To avoid the danger of having a key decoded by storing key tables for generating the public keys and the session keys of parties mutually on the sides of transmission and reception, and letting flow only the combination data of indexes of generating the keys for session to a network.
Corresponding to the session key obtained by combining indexes generated at random from portable recording media A and B, transmission information M is enciphered so that a code sentence C is prepared. On the other hand, a hash value Hc obtained by performing hash processing to the code sentence C and the combined information of indexes 3 and 4 generated at random are respectively digitally signed by using the secret keys of the portable recording media A and B and transmitted onto the network together with the code sentence C. On the side of reception, the table indexes 3 and 4 are decoded by public keys EA and EB of the held recording media A and B, and the session key is acquired from the same key table stored on the reception side. Then the code sentence C is decoded by this key so that the transmission information M is obtained.
HAYASHI MASAHIRO
HANDA TOMIO
HIRANO TANITAKE
