Create blockchain like server

.gitignore

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+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+node_modules
+.pnp
+.pnp.js
+.yarn/install-state.gz
+
+# testing
+coverage
+
+# next.js
+.next/
+out/
+
+# production
+build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# local env files
+.env*.local
+
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts

backend/README.md

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+# Bitcoin-like Server
+
+This code provides the Backend for a Bitcoin-like server. where it has  central websocket server that all miners connect to to exchange messages. Code that miners can run to be able to create blocks, do proof of work, broadcast the block via the central server. Code that verifies the signature, balances and creates / adds a block. It It able to catch up to the blockchain when the server starts.
+## Installation
+
+To set up the development environment, follow these steps:
+
+1. Navigate to the frontend directory:
+    ```bash
+    cd backend
+    ```
+
+2. Install all required dependencies:
+    ```bash
+   npm install
+    ```
+
+3. Start the development server:
+    ```bash
+    nodemon app.ts
+    ```
+4. Start the central server:
+    ```bash
+    cd central-server
+    nodemon index.ts    
+    ```
+
+5. Start the miner server:
+    ```bash
+    cd miner-server
+    nodemon index.ts    
+    ```
+
+6. Setup your frontend directory and start it
+
+7. Open your browser and navigate to [http://localhost:3000](http://localhost:3000) to view the application.
+
+## Testing the Application
+
+Before testing the frontend application, ensure that the backend server is running without any errors.
+
+### Steps to Test
+
+1. Open [http://localhost:3000](http://localhost:3000) in your browser.
+
+2. Open a new tab and enter [http://localhost:3000/all-blocks](http://localhost:3000/all-blocks). You should see a display showing 0 blocks created initially.
+
+3. On the homepage (`/`), create a new wallet and submit a transaction.
+
+4. Return to the "All Blocks" page. You should see that the newly created block has been added successfully.
+
+##

backend/app.ts

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+import express from "express";
+import * as bip39 from "bip39";
+import * as bitcoin from "bitcoinjs-lib";
+import BIP32Factory from "bip32";
+import * as ecc from "tiny-secp256k1";
+import cors from "cors";
+
+// Initialize bip32 with the ECC library
+const bip32 = BIP32Factory(ecc);
+
+const network = bitcoin.networks.testnet;
+const path = "m/44'/1'/0'/0";
+
+const app = express();
+const port = 5000;
+app.use(
+  cors({
+    origin: "http://localhost:3000",
+    methods: ["GET", "POST"],
+    allowedHeaders: ["Origin", "X-Requested-With", "Content-Type"],
+    credentials: true,
+  })
+);
+
+function generateWallet() {
+  let mnemonic = bip39.generateMnemonic();
+  const seed = bip39.mnemonicToSeedSync(mnemonic);
+  const root = bip32.fromSeed(seed, network);
+
+  let account = root.derivePath(path);
+  let node = account.derive(0).derive(0);
+
+  let btcAddress = bitcoin.payments.p2pkh({
+    pubkey: node.publicKey,
+    network,
+  }).address;
+
+  return {
+    address: btcAddress,
+    key: node.toWIF(),
+    mnemonic: mnemonic,
+  };
+}
+
+app.get("/create-wallet", (req, res) => {
+  const wallet = generateWallet();
+  res.json(wallet);
+});
+
+app.listen(port, () => {
+  console.log(`Server running at http://localhost:${port}`);
+});

backend/central-server/index.ts

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+import express from "express";
+import http from "http";
+import { Server } from "socket.io";
+import crypto from "crypto";
+import cors from "cors";
+
+const app = express();
+app.use(cors());
+const server = http.createServer(app);
+const io = new Server(server, {
+  cors: {
+    origin: ["http://localhost:3000"],
+    methods: ["GET", "POST"],
+  },
+});
+
+const blockchain: any[] = [];
+
+// Function to calculate hash for a block
+function calculateHash(
+  index: number,
+  prevHash: string,
+  timestamp: number,
+  data: string
+): string {
+  return crypto
+    .createHash("sha256")
+    .update(index + prevHash + timestamp + data)
+    .digest("hex");
+}
+
+// Validate the new block
+function isValidNewBlock(newBlock: any, previousBlock: any): boolean {
+  if (previousBlock.index + 1 !== newBlock.index) return false;
+  if (previousBlock.hash !== newBlock.prevHash) return false;
+  if (
+    calculateHash(
+      newBlock.index,
+      newBlock.prevHash,
+      newBlock.timestamp,
+      newBlock.data + newBlock.nonce
+    ) !== newBlock.hash
+  )
+    return false;
+
+  return true;
+}
+
+io.on("connection", (socket) => {
+  console.log("A miner connected");
+
+  // Broadcast blockchain to new miners
+  socket.emit("blockchain", blockchain);
+
+  // Listen for new blocks from miners
+  socket.on("newBlock", (block) => {
+    const lastBlock =
+      blockchain.length > 0 ? blockchain[blockchain.length - 1] : null;
+
+    // If there is no previous block, accept the first block as the genesis block
+    if (!lastBlock || isValidNewBlock(block, lastBlock)) {
+      blockchain.push(block);
+      io.emit("blockAdded", block);
+      io.emit("blockchain", blockchain);
+      console.log("New block added to the blockchain");
+      console.log(blockchain);
+    } else {
+      console.log("Invalid block rejected");
+    }
+  });
+});
+
+server.listen(3001, () => {
+  console.log("Central Server listening on port 3001");
+});

backend/miner-server/index.ts

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+import express from "express";
+import http from "http";
+import { Server } from "socket.io";
+import { io as ClientIO } from "socket.io-client";
+import crypto from "crypto";
+import cors from "cors";
+
+const app = express();
+app.use(cors());
+const server = http.createServer(app);
+const io = new Server(server, {
+  cors: {
+    origin: "http://localhost:3000", // Ensure this is correct
+    methods: ["GET", "POST"],
+  },
+});
+const centralServer = ClientIO("http://localhost:3001"); // Connect to Central Server
+
+let localBlockchain: any[] = [];
+
+// Function to calculate hash for a block
+function calculateHash(
+  index: number,
+  prevHash: string,
+  timestamp: number,
+  data: string
+): string {
+  return crypto
+    .createHash("sha256")
+    .update(index + prevHash + timestamp + data)
+    .digest("hex");
+}
+
+// Proof of Work
+function proofOfWork(
+  index: number,
+  prevHash: string,
+  timestamp: number,
+  data: string,
+  difficulty: number
+): { hash: string; nonce: number } {
+  let nonce = 0;
+  let hash: string;
+
+  do {
+    nonce++;
+    hash = calculateHash(index, prevHash, timestamp, data + nonce);
+  } while (hash.substring(0, difficulty) !== Array(difficulty + 1).join("0"));
+
+  return { hash, nonce };
+}
+
+// Validate the new block
+function isValidNewBlock(newBlock: any, previousBlock: any): boolean {
+  if (previousBlock.index + 1 !== newBlock.index) return false;
+  if (previousBlock.hash !== newBlock.prevHash) return false;
+  if (
+    calculateHash(
+      newBlock.index,
+      newBlock.prevHash,
+      newBlock.timestamp,
+      newBlock.data + newBlock.nonce
+    ) !== newBlock.hash
+  )
+    return false;
+
+  return true;
+}
+
+// Handle blockchain updates from central server
+centralServer.on("blockchain", (blockchain) => {
+  localBlockchain = blockchain;
+  console.log("Blockchain received from central server");
+});
+
+// Handle new block from miners
+io.on("connection", (socket) => {
+  let user = socket.id;
+  console.log("Miner connected to miner server", socket.id);
+  socket.emit("user", user)
+
+  // Send current blockchain to the newly connected miner
+  socket.emit("blockchain", localBlockchain);
+
+  // Listen for new block mining requests
+  socket.on("mineBlock", (data) => {
+    const lastBlock =
+      localBlockchain.length > 0
+        ? localBlockchain[localBlockchain.length - 1]
+        : null;
+    const index = localBlockchain.length;
+    const timestamp = Date.now();
+    const difficulty = 4; // Define the difficulty level
+
+    const { hash, nonce } = proofOfWork(
+      index,
+      lastBlock?.hash || "0",
+      timestamp,
+      data,
+      difficulty
+    );
+
+    const newBlock = {
+      index,
+      timestamp,
+      data,
+      prevHash: lastBlock?.hash || "0",
+      hash,
+      nonce,
+    };
+
+    // If there is no previous block, skip the validation for the first block
+    if (!lastBlock || isValidNewBlock(newBlock, lastBlock)) {
+      localBlockchain.push(newBlock);
+      centralServer.emit("newBlock", newBlock);
+      io.emit("blockAdded", newBlock); // Emit the new block to all connected clients
+      io.emit("blockchain", localBlockchain); // Update blockchain data for all clients
+      console.log("New block mined and added to the blockchain", user);
+    } else {
+      console.log("Invalid block was not added to the chain");
+    }
+  });
+});
+
+server.listen(3002, () => {
+  console.log("Miner Server listening on port 3002");
+});