04323921 is referenced by 373 patents and cites 5 patents.

A system for transmitting information between an emitting center and receiving stations, comprising: a subscription administration center generating a plurality of subscriber's keys C.sub.i changing randomly at relatively long intervals of the order of a month; in the emitting center: a generator of an operating key K changing randomly at relatively short intervals of the order of a few minutes; a circuit for forming messages M.sub.i obtained from said subscriber's keys C.sub.i and from the operating key K by means of an algorithm, all the messages M.sub.i then being directed towards the emitting center; and automatic encryption means using the operating key K, in each receiving station: a subscription holder on which is recorded a signal corresponding to at least one of the subscriber's keys C.sub.i ; a circuit for restoring the operating key receiving the messages M.sub.i and the subscriber's key C.sub.i, this circuit working out an algorithm for restoring the signal corresponding to the operating key K used in the emitting center; an automatic decryption means; and at least one charging station capable of temporarily receiving the subscription holders and permanently recording one of the subscriber's key C.sub.i thereon.

System for transmitting information provided with means for controlling access to the information transmitted
Application Number
Publication Number
Application Date
January 23, 1980
Publication Date
April 6, 1982
Louis C Guillou
L Etat Francais represente par le Secretaire d Etat aux Poste et Telecommunications
Etablissement Public de Diffusion dit Telediffusion de France
H04L 9/00
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