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US 5,208,856 AGranted
Scrambling and unscrambling method for composite video signals and implementing device
AssigneeLaboratoire Europeen de Recherches Electroniques Avancees
InventorsMichel Leduc, Joel Hamon, Jean-Claude Guillon, Francis Renard, Eric Diehl
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Abstract
The method of the invention consists, during the transmission of composite video signals, in the inclusion therein of series of access messages (ECM1, ECM2) and, during the unscrambling, carried out using a chip card reader whose chip card comprises encoded digital data, in using an interactive method of identification of a digital signature.
Claims12
A scrambling and unscrambling method for composite video signals, comprising:
- scrambling said video signals by a line permutation controlled by a first pseudo-random sequence using a variable control word;
- inserting, in predetermined unused lines of at least a portion of transmitted images included in said composite video signals, encoded digital data packets corresponding to different access messages, said digital data packets including said control word;
- transmitting said scrambled composite video signals including said access messages;
- receiving said transmitted scrambled composite video signal;
- extracting said access messages from said received composite video signal;
- combining said access messages in a confidential manner with data supplied to a receiver of the scrambled composite video signals;
- producing said control word for a pseudo-random sequence generator;
- and
- controlling unscrambling of said scrambled composite video signal using a second pseudo-random sequence based upon said control word, said second pseudo-random sequence being identical to and synchronized with said first pseudo-random sequence.
6 more elements
Device for scrambling and unscrambling composite video signals for an image transmission system, comprising:
- a transmitter and at least one receiver;
- a scrambling section comprising, in the transmitter, a digital scrambling circuit connected to a first pseudo-random sequence generator controlled by a first control unit;
- and
- an unscrambling section comprising, in said at least one receiver, a decoder comprising a digital unscrambling circuit connected to a second pseudorandom sequence generator controlled by a second control unit;
- the first control unit of the transmitter comprising means for producing access messages to be inserted in predetermined unused lines in a scrambled composite video signal, including a control word for controlling said first pseudo-random sequence generator;
- and
- the second variable control unit of each decoder being connected to a code checker connected to a microprocessor card reader which produces said control word from said scrambled composite video signal for controlling unscrambling of said scrambled composite video signal.
4 more elements
A decoder for unscrambling composition video signals, comprising:
- means for receiving a scrambled video signal and for converting said scrambled video signal into a digital video signal;
- message means for receiving said scrambled video signal from said receiving means and for producing access messages using said scrambled video signal;
- a card reader for reading data from a microprocessor card inserted in said reader;
- checker means for checking validity of processing carried out inside said microprocessor card;
- processing means, for receiving said access messages from said message means and receiving a variable control word from said checker means, said checker means producing said control word in response to said access messages output from said processing means while maintaining confidentiality in data exchanges between said processing means and said checker means, and for producing a pseudo-random number seed;
- a pseudo-random binary sequencer for generating a pseudo-random number sequence based upon said seed output by said processing means;
- a digital video memory for unscrambling said digital video signal based upon said pseudo-random number sequence output by said pseudo-random binary sequencer;
- and
- a digital-to-analog converter for converting said unscrambled digital video signal into an analog output video signal.
6 more elements
Dependencies are inferred from the claim text.