Abstract: An enciphering and deciphering apparatus in the form of a typewriter having an input device for the input of characters to be processed, a control device for the input of control commands determining the mode of operation of the apparatus and an output device possessing at least one page printer. A display device is connectable with the input device for the stepwise progressive display of the infed characters. The output side of the display device can be selectively connected with the printer, with a cipher computer or a key character storage associated with the cipher computer. The cipher computer has its output side connectable with the printer. A central control unit is provided which can be controlled by the control device.