Importance

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Abstract

A video system includes a central facility and a terminal. Video program means for provides the terminal with a video program including a series of television fields including a first field containing both a random digital code encrypted according to a code encryption key and program identification data, and a second field containing an unintelligible video signal previously transformed from an intelligible video signal according to the random digital code. The terminal includes means to store terminal identification data and a terminal specific encryption key; and means to send to the central facility the program idenficiation data and the terminal identification data. The central facility includes means for providing a session encryption key, means for encrypting the session encryption key according to the terminal specific encryption key, means for sending the encrypted session encryption key from the central facility to the terminal, a data base for storing and retrieving at least one code encryption key corresponding to the program identification data, means for encrypting the code encryption key according to the session encryption encryption key, and means for sensing the encrypted code encryption key from the central facility to the terminal. The terminal further includes means for receiving the encrypted session encryption key from the central facility, decryption means for decrypting the session encryption key according to the terminal specific encryption key, means for receiving the encrypted code encryption key from the central facility, decryption means for decrypting the code encryption key according to the session encryption encryption key, and decrypting the encrypted random digital code of the first frame in accordance with the code encryption key; and means for transforming the unintelligible video signal of the second frame to the intelligible video signal using the decrypted random digital code.

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First Claim