High security pay television system - Patent Review 4907273

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Drawing from US Patent 4907273

High security pay television system

Inventor

Wiedemer; John D. (c/o Signal Security Technologies, 1127 Texas Bank & Trust Tower, 6161 Savoy, Houston, TX 77036)

Owner/Assignee

Patent assignment
All assignments

Publication Date

March 6, 1990

Application Number

07/100,243

PAIR File History

Application Data Transaction History
Image File Wrapper Patent Term Fees
Litigation

Filing Date

September 22, 1987

US Classification

380/230 235/382 380/201 380/239 725/2 725/31 725/122

Int'l Classification

H04N 007/167 G06K 005/00

Examiner

Tarcza; Thomas H.

Assistant Examiner

Wallace; Linda J.

Attorney/Law Firm

Quarles & Brady
Address

Parent Case

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of U.S. patent application Ser. No. 660,512 filed Oct. 12, 1984, now U.S. Pat. No. 4,696,034. TECHNICAL FIELD The present invention relates to systems for pay broadcast television in general, and relates, in particular, to a secure scrambling and unscrambling system including a provision for the viewers to be billed only for the actual broadcasts or parts thereof watched by that viewer. BACKGROUND OF THE INVENTION It is becoming increasingly common for pay television systems to be utilized for the transmission of television programming to subscribers who are willing to pay either on a fixed periodic or pay per view basis for the programming. The most common pay television systems presently in use are operated in conjunction with cable system broadcast of television programming, but over-the-air systems also exist. The impetus behind the trend toward pay television broadcast is the need to generate monetary remuneration to program providers more than is normally obtainable through advertiser supported television or to program providers of programs for which the audience is more limited in size. In any pay television broadcast system, however, security needs to be a primary concern in order to ensure that viewers will pay for the programming broadcast rather than being able to gain unauthorized access to the broadcast programming in some fashion without the necessity for paying for the service. Many systems are currently in operation for pay broadcast television, whether in cable or over the air, which include electronic scrambling of the broadcast television signal. Such a system requires a descrambler associated with the television receiving station and the descrambler must be, of course, particularly adapted to descrambling the type of scrambling imposed by the broadcast station on the particular broadcast signal. Usually a particular fixed format of decoder or descrambler is used at each receiving station which will in some fashion modify the broadcast signal in a way exactly complimentary to the way the scrambling device, imposed a scrambling signal on the program signal at the broadcast station, so that the viewer views the complete unscrambled program at his location. The viewer is charged what is, in effect, a rental charge for use of the descrambler and usually this charge is made on a fixed periodic basis, i.e. monthly, regardless of how much programming is watched. One aspect of such systems is that it is possible for unauthorized or "pirate" descramblers to be constructed by persons knowledgeable in electronic design and these unauthorized descramblers can become available legally or illegally to those willing to pay for them. Once a potential viewer has legally or illegally purchased such a descrambler, he then has free and unimpeded access to the scrambled broadcast signals indefinitely. One system which has been utilized to try and avoid the possibility of unauthorized scramblers being obtained and used indefinitely makes use of a numerical code which is operated on by an algorithm to predictably derive either a scrambling or descrambling signal. The broadcast station imposes one polarity of the signal produced by the algorithm as a scrambling signal on the program signal while the receiving station imposes the exact complimentary signal using the same algorithm on the scrambled broadcast signal to descramble the program signal. In such a system it is necessary for the user to find out the code for the particular broadcast since the numerical code must be changed for each broadcast if unauthorized viewing is to be prevented for that broadcast. In the current systems in use, the viewer telephones the central billing station and requests the proper code for the particular broadcast he wishes to watch. The central station gets the identity of the viewer from his telephone call and gives the user the proper code which the user then enters onto a digital entry device contained on the decoding box at his viewing station to properly descramble the broadcast signal. The central station can then bill the viewer based on what programs the viewer has selected the proper code for. Such a system suffers from an obvious deficiency in that once the user knows the code, he can freely transmit that code to other subscribers to the system who have not given their names to the central billing station and the other subscribers may also then use that code to properly descramble and view the broadcast signal without paying for the service. Such a system may also occasionally have problems of access to the central billing facility during peak times when many viewers may call to request access to the proper codes to view particularly popular programs. The more common systems in actual use today involve so-called "addressable" converters. These converters are descramblers located at the viewers station which can be selectively turned on or off by the broadcast station. They are called "addressable" since each descrambler has a unique address or identification which can be called by the broadcast station in turning the converter on or off. Another aspect into which effort has been directed in developing pay television systems is in the method of billing to the subscriber of the system. Many current cable and premium cable channel systems are charged to their subscribers on a fixed monthly basis. It is believed by many in the industry that many additional viewers would subscribe to such systems if they were charged on a pay per view basis rather than on a monthly basis. Unfortunately, few cable or other pay broadcast systems are currently technically able to bill subscribers on a pay per view basis because of either the technical difficulty or practical inconvenience in monitoring actual program viewing. Some systems have been developed and are described in the prior art which are capable of billing pay television subscribers on a pay per view basis. Most of these prior art systems are based on a telephone data linkage between the decoder at the subscribers station and a central billing facility. The decoder is dialed up, or selectively accessed in some other way, by the central billing facility on a periodic, i.e., daily or weekly, basis to cause the decoder to transmit prerecorded viewing log information to the central facility. Such systems are obviously dependent upon a telephone linkage for their competent functioning. Other systems have been attempted in which some recording device is used at the receiving station which is sent to a billing facility to bill the viewer on a pay per view basis. These systems have not, however, had effective means to disable the viewers access to the programming if the viewer has not properly and timely paid his bill. One system has been described, in U.S. Pat. No. 4,081,832, to Sherman, which makes use of a punched card carrying descrambling information thereon and which is also punched by the decoder to record program viewing. Another factor important for consideration in the implementation of pay per view broadcast is the widespread availability and use of video cassette recorders (VCR's) to record programs for later view. Some program materials are, in fact, offered exclusively for home viewing by VCR. A pay per view broadcast system should thus be adapted for use with a VCR. No prior art television broadcast signal scrambling system is presently in actual use which cannot be overcome by a fixed electronic descrambler, if an unauthorized subscriber is willing to spend sufficient time and effort to develop or obtain such a descrambler in some unauthorized fashion. The present system is intended to provide such a system. SUMMARY OF THE INVENTION The present invention is summarized in that a pay television broadcast system includes: a broadcast station having scrambling means for imposing a scrambling signal on the program signal, the scrambling signal being generated through the use of an inverse of a signal generated from pre-selected changeable system code; a plurality of receiving station decoders each including descrambling means for imposing a descrambling signal complimentary to the scrambling signal on the received broadcast signal, the descrambling signal only being generated from the same system code, each receiving station decoder including therein a fixed, station-unique internal code; and a portable digital memory module for each receiving station decoder, each module carrying thereon a fixed, station-unique external code which can be combined with the internal code of the proper receiving station to generate the system code in the receiving station, the memory module being removable from the receiving stations and replaceable so that the system code can be periodically changed. It is the object of the present invention to provide a pay television broadcast system in which the scrambling to the broadcast signal is done in accordance with a numerical code which may be changed periodically and confidentially so as to make it difficult or impossible for a fixed invariable decoder to be developed by any unauthorized persons which could successfully descramble the scrambled broadcast code over any extended period of time. It is another object of the present invention to Provide a pay television broadcast system in which billing information is recorded by the user and transmitted to a central billing facility easily and conveniently without the need for cable or telephone access between the receiving station and a central billing facility. It is yet another object of the present invention to provide a pay television access system which further includes therein a method for attributing a broadcast program viewed by a subscriber to one particular broadcast station of many broadcasting the program and also a method for allowing parental or other selective control of the general content of programs being described and viewed at the receiving station. It is a feature of the present invention that the security and billing features of the system are adaptable for use with VCR's, as well as over-the-air broadcasts. Other objects, advantages and features of the present invention will become apparent from the following specification when taken in conjunction with the accompanying drawings.

Priority Data

USPTO Field of Search

380/3 380/4 380/5 380/7 380/16 380/20 380/21 380/23 380/25 235/379 235/380 235/382 235/382.5 340/825.31 340/825.33 358/84 455/2 455/5

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I claim:

1. A pay television broadcast system comprising

a broadcast station for distribution of programs in live and recorded formats including (1) scrambling means for imposing a scrambling signal on the program signal to create a scrambled broadcast signal, the scrambling signal being the inverse of a signal generated from a pre-selected changeable code, and (2) an encoder to imbed a broadcast code in the broadcast signal, the changeable codes being different for the live and the recorded formats so that the code for live formats broadcasts can be changed more often than the code for the recorded format;

an alterable, reusable memory module for each viewing station carrying the changeable codes thereon;

a receiving station decoder for each receiving station including (1) means for one of the changeable codes from a removable memory module inserted in that decoder, the changeable code being selected to match the program type to be viewed, (2) means for imposing a descrambling signal complementary to the scrambling signal on the received broadcast signal, the descrambling being generated from the changeable code, and (3) writing means for writing information derived from the broadcast code on the memory module, the information indicating whether the broadcast viewed was recorded or live; and

the memory module having pre-written into it information which can be recognized by the receiving station decoder to limit the extent of program descrambling which can occur in the receiving station decoder.

2. The system of claim 1 wherein the memory of the memory module being organized into blocks of fixed size, the information pre-written into the memory module including codes indicating to the receiving station decoder that at least a portion of the blocks are not available for writing information therein so that the amount of programming which may be decoded with a single memory module is limited by the available memory blocks in that particular memory module.

3. The system of claim 2 wherein the codes in the memory module are located at defined locations in each block of memory in the memory module.

4. The system of claim 2 wherein the information pre-written in the memory module also includes a numerical value representing an authorization limit for viewing over the air broadcasts, the broadcast code carrying information as to the program value, and the receiving station accumulating the values of the programs descrambled in the memory module until the limit is reached.

5. The system of claim 2 wherein the codes in the blocks of memory in the memory module also indicate the location of the changeable code carried thereon.

6. The system of claim 5 wherein the code for the recorded format is not changed over time for viewing time-independent broadcasts, with the codes in the memory blocks indicating the nature of the changeable code carried in each block.

7. The system of claim 1 wherein the information written into the memory module includes a numerical value corresponding to a limit on the amount of viewing authorized, and wherein the broadcast code carries information as to the value of any program, the receiving station decoder accumulating the values of the programs descrambled in a memory location in the memory module until the accumulated value reaches the limit after which the decoder will not descramble programming until the removable memory module is replaced.

8. The system of claim 7 wherein the accumulation of values of the programs descrambled is accomplished by decrementing the initial numeral value until it reaches zero.

9. The system of claim 7 wherein the accumulation of values of the programs descrambled is accomplished by successively adding the values in a single location and comparing the accumulated total to the numerical value of the limit until the accumulated value reaches the limit.

10. The system of claim 1 wherein the changeable code in the memory module is a station-unique external code and wherein the receiving station decoder also includes a station-unique internal code, the receiving station decoder combining the internal and the external codes to create the descrambling signal.

11. The system of claim 1 wherein the pre-written information in the billing memory module may be remotely altered by one of (1) a numerical value entered into a keypad on the receiving station, (2) a telephone link to the receiving station and (3) an addressable code carried in the broadcast code.

12. The system of claim 1 wherein the memory module is an electrically alterable read-only memory integrated circuit.

13. In a pay television system, a receiving station signal decoder for a scrambled broadcast signal also containing a broadcast code comprising:

a microprocessor;

a demodulator to derive the broadcast code from the broadcast signal;

an electrically alterable memory module containing at least two pre-written external codes which can be used to generate a systemwide system code, one code used for time-independent programming and one code used for time-dependent programming, and also a portion onto which program information may be entered being pre-written with information to limit the amount of programming which may be descrambled;

means for generating a descrambling signal complementary to the scrambling signal upon input of a proper numerical sequence; and

the microprocessor programmed by a program (1) to read one of the external codes from the memory module, the external code selected being appropriate for the program being broadcast, (2) to operate on the external code to generate the systemwide system code, (3) to generate and output to the descrambling signal generating means a numerical signal generated from the system code, (4) to receive the broadcast from the demodulator (5) to read the information in the memory module as to the limit on the amount of programming which may be viewed and to determine if that limit has been reached, and (6) to write information about the programs actually descrambled, as determined from the broadcast code, in the memory module if the limit has not been reached, so that use of the decoder can be limited by the information pre-written in the memory module.

14. The decoder of claim 13 wherein the broadcast code contains information about the billing charge for the programs which are unscrambled by the receiving station decoder, the information about the billing charges for each program descrambled being accumulated by the microprocessor in the memory module until the limit is reached.

15. The decoder of claim 14 wherein the accumulation of the charge information is accomplished by subtracting the value of the billing charges from the pre-written limit.

16. The decoder of claim 14 wherein the accumulation is accomplished by successively adding the values of the charges for the programs viewed and comparing that value to the pre-written limit.

17. The decoder of claim 13 wherein the memory module also has an area dedicated for writing information derived from the broadcast code therein and the size of the available portion of such area is determined by the information pre-written in the billing module.

18. The decoder of claim 13 wherein the memory of the memory module is arranged in blocks of defined size and wherein the limit of the amount of program descrambling is accomplished by limiting the blocks into which information as to the broadcasts descrambled ma be entered.

19. The decoder of claim 18 wherein the blocks in the memory module are identified by type codes resident in the memory module to segregate the blocks into blocks reserved for entry of information as to programs descrambled, blocks containing external code, and blocks which are unavailable for information entry or reading.

20. A decoder as claimed in claim 13 wherein there is more than one type of external code in the memory module and the particular external code as well as the type to be used for a particular program to be descrambled is selected by a portion of the broadcast code and the block identification code in the memory module.

21. A decoder as claimed in claim 13 wherein the descrambling signal generating means includes a digital to analog converter to convert the numerical output for the microprocessor to an analog descrambling signal.

22. A decoder as claimed in claim 13 wherein the memory module is an electrically alterable read-only memory integrated circuit.

23. A decoder as claimed in claim 13 wherein the information pre-written in the memory module may be remotely altered by information from at least one of (1) a user operable keypad, (2) a telephone link to the receiving station and (3) an addressable code in the broadcast code.