AES-256 encryption in PHP

Question

I need a PHP function, AES256_encode($dataToEcrypt) to encrypt the $data into AES-256 and another one AES256_decode($encryptedData) do the opposite. Does anyone know what code should this functions have?

Centromere

Here is a good blog post explaining how to work with MCrypt library: code-epicenter.com/how-to-use-mcrypt-library-in-php – Desman

Answer 1

Look at the mcrypt module

AES-Rijndael example taken from here

$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
$iv = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM);
$key = pack('H*', "bcb04b7e103a0cd8b54763051cef08bc55abe029fdebae5e1d417e2ffb2a00a3");
# show key size use either 16, 24 or 32 byte keys for AES-128, 192
# and 256 respectively
$key_size =  strlen($key);
echo "Key size: " . $key_size . "\n";
$text = "Meet me at 11 o'clock behind the monument.";
echo strlen($text) . "\n";

$crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $text, MCRYPT_MODE_CBC, $iv);
echo strlen($crypttext) . "\n";

This is the decrypt function

Clothesline

Yes, there are even examples on this page of how to encrypt/decrypt AES: php.net/manual/en/ref.mcrypt.php – Colettacolette

Thanks, this was what I was looking for. I thought RIJNDAEL and AES were two different algorithms. – Centromere

-1, AES-256 is different from RIJNDAEL-256. The 256 in AES refers to the key size, where the 256 in RIJNDAEL refers to block size. AES-256 is RIJNDAEL-128 when used with a 256 bit key. – Higgledypiggledy

-1 it's bad in several ways: 1) It doesn't use AES (see ircmaxell's comment) 2) It uses ECB 3) It doesn't include a MAC and thus is vulnerable to active attacks. 4) It uses a password as key. Either use a random key, or use properly hashed password. 5) It's better to use /dev/urandrom to generate the iv (simply pass MCRYPT_DEV_URANDOM to create_iv) – Wriggly

@Wriggly I've edited the answer according to your observations. Now the answer should be correct. – Clothesline

I just want to emphasize that MACs are really important if active attacks are possible. A well known attack is the "padding oracle" where the reaction of the recipient leaks information about the plaintext allowing byte-by-byte recovery of the plaintext by querying the recipient. – Wriggly

Padding is also important to note: as the mcrypt library in php only supports zero length padding. Where as most people using pkcs#5 or pkcs#7 padding. So always make sure you match the padding up if encrypting and decrypting in different platforms/places (for example: webserver vs mobile app) – Duvalier

PHP has deprecated mcrypt library, it will be removed from PHP version after 7.1. As such, using suggesting mcrypt makes this answer deprecated. See php.net/manual/en/migration71.deprecated.php – Filomenafiloplume

Answer 2

I need a PHP function, AES256_encode($dataToEcrypt) to encrypt the $data into AES-256 and another one AES256_decode($encryptedData) do the opposite. Does anyone know what code should this functions have?

There is a difference between encrypting and encoding.

Do you really need AES-256? The security of AES-256 versus AES-128 isn't that significant; you're more likely to screw up at the protocol layer than get hacked because you used a 128-bit block cipher instead of a 256-bit block cipher.

Important - Use A Library

• defuse/php-encryption
• PECL libsodium
• Halite (libsodium wrapper, now stable)

A Quick and Dirty AES-256 Implementation

If you're interested in building your own not for the sake of deploying it in production but rather for the sake of your own education, I've included a sample AES256

/**
 * This is a quick and dirty proof of concept for StackOverflow.
 * 
 * @ref https://mcmap.net/q/490021/-aes-256-encryption-in-php/2224584
 * 
 * Do not use this in production.
 */
abstract class ExperimentalAES256DoNotActuallyUse
{
    /**
     * Encrypt with AES-256-CTR + HMAC-SHA-512
     * 
     * @param string $plaintext Your message
     * @param string $encryptionKey Key for encryption
     * @param string $macKey Key for calculating the MAC
     * @return string
     */
    public static function encrypt($plaintext, $encryptionKey, $macKey)
    {
        $nonce = random_bytes(16);
        $ciphertext = openssl_encrypt(
            $plaintext,
            'aes-256-ctr',
            $encryptionKey,
            OPENSSL_RAW_DATA,
            $nonce
        );
        $mac = hash_hmac('sha512', $nonce.$ciphertext, $macKey, true);
        return base64_encode($mac.$nonce.$ciphertext);
    }

    /**
     * Verify HMAC-SHA-512 then decrypt AES-256-CTR
     * 
     * @param string $message Encrypted message
     * @param string $encryptionKey Key for encryption
     * @param string $macKey Key for calculating the MAC
     */
    public static function decrypt($message, $encryptionKey, $macKey)
    {
        $decoded = base64_decode($message);
        $mac = mb_substr($message, 0, 64, '8bit');
        $nonce = mb_substr($message, 64, 16, '8bit');
        $ciphertext = mb_substr($message, 80, null, '8bit');

        $calc = hash_hmac('sha512', $nonce.$ciphertext, $macKey, true);
        if (!hash_equals($calc, $mac)) {
            throw new Exception('Invalid MAC');
        }
        return openssl_decrypt(
            $ciphertext,
            'aes-256-ctr',
            $encryptionKey,
            OPENSSL_RAW_DATA,
            $nonce
        );
    }
}

Usage

First, generate two keys (yes, two of them) and store them somehow.

$eKey = random_bytes(32);
$aKey = random_bytes(32);

Then to encrypt/decrypt messages:

$plaintext = 'This is just a test message.';
$encrypted = ExperimentalAES256DoNotActuallyUse::encrypt($plaintext, $eKey, $aKey);
$decrypted = ExperimentalAES256DoNotActuallyUse::decrypt($encrypted, $eKey, $aKey);

If you don't have random_bytes(), get random_compat.

Catherinacatherine

Can you explain why it would not be a good idea to use the quick-and-dirty implementation in production if it does what is needed? – Casanova

You'll find that you want defuse/php-encryption rather than rolling your own or copying and pasting from StackOverflow. The only reason to roll your own is to create toy implementations to teach yourself. – Catherinacatherine

Yes, but say for example I wanted to handle something like stream ciphering from CPP over a socket to PHP. I've not personally looked into defuse's library, but is there a reason the generic AES256 written above wouldn't be suitable? Clearly not the exact code, but something similar as far as building the cipher. – Casanova

is this answer still up to date? (Just checking). I do not know the history of halite, but it seems to me that there is currently stable version of v3.2.0 that's available – Filomenafiloplume

Nothing has changed, except libsodium is due to land in PHP 7.2. – Catherinacatherine

What is "$ciphertext" in "decrypt" method – Prepotency

@ScottArciszewski, The other reason would be "not renting whole building just to store a piece of paper". – Satinwood

Answer 3

MCRYPT_RIJNDAEL_256 is not equivalent to AES_256.

The way to make RIJNDAEL be decrypted from AES is to use MCRYPT_RIJNDAEL_128 and padd the string to encrypt before encrypting

AES-256 has BlockSize=128bit and KeySize=256bit Rijndael-256 has BlockSize=256bit and KeySize=256bit

Just AES/Rijndael 128bit are identical. Rijndael-192 and Rijndael-256 are not identical to AES-192 and AES-256 (block sizes and number of rounds differ).

Crustacean

You're certainly correct, but this post doesn't really answer the question. – Wriggly

Thanks @CodesInChaos. The way to make RIJNDAEL be decrypted from AES with openssl is to use MCRYPT_RIJNDAEL_128 and padd the string to encrypt before encrypting with the follwing function: <?php function pkcs5_pad ($text, $blocksize) { $pad = $blocksize - (strlen($text) % $blocksize); return $text . str_repeat(chr($pad), $pad); } ?> – Crustacean

Answer 4

$key = '324325923495kdfgiert734t'; // key used for decryption in jasper code
$text = 'string_to_be_encrypted';
$encrypted = fnEncrypt($text, $key);




function fnEncrypt( $plaintext, $key )
{
$plaintext = pkcs5_pad($plaintext, 16);

return bin2hex(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, hex2bin($key), $plaintext, MCRYPT_MODE_ECB));

}


function pkcs5_pad ($text, $blocksize)
{
$pad = $blocksize - (strlen($text) % $blocksize);
return $text . str_repeat(chr($pad), $pad);
}



function hex2bin($hexdata) 
{
$bindata = "";

    for ($i = 0; $i < strlen($hexdata); $i += 2) 
    {
      $bindata .= chr(hexdec(substr($hexdata, $i, 2)));
    }

return $bindata;
}

Petrify

Please explain your answer in brief to make it more useful for OP and other readers. – Hett

Kindly add the decrypt function also. – Contredanse