const crypto = require('crypto');
const fs = require('fs');

// Generate a key pair for this example
const { privateKey, publicKey } = crypto.generateKeyPairSync('rsa', {
  modulusLength: 2048,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem'
  }
});

// Message to sign and verify
const message = 'This is a message to be verified';

// Create a signature for the example
const sign = crypto.createSign('SHA256');
sign.update(message);
const signature = sign.sign(privateKey, 'hex');

// Create a Verify object
const verify = crypto.createVerify('SHA256');

// Update with the message
verify.update(message);

// Verify the signature with the public key
const isValid = verify.verify(publicKey, signature, 'hex');

console.log('Message:', message);
console.log('Signature:', signature.substring(0, 32) + '...');
console.log('Is signature valid?', isValid);

// Try to verify with a tampered message
const tamperedVerify = crypto.createVerify('SHA256');
tamperedVerify.update(message + ' (tampered)');
const isTamperedValid = tamperedVerify.verify(publicKey, signature, 'hex');
console.log('Is tampered signature valid?', isTamperedValid);