SECRET COMMUNICATION METHOD AND DEVICE

摘要

PROBLEM TO BE SOLVED: To achieve secret communication for preventing information leakage to a third person even though one between two persons who transmit and receive information uses a PC whose security is not completed.SOLUTION: A software having a time stamp function for stamping a transmission time on a reply mail replying to an electronic mail received from a terminal I is transmitted to a terminal O from the terminal I (S14). The software received at the terminal O is installed (S16). An electronic mail including a question sentence having content which is to be known only by users of both terminals and a public key of a first terminal is transmitted to the terminal O from the terminal I (S22). The electronic mail including a reply relating to the question sentence and a common key for encryption communication is transmitted to the terminal I from the terminal O after being encrypted using the public key (S26). The terminal I decodes the electronic mail received from the terminal O using the secret key (S28), then the encryption communication therebetween with the terminal O is performed using the common key (S34) when confirmation is made that the reply is correct (S32).