Abstract: A method and system for authentication of accreditations and of messages with zero-knowledge proof and for the signing of messages, and a station for use in such system, in particular executed as a smart card station.Instead of using multiple accreditations and an iterative process of verification, use is made of a comprehensve accreditation (high exponent p) and a number D is drawn at random, which number is within the range between 0 and p-1. The operations of verifiction proceed by the computation of the D-th power of the inverse accreditation B.Application in particular, to smart cards and, more specifically, to bank cards.

Abstract: A pseudo-random binary sequence generator comprises at least one shift register (S, T) arranged in a recirculating loop and having a plurality of logic gates (G) for logically combining the outputs of selected stages of the register to provide a pseudo-random sequence, and a multiplexer (M), having a p data inputs and q address inputs all connected to selected shift register stages, and which selects at any instant one of the p data input bits in accordance with the q-bit address word to provide the generator output. The number s of logic gates is especially high and is related to the total number r of shift register stages (r>p+q) by the expression: 2.sup.s .gtoreq.r.sup.2. Some of the shift register stages of the or each shift register are connected to selected data inputs of the multiplexer and others of the stages of the same shift register are connected to selected address inputs of the multiplexer.

Abstract: The generator comprises three subassemblies, each comprising an adder and registers, said three subassemblies making it possible to provide three recursive sequences. Each sequence is dependent on variables constituted by initialization bytes. One state of the generator is defined by a particular combination of three sequences and each state determines an output variable, which is the desired coding or decoding byte.

Abstract: A television system with access control comprises a transmitter and receis. The transmitter comprises a video signal and sound signal formation circuit, means for transmitting these signals and a jamming circuit using a service key. Each receiver comprises means for receiving the transmitted signals, means for the display of the picture and for restoring the sound and an unjamming circuit connected to the reception means and working with the service key.It also comprises a subscription management center and in the transmitter a digital signal generator, a circuit for the formation of digital messages and a data broadcasting system and in the receiver a subscription card, an extraction circuit for the data, and a circuit for restoring the service key. There is also at least one subscription card loading station connected to the subscription management center.

Abstract: A subscription card for videotex receivers, comprising:(a) a support,(b) means for processing the information, comprising in particular a control unit governing an arithmetical and logical unit and a live memory,(c) an interface permitting exchanges between the card and the apparatus in which it is inserted (charging station or receiver), further comprising:(d) a programmable memory comprising a plurality of locations for receiving numerical subscription blocks C.sub.i,(e) a dead memory containing instructions for proceeding with the recording and selection of said subscription blocks, and for carrying out a calculation,(f) a calculation circuit receiving, from the receiver in which the card is inserted, numerical messages M.sub.i and receiving from said programmable memory a numerical subscription block C.sub.i, this circuit being adapted to work out an algorithm whose parameters are provided by the subscribers' keys C.sub.

Abstract: 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 decryption means using the operating key, wherein in this system, the encryption means of the emitting center comprise: a generator delivering a numerical signal representing an operating key K, this key changing randomly at predetermined intervals; an automatic encryption means comprising: a discriminator with an input connected to a magazine memorizing circuit from which it receives clear octets, this discriminator being capable of distinguishing, among these clear octets, those wherein the 7th and 6th binary elements are zero, an OR-exclusive logic circuit connected to the discriminator 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 receivin

Abstract: 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.