CA1277764C - System for enabling descrambling on a selective- subscription basis in a subscriber communication network - Google Patents
System for enabling descrambling on a selective- subscription basis in a subscriber communication networkInfo
- Publication number
- CA1277764C CA1277764C CA000483413A CA483413A CA1277764C CA 1277764 C CA1277764 C CA 1277764C CA 000483413 A CA000483413 A CA 000483413A CA 483413 A CA483413 A CA 483413A CA 1277764 C CA1277764 C CA 1277764C
- Authority
- CA
- Canada
- Prior art keywords
- signal
- credit
- subscriber
- scrambled
- descrambling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/162—Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
- H04N7/1675—Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
Abstract
SYSTEM FOR ENABLING DESCRAMBLING ON A SELECTIVE-SUBSCRIPTION
BASIS IN A SUBSCRIBER COMMUNICATION NETWORK
ABSTRACT OF THE DISCLOSURE
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 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 signals is changed.
BASIS IN A SUBSCRIBER COMMUNICATION NETWORK
ABSTRACT OF THE DISCLOSURE
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 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 signals is changed.
Description
SYSTEM FOR ENABLING DESCRAMBLING ON A SELECTIVE-SUBSCRIPTION
BASIS IN A SUBSCRIBER COMMUNICATION NETWORK
BACKGROUND OF T~E INVENTION
The present invention generally pertains to de~crambling systems for subscriber communication networks and i8 particularly directed to systems for enabling descrambling on a selective-subscription basis.
Selective-subscription subscriber communication networks provide for descrambling of signals on a prepaid basis and/or on an impulse-purchase basis.
In one type of prepaid descrambling system, a descrambler at the subscriber terminal i~ adapted to descramble all communications received over a given communications channel, such as, for example, all of the programs broadcast over a given television channel. when service is discontinued, the descrambler must be modified to prevent descrambling of signals received over the given channel. In another t~pe of prepaid de~crambling system, descrambling is enabled by an enable signal addressed to the descrambler at the subscriber terminal.
Typical impulse-purcha~e ~ub~criber communication network descrambling systems are described in U. S. Letters Patents Nos. 2,573,349 to Miller et als 2,788,387 to Druzs 2,864,885 to Morris$ 2,866,962 to Ellett; 3,531,586 to Bass et als 3,736,369 to Vogelman et al7 3,916,091 to Kirk, Jr.
et als and 4,130,833 to Chomet.
Bass et al describes an impulse-purchase system for a subscriber television network in which a debit (cost) signal $,~-S ;277764 related to the viewing cost of a given television program is transmitted to each subscriber terminal and processed in relation to an indication of the subscribe~'s established credit to determine whether the subscriber is authorized to view the given program. In the Bas~ et al system subscriber credit iB established in response to the insertion of coins into a coin mechanism included in the subscriber terminal.
If after a sub~criber has accepted a given program for viewing the program is cancelled, such as for technical reasons, a credit signal is transmitted to the subscriber terminals to restore the subscriber's established credit by an appropriate amount.
Druz describes an impul6e-purchase system for a subscriber television network in which a cost signal containing charging information related to the cost of viewing a given program is transmitted to the subscribers and upon acceptance by a ~ub~criber of the program for viewing, the charging information is recorded by a recording device at the ~ub~criber terminal. The recorded charging information is collected or read from the recording device periodically and the subscriber subsequently is billed for the total cost of programs selected for viewing during the previous period, Both of these prior art systems require some type of post-viewing collection rom the subscriber. With the Bass et al system coins must be collected from each individual subscriber's coin mechanism; and with the Druz system the recorded charging information must be collected from each individual subscriber's recording device.
~m~
One object of the present invention is to provide an impulse-purchase descrambling system which enables other payment methods in addition, or alternative, to such post-viewing collection from each individual subscriber terminal.
Another object of the present invention is to provide an impulse-purchase descrambling system that will enable special event television programs transmitted on a given pay-TV channel to be selected for viewing on an impulse-purchase basis by subscribers who do not regularly subscribe to all of the programming on such channel.
Still another object of the present invention is to provide a descrambling system that can be controlled by received signals to either descramble scrambled signals on a prepa~d basis or to offer descrambling on an impulse-purchase basis depending upon the subscription status of thesubscriber and whether the signal is authorized for descrambllng on an impulse-purchase basis.
A further ob~ect of the present invention i8 to provide a system for preventing a sub~criber from being able to enable descrambling in a selective-subscription subscriber communication network through such deceit as substltuting other signals for transmitted signals, such as a cost signal, that are received and processed at the subscriber terminal to enable descrambling.
The present invention provides improved systems for enabling descrambling of a received scrambled signal on an impulse-purchase basis in a subscriber terminal of a ~ubscriber communication network. One improved ~ystem includes a circuit for processing a received cost signal 1~77764 indicating the charge for descrambling the/scrambled signal and a received credit signal indicating^ ~he accumulated credit attributed to the subscriber to determine whether the subscriber has sufficient available credit to pay for descrambling of the scrambled signal, and for providing a credit-available signal when it is determined that there is su~ficient credit availableS a device that is 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 basist a dèvice which is enabled in response to the credit-available signal, for accepting said option and for providing an accepted signal upon acceptanceS and a circuit that is responsive to the accepted signal for enabling the scrambled signal to be descrambled.
The credit signal may indicate accumulated payments made by the subscriber and/or credit extended to the subscriber in advance of the signal being descrambled on an impulse-purchase basi~. This system does not require post-use collection of money or charge information from eachindividual subscriber terminal as with the prior art systems described hereinabove.
In a separate aspect, the present invention provides a system for descrambling scrambled signals on a prepald basis. This system includes a circuit for comparing a received mask signal related to the scrambled signal with a received authorization signal addressed to the subscriber terminal and indica~ing whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis and ~or providing a prepaid signal when the compared signals .
1 27r7~76~
match to a pre~cribed degrees and a circuit that is respon~ive to the prepaid signal for enabling the scrambled signal to be descrambled. This prepaid descrambling system iB compatible with the impulse-purchase descrambling system of the pre~ent invention such that both can be combined in a single system.
Such a combined system includes a circuit for comparing a received mask signal uniquely related to the scrambled signal with a received authorization signal indicating whether the subscriber i8 authorized to descramble the scrambled signal on a prepaid basis, and for providing a prepaid signal when the compared signals match to a prescrlbed degree and a not-prepaid signal when they do not match. This combined system further includes a circuit for proce~sing a received cost signal indicating the charge for descrambling the scrambled signal and a credit signal related to the subscr$ber's available credlt to determine whether the ~ubscriber has sufficient available credit to pay for descrambllng of the scrambled slgnal, and for providing a credit-available signal when it is determined that there is sufficient credit available; a device that is responsive to both the not-prepaid signal and the credit-available signal for indicating that the sub~criber has the option of causing the signal to be de~crambled on an impul~e-purchase basis a device which is enabled in response to both the not-prepaid signal and the credit available signal for the subscriber to operate to accept such option, and for providing an accepted signal upon acceptance; and a circuit that is responsive to the accepted signal for enabling th,e scrambled signal to be descrambled.
This system is particularly useful for enabling special event television programs transmitted on a given pay-TV
channel to be selected for viewing on an lmpulse-purchase basis by subscribers who do not regularly subscribe to all S of the programming on such channel. For such an application the authorization signal addressed to a given subscriber who regularly subscribes to all of the programming on the given pay-TV channel matches the mask signal to the prescribed degree. Since the regular subscriber receives all of the programs on the given channel there is no need for the impulse-purchase option to be made available for such subscriber. To provide a service wherein only certain special event programs are made available to the nonregular subscribers on an impulse-purchase basis, an impulse-purchase signal i8 included in the mask signal that is uniquely related to,scrambled special event programs, and the option of Causing the ~crambled ~ignal to be de~crambled is indicated to the subscriber and the acceptance device is enabled only when an impulse-purchase signal related to the acrambled signal is included in the mask signal that is received by the subscriber terminal.
Preferably, prepaid status i~ indicated by providing a "TRUE" bit in a given bit position of the authorizatlon signal. Other bit positions may be used for other 2S authorization functions. Since the bit-length of the authorization signal may be less than the number of authorization function~ and programs and/or channels for which prepaid service may be indicated, each subscriber terminal includes a memory for storing a plurality of the authorization signals,and for provlding a ~elected one of iZ~764 --7~
the stored authorization signals for comparison with the mask signal in response to an address signal received with the mask signal.
Still another improved system prevents a subscriber from being able to enable descrambling through such deceit as ~ubstituting other signals for transmitted signals, such as cost and credit signals, that are received and processed at the subscriber terminal to enable descrambling. This system is particularly useful in a subscriber communication network in which selective remote descrambling of the scrambled signal is controlled through the use of key signals, including encrypted key signals that are transmitted to the subscriber terminal and that must be decrypted in the subscriber terminal to enable the scrambled signal to be descrambled. This prevention system includes a circuit for encoding one or more of the key signals prior to encrypting a ~aid key signal and/or prior to u~ing a said key signal to encrypt another ~aid key signal by proce~sing ~ald one or more ~aid key ~ignal~ with the cost signal, and the credit ~ignal and/or the mask ~ignal and the authorization ~ignal prior to the transmis~ion of the encrypted key signalss and a circuit in each subscriber terminal for decoding the one or more of the key signals following decryption thereof, and/or prior to use thereof for keying decryption of a said encrypted key ~ignal by processing said key ~ignals with the re~pective cost signal and credit signal and/or mask signal and authorization signal u~ed to encode the one or more of the key signals.
Changing any of the credit signal, cost signal, ma~k ~ignal or authorization ~ignal prevents decryption of the key ' ,: ' ' ''. . " : ", .:,, i, ,.: ~, , - , . .
8 72046~7 sis~nals and thereby prevents descrambling.
Also disclosed is a system in a subscriber communication network for verlfying charge lnformation furnished to a broadcast company by a given subscriber and purported by the subscriber as having been displayed at the subscriber terminal. At the subscriber terminal there is generated a debit signal indicating the charges attributed to the subscriber terminal; and in response to the debit signal, a display of lnformation indicating the accumulated charges is provided to the subscriber. An authentication signal is provided at the subscriber terminal by processing the debit slgnal in accordance with an encryption algorithm upon the algorithm being keyed by a key slgnal that ls unique to the sub~crlher terminal; ~nd ln respon~e to the aut~entication ~lgnal, a dlsplay of informatlon repre~entative of the authenticatlon signal 1B provided to the subscriber. The subscrlber copies the displayed information and sends it to the broadcast company with his periodic bill payment. At the broadcast company the information furnished by the given subscriber that purportedly ls the displayed charges lnformation and the authentication information is entered in a processing system and converted into a received debit signal and a received authentication signal respectively. The received debit slgnal is processed wlth the received authentication signal to determine whether the information furnished by the given ~ubscrlber wa~
authentic.
Additional features of the present invention are descrlbed in relation to the description of the preferred embodlment.
~Z77764 _9_ 72046-7 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a combination functional and flow block diagram of an authorization processor embodying the systems of the present invention.
Figure 2 is a functional block diagram of a key signal encryption system included in broadcast terminal of a subscriber communication network including the system of the present invention.
Figure 3 is a functional block diagram of a key signal decryption system included in a subscriber terminal that includes the authorization processor of Figure 1.
Figure 4 is a functional block diagram of an infor-~ation processor which provides the credit signals that are transmitted to the respective subscriber terminals in the sys~em of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the present invention is included in an authorization processor which is described with reference to Figure 1. The authorization processor is included in a subscriber terminal in a subscriber television network, such as ~s described in Canadian Patent Application No. 454,444 filed May 16, 1984 by Klein S. Gilhousen and Charles F. Newby for "KEY SIGNAL ENCRYPTION AND DISTRIBUTION SYSTEM FOR CONTRO-LLING SCRAMBLING AND SELECTIVE REMOTE DESCRAMBLING OF TELEVISION
SIGNAL5." The authorization processor of Figure 1 enables 1*7776~
-9a- 72046-7 descrambling of a received scrambled television signal on an impulse-purchase or a prepaid basis.
The authorization processor receives a program cost signal on line 10 and a credit signal on line 11. The cost ~1.~7~4 signal indicates the charge for descrambling a given received scrambled television signal, and is provided to all of the subscriber terminals in the subscriber television network. Credit signals are unique to each subscriber and they are individually addressed to the respective subscriber terminals in the network. Each credit signal indicates the accumulated credit attributed to the respective individual subscriber.
The authorization processor includes a credit register 12, an overflow detection device 13, a debit register 14, an add register 15 and a comparison unit 16. The credit register 12 registers the credit signal received on line 11.
The debit register 14 registers the accumulated charges for scrambled signals accepted by the respective individual subscriber for de6crambling. The add register 15 adds and registers the sum of the charge indicated by the program cost signal on line 10 and the accumulated charges registered in the debit register 14. The comparlson unit 16 compares the credit signal registered in the credit register 12 with the sum of the addition registered in the add register 15 to determine whether the sub~criber has sufficient credit available to pay for de~crambling of the scrambled signal. If upon such comparison it is determined that the accumulated credit indicated by the credit signal registered in the credit register 12 is not less than the sum of the addition registered in the add register 15, a credit-available signal is provided on line 17 to a display driver and logic circuit 19. If upon such comparison it is determined that such accumulated credit is less than such 8um, an insufficient credit signal is provided on line 20 to 1~77764 the display driver and logic circuit 19.
The display driver and logic circuit 19 provides ~ignals on line 21 for controlling the content of a display on a video monitor display device 22, such as the television set that is attached to the subscriber terminal.
Alternatively, the display device 22 can be an alphanumeric display on the ~ront panel of the descrambler unit.
The authorization processor also receives a program mask signal on lines 23 and an authorization word signal on lines 24. The program mask signal is a 56-bit digital signal that is unique to each scrambled program that is broadcast over the subscriber television network. The program mask signal is provided to all of the subscriber terminals in the network, The authorization word signal i8 a 56-bit word lS signal that is individually addressed to the respective individual subscriber terminals in the network. If the re~pective subscriber regularly rece~ve~ all of the scrambled program~ on the given TV channel, the authoriæation word signal addressed to the respective ~ubscriber terminal will match the program mask signal that is provided to all of the subscriber terminals in the network to the prescribed degree. If the respective subscriber is not a regular subscriber to all of the scrambled programs on the given channel, the authorization word addressed to the respective subscriber terminal and received on lines 24 does not match the program mask signal that is received on lines 23.
The authorization processor includes a second comparison unit 25, which compares the received program mask signal on lines 23 with the received authorization word 1;~77764 signal on lines 24. When the compared signals do not match to the prescribed degree, a not-prepald signal is provided on line 26 to the display driver and logic circuit l9. When the compared signals do match, a prepaid signal is provided on line 27 to an enable gate 29.
The comparison unit 25 i~ logically AND's the corresponding bits from the program mask signal on line 23 with the authorization word signal on line 24 and then logically OR's the results of the logical AND operation. A
match in any one of the corresponding pairs of bits results in the prepaid signal being provided on line 27. Typically the different bit positions in the authorization word signal correspond to different TV channels and/or programs. Thus an authorization word signal for a given descrambler includes a "TRUE" bit in the bit position designated for each program and/or channel for which service has been prepaid. The program mask signal include8 a T~UE blt in each posltion corre8pond~ng to a given program and/or channel.
One of the bits of the program mask signal on line 23 indicates whether the received scrambled television signal may be descrambled on an impulse-purchase basis. When it may be 80 descrambled, an impulse-purchase signal is provided in this bit position and is provided on line 30 to the display driver and logic circuit 19.
Certain bits of the program mask signal and the authorization word signal may provide additional authorization functlons, such as stereo audio enable, remote control enable and alternate language selection.
.
.
1~76~
The display driver and logic 19 circuit contains logic circuitry which dictates the content of the signals that are provided on line 21 to the display device 22. When a credit-available signal i8 provided on line 17, a not-prepaid signal is provided on line 26 and an impulse-purchase ~ignal is provided on 30, the display driver and logic circuit 19, provides an enabling signal on line 31 to an acceptance ~witch 32 and further provides a signal on line 21 that results in the display device 22 displaying an indication to the subscriber that the subscriber has the option of causing the scrambled television signal to be displayed on an impulse-purchase basis.
The ~ubscriber may indicate acceptance of the option by operating the switch 32 only when the switch 32 is enabled by the enabling signal on line 31. If the subscriber so accepts the option, an accepted ~ignal i~ provided on llne 33 to the enable gate 29, The accepted ~ignal on llne 33 also is provided to the display driver and logic circuit 19, which respond~ thereto by causing the display device 22 to briefly indicate acknowledgement of the subscriber's acceptance. Thereafter, the de~crambled television signal is displayed on the given TV channel. If the subscriber indicates by operation of the switch 32 that the option is not accepted, a signal i8 provided on line 34 to the di~play driver and logic circuit 19, which responds thereto by causing the display device 22 to briefly indicate acknowledgement of the subscriber's non-acceptance.
Thereafter, only a blank screen signal is displayed on the given TV channel. The display driver and logic circult 19 responds to the insufficient credit signal on line 20 by . .
BASIS IN A SUBSCRIBER COMMUNICATION NETWORK
BACKGROUND OF T~E INVENTION
The present invention generally pertains to de~crambling systems for subscriber communication networks and i8 particularly directed to systems for enabling descrambling on a selective-subscription basis.
Selective-subscription subscriber communication networks provide for descrambling of signals on a prepaid basis and/or on an impulse-purchase basis.
In one type of prepaid descrambling system, a descrambler at the subscriber terminal i~ adapted to descramble all communications received over a given communications channel, such as, for example, all of the programs broadcast over a given television channel. when service is discontinued, the descrambler must be modified to prevent descrambling of signals received over the given channel. In another t~pe of prepaid de~crambling system, descrambling is enabled by an enable signal addressed to the descrambler at the subscriber terminal.
Typical impulse-purcha~e ~ub~criber communication network descrambling systems are described in U. S. Letters Patents Nos. 2,573,349 to Miller et als 2,788,387 to Druzs 2,864,885 to Morris$ 2,866,962 to Ellett; 3,531,586 to Bass et als 3,736,369 to Vogelman et al7 3,916,091 to Kirk, Jr.
et als and 4,130,833 to Chomet.
Bass et al describes an impulse-purchase system for a subscriber television network in which a debit (cost) signal $,~-S ;277764 related to the viewing cost of a given television program is transmitted to each subscriber terminal and processed in relation to an indication of the subscribe~'s established credit to determine whether the subscriber is authorized to view the given program. In the Bas~ et al system subscriber credit iB established in response to the insertion of coins into a coin mechanism included in the subscriber terminal.
If after a sub~criber has accepted a given program for viewing the program is cancelled, such as for technical reasons, a credit signal is transmitted to the subscriber terminals to restore the subscriber's established credit by an appropriate amount.
Druz describes an impul6e-purchase system for a subscriber television network in which a cost signal containing charging information related to the cost of viewing a given program is transmitted to the subscribers and upon acceptance by a ~ub~criber of the program for viewing, the charging information is recorded by a recording device at the ~ub~criber terminal. The recorded charging information is collected or read from the recording device periodically and the subscriber subsequently is billed for the total cost of programs selected for viewing during the previous period, Both of these prior art systems require some type of post-viewing collection rom the subscriber. With the Bass et al system coins must be collected from each individual subscriber's coin mechanism; and with the Druz system the recorded charging information must be collected from each individual subscriber's recording device.
~m~
One object of the present invention is to provide an impulse-purchase descrambling system which enables other payment methods in addition, or alternative, to such post-viewing collection from each individual subscriber terminal.
Another object of the present invention is to provide an impulse-purchase descrambling system that will enable special event television programs transmitted on a given pay-TV channel to be selected for viewing on an impulse-purchase basis by subscribers who do not regularly subscribe to all of the programming on such channel.
Still another object of the present invention is to provide a descrambling system that can be controlled by received signals to either descramble scrambled signals on a prepa~d basis or to offer descrambling on an impulse-purchase basis depending upon the subscription status of thesubscriber and whether the signal is authorized for descrambllng on an impulse-purchase basis.
A further ob~ect of the present invention i8 to provide a system for preventing a sub~criber from being able to enable descrambling in a selective-subscription subscriber communication network through such deceit as substltuting other signals for transmitted signals, such as a cost signal, that are received and processed at the subscriber terminal to enable descrambling.
The present invention provides improved systems for enabling descrambling of a received scrambled signal on an impulse-purchase basis in a subscriber terminal of a ~ubscriber communication network. One improved ~ystem includes a circuit for processing a received cost signal 1~77764 indicating the charge for descrambling the/scrambled signal and a received credit signal indicating^ ~he accumulated credit attributed to the subscriber to determine whether the subscriber has sufficient available credit to pay for descrambling of the scrambled signal, and for providing a credit-available signal when it is determined that there is su~ficient credit availableS a device that is 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 basist a dèvice which is enabled in response to the credit-available signal, for accepting said option and for providing an accepted signal upon acceptanceS and a circuit that is responsive to the accepted signal for enabling the scrambled signal to be descrambled.
The credit signal may indicate accumulated payments made by the subscriber and/or credit extended to the subscriber in advance of the signal being descrambled on an impulse-purchase basi~. This system does not require post-use collection of money or charge information from eachindividual subscriber terminal as with the prior art systems described hereinabove.
In a separate aspect, the present invention provides a system for descrambling scrambled signals on a prepald basis. This system includes a circuit for comparing a received mask signal related to the scrambled signal with a received authorization signal addressed to the subscriber terminal and indica~ing whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis and ~or providing a prepaid signal when the compared signals .
1 27r7~76~
match to a pre~cribed degrees and a circuit that is respon~ive to the prepaid signal for enabling the scrambled signal to be descrambled. This prepaid descrambling system iB compatible with the impulse-purchase descrambling system of the pre~ent invention such that both can be combined in a single system.
Such a combined system includes a circuit for comparing a received mask signal uniquely related to the scrambled signal with a received authorization signal indicating whether the subscriber i8 authorized to descramble the scrambled signal on a prepaid basis, and for providing a prepaid signal when the compared signals match to a prescrlbed degree and a not-prepaid signal when they do not match. This combined system further includes a circuit for proce~sing a received cost signal indicating the charge for descrambling the scrambled signal and a credit signal related to the subscr$ber's available credlt to determine whether the ~ubscriber has sufficient available credit to pay for descrambllng of the scrambled slgnal, and for providing a credit-available signal when it is determined that there is sufficient credit available; a device that is responsive to both the not-prepaid signal and the credit-available signal for indicating that the sub~criber has the option of causing the signal to be de~crambled on an impul~e-purchase basis a device which is enabled in response to both the not-prepaid signal and the credit available signal for the subscriber to operate to accept such option, and for providing an accepted signal upon acceptance; and a circuit that is responsive to the accepted signal for enabling th,e scrambled signal to be descrambled.
This system is particularly useful for enabling special event television programs transmitted on a given pay-TV
channel to be selected for viewing on an lmpulse-purchase basis by subscribers who do not regularly subscribe to all S of the programming on such channel. For such an application the authorization signal addressed to a given subscriber who regularly subscribes to all of the programming on the given pay-TV channel matches the mask signal to the prescribed degree. Since the regular subscriber receives all of the programs on the given channel there is no need for the impulse-purchase option to be made available for such subscriber. To provide a service wherein only certain special event programs are made available to the nonregular subscribers on an impulse-purchase basis, an impulse-purchase signal i8 included in the mask signal that is uniquely related to,scrambled special event programs, and the option of Causing the ~crambled ~ignal to be de~crambled is indicated to the subscriber and the acceptance device is enabled only when an impulse-purchase signal related to the acrambled signal is included in the mask signal that is received by the subscriber terminal.
Preferably, prepaid status i~ indicated by providing a "TRUE" bit in a given bit position of the authorizatlon signal. Other bit positions may be used for other 2S authorization functions. Since the bit-length of the authorization signal may be less than the number of authorization function~ and programs and/or channels for which prepaid service may be indicated, each subscriber terminal includes a memory for storing a plurality of the authorization signals,and for provlding a ~elected one of iZ~764 --7~
the stored authorization signals for comparison with the mask signal in response to an address signal received with the mask signal.
Still another improved system prevents a subscriber from being able to enable descrambling through such deceit as ~ubstituting other signals for transmitted signals, such as cost and credit signals, that are received and processed at the subscriber terminal to enable descrambling. This system is particularly useful in a subscriber communication network in which selective remote descrambling of the scrambled signal is controlled through the use of key signals, including encrypted key signals that are transmitted to the subscriber terminal and that must be decrypted in the subscriber terminal to enable the scrambled signal to be descrambled. This prevention system includes a circuit for encoding one or more of the key signals prior to encrypting a ~aid key signal and/or prior to u~ing a said key signal to encrypt another ~aid key signal by proce~sing ~ald one or more ~aid key ~ignal~ with the cost signal, and the credit ~ignal and/or the mask ~ignal and the authorization ~ignal prior to the transmis~ion of the encrypted key signalss and a circuit in each subscriber terminal for decoding the one or more of the key signals following decryption thereof, and/or prior to use thereof for keying decryption of a said encrypted key ~ignal by processing said key ~ignals with the re~pective cost signal and credit signal and/or mask signal and authorization signal u~ed to encode the one or more of the key signals.
Changing any of the credit signal, cost signal, ma~k ~ignal or authorization ~ignal prevents decryption of the key ' ,: ' ' ''. . " : ", .:,, i, ,.: ~, , - , . .
8 72046~7 sis~nals and thereby prevents descrambling.
Also disclosed is a system in a subscriber communication network for verlfying charge lnformation furnished to a broadcast company by a given subscriber and purported by the subscriber as having been displayed at the subscriber terminal. At the subscriber terminal there is generated a debit signal indicating the charges attributed to the subscriber terminal; and in response to the debit signal, a display of lnformation indicating the accumulated charges is provided to the subscriber. An authentication signal is provided at the subscriber terminal by processing the debit slgnal in accordance with an encryption algorithm upon the algorithm being keyed by a key slgnal that ls unique to the sub~crlher terminal; ~nd ln respon~e to the aut~entication ~lgnal, a dlsplay of informatlon repre~entative of the authenticatlon signal 1B provided to the subscriber. The subscrlber copies the displayed information and sends it to the broadcast company with his periodic bill payment. At the broadcast company the information furnished by the given subscriber that purportedly ls the displayed charges lnformation and the authentication information is entered in a processing system and converted into a received debit signal and a received authentication signal respectively. The received debit slgnal is processed wlth the received authentication signal to determine whether the information furnished by the given ~ubscrlber wa~
authentic.
Additional features of the present invention are descrlbed in relation to the description of the preferred embodlment.
~Z77764 _9_ 72046-7 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a combination functional and flow block diagram of an authorization processor embodying the systems of the present invention.
Figure 2 is a functional block diagram of a key signal encryption system included in broadcast terminal of a subscriber communication network including the system of the present invention.
Figure 3 is a functional block diagram of a key signal decryption system included in a subscriber terminal that includes the authorization processor of Figure 1.
Figure 4 is a functional block diagram of an infor-~ation processor which provides the credit signals that are transmitted to the respective subscriber terminals in the sys~em of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the present invention is included in an authorization processor which is described with reference to Figure 1. The authorization processor is included in a subscriber terminal in a subscriber television network, such as ~s described in Canadian Patent Application No. 454,444 filed May 16, 1984 by Klein S. Gilhousen and Charles F. Newby for "KEY SIGNAL ENCRYPTION AND DISTRIBUTION SYSTEM FOR CONTRO-LLING SCRAMBLING AND SELECTIVE REMOTE DESCRAMBLING OF TELEVISION
SIGNAL5." The authorization processor of Figure 1 enables 1*7776~
-9a- 72046-7 descrambling of a received scrambled television signal on an impulse-purchase or a prepaid basis.
The authorization processor receives a program cost signal on line 10 and a credit signal on line 11. The cost ~1.~7~4 signal indicates the charge for descrambling a given received scrambled television signal, and is provided to all of the subscriber terminals in the subscriber television network. Credit signals are unique to each subscriber and they are individually addressed to the respective subscriber terminals in the network. Each credit signal indicates the accumulated credit attributed to the respective individual subscriber.
The authorization processor includes a credit register 12, an overflow detection device 13, a debit register 14, an add register 15 and a comparison unit 16. The credit register 12 registers the credit signal received on line 11.
The debit register 14 registers the accumulated charges for scrambled signals accepted by the respective individual subscriber for de6crambling. The add register 15 adds and registers the sum of the charge indicated by the program cost signal on line 10 and the accumulated charges registered in the debit register 14. The comparlson unit 16 compares the credit signal registered in the credit register 12 with the sum of the addition registered in the add register 15 to determine whether the sub~criber has sufficient credit available to pay for de~crambling of the scrambled signal. If upon such comparison it is determined that the accumulated credit indicated by the credit signal registered in the credit register 12 is not less than the sum of the addition registered in the add register 15, a credit-available signal is provided on line 17 to a display driver and logic circuit 19. If upon such comparison it is determined that such accumulated credit is less than such 8um, an insufficient credit signal is provided on line 20 to 1~77764 the display driver and logic circuit 19.
The display driver and logic circuit 19 provides ~ignals on line 21 for controlling the content of a display on a video monitor display device 22, such as the television set that is attached to the subscriber terminal.
Alternatively, the display device 22 can be an alphanumeric display on the ~ront panel of the descrambler unit.
The authorization processor also receives a program mask signal on lines 23 and an authorization word signal on lines 24. The program mask signal is a 56-bit digital signal that is unique to each scrambled program that is broadcast over the subscriber television network. The program mask signal is provided to all of the subscriber terminals in the network, The authorization word signal i8 a 56-bit word lS signal that is individually addressed to the respective individual subscriber terminals in the network. If the re~pective subscriber regularly rece~ve~ all of the scrambled program~ on the given TV channel, the authoriæation word signal addressed to the respective ~ubscriber terminal will match the program mask signal that is provided to all of the subscriber terminals in the network to the prescribed degree. If the respective subscriber is not a regular subscriber to all of the scrambled programs on the given channel, the authorization word addressed to the respective subscriber terminal and received on lines 24 does not match the program mask signal that is received on lines 23.
The authorization processor includes a second comparison unit 25, which compares the received program mask signal on lines 23 with the received authorization word 1;~77764 signal on lines 24. When the compared signals do not match to the prescribed degree, a not-prepald signal is provided on line 26 to the display driver and logic circuit l9. When the compared signals do match, a prepaid signal is provided on line 27 to an enable gate 29.
The comparison unit 25 i~ logically AND's the corresponding bits from the program mask signal on line 23 with the authorization word signal on line 24 and then logically OR's the results of the logical AND operation. A
match in any one of the corresponding pairs of bits results in the prepaid signal being provided on line 27. Typically the different bit positions in the authorization word signal correspond to different TV channels and/or programs. Thus an authorization word signal for a given descrambler includes a "TRUE" bit in the bit position designated for each program and/or channel for which service has been prepaid. The program mask signal include8 a T~UE blt in each posltion corre8pond~ng to a given program and/or channel.
One of the bits of the program mask signal on line 23 indicates whether the received scrambled television signal may be descrambled on an impulse-purchase basis. When it may be 80 descrambled, an impulse-purchase signal is provided in this bit position and is provided on line 30 to the display driver and logic circuit 19.
Certain bits of the program mask signal and the authorization word signal may provide additional authorization functlons, such as stereo audio enable, remote control enable and alternate language selection.
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1~76~
The display driver and logic 19 circuit contains logic circuitry which dictates the content of the signals that are provided on line 21 to the display device 22. When a credit-available signal i8 provided on line 17, a not-prepaid signal is provided on line 26 and an impulse-purchase ~ignal is provided on 30, the display driver and logic circuit 19, provides an enabling signal on line 31 to an acceptance ~witch 32 and further provides a signal on line 21 that results in the display device 22 displaying an indication to the subscriber that the subscriber has the option of causing the scrambled television signal to be displayed on an impulse-purchase basis.
The ~ubscriber may indicate acceptance of the option by operating the switch 32 only when the switch 32 is enabled by the enabling signal on line 31. If the subscriber so accepts the option, an accepted ~ignal i~ provided on llne 33 to the enable gate 29, The accepted ~ignal on llne 33 also is provided to the display driver and logic circuit 19, which respond~ thereto by causing the display device 22 to briefly indicate acknowledgement of the subscriber's acceptance. Thereafter, the de~crambled television signal is displayed on the given TV channel. If the subscriber indicates by operation of the switch 32 that the option is not accepted, a signal i8 provided on line 34 to the di~play driver and logic circuit 19, which responds thereto by causing the display device 22 to briefly indicate acknowledgement of the subscriber's non-acceptance.
Thereafter, only a blank screen signal is displayed on the given TV channel. The display driver and logic circult 19 responds to the insufficient credit signal on line 20 by . .
3 2777t~4 causing the display device 22 to briefly indicate that the subscriber's credit is insufficient to enable descrambling of the scrambled signa]. Alternatively the display may provide a continuous indication that the program is not authorized because either it is not prepaid or because sufficient credit is not available.
The accepted signal on line 33 is further provided to the enter enable input of the debit register 14 and causes the sum registered in the add register 15 to be entered into the debit register 14, thereby effectively incrementing the accumulated charges in the debit register 14 by the charge indicated by the program cost signal received on line 10.
The overflow detection device 13 is coupled to the add register 15 for detecting when the arithmetic limit of the debit register 14 would be exceeded by incrementing the accumulated charge~ in the debit register 14 by the charge indicated by the program co~t ~ignal on line 10 and for providing an overflow ~ignal on line 18 upon said detection.
The display driver and logic circuit 19 responds to the overflow signal on line 18 by preventing an enabling signal from otherwise belng provided on line 31 in response to a credit-available signal on line 17. This eature is provided in order to prevent a ~ubscriber from feeding fal~e co~t and credit signals into the authentication processor in order to increment the debit register 14 until it overflows to thereby store an amount less than the actual accumulated charges attributed to the subscriber terminal.
Whenever either the prepaid signal is provided on line 27 or the accepted signal iB provided on line 33 to the enable gate input line 35, the enable gate 29 provides a , ~777S4 decrypted and decoded channel key signal from line 36 onto line 37 and thereby enable~ the scrambled television signal to be de~crambled. The significance of passing this key signal onto line 37 is explalned somewhat later below with reference to Figures 2 and 3.
Figure 2 and 3 respectively ~how the encryption and decryption systems included in the broadcast terminal and each subscriber tèrminal of a subscrlber television network with which the system~ of the present invention are particularly useful. The encryption and decryption systems of Figures 2 and 3 are especially adapted to prevent a subscriber from being able to enable descrambling of the scrambled signal through deceit by substituting other ~ignal~ for one or more of the respective transmitted program mask signal, authorization word signal, program cost signal and credit signal recelved by the subscriber terminal in order to obtain a match upon ~aid comparison and/or to cau~e a credit-available signal to be provided when in fact the sub~criberls credit iB inadequate.
Referring to the encryption system of the broadcast terminal (Figure 2) a keystream generator 39 produce~ a keystream signal on line 40 that i8 used to scramble the television signal. An identical keystream ~ignal must be reproduced on line 42 by the keystream generator 44 in the decryption system of the subscriber terminal (Figure 3) in order for the descrambler in the subscriber terminal to be able to descramble the ~crambled television signal.
Referring again to Figure 2, the keystream generator 39 of the encryption system generates the keystream signal on line 40 by processing an initialization vector (IV) frame : ;. .; : . .
.,' . ~ ~ ~. ........ ..
:: -count signal on line 45 in accordance with the Data Encryption Standard (DES) algorithm upon the algorithm being keyed by a working key signal on line 46.
~ working key generator 47 generate6 the working key ~ignal on line 46 by processing the frame count signal on line 45 in accordance with the DES algorithm upon the algorithm being keyed by a channel key signal on line 49.
The channel key signal on line 49 is provided by a control computer ~not shown) at the broadcast terminal.
The channel key signal on line 49 is encrypted for transmission to the subscriber terminals. A channel key generator 50 encrypts the channel key signal by generating an encrypted channel key signal on line 51 by processing an encoded channel key signal on line 52 in accordance with the DES algorithm upon the algorithm being keyed by an encoded category key signal on line 54.
Incident to the scheme for preventing descrambling by deceit through 8ub~titution of one or more of the program mask ~ignal, the authorization word signal, the program cost signal and the credit ~ignal, the program mask signal on line 55 i8 used to encode the channel key signal on line 49 by exclusive- OR'ing the channel key ~ignal on line 49 with the program mask signal on line 55 to provide the encoded channel key signal on line 52. Incident to the same scheme the encoded category key signal on line 54 i8 produced by exclusive-OR'ing a category key signal provided on line 56 by the control computer with a program cost signal provided on line 57 by the control computer. The program cost slgnal on line 57 also is provided by the control computer.
i~7~4 The symbols 59, 60, 61 and 62 in Figure 2 represent exclusive-OR logic elements.
The category key signal on line 56 also is encrypted for tran~mission to the ~ubscriber terminals. Prior to such encryptlon the category key signal on line 56 is encoded by being exclusive-OR'd with a credit signal provided on line 64 by the control computer to thereby provide an encoded category key signal on line 65. This is incident to the aforementioned prevention scheme.
The position of the bits of the category key signal on line 56 that are exclusive-OR'd with the credit signal on line 64 must be different from the position of the bits of the category key 6ignal on line 56 that are exclusive-OR'd with the program cost signal on line 57. The derivation of the credit ~ignal is described below with reference to Figure 4.
A category key generator 65 encrypts the category key ~lgnal by ~eneratlng a plurallty of unlque encrypted category key slgnal~ on line 67 by proces~ing the encoded category key signal on line 65 in accordance with the DES
algorlthm upon the algorithm being keyed by a corresponding plurality of encoded unique ~ubscriber key 6ignal6 on line 69. The sub~criber key signal~ are unique to the individual subscriber terminals.
A plurality of unique subscriber key signals are provided on line 70 from a sub~criber key storage memory 71 upon the memory 71 being acces6ed by a plurality of respective subscriber addre6ses provided on line 72 by the control computer. The subscriber key signals on line 70 are exclu~ive-OR'd with an authorization word ~gnal provided on ~27776~
line 74 by the control computer to provide the encoded subscriber key ~ignal~ on line 69. The authorization word signal on line 74 that i8 used for encoding the subscriber key signal on line 70 either matches or doesn't match the program mask signal on line 55 in accordance with whether the subscriber terminal corresponding to the individual subscriber key slgnal being decoded is assigned to a subscriber who is a regular subscriber to all of the programs on the given TV channel. The use of the authorization word signals on line 77 also is incident to the aforementioned prevention scheme.
The control computer also provides a subscriber key generation number on line 75 that is unique to the broadcaster.
The combination of the credit signal on line 64, the encrypted category key signal on line 67, the subscriber address on line 72, and the authorization word ~ignal on line 74 that all pertain to a given ~ub~criber terminal are transmitted together as a category rekey message that is addressed to the given subscrlber terminal by the subscriber address included in such me~sage. Accordlngly, unique category rekey mes~ages are transmitted to each of the subscriber terminals.
When the number of alternative authorization functions and the number of alternative programs and/or channels that are provided to the subscribers over the network exceeds the 56 bit positions of the authorization word signals are provided and included in separate re~pective category rekey mes~age addressed to each given subscriber terminal, where they are stored upon receipt.
~77764 The program mask signal on line 55, the encry~ted Ghannel key signal on line 51 and the program cost signal on 1ine 57 pertain to all of the subscriber terminals and are transmitted together as a channel rekey message to all of the subscriber terminals. The channel rekey message also contains a category rekey address signal on line 76 for selecting one of the stored category rekey messages from st~rage in the subscriber terminal in accordance with which programs and/or channels and authorization functions are indicated by TRUE bits in the res-pective bit positions of the program mask signal on line 55.
The frame count signal on line 45 and the subscriber key generation number on line 75 also are transmitted to all of the sub8criber terminals.
The encryption system of Figure 2, the manner in which the frame count signal, the channel rekey message, the category rekey messages and the subscriber key generation number are further processed prior to transmission; and the use of the keystream sianal for scrambling the television signal are described in greater detail in the aforementioned Canadian Patent Application No. 454,444.
The decryption system of each subscriber terminal, as shown in Figure 3, includes an authorization processor 77, a rekey message memory 78 and the enable gate 29. The authorization processor 77 is as described above with reference to Figure 1. The rekey message memory 78 stores all of the different rekey messages addressed to the given subscriber termin-al.
12~7764 -19a- 72046-7 The decryption system of each subscriber terminal receives the frame count signal on line 79, the program ~,, `
, :
~ :, ':
~, ' ~Z~764 mask signal on line 23, the encrypted channel key signal on line 80, the program cost signal on line 10, the credit signal on line 11, the encrypted category key signal on line 81, the authorization word signal on line 24 and the S ~ubscriber key generation number on line 82, and the category rekey address signal on line 83. The credit signal on line 11, the encrypted category key signal on line 81 and the authorization word signal on line 24 are retrieved from the storage location of the memory 78 that is accessed by the address signal on line 83.
The received subscriber key generation number on line 82 is combined with the subscribe address on line 84 from a subscriber address memory 85 to provide a subscriber key generation signal on line 86.
Two bits in a given position of the received subscriber key generation number on line 82 are also provided on line 87 to access a given address in a subscriber key seed memory 88. The memory 88 store~ four sub~crlber key seed signals that are unique to the ~ubscriber and provides a prescribed key seed ~ignal on line 89 in accordance with the address on line 87.
A subscriber key generator 90 reproduces the 6ubscriber key ~ignal on line 91 corresponding to the subscriber key ~ignal on line 7Q in the system of Figure 2 that wa~ used in encrypting the encrypted category key signal included in the category rekey message addressed to the given subscriber and received on line 81.
The subscriber key generator 90 generates the subscriber key signal on line 91 by processing the subscriber key generation signal on line B6 in accordance with the DES algorithm upon the algorithm being keyed by the prescribed key seed signal on line 89.
The above-described system for reproducing subscriber key signals through use of stored key see~ signals is the subject of a Canadian Patent Application entitled "Descrambler Subscriber Key Production Utilizing Key Seeds Stored In Descrambler" filed on March 14, 1985 by Karl E. Moerder, Serial No. 476,474.
The subscriber key signal on line 91 is exclusive-OR'd with the received authorization word signal received on line 24 to provide an encoded subscriber key signal on line 92 corres-ponding to the subscriber key signal for the given subscriber on line 69 in the system of Figure 2.
A categor~ key generator 94 decrypts the encrypted category key signal received on line 80 by generating an encoded category key signal on line 95 corresponding to the signal on line 65 in the system of Figure 2 by processing the encrypted category key signal on line 81 in accordance with the DES algorithm upon the algorithm being keyed by the subscriber key signal on line 92.
: The encoded category key signal on line 95 is exclusive-OR'd with the received credit signal on line 11 to provide a decoded category key signal on line g6 corresponding to the category key signal on line 56 in the system of Figure 2.
The symbols 97, 98, 99 and 100 in Figure 3 represent exclusive-OR'd logic elements.
12 777f~4 -21a- 72046-7 The decoded cateaory key signal on line 96 is ex:clusive-OR'd with the received program cost signal on line ,~
, ~2~764 to provide an encoded category key signal on line lOl corresponding to the encoded category key signal on line 54 in the system of Figure 2, A channel key generator 102 decrypts the encrypted channel key signal received on llne 80 by generating an encoded channel key slgnal on line 104 corresponding to the signal on line 52 in the system of Figure 2 by processing the encrypted channel key signal on llne 80 in accordance with the DES algorithm upon the algorithm being keyed by the encoded category key signal on line lOl.
The encoded channel key signal on line 104 is exclusive-OR'd with the program mask signal on line 23 to provide a decoded channel key signal on line 36 corresponding to the channel key signal on line 49 in the system of Figure 2.
The enable gate 29 passes the channel key signal from line 36 onto line 37 only when the input line 35 of the ena~le gate 29 receives either a prepaid signal or an accepted slgnal from the authorizatlon processor 77, whlch is descrlbed above wlth reference to Figure 1.
A working key generator 106 generates a working key slgnal on line 107 corresponding to the working key signal on line 46 ln the system of Figure 2 by proce~ing the frame count signal received on line 79 in accordance with the DES algorithm upon the algorithm being keyed by the channel key signal on line 37.
The keystream generator 44 generates a keystream ~ignal on line 42 corresponding to the keystream signal on line 40 in the system of Figure 2 by processing the frame count signal on line 79 in accordance with the DES algorithm upon lZ77764 the algorithm being keyed by the working key signal on line 107.
The subscriber key seed memory 88 and the debit register 14 of each subscriber terminal are included in a non-volatile ran-dom access memory (RAM) of an integrated circuit chip that has an architecture which prevents the debit register from being accessed from off the chip. The chip must be capable of performing the computation, comparison and authorization functions of the authori-zation processor 77 described with reference to Figure l and the decryption and decoding functions of the key signal decryption systems of Figure 3. A model TMS70C40 chip manufactured by Texas Instruments is preferred. This chip is modified for use in the system of the present invention by disabling the capability for accepting instructions from off the chip, thereby preventing an instruction to read the secure memor~ from being accepted.
A more detailed description of the decryption system of Figure 3 and the use of the keystream for descrambling the received scrambled television signal is set forth in the above-referenced Canadian Patent Application No. 454,444.
Referring again to Figure 1, a debit signal on line 109 indicating the contents of the debit register is provided to the display driver and logic circuit 19, which upon operator command provides a signal on line 21 to the display 22 for enabling a display of an indication of the accumulated charges attributed to the subscriber terminal. This enables the subscriber to record the accumulated charges information ~,, s .
1~77764 that is displayed and to transmit the same to the broadcast company whenever called for, such as when service is discontinued, when the subscriber terminal equipment is transferred to another sub6criber or upon payment of the subscriber's periodic billing. This accumulated charges information i~ used by the broadcaster to resolve any billing disputes that may arise with the subscriber or to facilitate computation of a refund when service is discontinued or the equipment i8 transferred.
In order to verify the accumulated charge information provided to the broadcast company by the subscriber, authentication information also is displayed on the display 22 for copying and transmittal to the broadcast company by the subscriber. The authentication information is displayed in response to an authentication signal provided on line 110 to the display driven and logic circuit 19 by an authentication generator 1}1. The authentication generator 111 generates the authentication signal on line 110 by proce~ing the debit slgnal on line 109 in accordance with the DES algorithm upon the algorithm being keyed by the sub~criber key signal on line 91.
In a ~ubscriber televi~ion network having a two-way communication link between the broadcast terminal and the subscriber terminal the debit signal on line 109 and/or the authentication signal on line 110 could be stored in a memory (not shown) in the subscriber terminal and accessed from such memory upon command for transmission to the broadcast terminal.
Referring again to the system in which the subscriber records and transmits the displayed accumulated charges -25~ 4 information and the authentication information, upon receipt of what is purported by the subscriber to be the displayed accumulated charge information and the authentication information, the broadcast company enters the same into the control computer. The control computer converts the entered information into debit and authentication signals having the same format as the signals provided to the display driver and logic circuit 19 on lines 109 and 110 respectively.
Referring to Figure 4, the converted debit and authentication signals in the control computer are provided on lines 114 and 115 respectively. The debit signal is entered in a debit register 116 and the authentication signal is entered in an authentication register 117. The debit signal from the debit register 116 is processed by a debit generator 118 in accordance with the DES algorithm upon the algorithm being keyed by the sub~criber key ~ignal on line 70 that iB related to the ~ub#criber terminal belonging to the ~ubscriber who tran~mitted the authentication info~mation. The debit generator 118 thereby generates an authenticating debit signal on line 119 which i8 compared by a comparison unit 120 with the authentication signal reqistered in the authentication register 117. If this compari~on results in a match/ the information provided by the subscriber is verified, and a signal is provided on line 121 to enable entry of the content~ of the debit register 116 into a debit memory 122.
Figure 4 further illustrates how a credit signal for a given subscriber is provided on line 64 (Figure 2) for transmission to the subscriber terminal.
-26- i2~64 An indication of the amount of each payment made by a given subscriber is entered into the control computer to provide a payment signal on line 122 to an add register 124.
The add register 124 adds and registers the ~um of the amount indicated by the payment signal on line 124 and an amount ~tored in a payment memory 125, which i8 incremented by the amount of each payment, When service begins for the sub~criber, the amount initially stored in the payment memory 125 is the amount then stored in the debit memory 122 1~ for the corresponding subscriber terminal. Upon the amount of each new payment being entered into the control computer the sum registered in the add register 124 is stored in the payment memory 125 to thereby increment the stored payment record by the amount of the new payment.
A signal indicating the amount of any credit extended to the given subscriber is provided on line 126 and stored in a credit memory 127. An add register 128 ~um6 and regi~ter~ the amount of the credlt advance from the credit memory 124 and the amount stored in the payment memory 125 to provide the credit signal on line 64 indicating the accumulated credit attributed to the given ~ubscriber.
When service to the given subscriber i8 terminated, the amount of any refund due the subscriber is determined by a difference regi~ter 129, which registers and provides on line 130 a signal indicating the difference in the amount~
stored in the payment memory 125 and the debit memory 122.
The accepted signal on line 33 is further provided to the enter enable input of the debit register 14 and causes the sum registered in the add register 15 to be entered into the debit register 14, thereby effectively incrementing the accumulated charges in the debit register 14 by the charge indicated by the program cost signal received on line 10.
The overflow detection device 13 is coupled to the add register 15 for detecting when the arithmetic limit of the debit register 14 would be exceeded by incrementing the accumulated charge~ in the debit register 14 by the charge indicated by the program co~t ~ignal on line 10 and for providing an overflow ~ignal on line 18 upon said detection.
The display driver and logic circuit 19 responds to the overflow signal on line 18 by preventing an enabling signal from otherwise belng provided on line 31 in response to a credit-available signal on line 17. This eature is provided in order to prevent a ~ubscriber from feeding fal~e co~t and credit signals into the authentication processor in order to increment the debit register 14 until it overflows to thereby store an amount less than the actual accumulated charges attributed to the subscriber terminal.
Whenever either the prepaid signal is provided on line 27 or the accepted signal iB provided on line 33 to the enable gate input line 35, the enable gate 29 provides a , ~777S4 decrypted and decoded channel key signal from line 36 onto line 37 and thereby enable~ the scrambled television signal to be de~crambled. The significance of passing this key signal onto line 37 is explalned somewhat later below with reference to Figures 2 and 3.
Figure 2 and 3 respectively ~how the encryption and decryption systems included in the broadcast terminal and each subscriber tèrminal of a subscrlber television network with which the system~ of the present invention are particularly useful. The encryption and decryption systems of Figures 2 and 3 are especially adapted to prevent a subscriber from being able to enable descrambling of the scrambled signal through deceit by substituting other ~ignal~ for one or more of the respective transmitted program mask signal, authorization word signal, program cost signal and credit signal recelved by the subscriber terminal in order to obtain a match upon ~aid comparison and/or to cau~e a credit-available signal to be provided when in fact the sub~criberls credit iB inadequate.
Referring to the encryption system of the broadcast terminal (Figure 2) a keystream generator 39 produce~ a keystream signal on line 40 that i8 used to scramble the television signal. An identical keystream ~ignal must be reproduced on line 42 by the keystream generator 44 in the decryption system of the subscriber terminal (Figure 3) in order for the descrambler in the subscriber terminal to be able to descramble the ~crambled television signal.
Referring again to Figure 2, the keystream generator 39 of the encryption system generates the keystream signal on line 40 by processing an initialization vector (IV) frame : ;. .; : . .
.,' . ~ ~ ~. ........ ..
:: -count signal on line 45 in accordance with the Data Encryption Standard (DES) algorithm upon the algorithm being keyed by a working key signal on line 46.
~ working key generator 47 generate6 the working key ~ignal on line 46 by processing the frame count signal on line 45 in accordance with the DES algorithm upon the algorithm being keyed by a channel key signal on line 49.
The channel key signal on line 49 is provided by a control computer ~not shown) at the broadcast terminal.
The channel key signal on line 49 is encrypted for transmission to the subscriber terminals. A channel key generator 50 encrypts the channel key signal by generating an encrypted channel key signal on line 51 by processing an encoded channel key signal on line 52 in accordance with the DES algorithm upon the algorithm being keyed by an encoded category key signal on line 54.
Incident to the scheme for preventing descrambling by deceit through 8ub~titution of one or more of the program mask ~ignal, the authorization word signal, the program cost signal and the credit ~ignal, the program mask signal on line 55 i8 used to encode the channel key signal on line 49 by exclusive- OR'ing the channel key ~ignal on line 49 with the program mask signal on line 55 to provide the encoded channel key signal on line 52. Incident to the same scheme the encoded category key signal on line 54 i8 produced by exclusive-OR'ing a category key signal provided on line 56 by the control computer with a program cost signal provided on line 57 by the control computer. The program cost slgnal on line 57 also is provided by the control computer.
i~7~4 The symbols 59, 60, 61 and 62 in Figure 2 represent exclusive-OR logic elements.
The category key signal on line 56 also is encrypted for tran~mission to the ~ubscriber terminals. Prior to such encryptlon the category key signal on line 56 is encoded by being exclusive-OR'd with a credit signal provided on line 64 by the control computer to thereby provide an encoded category key signal on line 65. This is incident to the aforementioned prevention scheme.
The position of the bits of the category key signal on line 56 that are exclusive-OR'd with the credit signal on line 64 must be different from the position of the bits of the category key 6ignal on line 56 that are exclusive-OR'd with the program cost signal on line 57. The derivation of the credit ~ignal is described below with reference to Figure 4.
A category key generator 65 encrypts the category key ~lgnal by ~eneratlng a plurallty of unlque encrypted category key slgnal~ on line 67 by proces~ing the encoded category key signal on line 65 in accordance with the DES
algorlthm upon the algorithm being keyed by a corresponding plurality of encoded unique ~ubscriber key 6ignal6 on line 69. The sub~criber key signal~ are unique to the individual subscriber terminals.
A plurality of unique subscriber key signals are provided on line 70 from a sub~criber key storage memory 71 upon the memory 71 being acces6ed by a plurality of respective subscriber addre6ses provided on line 72 by the control computer. The subscriber key signals on line 70 are exclu~ive-OR'd with an authorization word ~gnal provided on ~27776~
line 74 by the control computer to provide the encoded subscriber key ~ignal~ on line 69. The authorization word signal on line 74 that i8 used for encoding the subscriber key signal on line 70 either matches or doesn't match the program mask signal on line 55 in accordance with whether the subscriber terminal corresponding to the individual subscriber key slgnal being decoded is assigned to a subscriber who is a regular subscriber to all of the programs on the given TV channel. The use of the authorization word signals on line 77 also is incident to the aforementioned prevention scheme.
The control computer also provides a subscriber key generation number on line 75 that is unique to the broadcaster.
The combination of the credit signal on line 64, the encrypted category key signal on line 67, the subscriber address on line 72, and the authorization word ~ignal on line 74 that all pertain to a given ~ub~criber terminal are transmitted together as a category rekey message that is addressed to the given subscrlber terminal by the subscriber address included in such me~sage. Accordlngly, unique category rekey mes~ages are transmitted to each of the subscriber terminals.
When the number of alternative authorization functions and the number of alternative programs and/or channels that are provided to the subscribers over the network exceeds the 56 bit positions of the authorization word signals are provided and included in separate re~pective category rekey mes~age addressed to each given subscriber terminal, where they are stored upon receipt.
~77764 The program mask signal on line 55, the encry~ted Ghannel key signal on line 51 and the program cost signal on 1ine 57 pertain to all of the subscriber terminals and are transmitted together as a channel rekey message to all of the subscriber terminals. The channel rekey message also contains a category rekey address signal on line 76 for selecting one of the stored category rekey messages from st~rage in the subscriber terminal in accordance with which programs and/or channels and authorization functions are indicated by TRUE bits in the res-pective bit positions of the program mask signal on line 55.
The frame count signal on line 45 and the subscriber key generation number on line 75 also are transmitted to all of the sub8criber terminals.
The encryption system of Figure 2, the manner in which the frame count signal, the channel rekey message, the category rekey messages and the subscriber key generation number are further processed prior to transmission; and the use of the keystream sianal for scrambling the television signal are described in greater detail in the aforementioned Canadian Patent Application No. 454,444.
The decryption system of each subscriber terminal, as shown in Figure 3, includes an authorization processor 77, a rekey message memory 78 and the enable gate 29. The authorization processor 77 is as described above with reference to Figure 1. The rekey message memory 78 stores all of the different rekey messages addressed to the given subscriber termin-al.
12~7764 -19a- 72046-7 The decryption system of each subscriber terminal receives the frame count signal on line 79, the program ~,, `
, :
~ :, ':
~, ' ~Z~764 mask signal on line 23, the encrypted channel key signal on line 80, the program cost signal on line 10, the credit signal on line 11, the encrypted category key signal on line 81, the authorization word signal on line 24 and the S ~ubscriber key generation number on line 82, and the category rekey address signal on line 83. The credit signal on line 11, the encrypted category key signal on line 81 and the authorization word signal on line 24 are retrieved from the storage location of the memory 78 that is accessed by the address signal on line 83.
The received subscriber key generation number on line 82 is combined with the subscribe address on line 84 from a subscriber address memory 85 to provide a subscriber key generation signal on line 86.
Two bits in a given position of the received subscriber key generation number on line 82 are also provided on line 87 to access a given address in a subscriber key seed memory 88. The memory 88 store~ four sub~crlber key seed signals that are unique to the ~ubscriber and provides a prescribed key seed ~ignal on line 89 in accordance with the address on line 87.
A subscriber key generator 90 reproduces the 6ubscriber key ~ignal on line 91 corresponding to the subscriber key ~ignal on line 7Q in the system of Figure 2 that wa~ used in encrypting the encrypted category key signal included in the category rekey message addressed to the given subscriber and received on line 81.
The subscriber key generator 90 generates the subscriber key signal on line 91 by processing the subscriber key generation signal on line B6 in accordance with the DES algorithm upon the algorithm being keyed by the prescribed key seed signal on line 89.
The above-described system for reproducing subscriber key signals through use of stored key see~ signals is the subject of a Canadian Patent Application entitled "Descrambler Subscriber Key Production Utilizing Key Seeds Stored In Descrambler" filed on March 14, 1985 by Karl E. Moerder, Serial No. 476,474.
The subscriber key signal on line 91 is exclusive-OR'd with the received authorization word signal received on line 24 to provide an encoded subscriber key signal on line 92 corres-ponding to the subscriber key signal for the given subscriber on line 69 in the system of Figure 2.
A categor~ key generator 94 decrypts the encrypted category key signal received on line 80 by generating an encoded category key signal on line 95 corresponding to the signal on line 65 in the system of Figure 2 by processing the encrypted category key signal on line 81 in accordance with the DES algorithm upon the algorithm being keyed by the subscriber key signal on line 92.
: The encoded category key signal on line 95 is exclusive-OR'd with the received credit signal on line 11 to provide a decoded category key signal on line g6 corresponding to the category key signal on line 56 in the system of Figure 2.
The symbols 97, 98, 99 and 100 in Figure 3 represent exclusive-OR'd logic elements.
12 777f~4 -21a- 72046-7 The decoded cateaory key signal on line 96 is ex:clusive-OR'd with the received program cost signal on line ,~
, ~2~764 to provide an encoded category key signal on line lOl corresponding to the encoded category key signal on line 54 in the system of Figure 2, A channel key generator 102 decrypts the encrypted channel key signal received on llne 80 by generating an encoded channel key slgnal on line 104 corresponding to the signal on line 52 in the system of Figure 2 by processing the encrypted channel key signal on llne 80 in accordance with the DES algorithm upon the algorithm being keyed by the encoded category key signal on line lOl.
The encoded channel key signal on line 104 is exclusive-OR'd with the program mask signal on line 23 to provide a decoded channel key signal on line 36 corresponding to the channel key signal on line 49 in the system of Figure 2.
The enable gate 29 passes the channel key signal from line 36 onto line 37 only when the input line 35 of the ena~le gate 29 receives either a prepaid signal or an accepted slgnal from the authorizatlon processor 77, whlch is descrlbed above wlth reference to Figure 1.
A working key generator 106 generates a working key slgnal on line 107 corresponding to the working key signal on line 46 ln the system of Figure 2 by proce~ing the frame count signal received on line 79 in accordance with the DES algorithm upon the algorithm being keyed by the channel key signal on line 37.
The keystream generator 44 generates a keystream ~ignal on line 42 corresponding to the keystream signal on line 40 in the system of Figure 2 by processing the frame count signal on line 79 in accordance with the DES algorithm upon lZ77764 the algorithm being keyed by the working key signal on line 107.
The subscriber key seed memory 88 and the debit register 14 of each subscriber terminal are included in a non-volatile ran-dom access memory (RAM) of an integrated circuit chip that has an architecture which prevents the debit register from being accessed from off the chip. The chip must be capable of performing the computation, comparison and authorization functions of the authori-zation processor 77 described with reference to Figure l and the decryption and decoding functions of the key signal decryption systems of Figure 3. A model TMS70C40 chip manufactured by Texas Instruments is preferred. This chip is modified for use in the system of the present invention by disabling the capability for accepting instructions from off the chip, thereby preventing an instruction to read the secure memor~ from being accepted.
A more detailed description of the decryption system of Figure 3 and the use of the keystream for descrambling the received scrambled television signal is set forth in the above-referenced Canadian Patent Application No. 454,444.
Referring again to Figure 1, a debit signal on line 109 indicating the contents of the debit register is provided to the display driver and logic circuit 19, which upon operator command provides a signal on line 21 to the display 22 for enabling a display of an indication of the accumulated charges attributed to the subscriber terminal. This enables the subscriber to record the accumulated charges information ~,, s .
1~77764 that is displayed and to transmit the same to the broadcast company whenever called for, such as when service is discontinued, when the subscriber terminal equipment is transferred to another sub6criber or upon payment of the subscriber's periodic billing. This accumulated charges information i~ used by the broadcaster to resolve any billing disputes that may arise with the subscriber or to facilitate computation of a refund when service is discontinued or the equipment i8 transferred.
In order to verify the accumulated charge information provided to the broadcast company by the subscriber, authentication information also is displayed on the display 22 for copying and transmittal to the broadcast company by the subscriber. The authentication information is displayed in response to an authentication signal provided on line 110 to the display driven and logic circuit 19 by an authentication generator 1}1. The authentication generator 111 generates the authentication signal on line 110 by proce~ing the debit slgnal on line 109 in accordance with the DES algorithm upon the algorithm being keyed by the sub~criber key signal on line 91.
In a ~ubscriber televi~ion network having a two-way communication link between the broadcast terminal and the subscriber terminal the debit signal on line 109 and/or the authentication signal on line 110 could be stored in a memory (not shown) in the subscriber terminal and accessed from such memory upon command for transmission to the broadcast terminal.
Referring again to the system in which the subscriber records and transmits the displayed accumulated charges -25~ 4 information and the authentication information, upon receipt of what is purported by the subscriber to be the displayed accumulated charge information and the authentication information, the broadcast company enters the same into the control computer. The control computer converts the entered information into debit and authentication signals having the same format as the signals provided to the display driver and logic circuit 19 on lines 109 and 110 respectively.
Referring to Figure 4, the converted debit and authentication signals in the control computer are provided on lines 114 and 115 respectively. The debit signal is entered in a debit register 116 and the authentication signal is entered in an authentication register 117. The debit signal from the debit register 116 is processed by a debit generator 118 in accordance with the DES algorithm upon the algorithm being keyed by the sub~criber key ~ignal on line 70 that iB related to the ~ub#criber terminal belonging to the ~ubscriber who tran~mitted the authentication info~mation. The debit generator 118 thereby generates an authenticating debit signal on line 119 which i8 compared by a comparison unit 120 with the authentication signal reqistered in the authentication register 117. If this compari~on results in a match/ the information provided by the subscriber is verified, and a signal is provided on line 121 to enable entry of the content~ of the debit register 116 into a debit memory 122.
Figure 4 further illustrates how a credit signal for a given subscriber is provided on line 64 (Figure 2) for transmission to the subscriber terminal.
-26- i2~64 An indication of the amount of each payment made by a given subscriber is entered into the control computer to provide a payment signal on line 122 to an add register 124.
The add register 124 adds and registers the ~um of the amount indicated by the payment signal on line 124 and an amount ~tored in a payment memory 125, which i8 incremented by the amount of each payment, When service begins for the sub~criber, the amount initially stored in the payment memory 125 is the amount then stored in the debit memory 122 1~ for the corresponding subscriber terminal. Upon the amount of each new payment being entered into the control computer the sum registered in the add register 124 is stored in the payment memory 125 to thereby increment the stored payment record by the amount of the new payment.
A signal indicating the amount of any credit extended to the given subscriber is provided on line 126 and stored in a credit memory 127. An add register 128 ~um6 and regi~ter~ the amount of the credlt advance from the credit memory 124 and the amount stored in the payment memory 125 to provide the credit signal on line 64 indicating the accumulated credit attributed to the given ~ubscriber.
When service to the given subscriber i8 terminated, the amount of any refund due the subscriber is determined by a difference regi~ter 129, which registers and provides on line 130 a signal indicating the difference in the amount~
stored in the payment memory 125 and the debit memory 122.
Claims (10)
1. A system in a subscriber terminal of a subscriber communication network for enabling descrambling of a received scrambled signal on an impulse-purchase basis, comprising means for processing a received cost signal indicating the charge for descrambling said scrambled signal and a received credit signal indicating only the accumulated credit attributed to the subscriber 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 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, enabled in response to the credit-available signal, for accepting said option, and for providing an accepted signal upon acceptance; and means responsive to the accepted signal for enabling the scrambled signal to he descrambled.
means 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, enabled in response to the credit-available signal, for accepting said option, and for providing an accepted signal upon acceptance; and means responsive to the accepted signal for enabling the scrambled signal to he descrambled.
2. A system according to Claim 1, wherein the processing means includes a debit register for registering only the accumulated charges for scrambled signals accepted by the subscriber for descrambling;
means for adding the charge indicated by the cost signal to the accumulated charges registered in the debit register;
and means for comparing the 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.
means for adding the charge indicated by the cost signal to the accumulated charges registered in the debit register;
and means for comparing the 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 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 accumulated charges in the deibt 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.
and means responsive to the overflow signal for preventing the debit register from being incremented.
5. A system in a subscriber terminal of a subscriber communication network for enabling descrambling of a received scrambled signal on an impulse-purchase basis, 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, and for providing a not-prepaid signal when the compared signals do not match to a prescribed degree;
means for processing a received cost signal indicating the charge for descrambling said scrambled signal and a received credit signal indicating only the accumulated credit attributed to the subscriber 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 responsive to both the not-prepaid signal and the credit-available signal for indicating that the subscriber has the option of causing the signal to be descrambled on an impulse-purchase basis;
means, 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 responsive to the accepted signal for enabling the scrambled signal to be descrambled.
means for processing a received cost signal indicating the charge for descrambling said scrambled signal and a received credit signal indicating only the accumulated credit attributed to the subscriber 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 responsive to both the not-prepaid signal and the credit-available signal for indicating that the subscriber has the option of causing the signal to be descrambled on an impulse-purchase basis;
means, 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 responsive to the accepted signal for enabling the scrambled signal to be descrambled.
6. A system according to Claim 5, 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.
7. A system according to Claim 6, wherein the impulse-purchase signal is included in the mask signal.
8. In a subscriber communication network, a system for enabling descrambling of a scrambled signal on an impulse-purchase basis, comprising means for transmitting to the subscribers a mask signal uniquely related to the scrambled signal;
means for transmitting authorization signals to individually addressed subscribers indicating whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis;
means for transmitting to the subscribers a cost signal indicating the charge for descrambling the scrambled signal;
means for transmitting to individually addressed subscribers credit signals respectively indicating only the accumulated credit attributed to the subscriber; and a system in each subscriber terminal of the network for enabling descrambling of the scrambled signal received by the subscriber terminal on an impulse-purchase basis, said enabling system comprising means for receiving the mask signal, the authorization signal, the cost signal and the credit signal;
means for comparing the received mask signal with the received authorization signal, and for providing a not-prepaid signal when the compared signals do not match to a prescribed degree;
means for processing the received cost signal and the received 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 responsive to both the not-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, 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 acceptance;
and means responsive to the accepted signal for enabling the scrambled signal to be descrambled.
means for transmitting authorization signals to individually addressed subscribers indicating whether the subscriber is authorized to descramble the scrambled signal on a prepaid basis;
means for transmitting to the subscribers a cost signal indicating the charge for descrambling the scrambled signal;
means for transmitting to individually addressed subscribers credit signals respectively indicating only the accumulated credit attributed to the subscriber; and a system in each subscriber terminal of the network for enabling descrambling of the scrambled signal received by the subscriber terminal on an impulse-purchase basis, said enabling system comprising means for receiving the mask signal, the authorization signal, the cost signal and the credit signal;
means for comparing the received mask signal with the received authorization signal, and for providing a not-prepaid signal when the compared signals do not match to a prescribed degree;
means for processing the received cost signal and the received 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 responsive to both the not-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, 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 acceptance;
and means responsive to the accepted signal for enabling the scrambled signal to be descrambled.
9. In a subscriber communication network, a system for enabling descrambling of a scrambled signal on an impulse-purchase basis, comprising means for transmitting to the subscribers a cost signal indicating the charge for descrambling the scrambled signal:
means for transmitting to individually addressed subscribers credit signals respectively indicating only the accumulated credit attributed to the individual subscribers;
and a system in each subscriber terminal of the network for enabling descrambling of the scrambled signal received by the subscriber terminal on an impulse-purchase basis, said enabling system comprising means for receiving the cost signal and the credit signal;
means for processing the received cost signal and the received 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 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, enabled in response to the credit available signal, for accepting said option, and for providing an accepted signal upon said acceptance; and means responsive to the accepted signal for enabling the scrambled signal to be descrambled.
means for transmitting to individually addressed subscribers credit signals respectively indicating only the accumulated credit attributed to the individual subscribers;
and a system in each subscriber terminal of the network for enabling descrambling of the scrambled signal received by the subscriber terminal on an impulse-purchase basis, said enabling system comprising means for receiving the cost signal and the credit signal;
means for processing the received cost signal and the received 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 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, enabled in response to the credit available signal, for accepting said option, and for providing an accepted signal upon said acceptance; and means responsive to the accepted signal for enabling the scrambled signal to be descrambled.
10. A system according to Claim 9, further comprising means for providing the credit signals for transmission, including a first memory for storing an indication of 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.
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.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000615869A CA1303208C (en) | 1984-06-08 | 1990-09-19 | System for enabling descrambling on a selective-subscription basis in a subscriber communication network |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US618,917 | 1984-06-08 | ||
| US06/618,917 US4712238A (en) | 1984-06-08 | 1984-06-08 | Selective-subscription descrambling |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000615869A Division CA1303208C (en) | 1984-06-08 | 1990-09-19 | System for enabling descrambling on a selective-subscription basis in a subscriber communication network |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1277764C true CA1277764C (en) | 1990-12-11 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000483413A Expired - Lifetime CA1277764C (en) | 1984-06-08 | 1985-06-07 | System for enabling descrambling on a selective- subscription basis in a subscriber communication network |
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|---|---|
| US (2) | US4712238A (en) |
| EP (2) | EP0164983B1 (en) |
| JP (4) | JPS613546A (en) |
| AT (2) | ATE89972T1 (en) |
| AU (4) | AU575950B2 (en) |
| CA (1) | CA1277764C (en) |
| DE (2) | DE3577961D1 (en) |
| DK (1) | DK175419B1 (en) |
| NO (1) | NO168080C (en) |
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- 1985-06-03 DK DK198502479A patent/DK175419B1/en not_active IP Right Cessation
- 1985-06-03 EP EP85303897A patent/EP0164983B1/en not_active Expired - Lifetime
- 1985-06-03 DE DE8888120288T patent/DE3587370T2/en not_active Expired - Lifetime
- 1985-06-03 AT AT88120288T patent/ATE89972T1/en not_active IP Right Cessation
- 1985-06-03 AT AT85303897T patent/ATE53160T1/en not_active IP Right Cessation
- 1985-06-03 EP EP88120288A patent/EP0314203B1/en not_active Expired - Lifetime
- 1985-06-06 NO NO852280A patent/NO168080C/en unknown
- 1985-06-07 CA CA000483413A patent/CA1277764C/en not_active Expired - Lifetime
- 1985-06-07 AU AU43401/85A patent/AU575950B2/en not_active Expired
- 1985-06-07 JP JP60124062A patent/JPS613546A/en active Granted
-
1987
- 1987-12-04 US US07/128,889 patent/US4792973A/en not_active Expired - Lifetime
-
1988
- 1988-06-28 AU AU18437/88A patent/AU612375B2/en not_active Expired
- 1988-06-28 AU AU18438/88A patent/AU587942B2/en not_active Expired
- 1988-06-28 AU AU18436/88A patent/AU612374B2/en not_active Expired
-
1992
- 1992-09-30 JP JP4262597A patent/JP2601604B2/en not_active Expired - Lifetime
- 1992-09-30 JP JP4286862A patent/JP2589031B2/en not_active Expired - Lifetime
- 1992-09-30 JP JP4262596A patent/JP2609406B2/en not_active Expired - Lifetime
Also Published As
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|---|---|
| AU587942B2 (en) | 1989-08-31 |
| NO852280L (en) | 1985-12-09 |
| AU1843888A (en) | 1988-09-22 |
| JPH0562852B2 (en) | 1993-09-09 |
| AU4340185A (en) | 1985-12-12 |
| ATE53160T1 (en) | 1990-06-15 |
| JPS613546A (en) | 1986-01-09 |
| AU575950B2 (en) | 1988-08-11 |
| DE3587370D1 (en) | 1993-07-01 |
| AU1843688A (en) | 1988-09-22 |
| AU1843788A (en) | 1988-09-22 |
| NO168080C (en) | 1992-01-08 |
| JPH05304670A (en) | 1993-11-16 |
| JP2609406B2 (en) | 1997-05-14 |
| JP2601604B2 (en) | 1997-04-16 |
| EP0314203A2 (en) | 1989-05-03 |
| EP0164983A3 (en) | 1986-12-10 |
| NO168080B (en) | 1991-09-30 |
| ATE89972T1 (en) | 1993-06-15 |
| EP0314203A3 (en) | 1989-08-23 |
| DK247985A (en) | 1985-12-09 |
| AU612375B2 (en) | 1991-07-11 |
| US4792973A (en) | 1988-12-20 |
| JPH05304667A (en) | 1993-11-16 |
| DE3587370T2 (en) | 1993-09-16 |
| DK175419B1 (en) | 2004-10-04 |
| DK247985D0 (en) | 1985-06-03 |
| DE3577961D1 (en) | 1990-06-28 |
| US4712238A (en) | 1987-12-08 |
| EP0164983B1 (en) | 1990-05-23 |
| EP0314203B1 (en) | 1993-05-26 |
| EP0164983A2 (en) | 1985-12-18 |
| JP2589031B2 (en) | 1997-03-12 |
| JPH05304671A (en) | 1993-11-16 |
| AU612374B2 (en) | 1991-07-11 |
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