PLAINTEXT ENCIPHERING/DECIPHERING METHOD, PLAINTEXT ENCIPHERING/DECIPHERING DEVICE, AND COMPUTER-READABLE RECORDING MEDIUM RECORDING PLAINTEXT ENCIPHERING/ DECIPHERING ALGORITHM

摘要

PROBLEM TO BE SOLVED: To make this device transmit an important ducument or the like safely by making a fear that a secret password is decoded roughly zero even when an original plaintext and an enciphered text in which the plaintext is enciphered are understood by burglary or the like. SOLUTION: When plaintext to be an object to be transmitted is inputted to a transmitter-receiver 3, an enciphered text is produced by enciphering the plaintext while using an NGDp enciphering/deciphering algorithm in which a previously inputted secret password is used by the transmitter-receiver 3 and the plaintext is deciphered by using the NGDp algorithm in which the previously set secret password is used by a transmitter-receiver 4 which received this enciphered text and the plaintext obtained by this (the plaintext inputted to the transmitter-receiver 3 being the origin of the transmission) is stored in a floppy disk 19 or the like and the floppy disk is delivered to a recipient.