Whats is the best way to encrypt a big array with AES in PHP?

Question

State

I have a big array of data (~2000 strings with 2000 chars each) to encrypt using symetric encryption AES.

My code is currently the following :

Encryption function

function encryptAES($content, $key) {
    $iv = mcrypt_create_iv(256, MCRYPT_DEV_RANDOM);
    $iv_base64 = rtrim(base64_encode($iv), '=');
    $encrypted = base64_encode(mcrypt_encrypt(
         MCRYPT_RIJNDAEL_256, 
         $key, 
         $content . md5($content), 
         MCRYPT_MODE_CBC, 
         $iv
    );
    return  $iv_base64 . $encrypted;
}

Array Encryption

foreach ($fields as $field) {
   $field['encryptedValue'] = encryptAES($field['value'], $SymKey);
}

.

Question

Only strings can be passed to $content. And this code might be slow if I just make a loop over the thousands strings.

Can you suggest a more performant way ?

Answer 1

1. serialize() your array. The result of serialization is a binary string, which is acceptable by mcrypt_encrypt.

2. Encrypt serialized array with one function call, and base64 the result:

   $myArray = [ ... ];
   $content = serialize($myArray);
   
   $iv = mcrypt_create_iv(256, MCRYPT_DEV_RANDOM);
   $encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $content, MCRYPT_MODE_CBC, $iv);
   

3. There is no need for base64 encription of data passed to mcrypt_encrypt.