Access control method, and associated lock device and administration server

An access control method is disclosed in which a lock device provides conditional access to a protected environment by short-range wireless communication with a key device having a key device identifier (KD_ID). In the method, the lock device requests the key device to provide a challenge response to a challenge generated by the lock device based on a challenge code kept by the lock device. The lock device receives the challenge response from the key device. The challenge response is generated by a remote administration server and is based on the key device identifier of the key device. The generated response is sent to the key device and forwarded from the key device to the lock device. The lock device then verifies the received challenge response based on the challenge code and on the key device identifier of the key device.