Help with decription on arduino

I currently have a project that I am working on and was wondering if someone could help

The project is to create a secure key that ends an encrypted password over MQTT to an esp8266.

The issue that I am having is to do with encryption and decryption.

In PHP I have the following that encrypts and decrypts the password but needs help with the esp side of things

//Key
$key = 'opc$5304#*&230+@$#&y_2483hf782e4';

//Function for Encryption

function encryptthis($data, $key) {
$encryption_key = base64_decode($key);
$iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-256-cbc'));
$encrypted = openssl_encrypt($data, 'aes-256-cbc', $encryption_key, 0, $iv);
return base64_encode($encrypted . '::' . $iv);
}

//Function for Decryption
function decryptthis($data, $key) {
$encryption_key = base64_decode($key);
list($encrypted_data, $iv) = array_pad(explode('::', base64_decode($data), 2),2,null);
return openssl_decrypt($encrypted_data, 'aes-256-cbc', $encryption_key, 0, $iv);
}


Kind Regards,
Jason Toland