Method and apparatus for fast re-autehentication in broadband wireless communication system

A method and an apparatus for a fast re-authentication in a broadband wireless communication system are provided to reduce a roaming time between a wireless LAN and a broadband wireless communication network by performing a re-authentication using a PMKID(Pairwise Master Key IDentifier). A method for a fast re-authentication in a broadband wireless communication system includes the steps of: generating a PMK(Pairwise Master Key) necessary for the security in an initial authentication process, converting and storing the PMK into a size for a PMKID calculation(202); transmitting a message having the stored PMKID list information to a base station in a re-authentication process, and receiving a response message(214); receiving an authentication success message from the base station(216); performing an exchange of a 3way handshake authentication key with the base station(230); and performing an exchange of 2way handshake security key with the base station(240).