Addressable subscription television system having multiple scram

Details Addressable subscription television system having multiple scram Addressable subscription television system having multiple scram

1985-10-29

1987-12-29

Buczinski, Stephen C.

Cryptography

Particular algorithmic function encoding

Nbs/des algorithm

380 11, 380 15, 380 17, H04N 7167

Patent

active

047165880

ABSTRACT:
A multimode scrambling system for video signal transmission systems is described. The system provides for baseband video scrambling controlled by a central originating computer facility. The scrambling of each field of a video changes on a per field basis. The video signal is scrambled in several modes including vertical interval scrambling, alternate line inversion, bogus sync pulse generation, video compression and video offset techniques. A scrambling sequence is sent by a unique algorithm, sent during the vertical interval to each system decoder. The algorithm is reordered for each of a plurality of fields of the video signal and the reordering position is identified by a unique synchronization pulse transmitted during the vertical interval of the video signal. Additional security measures are provided to inhibit a subscriber from avoiding a transmitted disable command, or an attempt to invade the subscriber decoder mechanical packaging security.

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