code: public void init(
              boolean forEncryption,
              KeyParameter params) {
  
          WorkingKey = generateWorkingKey(params.getKey(), forEncryption);
          this.forEncryption = forEncryption;
      }
docs: initialise an AES cipher.
  
  @param forEncryption whether or not we are for encryption.
  @param params        the parameters required to set up the cipher.
  @throws IllegalArgumentException if the params argument is
  inappropriate.