COMMUNICATIONS SYSTEM, TRANSMITTER, RECEIVER AND COMMUNICATION METHOD

PROBLEM TO BE SOLVED: To provide a communications system ensuring secure communication using a public key, in which the genuineness of the public key of a receiver for receiving information can be verified easily, and to provide a transmitter, a receiver and a communication method. SOLUTION: A terminal 20 transmits key data operation results obtained by operating an object public key and verification data, and encryption results by secret information to a server 10. The server 10 receives encryption results of the key data operation results from the terminal 20 and decrypts it by the secret information. The server 10 calculates the verification data from its decryption results, using the public key thereof and transmits verification data calculated results thus obtained to the terminal 20. The terminal 20 receives the verification data calculated results, acquired by the server 10 from the encryption results of the key data calculated results. The terminal 20 decides whether an object public key is the public key of the server 10, by comparing the verification data with the verification data operation results. COPYRIGHT: (C)2005,JPO&NCIPI