Encipher-decipher device having semi-automatic generation of the code key during data entry

摘要

An encipher-decipher apparatus including an input keyboard and a processing and control stage which enciphers or deciphers data received directly from the keyboard or preferably from a text store with the aid of a cipher generator. The cipher generator produces a cipher sequence dependent on two code data items that determine the initial state of the cipher generator. One item for encryption is supplied as a set of random code characters from a random generator. The random generator comprises a continually cycled modulo-n counter and a FIFO memory into which the instantaneous state of the counter is entered at each of successive actuations of keys of the keyboard, such key operations being those done in any event in the use of the apparatus. The cycle time of the counter is much less than the time between consecutive key operations. A clock rate of 100 kHz is suggested. The set of characters is read out of the FIFO store at the start of data processing for use by the cipher generator.