script.js

// Import necessary libraries
const EC = require('elliptic').ec;
const crypto = require('crypto');

// 1. Create elliptic curve object (secp256k1, same as Bitcoin and Ethereum)
const ec = new EC('secp256k1');

// 1. Generate Private Key
const keyPair = ec.genKeyPair();
const privateKey = keyPair.getPrivate('hex');
console.log("Private Key:", privateKey);

// 2. Derive Public Key
const publicKey = keyPair.getPublic('hex');
console.log("Public Key:", publicKey);

// 3. Generate Address from Public Key (Using SHA-256 and then RIPEMD160 like in BTC)
const publicKeyBuffer = Buffer.from(publicKey, 'hex');
const sha256Hash = crypto.createHash('sha256').update(publicKeyBuffer).digest();
const ripemd160Hash = crypto.createHash('ripemd160').update(sha256Hash).digest('hex');
const address = ripemd160Hash;
console.log("Generated Address:", address);

// 4. Create a message
function createNameMessage(firstName, lastName) {
  // Regex to match only letters (uppercase and lowercase)
  const letterOnlyRegex = /^[A-Za-z]+$/;

  if (!letterOnlyRegex.test(firstName)) {
    throw new Error("First name must contain only letters.");
  }

  if (!letterOnlyRegex.test(lastName)) {
    throw new Error("Last name must contain only letters.");
  }

  const message = `My name is ${firstName} ${lastName}`;
  console.log("Original Message:", message);
}

// Example usage
try {
  createNameMessage("Mohammed", "Mshelbwala");     
} catch (error) {
  console.error("Error:", error.message);
}


// 5. Hash the message
const messageHash = crypto.createHash('sha256').update(message).digest('hex');
console.log("Hashed Message:", messageHash);

// 6. Create Digital Signature using the private key
const signature = keyPair.sign(messageHash);
const signatureHex = signature.toDER('hex');
console.log("Digital Signature:", signatureHex);

// 7. Verify Signature (Receiver side)
const publicKeyFromSender = ec.keyFromPublic(publicKey, 'hex');
const isVerified = publicKeyFromSender.verify(messageHash, signatureHex);
console.log("Is the signature valid?", isVerified);