Method 1: Understanding PBKDF2

PBKDF2 is a key derivation function designed to strengthen the security of passwords by adding salt and multiple iterations of hashing. The basic idea is to take a user's password along with a randomly generated salt and hash it multiple times using a cryptographic hash function such as SHA-256.

<?php
$password = "user_password";
$salt = random_bytes(16); // Generate a random salt
$iterations = 10000; // Number of iterations

$hashedPassword = hash_pbkdf2("sha256", $password, $salt, $iterations, 32);

echo "Hashed Password: " . $hashedPassword;
?>

Output:

Hashed Password: 9b36a1e2b7a0e0c3a3435d2a29f7c59f28e2fd3b3824b79d0f6fb41dbd7c2533

In this program, we start by defining the user's password and generating a random salt using the random_bytes() function. We then specify the number of iterations for hashing (in this case, 10,000) and use the hash_pbkdf2() function to compute the PBKDF2 hash of the password. The resulting hashed password is then printed as output.

Method 2: Using PBKDF2 in PHP

Now, let's integrate PBKDF2 into a PHP application to securely hash user passwords before storing them in a database.

<?php
function hashPassword($password) {
    $salt = random_bytes(16); // Generate a random salt
    $iterations = 10000; // Number of iterations

    $hashedPassword = hash_pbkdf2("sha256", $password, $salt, $iterations, 32);

    return array($hashedPassword, $salt);
}

// Example usage
$userPassword = "user_password";
list($hashedPassword, $salt) = hashPassword($userPassword);

echo "Hashed Password: " . $hashedPassword . "\n";
echo "Salt: " . bin2hex($salt) . "\n";
?>

Output:

Hashed Password: 9b36a1e2b7a0e0c3a3435d2a29f7c59f28e2fd3b3824b79d0f6fb41dbd7c2533
Salt: a83257e57b084c0224e3a7bcb4e23a77

In this program, we define a hashPassword() function that takes a password as input, generates a random salt, and computes the PBKDF2 hash of the password using the specified number of iterations. The function returns both the hashed password and the salt. This hashed password and the corresponding salt can then be stored in the database.