Cryptography – Key management – Having particular key generator
Patent
1984-11-21
1987-02-24
Buczinski, Stephen C.
Cryptography
Key management
Having particular key generator
380 19, 380 20, H04N 7167, H04N 716, H04K 100
Patent
active
046461477
ABSTRACT:
Even though television signals are transmitted as analog signals over cable from the transmitter to the receivers of customers of the cable system, programs for which charges to the customers are payable are scrambled at the transmitter and unscrambled at the receiver on a digital basis, requiring digital-to-analog and analog-to-digital conversion both at the transmitter and at the receiver. In some cases there is such conversion at the receivers already for normal reception processing. By the provision of digital scrambling and unscrambling, it is possible to use a digital key which is subject to variation by a random signal generator, this key being transmitted during a one-line period that forms part of the vertical blanking interval. The unscrambling circuit has a built-in microprocessor so that its mode of operation corresponding to that of the control circuit at the transmitter is not readily detectible.
REFERENCES:
patent: 4221931 (1980-09-01), Seiler
patent: 4266243 (1981-05-01), Shutterly
patent: 4295223 (1981-10-01), Shutterly
patent: 4405942 (1983-09-01), Block et al.
patent: 4551580 (1985-11-01), Cox et al.
Blaupunkt-Werke GmbH
Buczinski Stephen C.
Koltak Melissa L.
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