ENCRYPTED COMMUNICATION SYSTEM THAT LIMITS THE DAMAGE CAUSED WHEN A SECRET KEY HAS BEEN LEAKED

摘要

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for encrypting data such as a digitized document, a voice, an image, a program, etc. through a transmission medium or a recording medium and includes a transmission device 10 and seven groups A to G In the cryptographic communication system comprising a total of 28 receiving apparatuses (A1 to G4), two secret keys selected from 14 different secret keys are preliminarily distributed to each group. The transmitting apparatus 10 encrypts the same message M by using any one of the two secret keys distributed to the respective groups, and transmits the same to the receiving apparatus of the corresponding group. The receiving apparatus decrypts the received ciphertext by using two secret keys distributed to the group to which it belongs, judges whether or not there is a certain regularity for each of the obtained two deciphered sentences, Specify.