A method of securely communicating a digital message between first and second information processing devices. The first and second information processing devices each continuously and sequentially generate and store, in real time, the digits of a pseudo-random number such that the number of digits in the pseudo-random number generated by the first processing device and the second processing device increases with time. The first information processing device generating an encrypted message by calculating a function of the digital message and the sequentially generated digits of the pseudo-random number, the calculated function being the encrypted message. The first information processing device communicates the encrypted message to the second information processing device. The second information processing device decrypts the encrypted message by calculating the inverse of the function to obtain the digital message.