A Practical Guide to the Node.js `crypto` Module

The built-in `crypto` module in Node.js provides a set of cryptographic functionalities, including tools for hashing, encryption, and decryption. This guide covers two of the most common use cases.

Hashing with SHA256

Hashing is a one-way process that converts an input into a fixed-size string of bytes. It's commonly used for verifying data integrity and storing passwords securely (always with a salt!).

const crypto = require('crypto');

const secret = 'my-secret-message';

const hash = crypto.createHash('sha256')
                   .update(secret)
                   .digest('hex');

console.log(hash);
// Outputs a 64-character hexadecimal string

Symmetric Encryption with AES

Encryption is a two-way process. AES (Advanced Encryption Standard) is a widely used symmetric encryption algorithm. You need a secret key and an initialization vector (IV) for both encryption and decryption.

const crypto = require('crypto');

const algorithm = 'aes-256-cbc';
const key = crypto.randomBytes(32); // 256-bit key
const iv = crypto.randomBytes(16);  // 128-bit IV

function encrypt(text) {
  let cipher = crypto.createCipheriv(algorithm, Buffer.from(key), iv);
  let encrypted = cipher.update(text);
  encrypted = Buffer.concat([encrypted, cipher.final()]);
  return { iv: iv.toString('hex'), encryptedData: encrypted.toString('hex') };
}

function decrypt(data) {
  let iv = Buffer.from(data.iv, 'hex');
  let encryptedText = Buffer.from(data.encryptedData, 'hex');
  let decipher = crypto.createDecipheriv(algorithm, Buffer.from(key), iv);
  let decrypted = decipher.update(encryptedText);
  decrypted = Buffer.concat([decrypted, decipher.final()]);
  return decrypted.toString();
}

const hw = encrypt("Hello World");
console.log(hw);
console.log(decrypt(hw));