Does this use something like asymmetric keys so door can verify a key came from the issuing system or is there still some online/network portion? Assuming it d

Does this use something like asymmetric keys so door can verify a key came from the issuing system or is there still some online/network portion? Assuming it does use asymmetric keys to prevent someone from creating counterfeit access cards, there would still be a window (if the network is unavailable) where the old key would continue to work until a new key is scanned the first time on the door lock?