Patent ID: 8072939

Claim:
A mobile communication method of performing a handover process for allowing a mobile station to perform a handover from a handover-source cell under control of a handover-source radio base station to a handover-target cell under control of a handover-target radio base station, the method comprising the steps of : (A) generating, at the handover-source radio base station, an intermediate key, by inputting, into a first function, a base station key which is necessary for generating a key for communication of the mobile station in the handover-source cell, identification information of the handover-target cell, and identification information of a frequency for the handover-target cell; and transmitting, from the handover-source radio base station to the handover-target radio base station, the intermediate key, in the handover process; and (B) generating, at the handover-target radio base station, a base station key, on the basis of the intermediate key in the handover process, the base station key being necessary for generating a key for communication of the mobile station in the handover-target cell.