| 摘要 |
PROBLEM TO BE SOLVED: To ensure the intensity of a cryptograph, even by using a standard ciphering system and to ensure security by preventing the acquisition of decoding key information due to illegal conspiracy or the like between users. SOLUTION: A user side transmits user identification information IP and request information to a transmitter, the transmitter obtains key information (K) and gives it to the user side by using a unidirectional function to be used in the public key ciphering technique, on the basis of a cryptographic key Ki regarding the demand information and the user identification information IP, the user side decodes the cryptographic key Ki on the basis of the key information (K) and the user identification information IP, and information which is enciphered on the basis of the cryptographic key Ki and is distributed by the transmitter is restored to a form that can be used on the basis of the decoded cryptographic key Ki. |
