Abstract: A system and method for transmitting enciphered data between first and second terminals over a data transmission channel. The system comprises a transmitter located at the first terminal, a receiver located at the second terminal and cipher computers located at each of the first and second terminals. At least one of the cipher computers is programmable and has a program memory. Storage means are provided for storing a program code or algorithm and a secret cipher key, and means are further provided for transmitting the algorithm to the programmable computer for storage in its program memory. The data transmitted between the first and second terminals is enciphered in accordance with the algorithm stored in the program memory of the programmable computer and determined by the secret cipher key.

Abstract: A dialing device and method for using the device in a common dial network consisting of a central office and a plurality of user stations connected to the central office by subscriber telephone lines. At least one of the user stations is a calling station having a dialing device which incorporates a memory for storing calling number and identification number. The method comprises the steps of establishing a connection between the calling station and the central station via the subscriber terminal lines and via the central office, transmitting the new calling number of the central station and/or the new identification number of the calling station from the central station to the calling station and storing the numbers in the memory of the calling station.