<p>A mobile station is provided. The mobile station includes one or more radio transceiver module and a processor. The processor performs a handover negotiation procedure with a serving base station so as to handover communication services to a target base station by transm itting and r eceiving a plurality of handover negotiation messages via the radio transceiver m odule, and generates an Authorization Key (AK) context and derives at least one Traffic Encryption Key (TEK) for the target base station. The AK context includes a plurality of keys shared with the target base station for encrypting messages to be transmitted to the target base station, and the TEK is a secret key shared with the target base station for encrypting traffic data.</p>
