Cryptography – Communication system using cryptography – Data stream/substitution enciphering
Reexamination Certificate
2000-05-01
2001-10-23
Cangialosi, Salvatore (Department: 2732)
Cryptography
Communication system using cryptography
Data stream/substitution enciphering
C380S044000
Reexamination Certificate
active
06307937
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of communications, and more specifically to conditional access by computers to data streams transmitted via satellite.
BACKGROUND OF THE INVENTION
Satellite communication has long been used to broadcast data to computers. In situations requiring the same data to be transmitted to multiple sites, satellite communication, which allows a single transmission of data to be received at multiple sites, can be more cost effective than terrestrial communication, which requires separate transmission to each site.
In the past, data broadcast via satellite to a computer typically was received by an external satellite receiver, which serially passed a single data stream to the computer through a serial adapter interface. An example of such a system is the Opportunistic Data File Broadcast system developed by Hughes Network Systems, which employs a Compression Labs Spectrum Saver satellite receiver to pass RS-422 serial data to high-speed adapters in computers at remote sites. This particular system has been used by financial institutions to broadcast financial data from central data centers to branch offices.
For commercial data broadcasts, conditional access technology enabling only authorized users to access the broadcast data is essential to ensure payment for the data. Conditional access is typically implemented by encrypting the broadcast data and providing the decryption keys only to authorized receivers. In prior satellite data communication systems, such as the Opportunistic Data File Broadcast system, conditional access functions have been performed by the external satellite receiver, which outputs a single decrypted data stream to the receiving computer. In these systems, conditional access is provided for only a single data stream. Thus, to access multiple data streams simultaneously transmitted would require users to have a complete set of receiving equipment for each data stream.
Another type of satellite communication system has been suggested in which an adapter card, insertable into a computer, enables satellite reception without the need for the external satellite receiver. Examples of such systems are disclosed in U.S. Pat. No. 4,777,657 to Gillaspie, U.S. Pat. No. 5,019,910 to Filmer, and U.S. Pat. No. 5,359,367 to Stockill.
However, these references fail to teach a system incorporating conditional access technology, and similarly fail to provide for simultaneous receipt of multiple data streams where the data streams are individually conditional access controlled. Furthermore, to the extent that the prior art discloses use of decryption hardware, none of the prior art systems extends the use of the hardware beyond decrypting an incoming broadcast data stream to providing encryption and decryption operations for the connected computer.
SUMMARY OF THE INVENTION
The present invention addresses the shortcomings of prior art systems by teaching a secure satellite communication system for providing subscribers with conditional access to broadcast satellite data through their computers. This system maintains the security of information by providing access only to authorized users, and provides an additional benefit by enabling users to concurrently receive and decrypt multiple data streams.
In a preferred embodiment, the present invention teaches a method for an adapter card, for use in a computer, to provide conditional access by the computer to input data, including data streams transmitted via satellite, wherein a data stream is comprised of at least one frame and each frame includes an address identifying the data stream. This method includes the steps of maintaining an Access Table, in which each table entry includes an address field for storing an address corresponding to a data stream which the computer is authorized to receive, receiving a frame and determining its address, and determining whether the frame address matches an address maintained in the Access Table in order to determine whether the computer has access to the data stream corresponding to the frame. If a match is not found, the adapter card discards the frame, but if a match is found, the adapter card processes and transmits the frame to the computer through a bus interface.
In a preferred embodiment, the adapter card additionally is capable of processing data transmitted from the computer.
In addition to the method described above, the present invention is also directed to an adapter card for use in a computer, for providing conditional access by the computer to input data including frames of data streams transmitted via satellite, wherein each data stream is comprised of at least one frame and each frame includes an address identifying the data stream. The adapter card includes a receiver for receiving a data stream frame, an Access Table, in which each table entry includes an address field for storing an address corresponding to a data stream which the computer is authorized to receive, an integrated filter/crypto (IFC) block for determining an address of the received frame and determining whether the frame address matches an address maintained in the Access Table, and a bus interface for enabling communication between the adapter card and the computer. If the IFC finds that the frame address does not match a table address, the IFC block discards the frame, but if it finds a match, the IFC block processes the frame into output data, to be transmitted to the computer via the bus interface. The IFC preferably is also capable of processing data input from the computer into output data.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings.
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patent:
Cassagnol Robert D.
Dillon Douglas M.
Cangialosi Salvatore
Hughes Electronics Corporation
Sales Michael W.
Whelan John T.
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