How Does PHP's `password_hash` Securely Hash and Verify Passwords?

Password Hashing and Verification with PHP's password_hash

When implementing security measures for your login script, it's essential to understand the mechanics of hashing passwords. password_hash, a built-in PHP function, simplifies this process.

Salt Incorporation in password_hash

Your assumption is correct. password_hash automatically generates a salt and incorporates it into the hashed password. This salt adds randomness, making it challenging for attackers to brute-force the password even if they have access to the hashed value.

Storing Salts

It's generally not recommended to store salts externally (e.g., in files or separate database tables) due to the following reasons:

• Security Risk: If the salt is compromised, attackers can use it to reverse the hashing process, exposing the stored passwords.
• Complexity: Managing multiple salt sources introduces unnecessary complexity and maintenance overhead.
• Unnecessary: The salt generated by password_hash is sufficient for password security.

Usage Guide

To utilize password_hash:

1. Hash the plaintext password:

   $hashed_password = password_hash($password, PASSWORD_DEFAULT);

2. Store the hashed password securely in your database, ensuring it can accommodate the hashed value's length (typically 60 characters).

3. When verifying a user's login attempt, compare the entered password against the stored hash using password_verify:

   if (password_verify($password, $hashed_password)) {
    // Password matches the hash, log in the user.
   }

For more information and official documentation, refer to the official PHP manual page: [password_hash](https://www.php.net/manual/en/function.password-hash.php).

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