Patent ID: 7907733

Claim:
A method for a base station to manage a traffic encryption key (TEK) for encrypting traffic data for a multicast service or a broadcast service provided to a subscriber station in a wireless portable Internet system, the method comprising: (a) generating a new traffic encryption key so as to update a current traffic encryption key when a predetermined time elapses from a start time of an active lifetime of the current traffic encryption key used for encrypting traffic data currently transmitted to the subscriber station; and (b) transmitting the new traffic encryption key to subscriber stations provided with the multicast service or the broadcast service through a broadcast connection, upon generation of the new traffic encryption key; wherein the predetermined time from the start time is managed by the base station and is less than a second predetermined time from the start time managed by the subscriber station, and wherein expiration of the second predetermined time triggers a request for the new traffic encryption key from the subscriber station when the subscriber station fails to receive the new traffic encryption key, and the base station transmits the new traffic encryption key generated in (a) to the subscriber station in response to the request.