Secure PHP Password Storage: md5, password_hash, and crypt Explained with Code

Password Hashing in PHP

1. Using md5 (insecure)

The md5 function produces a 32‑character hash but does not use a salt and is vulnerable to collisions and brute‑force attacks. It should never be used for production password storage.

<?php
// Registration
$username = $_POST['username'];
$password = $_POST['password'];
$hashed = md5($password); // insecure
// Store $hashed in the database

// Login
$input = $_POST['password'];
if (md5($input) === $stored_hash) {
    // authenticated (but insecure)
}
?>

2. Using password_hash (recommended)

PHP 5.5+ provides password_hash, which automatically selects a strong algorithm (default PASSWORD_BCRYPT), generates a random salt, and stores the salt together with the hash. Verification is performed with password_verify.

<?php
// Registration
$username = $_POST['username'];
$password = $_POST['password'];
$hash = password_hash($password, PASSWORD_DEFAULT); // bcrypt with random salt
// Store $hash in the database

// Login
$input = $_POST['password'];
$stored_hash = $row['password']; // fetched from DB
if (password_verify($input, $stored_hash)) {
    // login successful
} else {
    // invalid credentials
}
?>

password_hash

handles salting, algorithm upgrades, and provides resistance against modern attacks, making it the preferred method.

3. Using crypt with a manual salt

The low‑level crypt function can be used with a manually generated salt (e.g., via random_bytes or openssl_random_pseudo_bytes). The salt must include the algorithm identifier, such as $2y$10$ for bcrypt with a cost of 10.

<?php
// Registration
$username = $_POST['username'];
$password = $_POST['password'];
// Generate a 22‑character base64 salt
$salt = substr(str_replace('+', '.', base64_encode(random_bytes(16))), 0, 22);
$hash = crypt($password, '$2y$10$' . $salt); // bcrypt with manual salt
// Store $hash in the database

// Login
$input = $_POST['password'];
$stored_hash = $row['password']; // fetched from DB
if (crypt($input, $stored_hash) === $stored_hash) {
    // login successful
} else {
    // invalid credentials
}
?>

While crypt works, it requires careful construction of the salt and algorithm identifier. Using password_hash is simpler and less error‑prone.

Conclusion

For secure password storage in PHP, avoid md5 and raw crypt. Prefer password_hash (bcrypt) together with password_verify, which automatically manages salts and provides strong resistance to attacks.