METHOD AND SYSTEM FOR CIPHER COMMUNICATION, AND RECORDING MEDIUM STORED WITH CIPHER COMMUNICATION PROGRAM

摘要

PROBLEM TO BE SOLVED: To confirm if a communication sentence is transferred to the other party being safe and legal by generating either a common key or a session ID and transmitting the communication text with either of them utilized for an electronic envelope. SOLUTION: A transmission application part 11 of an entity A10 transmits destination information to a key server C20 and requests client authentication. A decoding part 13 of a one-time common key decodes a one-time common key Kc transmitted from the server C20 and takes out the key Kc. And, an electronic envelope preparing part 15 enters a communication text M of plaintext to be transmitted to a receiving client B by a transmitting client A into an electronic envelope E and directly transmits it to an entity B30 without going through the server C20. Further, a key use state managing part 25 issues a session ID which is generated by a random number generator including a session ID proper to this transaction and is enciphered to a public key with the public key Kpc of the server C20 and a public key Kpb of the transmission destination entity B30 in each transmission destination.