SECURITY MAINTAINING METHOD, ITS EXECUTION SYSTEM AND ITS PROCESSING PROCESS

PROBLEM TO BE SOLVED: To provide technique capable of detecting and excluding completely pretending equipment. SOLUTION: A plurality of sets of equipment obtained by connecting center equipment and home equipment is set with respect to the single equipment in a network security maintaining method. The method has a step for setting an access number and a ciphering key different by each set of the equipments obtained by connecting the center equipment and the home equipment, a step of updating the access number by a prescribed sequence every ciphering processing and deciphering processing using the ciphering key, which are performed when transmitting or receiving data in the set of the equipments obtained by connecting the center equipment and the home equipment, and a step of giving notice of the access number updated in the set of the equipments obtained by connecting the center equipment and the home equipment.