decrypt data encrypted by CI 2.4 with CI 3.1

Hi,

After upgrading my application from CI 2.4 to CI 3.1, including changing Encrypt lib to Encryption, I found all decoded data returned empty strings.

Is there an easy way to make the new encryption library decode this data?

I think I need to use the correct parameters here:

PHP Code:

$this->encryption->decrypt($legacy_encoded_string,array(
                'cipher' => MCRYPT_RIJNDAEL_256,
                'mode' => MCRYPT_MODE_CBC,
                'key' => $my_key,
        )) 


any idea?

Thank you