CIPHERING SYSTEM USING INFORMATION COMMUNICATION NETWORK

摘要

PROBLEM TO BE SOLVED: To protect communication data from attack by a malicious user even without making a user to consciously start a security function on an application layer. SOLUTION: This system is provided with plural slave stations 131 to 133, a master station 12 which transmits and receives ATM(asynchronous transfer mode) cells to/from the plural slave stations by using a transmission medium and a cell ciphering key updation notifying means which notifies a cell ciphering key that is given to a pair of one of the plural slave stations and the master station and is used for ciphering processing and decoding processing performed when the ATM cells are transmitted and received and the updation items of the cell ciphering key used for ciphering or items obtained by using the updated ciphering key from the transmitting side of the ATM cells to the receiving side of the ATM cells to take synchronization in accordance with the updation of the cell ciphering key between the slave station and the master station.