Encryption in PHP leaves unwanted characters - php

Question

I have made an encryption function which encrypts a simple value and stores it in the database. Here is the code to encrypt and decrypt:
public function encrypt($string){
$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$value = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $this->key256, $string, MCRYPT_MODE_ECB, $iv);
$value = base64_encode($value);
return $value;
}
public function decrypt($string){
$value = base64_decode($string);
$value = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $this->key256, $value, MCRYPT_MODE_ECB);
return $value;
}
When I encrypt a simple value such as 'Michael' and decrypt again, I get the value:
Michael���������
Is there a reason I get all those question marks or a way to get rid of them?

Answer 1

In my experience, those extra character are NULL-bytes used for padding, that has been preserved after decryption.
You should try changing your decrypt() function to:
public function decrypt($string){
$value = base64_decode($string);
$value = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $this->key256, $value, MCRYPT_MODE_ECB);
return trim($value, "\0");
}

Answer 2

use bin2hex() instead of bas64_encode() and you can use the hex2bin() before decryption instead of base64_decode()
protected function hex2bin($hexdata)
{
$bindata = '';
for ($i = 0; $i < strlen($hexdata); $i += 2) {
$bindata .= chr(hexdec(substr($hexdata, $i, 2)));
}
return $bindata;
}
Ofcourse you can use hex2bin() in PHP., this custom code is for compatibility with Java like platforms.
I do it this way. May be you can give a try.
Thanks