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Intermediate 18 min readModule: Module 4: Hashing & Secure Password Storage

Password Hashing with Bcrypt & Argon2

Understand why fast hashes (MD5, SHA-256) are dangerous for passwords, and use adaptive salted hashes (bcrypt, Argon2).

What You Will Learn in This Lesson

  • Why cryptographic hashes (SHA-256) are one-way and irreversible
  • How unique random salts defeat Rainbow Table lookup attacks
  • Adaptive work factors in bcrypt and Argon2 to resist GPU brute-forcing

Introduction & Core Concept

Passwords must NEVER be stored in plain text or encrypted with reversible keys. Passwords must be hashed using slow, salted, adaptive cryptographic algorithms like bcrypt or Argon2id.
WHY DOES THIS MATTER IN THE REAL WORLD?

GPUs can compute 10,000,000,000 SHA-256 hashes per second. Bcrypt forces work factor delays, limiting attackers to a few hundred attempts per second.

Bcrypt Password Hashing & Verification

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const bcrypt = require("bcryptjs");
 
async function hashPassword(plainPassword) {
  const saltRounds = 12; // 2^12 computational cost iterations
  const hash = await bcrypt.hash(plainPassword, saltRounds);
  return hash;
}
 
async function verify(plain, hash) {
  return await bcrypt.compare(plain, hash);
}

Line-by-Line Technical Breakdown

1Argon2id is the winner of the Password Hashing Competition (PHC) and adds memory-hardness against custom ASIC cracking hardware.

Try It Yourself (Interactive Editor)

Modify the code in real-time and click Run to test live browser output and console logs.

Intelligent Code Runner & Live Sandbox[JAVASCRIPT]
JAVASCRIPT SOURCE EDITOR
Interactive Live Code

Industry Best Practices & Professional Standards

  • Use a minimum of 12 rounds for bcrypt in production authentication systems.

Lesson Summary & Core Takeaways

  • Slow, salted hashes protect user credentials against data breach cracking.