A network system includes a server, an access point connected to the server for transmitting wireless data or receiving wireless data for the server, and a station for receiving wireless data from the access point and transmitting wireless data to the access point. The station has a first key. A ciphering key updating method includes: authenticating the station with the first key; if authentication succeeds, the station transmitting identification data to the access point; and if the identification data matches registration data stored in the server, transmitting a second key to replace or update the first key.