Stream cipher system with feedback

摘要

A cipher system in which a key is initially inserted into a shift register and the serial output of the shift register is added to the plain text message and the sum is fed back into the serial input of the shift register. Parallel outputs of the shift register are led to a logic function which transforms the multiple inputs into a single output, the value of which is evenly distributed among the possible combinations on the input. The logic function output is then added to the message to produce the enciphered message. In the decipherer, the deciphered message is added to the serial output of the shift register to produce the serial input to the shift register. Otherwise, the decipherer closely resembles the encipherer.