finish the first exchnage project

server/index.js

@@ -2,31 +2,85 @@ const express = require('express');
 const app = express();
 const cors = require('cors');
 const port = 3042;
+const EC = require('elliptic').ec;
+global.fetch = require("node-fetch");
+
 
 // localhost can have cross origin errors
 // depending on the browser you use!
 app.use(cors());
 app.use(express.json());
 
+const ec = new EC('secp256k1');
+const keyPair = [];
+// ECDSA
+while (keyPair.length < 3) {
+    const key = ec.genKeyPair();
+    keyPair.push({
+        key: key,
+        privateKey: key.getPrivate().toString(16),
+        publicX: key.getPublic().x.toString(16),
+        publicY: key.getPublic().y.toString(16),
+        publicKey: key.getPublic().encode('hex')
+    })
+}
+console.log(keyPair);
+
+const addr1 = keyPair[0]['publicKey'];
+const addr2 = keyPair[1]['publicKey'];
+const addr3 = keyPair[2]['publicKey'];
+
 const balances = {
-  "1": 100,
-  "2": 50,
-  "3": 75,
+    [addr1]: 100,
+    [addr2]: 50,
+    [addr3]: 75,
 }
+console.log(balances);
+
+const balancesPair = [{
+        [addr1]: 100,
+        privateKey: keyPair[0]['privateKey']
+    },
+    {
+        [addr2]: 50,
+        privateKey: keyPair[1]['privateKey']
+    },
+    {
+        [addr3]: 75,
+        privateKey: keyPair[2]['privateKey']
+    }
+]
+console.log(balancesPair);
 
 app.get('/balance/:address', (req, res) => {
-  const {address} = req.params;
-  const balance = balances[address] || 0;
-  res.send({ balance });
+    const { address } = req.params;
+    const balance = balances[address] || 0;
+    console.log(balance);
+    res.send({ balance });
 });
 
 app.post('/send', (req, res) => {
-  const {sender, recipient, amount} = req.body;
-  balances[sender] -= amount;
-  balances[recipient] = (balances[recipient] || 0) + +amount;
-  res.send({ balance: balances[sender] });
+    const { sender, recipient, amount } = req.body;
+    // console.log({ sender, recipient, amount });
+    // console.log(sender);
+
+    const msgHash = ['Alica send 2 ETH to Bobbie', 2, 'ETH'];
+    var signKey = "";
+    keyPair.map((pair) => {
+            if (pair['publicKey'] === sender) {
+                signKey = pair['key']
+            }
+        })
+        // console.log(signKey);
+    const signature = signKey.sign(msgHash);
+    const derSign = signature.toDER();
+    console.log(signKey.verify(msgHash, derSign));
+
+    balances[sender] -= amount;
+    balances[recipient] = (balances[recipient] || 0) + +amount;
+    res.send({ balance: balances[sender] });
 });
 
 app.listen(port, () => {
-  console.log(`Listening on port ${port}!`);
+    console.log(`Listening on port ${port}!`);
 });