Cryptography – Key management – Having particular key generator
Patent
1991-03-07
1992-11-03
Swann, Tod
Cryptography
Key management
Having particular key generator
380 20, 380 21, H04N 7167
Patent
active
051611872
ABSTRACT:
A cable television system includes a transmitter and at least one receiver. In the transmitter, sync information is suppressed in amplitude to execute scrambling, and a sync width information signal and key data are superimposed on a television signal during a vertical blanking period. The sync width information signal has a burst form and a predetermined width, and represents whether sync information is present or absent. The key data represents contents of the scrambling. In the receiver, the sync width information signal is recovered, and a sync width information pulse corresponding to the sync width information signal is generated. A reference signal is generated on the basis of an edge of the sync width information pulse. The key data is extracted from the scrambled video information in response to the reference signal. Pseudo sync signals are generated in response to an edge of the sync width information pulse. The sync information of the scrambled video information is increased in amplitude in response to the extracted key data at timings determined by the pseudo sync signals.
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Kajita Harumasa
Kariya Tetsuo
Kawashima Ichiro
Nakanami Satoshi
Tanaka Masami
Matsushita Electric - Industrial Co., Ltd.
Swann Tod
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