Best way to use PHP to encrypt and decrypt passwords? [duplicate]

You should not encrypt passwords, instead you should hash them using an algorithm like bcrypt. This answer explains how to properly implement password hashing in PHP. Still, here is how you would encrypt/decrypt:

$key = 'password to (en/de)crypt';
$string = ' string to be encrypted '; // note the spaces

To Encrypt:

$iv = mcrypt_create_iv(
    mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC),
    MCRYPT_DEV_URANDOM
);

$encrypted = base64_encode(
    $iv .
    mcrypt_encrypt(
        MCRYPT_RIJNDAEL_128,
        hash('sha256', $key, true),
        $string,
        MCRYPT_MODE_CBC,
        $iv
    )
);

To Decrypt:

$data = base64_decode($encrypted);
$iv = substr($data, 0, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC));

$decrypted = rtrim(
    mcrypt_decrypt(
        MCRYPT_RIJNDAEL_128,
        hash('sha256', $key, true),
        substr($data, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC)),
        MCRYPT_MODE_CBC,
        $iv
    ),
    "\0"
);

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Warning: The above example encrypts information, but it does not authenticate the ciphertext to prevent tampering. You should not rely on unauthenticated encryption for security, especially since the code as provided is vulnerable to padding oracle attacks.

See also:

• https://stackoverflow.com/a/30189841/2224584
• https://stackoverflow.com/a/30166085/2224584
• https://stackoverflow.com/a/30159120/2224584

Also, don’t just use a “password” for an encryption key. Encryption keys are random strings.

---

Demo at 3v4l.org:

echo 'Encrypted:' . "\n";
var_dump($encrypted); // "m1DSXVlAKJnLm7k3WrVd51omGL/05JJrPluBonO9W+9ohkNuw8rWdJW6NeLNc688="

echo "\n";

echo 'Decrypted:' . "\n";
var_dump($decrypted); // " string to be encrypted "