private void SetupDecRoundKeys() {
_keySize.ShouldNotBeZero("_keySize");
if(_encRoundKeys == null) {
_masterKey.ShouldNotBeNull("_masterKey");
SetupEncRoundKeys();
}
_decRoundKeys = (int[])_encRoundKeys.Clone();
DoDecKeySetup(_encRoundKeys, _keySize);
}