registration</title>
</head>
<body>
    <h1>DID System Registration</h1>
    <form id="registrationForm">
        <label for="publicKey">Enter Your Public Key:</label><br>
        <input type="text" id="publicKey" name="publicKey"><br>
        <button type="submit">Register</button>
    </form>
</body>
</html>

Add JavaScript code to handle the form submission and call the smart contract's registerIdentity function.

// app.js

const contractAddress = 'YOUR_CONTRACT_ADDRESS';
const contractABI = [...]; // ABI of the deployed contract

const contract = new web3.eth.Contract(contractABI, contractAddress);

document.getElementById('registrationForm').addEventListener('submit', async function (event) {
    event.preventDefault();
    const publicKey = document.getElementById('publicKey').value;
    const accounts = await web3.eth.getAccounts();
    await contract.methods.registerIdentity(publicKey).send({ from: accounts[0] });
    alert('Identity registered successfully!');
});

Step 4: Public Key Retrieval

Create another HTML form to retrieve the public key of a registered user.

<!-- index.html -->

<!-- Add this section after the previous form -->
<h2>Get Public Key</h2>
<form id="getKeyForm">
    <label for="userAddress">Enter User Address:</label><br>
    <input type="text" id="userAddress" name="userAddress"><br>
    <button type="submit">Get Public Key</button>
</form>
<p id="publicKeyDisplay"></p>

Add JavaScript code to fetch and display the user's public key.

// app.js

document.getElementById('getKeyForm').addEventListener('submit', async function (event) {
    event.preventDefault();
    const userAddress = document.getElementById('userAddress').value;
    const publicKey = await contract.methods.getPublicKey(userAddress).call();
    document.getElementById('publicKeyDisplay').innerText = `Public Key: ${publicKey}`;
});

Conclusion

Congratulations! You've built a simple Decentralized Identity (DID) system using blockchain technology and the QuickNode platform. This tutorial covered the essential steps to deploy a smart contract, interact with it using the QuickNode API, and create a user interface for identity registration and retrieval.

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