Password hashing with bcrypt in Node.js - Mini Project: Build & Apply

Password hashing with bcrypt in Node.js

📖 Scenario: You are building a simple user registration system. To keep user passwords safe, you need to hash them before saving.

🎯 Goal: Create a Node.js script that uses bcrypt to hash a plain password securely.

📋 What You'll Learn

Create a variable with the plain password string exactly as specified

Set a salt rounds variable for bcrypt configuration

Use bcrypt to hash the password with the salt rounds

Export or log the hashed password variable

💡 Why This Matters

🌍 Real World

Password hashing is essential for protecting user credentials in web applications to prevent password theft.

💼 Career

Understanding bcrypt hashing is a key skill for backend developers working on authentication and security.

1

Set up the plain password variable

Create a variable called plainPassword and set it to the string "MySecret123".

Node.js

// Create a variable called plainPassword with the value "MySecret123"
// Your code here

Hint

Use const to declare the variable and assign the exact string.

2

Set the salt rounds for bcrypt

Create a variable called saltRounds and set it to the number 10.

Node.js

const plainPassword = "MySecret123";
// Create a variable called saltRounds and set it to 10
// Your code here

Hint

Use const and assign the number 10 exactly.

3

Hash the password using bcrypt

Import bcrypt at the top. Then create an async function called hashPassword that uses bcrypt.hash with plainPassword and saltRounds. Inside the function, assign the hashed result to a variable called hashedPassword and return it.

Node.js

const plainPassword = "MySecret123";
const saltRounds = 10;

// Import bcrypt
// Create async function hashPassword
// Use bcrypt.hash with plainPassword and saltRounds
// Assign result to hashedPassword and return it
// Your code here

Hint

Use import bcrypt from 'bcrypt'; and an async function with await bcrypt.hash() and return hashedPassword;.

4

Export the hashed password function

Add export default hashPassword; at the end of the file to export the hashPassword function.

Node.js

import bcrypt from 'bcrypt';

const plainPassword = "MySecret123";
const saltRounds = 10;

async function hashPassword() {
    const hashedPassword = await bcrypt.hash(plainPassword, saltRounds);
    return hashedPassword;
}

// Export the hashPassword function as default
// Your code here

Hint

Use export default followed by the function name.

Practice

1. What is the main purpose of using bcrypt in a Node.js application?

easy

A. To securely hash user passwords before storing them

B. To encrypt user data for faster retrieval

C. To compress files on the server

D. To generate random user IDs

Solution

1. Step 1: Understand bcrypt's role

   Bcrypt is designed to hash passwords securely, making them hard to reverse.

2. Step 2: Identify the correct purpose

   Encrypting data or compressing files are not bcrypt's functions; it focuses on password hashing.

3. Final Answer:

   To securely hash user passwords before storing them -> Option A

4. Quick Check:

   Password hashing = Secure storage [OK]

Hint: Bcrypt is for password security, not encryption or compression [OK]

Common Mistakes:

• Confusing hashing with encryption
• Thinking bcrypt compresses data
• Assuming bcrypt generates IDs

2. Which of the following is the correct way to hash a password asynchronously using bcrypt in Node.js?

easy

A. const hashed = await bcrypt.hash(password, 10);

B. const hashed = bcrypt.hashSync(password, 10);

C. const hashed = bcrypt.compare(password, 10);

D. const hashed = bcrypt.hash(password);

Solution

1. Step 1: Identify asynchronous hashing syntax

   Bcrypt's async hash function requires await and two arguments: password and salt rounds.

2. Step 2: Check each option

   hashSync uses the synchronous method, compare is for verification not hashing, and the hash call misses salt rounds.

3. Final Answer:

   const hashed = await bcrypt.hash(password, 10); -> Option A

4. Quick Check:

   Async hash needs await and salt rounds [OK]

Hint: Async bcrypt hash needs await and salt rounds [OK]

Common Mistakes:

• Using hashSync instead of async hash
• Calling compare instead of hash
• Omitting salt rounds argument

3. What will the following code output if the password matches the hash?

const bcrypt = require('bcrypt');

async function check() {
  const password = 'secret123';
  const hash = await bcrypt.hash(password, 10);
  const result = await bcrypt.compare('secret123', hash);
  console.log(result);
}
check();

medium

A. false

B. true

C. undefined

D. Error

Solution

1. Step 1: Understand bcrypt.compare behavior

   It returns true if the plain password matches the hashed password.

2. Step 2: Analyze the code flow

   The password 'secret123' is hashed and then compared with the same password, so result is true.

3. Final Answer:

   true -> Option B

4. Quick Check:

   Matching password returns true [OK]

Hint: Compare returns true if passwords match [OK]

Common Mistakes:

• Expecting false for matching passwords
• Confusing compare with hash
• Ignoring async/await in code

4. Identify the error in this bcrypt usage:

const bcrypt = require('bcrypt');

async function verify() {
  const password = 'mypassword';
  const hash = bcrypt.hash(password, 10);
  const match = await bcrypt.compare(password, hash);
  console.log(match);
}
verify();

medium

A. Incorrect salt rounds value

B. Using compare instead of hash to create hash

C. Password variable is not defined

D. Missing await before bcrypt.hash causing hash to be a Promise

Solution

1. Step 1: Check bcrypt.hash usage

   Bcrypt.hash is async and returns a Promise, so it needs await to get the hashed string.

2. Step 2: Identify the error impact

   Without await, hash is a Promise, causing compare to fail or behave unexpectedly.

3. Final Answer:

   Missing await before bcrypt.hash causing hash to be a Promise -> Option D

4. Quick Check:

   Async hash needs await [OK]

Hint: Always await async bcrypt.hash calls [OK]

Common Mistakes:

• Forgetting await on async functions
• Confusing compare with hash
• Using invalid salt rounds

5. You want to securely store user passwords and verify them later. Which approach correctly combines hashing and verification using bcrypt in an async function?

hard

A. Hash password synchronously with bcrypt.hashSync(password, 12) and verify asynchronously with await bcrypt.compare(input, storedHash)

B. Store the plain password and verify by hashing input with bcrypt.hashSync(input, 12) and comparing strings

C. Hash the password with await bcrypt.hash(password, 12) and verify with await bcrypt.compare(input, storedHash)

D. Encrypt password with bcrypt.encrypt(password) and decrypt for verification

Solution

1. Step 1: Choose secure async hashing and verification

   Using async bcrypt.hash with salt rounds (12) and async bcrypt.compare is best practice.

2. Step 2: Evaluate other options

   Storing plain passwords and hashing input for string comparison is insecure, mixing sync hashing with async verification is inconsistent, and bcrypt has no encrypt/decrypt methods.

3. Final Answer:

   Hash the password with await bcrypt.hash(password, 12) and verify with await bcrypt.compare(input, storedHash) -> Option C

4. Quick Check:

   Async hash and compare with salt rounds = secure [OK]

Hint: Use async hash and compare with salt rounds for security [OK]

Common Mistakes:

• Storing plain passwords
• Mixing sync and async bcrypt calls
• Assuming bcrypt can encrypt/decrypt