General Instrument Corporation

Richard Westerfer

Clyde N Robbins

Robert M Simons

Anthony M Radice

Henry S Landgraf

William A Frezza

William Frezza

In order to defeat pirate descramblers that detect the occurrence of a vertical blanking interval from a gap in timing data provided on the sound carrier of a scrambled television signal, diversionary pulse information is inserted into the sound carrier during the vertical blanking interval. A pirate descrambler that looks for a gap in data transmitted on the sound carrier will then detect a 'false' second gap, and incorrectly phase lock its horizontal oscillator to random video instead of to horizontal timing information that is recoverable during the vertical blanking interval.

Method and apparatus for frustrating vertical interval detection in

The scrambling security of a sync suppressed television signal is enhanced by eliminating the fixed time relationship between the normal color burst component and synchronization information in successive lines of the television signal. Transmission of a first plurality of television lines is delayed to achieve a cumulative delay corresponding at least to the duration of a color burst component of the television signal. The transmission of a second plurality of television lines is subsequently accelerated to reduce the cumulative delay. By repeating the delaying and accelerating steps, the location of the color burst component is varied within the television signal over time. Derivation of a substitute horizontal synchronization pulse from the color burst component is thereby prevented.

Method and apparatus for enhancing the security of a scrambled

A method and apparatus prevent unauthorized programming viewing via a downloadable cable television converter. A booter checksum is computed from data contained in a downloaded booter image. A valid checksum is extracted from tag data associated with a scrambled program signal transmitted on the cable system. The booter checksum is compared to the extracted valid checksum. If the booter checksum and valid checksums match, a descrambler is enabled to descramble the scrambled program signal. If the checksums do not match, the descrambler is not enabled. In this manner, a pirate is prevented from downloading a false booter image to defeat the integrity of the converter.

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Blue Bell, PA, United States of America

Richard Westerfer