H - Electricity – 04 – N
Patent
H - Electricity
04
N
350/29
H04N 7/16 (2006.01) H04N 7/167 (2006.01)
Patent
CA 1150820
ABSTRACT OF THE DISCLOSURE A text video-transmission system comprising an information emitting center and receiving stations, the emitting center comprising encryption means using an operating key, each receiving station comprising de- cryption means using the operating key, wherein in this system, the encryption means of the emitting center comprise: generator delivering a numerical signal re- presenting an operating key K, this key changing ran- domly at predetermined intervals; automatic encryption means comprising: a discriminator with an input con- nected to the magazine memorising circuit from which it receives clear octets, this discriminator being ca- pable of distinguishing, among these clear octets, those wherein the 7th and 6th binary elements are zero, an OR-exclusive logic circuit connected to the discri- minator from which it receives octets wherein the 6th and/or 7th binary elements are not zero, this logic circuit having an output which carries encrypted octets; a generator of encoding octets, the decoding means of each receiving station comprising: a generator of a numerical signal representing the operating key K in use in the emitting center, automatic decryption means comprising: a discriminator adapted to distinguish, among the encrypted octets, those wherein the 7th and 6th binary elements are zero, an OR-exclusive logic circuit connected to the discriminator; and a generator for decoding octets.
344659
Etablissement Public de Diffusion Dit "telediffusion de France"
Etat Francais Represente Par Le Secretaire D'etat Aux Postes Et Telecommunicat
Goudreau Gage Dubuc
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