PWD Hasher

pwd-hasher is a simple, zero-dependency Node.js utility for hashing, verifying, and generating strong passwords using the built-in crypto module. It uses the modern and secure scrypt key derivation function.

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## Installation

You can install the package using npm or yarn:

npm install pwd-hasher

or

yarn add pwd-hasher

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## Core Concept: Why Hashing is Essential 🔒

You should never store passwords in plain text. If your database is ever compromised, attackers would gain access to every user's account information.

Password hashing is a one-way process that turns a password into a fixed-length string of characters, called a hash. This process is not reversible, meaning you cannot "un-hash" a password to get back to the original text. The only way to verify a password is to hash it again using the same "salt" (a random string) and see if the resulting hashes match.

This package handles the entire process for you.

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## Real-World Usage: Authentication Workflow

Here’s how you would use pwd-hasher in a typical web application for user sign-up, login, and password updates.

### 1. User Registration (Sign-Up)

When a new user creates an account, you must hash their password before saving it to your database.

import { getHashedPassword } from 'pwd-hasher';

async function handleUserSignUp(email, password) {
  try {
    // 1. Hash the user's chosen password.
    const hashedPassword = await getHashedPassword(password);
    
    // Example hash: '16#a4e8b3f2c1d0.c8e7a6b4d2f0a1b9c3e8d7f6a5b4c3d2'

    // 2. Save the user's email and the *hashedPassword* to your database.
    // DO NOT save the original password.
    await db.collection('users').insertOne({
      email: email,
      passwordHash: hashedPassword // Store the hash, not the password
    });

    console.log('User registered successfully!');
  } catch (error) {
    console.error('Error during registration:', error);
  }
}

// Simulate a new user signing up
handleUserSignUp('test@example.com', 'mySecurePassword123');

### 2. User Login

When a user tries to log in, you retrieve their stored hash from the database and use verifyHash to securely compare it with the password they just entered.

import { verifyHash } from 'pwd-hasher';

async function handleUserLogin(email, passwordFromLoginForm) {
  try {
    // 1. Find the user in the database by their email.
    const user = await db.collection('users').findOne({ email: email });

    if (!user) {
      console.log('Login failed: User not found.');
      return;
    }

    // 2. Compare the password from the login form with the stored hash.
    const isPasswordCorrect = await verifyHash(
      passwordFromLoginForm,
      user.passwordHash
    );

    if (isPasswordCorrect) {
      console.log('✅ Password is correct. Logging in...');
      // Proceed with creating a session, JWT, etc.
    } else {
      console.log('❌ Invalid credentials.');
    }
  } catch (error) {
    console.error('An error occurred during login:', error);
  }
}

// Simulate a login attempt
handleUserLogin('test@example.com', 'mySecurePassword123');

### 3. Updating or Resetting a Password

The process for updating a password is the same as registration: you hash the new password and replace the old hash in the database.

import { getHashedPassword } from 'pwd-hasher';

async function updateUserPassword(email, newPassword) {
  try {
    // 1. Hash the new password.
    const newHashedPassword = await getHashedPassword(newPassword);

    // 2. Find the user and update their passwordHash in the database.
    await db.collection('users').updateOne(
      { email: email },
      { $set: { passwordHash: newHashedPassword } }
    );

    console.log('Password updated successfully!');
  } catch (error) {
    console.error('Error updating password:', error);
  }
}

// Simulate a user changing their password
updateUserPassword('test@example.com', 'myNewStrongerPassword456');

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## API Reference

### getHashedPassword(password, [salt], [len])

Hashes a password with a salt using scrypt.

• password: string: The plaintext password to hash.
• salt?: string (optional): A salt to use. If not provided, a random one is generated.
• len?: number (optional): The length of the derived key. Defaults to 16.
• Returns: Promise<string> - The final hash in the format len#salt.hash.

### verifyHash(password, hashPassword)

Verifies a plaintext password against a hash generated by this package.

• password: string: The plaintext password to check.
• hashPassword: string: The stored hash string (e.g., from your database).
• Returns: Promise<boolean> - true if the password matches, false otherwise.

### generateStrongPassword([length])

Generates a cryptographically-random password.

• length?: number (optional): The desired password length. Must be at least 8. Defaults to 12.
• Returns: string - The generated strong password.

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## License

This project is licensed under the ISC License.