General Instrument Corporation

Ricoh Company, Ltd.

Donald R Horne

John M Jeffers

Joseph B Glaab

S Wayne Mundy

A three key cryptographic system is used in the transmission of digitized signals to a plurality of receivers, each having a unique address number and a factory stored signature key which is a function of the address number. At the transmission end, a common key is generated and used to encrypt the signals to be transmitted. The signature key is generated for each receiver unit by encrypting the address number of the unit using a secret master key. The common key is then encrypted for use by each receiver using the generated signature key for that receiver. A data stream is inserted into the horizontal blanking intervals of the composite video signal. The data stream includes the encrypted signals receivable by all receivers and addressed portions, each receivable by a different receiver, containing the encrypted common key for that receiver. The receiver decrypts the common key with the stored signature key and uses it to decrypt the signals. Only a single master key must be stored and protected.

Cryptographic system for direct broadcast satellite system

A cryptographic system is used for the secure transmission of digitized signals to a plurality of receivers. At the transmission end, a key consisting of two blocks, each including a plurality of key fragments, is generated. For each transmission session, different sets of key fragments may be periodically selected from one of the key blocks and used to encrypt the signals. Data indicative of the set selection is generated. The key is distributed to each receiver. The set selection data is transmitted to all receivers along with the encrypted signals and used to construct the key fragment set for decryption of the transmitted signals. During the transmission session, the other key block may be varied to form a replacement key which is distributed to each receiver. At the end of the session, the functions of the key blocks are interchanged in all receivers at one time by selecting a set in the varied key block for use in encryption and decryption.

Cryptographic system using interchangeable key blocks and selectable key

Audio and control signals are digitized and inserted in the horizontal blanking intervals of the distributed composite television signal. The control signals are in the form of a data stream which includes a header containing group address, sync, and program-related information applicable to all receiving units, and a plurality of portions which are addressable to and contain information applicable to the control of particular individual receiving units in the addressed group. The information in the addressable portions can be altered on a real time basis such that the system operator has direct control over certain functions of individual receiving units from the transmission end.

Direct broadcast satellite signal transmission system

Programming tiers are authorized for viewing on an impulse pay-per-view basis. The system operator controls individual receiver units to block the display of programming on selected tiers because the subscriber finds the content of same objectionable or to prevent members of the household from incurring charges without the subscriber's consent. The broadcast signal includes portions addressable to particular receiver units. These portions include a designation of tiers to be blocked and a command to store same in the unit memory. Upon command to display a program on a selected tier, the memory is accessed and the stored designation compared with the selected tier. Receivers having stored designations corresponding to the selected tier are unable to display the program.

Growing community of inventors

Don Mills, Canada

Donald R Horne