A general interface for creating multiple key encryption schemes.
This is a semi-classical double encryption scheme in which we use a PRF (here, we use AES) twice on each value with different keys to double encrypt.
This encryption scheme uses AES with a fixed key and thus has the benefit of not needing to repeatedly perform the costly setKey procedure for AES.
We implement this double encryption scheme using Hashing.
This class is the Key to be used when encrypting with any @link MultiKeyEncryption} scheme.