Selective enablement of descramblers

• US 4,792,973 A
• Filed: 12/04/1987
• Issued: 12/20/1988
• Est. Priority Date: 06/08/1984
• Status: Expired due to Term

• Current Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Original Assignee: Cable/Home Communication Corporation, MACOM Technology Solutions Holdings, Inc.
• Inventors: Blakeney, Robert D. II, Gilhousen, Klein S., Harding, Michael V., Heller, Jerrold A.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US07/128,889
• Time in Patent Office: 382 Days
• Field of Search: 358/84, 455/2, 340/825.33, 340/825.34, 380/20, 380/23, 380/29, 380/44, 380/45, 380/24
• US Class Current: 380/231
• CPC Class Codes: H04N 7/162 Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58

Abstract

A system in a subscriber television network for enabling descrambling of a received scrambled signal on a prepaid basis and/or an impulse-purchase basis. A received mask signal uniquely related to the scrambled signal is compared with a received authorization signal indicating whether the subscriber is authorized to receive the scrambled signal on a prepaid basis and a prepaid signal for enabling descrambling is provided when the compared signals match. A not-prepaid signal is provided when they do not match. A received cost signal indicating the charge for descrambling the scrambled signal and a received credit signal indicating the subscriber'"'"'s endlessly accumulated credit are processed with reference to a stored record of the subscriber'"'"'s prior accumulated charges to determine whether the subscriber has sufficient available credit to pay for descrambling of the scrambled signal. If a program is not prepaid and if sufficient credit is available, the subscriber is given the option of causing the signal to be descrambled on an impulse-purchase basis. To prevent a subscriber from obtaining descrambling through such deceit as changing the mask, authorization, cost and/or credit signals, these signals are processed with key signals which are used in scrambling and descrambling the television signal such that descrambling is prevented if any of the mask et al authorization, cost and/or credit signals is changed.

Claims

1. In a subscriber communication network, a system for enabling descrambling in a subscriber terminal of a received scrambled signal on an impulse-purchase basis, comprising:

means in a central station for providing a credit signal indicating endlessly accumulated credit attributed to the subscriber terminal;

means for sending said credit signal to the subscriber terminal;

means in the subscriber terminal for processing a received cost signal indicating the charge for descrambling said given scrambled signal together with said credit signal to determine whether the subscriber terminal has sufficient available credit to pay for descrambling of said scrambled signal, and for providing a credit-available signal when it is determined that there is sufficient credit available;

means in the subscriber terminal responsive to the credit-available signal for indicating that the subscriber has the option of causing the scrambled signal to be descrambled on an impulse-purchase basis;

means in the subscriber terminal that are enabled in response to the credit-available signal for accepting said option, and for providing an accepted signal upon said acceptance; and

means in the subscriber terminal responsive to the accepted signal for enabling the scrambled signal to be descrambled.

2. A system according to claim 1, wherein the processing means includes:

a debit register for registering the endlessly accumulated charges for scrambled signals accepted by the subscriber for descrambling;

means for adding the charge indicated by the cost signal to the endlessly accumulated charges registered in the debit register; and

means for comparing the endlessly accumulated credit indicated by said credit signal with the sum of said addition and for providing said credit-available signal when the accumulated credit is not less than said sum.

3. A system according to claim 2, further comprising:

means responsive to said accepted signal for incrementing the endlessly accumulated charges in the debit register by the charge indicated by the cost signal.

4. A system according to claim 3, further comprising:

means for detecting when the arithmetic limit of the debit register would be exceeded by incrementing the endlessly accumulated charges in the debit register by the charge indicated by the cost signal, and for providing an overflow signal upon said detection; and

means responsive to the overflow signal for preventing the debit register from being incremented.

5. A system according to claim 1, wherein the means for providing the credit signal includes:

a first memory for storing an indication of endlessly accumulated prior payments made by a given subscriber;

a second memory for storing an indication of the amount of credit advanced to the given subscriber; and

means for summing the stored prior payments indication and the stored credit advanced indication to provide the credit signal for the given subscriber.

6. A system according to claim 5, wherein the processing means in the subscriber terminal includes:

a debit register for registering the endlessly accumulated charges for scrambled signals accepted by the subscriber for descrambling;

means for adding the charge indicated by the cost signal to the endlessly accumulated charges registered in the debit register; and

means for comparing the endlessly accumulated credit indicated by said credit signal with the sum of said addition, and for providing said credit-available signal when the endlessly accumulated credit is not less than said sum; and

wherein the system further includes;

means for initializing the first memory with an indication of the endlessly accumulated charges attributed to the subscriber terminal of the given subscriber upon commencement of service to the given subscriber; and

means for incrementing the first memory by the amount of each payment made by the given subscriber.

7. A system according to claim 1, further comprising:

means in the subscriber terminal for using a given key signal for descrambling the scrambled signal;

wherein the enabling means in the subscriber terminal are responsive to said accepted signal for enabling the scrambled signal to be descrambled by said given key signal; and

means for preventing a subscriber from being able to enable descrambling of the scrambled signal through such deceit as substituting another signal for either of said credit signal and said cost signal in order to cause said determining means to determine that the subscriber terminal has sufficient available credit to pay for descrambling of said scrambled signal, said preventing means comprising;

means in the central station for encoding said given key signal by processing said given key signal with a first control signal selected from a group consisting of the credit signal and the cost signal; and

means in the subscriber terminal for processing said given key signal with said first control signal to enable said given key signal to be used to descramble said scrambled signal;

wherein said given key signal, said credit signal, said cost signal and said enable signal are separate signals.

8. In a subscriber communication network, a system for enabling descrambling in a subscriber terminal of a received scrambled signal on an impulse-purchase basis, comprising:

means in a central station for providing a credit signal indicating endlessly accumulated credit attributed to the subscriber terminal;

means for sending said credit signal to the subscriber terminal;

means in the subscriber terminal for comparing a received mask signal uniquely related to said scrambled signal with an authorization signal indicating whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis, and for providing a not-prepaid signal when the compared signals do not match to a prescribed degree;

means in the subscriber terminal for processing a received cost signal indicating the charge for descrambling said given scrambled signal together with said credit signal to determine whether the subscriber has sufficient available credit to pay for descrambling of said scrambled signal, and for providing a credit-available signal when it is determined that there is sufficient credit available;

means in the subscriber terminal responsive to both the non-prepaid signal and the credit-available signal for indicating that the subscriber has the option of causing the scrambled signal to be descrambled on an impulse-purchase basis;

means in the subscriber terminal that are enabled in response to both the not-prepaid signal and the credit-available signal for accepting said option, and for providing an accepted signal upon said acceptance; and

means in the subscriber terminal responsive to the accepted signal for enabling the scrambled signal to be scrambled.

9. A system according to claim 8, wherein the means for indicating said option to the subscriber so provides said indication and the acceptance means are so enabled only when an impulse-purchase signal related to said scrambled signal also is received by the subscriber terminal and said indicating means.

10. A system according to claim 9, wherein the impulse-purchase signal is included in the mask signal.

11. A system according to claim 8, wherein the processing means includes:

a debit register for registering the endlessly accumulated charges for scrambled signals accepted by the subscriber for descrambling;

means for adding the charge indicated by the cost signal to the endlessly accumulated charges registered in the debit register; and

means for comparing the endlessly accumulated credit indicated by said credit signal with the sum of said addition, and for providing said credit-available signal when the accumulated credit is not less than said sum.

12. A system according to claim 11, further comprising:

means responsive to said accepted signal for incrementing the endlessly accumulated charges in the debit register by the charge indicated by the cost signal.

13. A system according to claim 12, further comprising:

means for detecting when the arithmetic limit of the debit register would be exceeded by incrementing the endlessly accumulated charges in the debit register by the charge indicated by the cost signal, and for providing an overflow signal upon said detection; and

means responsive to the overflow signal for preventing the debit register from being incremented.

14. A system according to claim 8, wherein the mask signal contains a given number of bits, the system further comprising:

means for storing a plurality of said authorization signals having a combined bit capacity in excess of said given number of bits so as to enable authorization of a quantity of different features in excess of said given number of bits, and for providing a selected one of the stored authorization signals for comparison with the mask signal in response to an address signal received with the mask signal.

15. A system according to claim 8, further comprising:

means in the subscriber terminal for using a given key signal for descrambling the scrambled signal;

wherein the enabling means in the subscriber terminal are responsive to said accepted signal for enabling the scrambled signal to be descrambled by said given key signal; and

means for preventing a subscriber from being able to enable descrambling of the scrambled signal through such deceit as substituting another signal for any of said mask signal, said authorization signal, said credit signal and said cost signal in order to cause said comparing means to determine whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis and/or to cause said determining means to to determine that the subscriber terminal has sufficient available credit to pay for descrambling of said scrambled signal, said preventing means comprising;

means in the central station for encoding said given key signal by processing said given key signal with a first control signal selected from a group consisting of said mask signal, said authorization signal, said credit signal and said cost signal; and

means in the subscriber terminal for processing said given key signal with said first control signal to enable said given key signal to be used to descramble said scrambled signal;

wherein said given key signal, said mask signal, said authorization signal, said credit signal, said cost signal and said enable signal are separate signals.

16. A system in a subscriber terminal of a subscriber communication network for enabling descrambling of a received scrambled signal, comprising:

means for comparing a received mask signal uniquely related to said scrambled signal with an authorization signal indicating whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis, wherein the mask signal contains a given number of bits, and for providing a not-prepaid signal when the compared signals do not match to a prescribed degree; and

means for storing a plurality of said authorization signals having a combined bit capacity in excess of said given number of bits so as to enable authorization of a quantity of different features in excess of said given number of bits, and for providing a selected one of the stored authorization signals for comparison with the mask signal in response to an address signal received with the mask signal.

17. A system in a subscriber terminal of a subscriber communication network for enabling descrambling of a received scrambled signal, comprising:

means for comparing a received mask signal uniquely related to said scrambled signal with an authorization signal addressed to the subscriber terminal and indicating whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis, wherein the mask signal contains a given number of bits, and for providing a prepaid signal when the compared signals match to a prescribed degree;

means for storing a plurality of said authorization signals having a combined bit capacity in excess of said given number of bits so as to enable authorization of a quantity of different features in excess of said given number of bits, and for providing a selected one of the stored authorization signals for comparison with the mask signal in response to an address signal received with the mask signal; and

means responsive to the prepaid signal for enabling the scrambled signal to be descrambled.

18. A system according to claim 17, wherein the authorization signal is a digital signal having a plurality of bit positions, with at least some of the bit positions individually containing signals that indicate the prepaid status of different respective channels and/or programs.

19. In a subscriber communication network, a system for enabling descrambling in a subscriber terminal of a received scrambled signal, comprising:

means in a subscriber terminal for determining whether a first control signal received by the subscriber terminal bears a predetermined relationship to a second control signal, and for providing an enable signal upon determining that said first control signal bears said predetermined relationship to said second control signal;

means in the subscriber terminal for using a given key signal for descrambling the scrambled signal;

means in the subscriber terminal responsive to said enable signal for enabling the scrambled signal to be descrambled by said given key signal; and

means for preventing a subscriber from being able to enable descrambling of the scrambled signal through such deceit as substituting another signal for said received first control signal in order to cause said determining means to determine that said predetermined relationship with said second control signal exists, said preventing means comprising;

means in the central station for encoding said given key signal by processing said given key signal with said first control signal; and

means in the subscriber terminal for processing said given key signal with said received first control signal to enable said given key signal to be used to descramble said scrambled signal;

wherein said given key signal, said first control signal, said second control signal and said enable signal are separate signals.

20. A system according to claim 19:

wherein the control signals include a mask signal uniquely related to said scrambled signal and an authorization signal indicating whether the subscriber is authorized to descramble the scrambled signal; and

wherein the determining means compare the mask signal with the authorization signal, and provide said enable signal when the compared signals match to a prescribed degree.

21. A system according to claim 19:

wherein the control signals include a cost signal including the charge for descrambling said scrambled signal and a credit signal indicating credit available to the subscriber; and

wherein the determining means process the cost signal with the credit signal to determine whether the subscriber has sufficient credit available to pay for descrambling of said scrambled signal, and provide said enable signal when it is determined that there is sufficient credit available.