METHOD FOR DISCOVERING REPLICA TERMINAL

摘要

PROBLEM TO BE SOLVED: To allow a communication system comprising a center and a plurality of terminals to automatically find out a replica terminal and exclude it at a low cost. SOLUTION: The center and a plurality of the terminals are interconnected through a communication network where encryption communication is implemented by using individual session keys. When the center distributes a new session key to the terminals, the center transmits challenge information to the terminals. Each terminal transmits response information comprising a terminal ID and a temporary public key to the center. The center retrieves a communication log and inspects whether or not a terminal with the same terminal ID but having a different temporary public key exists. When the terminal exists, the center determines the presence of a replica terminal and distributes no session key thereto. Since the copy of the temporary public key produced by the terminals can hardly be copied and the replica terminal cannot produce the same temporary public key, the center can detect the presence of the replica terminal.