(19)
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`J
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`Europaisches Patentamt
`European Patent Office
`Office europeen des brevets
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`| | | | 1 1| || | | | | 1 1| | | || | | | | ||
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`(11)
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`E P 0 9 3 4 7 6 5 A 1
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`(12)
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`EUROPEAN PATENT A P P L I C A T I O N
`
`(43) Date of publication:
`ation:
`11.08.1999 Bulletin 1999/32
`
`(21) Application number: 98400285.7
`
`(22) Date of filing: 09.02.1998
`
`(51) |nt. CI.6: A63F 9/22
`
`(84) Designated Contracting States:
`AT BE CH DE DK ES Fl FR GB GR IE IT LI LU MC
`NL PT SE
`Designated Extension States:
`AL LT LV MK RO SI
`
`(72) Inventors:
`• Agasse, Bernard
`9561 0 Eragny/Oise (FR)
`• Bayassi, Mulham
`7501 5 Paris (FR)
`
`(60) Divisional application:
`98202314.5
`
`(71 ) Applicant:
`CANAL+ Societe Anonyme
`7571 1 Paris Cedex 1 5 (FR)
`
`(74) Representative:
`Cozens, Paul Dennis et al
`Mathys & Squire
`1 00 Grays Inn Road
`London WC1 X 8AL (GB)
`Remarks:
`The application is published incomplete as filed
`(Article 93 (2) EPC).
`
`(54)
`
`Interactive gaming system
`An interactive gaming and audiovisual trans-
`(57)
`mission system comprising a central gaming computer
`4002 for processing gaming data, a decoder 2020
`adapted to receive gaming data from the central gaming
`computer 4002 together with transmitted audiovisual
`data, the decoder further including a card reading
`
`device for interacting with a user's bank card in order to
`credit a gaming account held by the central gaming
`computer means in response to a transfer of credit from
`the user's bank account.
`
`2014
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`4004
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`10
`CO
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`CO
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`o
`Q_
`LU
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`3022 ■>
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`J COMMUNICATION
`SERVER
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`Printed by Xerox (UK) Business Services
`2.16.7/3.6
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`

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`1
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`EP 0 934 765 A1
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`2
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`Description
`
`s
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`is
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`[0001 ] The present invention relates to an interactive
`gaming and digital audiovisual transmission system, in
`particular a gaming and digital television transmission
`system.
`[0002] Broadcast transmission of digital data is well-
`known in the field of pay TV systems, where scrambled
`audiovisual information is sent, usually by a satellite or
`satellite/cable link, to a number of subscribers, each w
`possessing a decoder capable of descrambling the
`transmitted program for subsequent viewing. Terrestrial
`digital broadcast systems are also known. Recent sys-
`tems have also used the broadcast link to transmit other
`data, in addition to or as well as audiovisual data, such
`as computer programs or interactive applications to the
`decoder or to a connected PC.
`[0003] The increasing sophistication of such technol-
`ogy, in particular in relation to the receiver/decoder
`devices used in the systems, has led to an increase in 20
`the possible services that may be provided thereby. In
`particular, a number of systems have been proposed
`using interactive technology to enable a viewer to, for
`example, participate in a quiz show, or to select further
`information regarding a product currently being dis- 25
`played on a shopping channel.
`In the case of gaming applications, a number
`[0004]
`of largely theoretical systems have been proposed to
`enable a viewer to gamble a sum of money on the out-
`come of a sporting event or casino-type game broad- 30
`cast over a television network. In most of these
`systems, a viewer is usually obliged to open an initial
`account with the controlling gaming authority by phon-
`ing or mailing a money transfer to the gaming authority
`before any gambling can be carried out. The disadvan- 35
`tages of this sort of procedure will be apparent.
`[0005] Alternative systems are also known, in which
`the viewer buys credits to be gambled in the form of an
`electronic purse, i.e. a smart card or the like, the credits
`in the purse being available for subsequent gaming 40
`operations. The card is inserted in the decoder and the
`credits used thereafter in the subsequent gaming oper-
`ations. When the contents of the purse are exhausted,
`the viewer buys a new card or re-charges the card at a
`suitable sales point. This system again implies a certain 45
`infra-structure to be put in place to enable a user to
`obtain the necessary credits to be gambled.
`[0006] The present invention seeks to overcome some
`or all of the disadvantages of these prior art systems.
`[0007] According to the present invention, there is pro-
`vided an interactive gaming and audiovisual transmis-
`sion system comprising a central gaming computer
`means for processing gaming data, a decoder adapted
`to receive gaming data from the central gaming compu-
`ter together with transmitted audiovisual data, the 55
`decoder further including a card reading device for inter-
`acting with a user's bank card in order to credit a gam-
`ing account held by the central gaming computer means
`
`so
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`2
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`in response to a transfer of credit from the user's bank
`account.
`In this way, the present invention enables a
`[0008]
`user to simply and quickly open and credit a gaming
`account from the comfort of his home, avoiding the
`more elaborate payment methods of the known sys-
`tems.
`[0009] The type of bank card used in this transaction
`may be of the debit or credit type. The card reading
`device may in particular comprise a smart card reader
`adapted to interact with a bank card in the form of a
`smart card.
`Advantageously, the decoder is further
`[0010]
`equipped with a second card reading device. For exam-
`ple, in the case where the decoder forms part of a tele-
`vision subscription service, the subscriber may be
`provided with a subscription card in the form of a smart
`card or the like. The provision of two card reader
`devices in the decoder permits the decoder to carry out
`credit transactions on a bank card inserted in one
`reader whilst the subscription card is held in the second
`reader.
`In one realisation, the decoder may be adapted
`[001 1 ]
`to obtain transfer of credit information in the form of an
`electronic certificate generated by the bank card in
`response to transaction data submitted by the decoder.
`This transaction information may include, for example,
`the details of the bank account of the gaming authority
`to be credited in the operation, the sum of money to be
`transferred etc.
`[0012] Typically, data is entered by the user into the
`decoder using a handheld remote control. In the case
`where a credit transaction is to be carried out, it may be
`necessary to enter the bank card PIN number using the
`remote control. In one embodiment, the decoder is pro-
`vided with a handheld remote control, some or all of the
`data sent to the decoder being encrypted by the hand-
`held remote control and subsequently decrypted by the
`decoder. In this way, interception by third parties of sen-
`sitive data emitted by the remote control may be
`avoided.
`[001 3] Preferably, the decoder is adapted to transmit
`transfer of credit information from the decoder to a bank
`server via a network communication link, for example,
`using an modem integrated in the decoder.
`[0014] The decoder may be adapted to directly com-
`municate transfer of credit information to a bank compu-
`ter. However, preferably, the system further comprises
`an intermediate communications server, adapted to
`receive transfer of credit information communicated
`from the decoder and to forward this information on to a
`bank server.
`[0015] The intermediate communications server may
`further be adapted to communicate with the central
`gaming computer means, for example, to inform the
`central communication means of a transfer of credit
`instruction being forwarded from the intermediate com-
`munication means to a bank computer, so as to permit
`
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`EP 0 934 765 A1
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`is
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`the gaming computer means to set up an account with-
`out having to verify the transaction carried out at an
`associated bank server.
`The central gaming computer means may
`[0016]
`equally be adapted to receive and transmit credit infer-
`mation to or from a bank server via a network communi-
`cation link. This may be necessary, for example, in the
`case of a win or in order to verify the transfer of funds
`from the bank account of a user to the gaming authori-
`ties bank account before opening a gaming account.
`[001 7] Preferably, the decoder is adapted to commu-
`nicate gaming information to the central gaming compu-
`ter during gaming operation via
`a network
`communication link. This may be the same link as used
`to communicate transfer of credit information to a bank
`computer, for example, using a modem device inte-
`grated in the decoder.
`[0018] Some or all of the gaming information commu-
`nicated from the decoder to the central gaming compu-
`ter during gaming operation may be encrypted by the 20
`decoder. For example, the decoder may be adapted to
`transmit in encrypted form a code word entered by the
`user associated with the gaming account of the user
`held by the central gaming computer.
`[001 9] The decoder may be adapted to directly com- 25
`municate information to the central gaming computer
`during gaming operation. However, preferably, the sys-
`tem further comprises an intermediate communications
`server, adapted to receive information communicated
`from the decoder during gaming operation and to for- 30
`ward this information on to the central gaming compu-
`ter. This may be the same intermediate server as used
`for the transfer of credit information between the
`decoder and a bank.
`In the case where gaming information is 35
`[0020]
`encrypted by the decoder, the intermediate communica-
`tions server may be adapted to simply pass this infor-
`mation "as is" to the central gaming computer. However,
`in one embodiment, the intermediate communications
`server is adapted to decrypt information received from 40
`the decoder and to re-crypt this information for subse-
`quent communication to the central gaming computer.
`This may be required, for example, in the case where
`different encryption algorithms are used by the decoder
`and central gaming computer.
`[0021 ] The intermediate communications server may
`further be adapted to communicate information to and
`from other computer devices, for example, computer
`databases holding TV subscriber information. In this
`way, the intermediate communications server may
`obtain directly information regarding the user of the sys-
`tem (name, address etc) to be used in setting up a gam-
`ing account, without the user having to re-enter the
`same information.
`The communication means used to transmit
`[0022]
`gaming data from the central gaming computer to the
`decoder may be defined in a number of different ways
`and by a number of different communication elements.
`
`45
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`so
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`ss
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`For example, some or all of the gaming data sent from
`the gaming computer to the decoder may be transmitted
`via a transmitter means used to transmit audiovisual
`data to the decoder.
`In addition, or alternatively, some or all of the
`[0023]
`gaming data sent from the central gaming computer to
`the decoder may be sent via a network communication
`link, for example, the same network used to communi-
`cate information from the decoder to the central gaming
`computer during gaming operation.
`In practice, a mixture of these two communica-
`[0024]
`tion paths may prove optimal, the network path being
`used for rapid dialogue between the decoder and the
`gaming computer during real-time operation and the
`transmission path being used for relatively fixed data,
`such as screen format display data or the like.
`[0025] The present invention also extends to a gaming
`system for processing gaming data, comprising:
`
`means for transmitting gaming data to a user's
`decoder;
`means for receiving data from the user's decoder;
`and
`means for connection to a bank server holding the
`user's bank account in order to transfer credit to or
`from the account.
`
`The gaming system may include a gaming
`[0026]
`account held by the gaming system which can be cred-
`ited in response to the transfer of credit.
`[0027] The gaming system may be adapted to com-
`municate with the decoder and the bank server via a
`communications server. If so, the gaming system may
`be adapted to receive encrypted information from the
`communications server.
`[0028] The present invention also provides a interac-
`tive gaming and audiovisual transmission system com-
`prising a gaming system as aforementioned, said user's
`decoder, and said bank server.
`[0029] As mentioned above the system may be used
`to permit gaming in relation to various events. For exam-
`ple, the central gaming computer may be adapted to
`generate a computer game (computer blackjack or the
`like), the computer generated images being transmitted
`via the audiovisual link to the decoder.
`[0030] However, as will be appreciated, the combina-
`tion of gaming and audiovisual systems makes the
`present invention particularly adapted to permit gaming
`in relation to televised sports, such as horse racing or
`the like. In one embodiment, the present invention com-
`prises a central gaming computer adapted to provide
`gaming data related to a real-time sporting event, the
`decoder being adapted to receive both gaming data and
`associated audiovisual data of the event.
`In the context of the present application the
`[0031]
`term < (audiovisual transmission system >> refers to all
`transmission systems for transmitting or broadcasting
`primarily audiovisual or multimedia digital data. The
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`EP 0 934 765 A1
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`6
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`present invention is particularly, but not exclusively,
`applicable to a broadcast digital television system.
`In this application the term < < smart card > > is
`[0032]
`used to mean any conventional chip-based card device
`possessing, for example, microprocessor and/or mem-
`ory storage. Also included in this term are chip devices
`having alternative physical forms, for example key-
`shaped devices such as are often used in TV decoder
`systems.
`In the present application, the term "decoder"
`[0033]
`is used to apply to an integrated receiver/decoder for
`receiving and decrypting an encrypted transmission,
`the receiver and decoder elements of such a system as
`considered separately, as well as to a receiver capable
`of receiving non-encrypted broadcasts. The term
`equally covers decoders including additional functions,
`such as web browsers, together with decoder systems
`integrated with other devices, for example, integrated
`VHS/decoder devices or the like.
`
`Figure 1 shows the overall architecture of a digital
`television system, as may be incorporated in the
`gaming system of the present invention;
`
`Figure 2 shows the conditional access system of
`the television system of Figure 1 ;
`
`Figure 3 shows the structure of the decoder of Fig-
`ures 1 and 2;
`
`Figure 4 shows a gaming system incorporating the
`television system of Figures 1 and 2; and
`
`Figure 5 shows a flow diagram of the logical steps
`involved in a gaming transaction
`
`Digital Television System
`
`[0034] An overview of a digital television broadcast
`and reception system 1000 adaptable to the present
`invention is shown in Figure 1. The system includes a
`mostly conventional digital television system 2000,
`which uses the known MPEG-2 compression system to
`transmit compressed digital signals. In more detail, the
`MPEG-2 compressor 2002 in a broadcast centre
`receives a digital signal stream (typically a stream of
`video signals). The compressor 2002 is connected to a
`multiplexer and scrambler 2004 by linkage 2006. The
`multiplexer 2004 receives a plurality of further input sig-
`nals, assembles one or more transport streams and
`transmits compressed digital signals to a transmitter
`2008 of the broadcast centre via linkage 2010, which
`can of course take a wide variety of forms including tel-
`ecom links.
`The transmitter 2008 transmits electromag-
`[0035]
`netic signals via uplink 2012 towards a satellite trans-
`ponder 2014, where they are electronically processed
`and broadcast via notional downlink 2016 to earth
`
`10
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`is
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`5
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`receiver 2018, conventionally in the form of a dish
`owned or rented by the end user. The signals received
`by receiver 2018 are transmitted to an integrated
`receiver/decoder 2020 owned or rented by the end user
`and connected to the end user's television 2022. The
`receiver/decoder 2020 decodes
`the compressed
`MPEG-2 signal into a television signal for the television
`set 2022.
`[0036] A conditional access system 3000 is connected
`to the multiplexer 2004 and the receiver/decoder 2020,
`and is located partly in the broadcast centre and partly
`in the decoder. It enables the end user to access digital
`television broadcasts from one or more broadcast sup-
`pliers. A smart card, capable of decrypting messages
`relating to commercial offers (that is, on or several tele-
`vision programmes sold by the broadcast supplier), can
`be inserted into the receiver/decoder 2020. Using the
`decoder 2020 and smart card, the end user may pur-
`chase events in either a subscription mode or a pay-per-
`20 view-mode.
`[0037] An interactive system 4000, also connected to
`the multiplexer 2004 and the receiver/decoder 2020 and
`again located partly in the broadcast and partly in the
`decoder, enables the end user to interact with various
`25 applications via a modemmed back channel 4002. Such
`interactive applications may include an interactive shop-
`ping service, a quiz application, an interactive pro-
`gramme guide etc.
`In point of fact, whilst the interactive system
`[0038]
`30 4000 has been represented as a discrete logical block,
`the physical elements of this system, such as the server
`or servers used to handle communications between the
`receiver/decoder and central servers, may be elements
`shared with the conditional access system 3000. This
`35 will become clear in the description of the gaming sys-
`tem of Figure 4.
`
`Conditional Access System
`
`45
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`40
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`[0039] With reference to Figure 2, the conditional
`access system 3000 includes a Subscriber Authoriza-
`tion System (SAS) 3002. The SAS 3002 is connected to
`one or more Subscriber Management Systems (SMS)
`3004, one SMS for each broadcast supplier, by a
`respective TCP-IP link 3006 (although other types of
`linkage could alternatively be used). Alternatively, one
`SMS could be shared between two broadcast suppliers,
`or one supplier could use two SMSs, and so on.
`[0040] First encrypting units in the form of ciphering
`so units 3008 utilising << mother >> smart cards 3010 are
`connected to the SAS by linkage 3012. Second encrypt-
`ing units again in the form of ciphering units 3014 utilis-
`ing mother smart cards 3016 are connected to the
`multiplexer 2004 by linkage 3018. The receiver/decoder
`55 2020 receives a << daughter >> smart card 3020. It is
`connected directly to the SAS 3002 by Communications
`Servers 3022 via the modemmed back channel 4002.
`The SAS sends amongst other things subscription
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`rights to the daughter smart card on request.
`[0041 ] The smart cards contain the secrets of one or
`more commercial operators. The << mother >> smart
`card encrypts different kinds of messages and the
`< < daughter > > smart cards decrypt the messages, if
`they have the rights to do so.
`[0042] The first and second ciphering units 3008 and
`3014 comprise a rack, an electronic VME card with soft-
`ware stored on an EEPROM, up to 20 electronic cards
`and one smart card 3010 and 3016 respectively, for w
`each electronic card, one (card 3016) for encrypting the
`ECMs and one (card 3010) for encrypting the EMMS.
`[0043] Also shown in Figure 2 is a handheld remote
`control used by the viewer to control and program func-
`tions of the receiver/decoder 2020.
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`s
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`is
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`Multiplexer and Scrambler
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`25
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`[0044] With reference to Figures 1 and 2, in the broad-
`cast centre, the digital video signal is first compressed 20
`(or bit rate reduced), using the MPEG-2 compressor
`2002. This compressed signal is then transmitted to the
`multiplexer and scrambler 2004 via the linkage 2006 in
`order to be multiplexed with other data, such as other
`compressed data.
`[0045] The scrambler generates a control word CW
`used in the scrambling process and included in the
`MPEG-2 stream in the multiplexer 2004. The control
`word CW is generated internally and enables the end
`user's integrated receiver/decoder 2020 to descramble 30
`the programme. Access criteria, indicating how the pro-
`gramme is commercialised, are also added to the
`MPEG-2 stream. The programme may be commercial-
`ised in either one of a number of << subscription >>
`modes and/or one of a number of << Pay Per View >> 35
`(PPV) modes or events.
`In the subscription mode, the end user sub-
`[0046]
`scribes to one or more commercial offers, of << bou-
`quets > > , thus getting the rights to watch every channel
`inside those bouquets. In the preferred embodiment, up 40
`to 960 commercial offers may be selected from a bou-
`quet of channels. In the Pay Per View mode, the end
`user is provided with the capability to purchase events
`as he wishes. This can be achieved by either pre-book-
`ing the event in advance (<< pre-book mode >>), or by 45
`purchasing the event as soon as it is broadcast
`(<< impulse mode >>).
`[0047] Both the control word CW and the access cri-
`teria are used to build an Entitlement Control Message
`(ECM); this is a message sent in relation with a scram-
`bled program. The message contains a control word
`(which allows for the descrambling of the program) and
`the access criteria of the broadcast program. The
`access criteria and control word are transmitted to the
`second encrypting unit 3014 via the linkage 3018. In
`this unit an ECM is generated, encrypted with an exploi-
`tation key Cex and transmitted on to the multiplexer and
`scrambler 2004.
`
`so
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`ss
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`Programme Transmission
`
`The multiplexer 2004 receives encrypted
`[0048]
`EMMs from the SAS 3002, encrypted ECMs from the
`second encrypting unit 3014 and compressed pro-
`grammes from the compressor 2002. The multiplexer
`2004 scrambles the programmes and communicates
`the scrambled programmes, the encrypted EMM (if
`present) and the encrypted ECMs to a transmitter 2008
`of the broadcast centre via linkage 2010. The transmit-
`ter 2008 transmits electromagnetic signals towards the
`satellite transponder 2014 via uplink 2012.
`
`Programme Reception
`
`[0049] The satellite transponder 2014 receives and
`processes the electromagnetic signals transmitted by
`the transmitter 2008 and transmits the signals on to the
`earth receiver 2018, conventionally in the form of a dish
`owned or rented by the end user, via downlink 2016.
`The signals received by receiver 201 8 are transmitted to
`the integrated receiver/decoder 2020 owned or rented
`by the end user and connected to the end user's televi-
`sion set 2022. The receiver/decoder 2020 demulti-
`plexes the signals to obtain scrambled programmes with
`encrypted EMMs and encrypted ECMs.
`If the programme is not scrambled the
`[0050]
`receiver/decoder 2020 decompresses the data and
`transforms the signal into a video signal for transmission
`to television set 2022.
`the
`is scrambled,
`If the programme
`[0051]
`receiver/decoder 2020 extracts the corresponding ECM
`from the MPEG-2 stream and passes the ECM to
`the < < daughter > > smart card 3020 of the end user.
`This slots into a housing in the receiver/decoder 2020.
`The daughter smart card 3020 controls whether the end
`user has the right to decrypt the ECM and to access the
`programme. If not, a negative status is passed to the
`receiver/decoder 2020 to indicate that the programme
`cannot be descrambled. If the end user does have the
`rights, the ECM is decrypted and the control word
`extracted. The decoder 2020 can then descramble the
`programme using this control word. The MPEG-2
`stream is decompressed and translated into a video sig-
`nal onward transmission to television set 2022.
`
`Subscriber Management System (SMS)
`
`A Subscriber Management System (SMS)
`[0052]
`3004 includes a database 3024 which manages,
`amongst others, all of the end user files, commercial
`offers (such as tariffs and promotions), subscriptions,
`PPV details, and data regarding end user consumption
`and authorization. The SMS may be physically remote
`from the SAS
`Each SMS 3004 transmits messages to the
`[0053]
`SAS 3002 via respective linkage 3006 to enable modifi-
`cations to or creations of Entitlement Management Mes-
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`sages (EMMs) to be transmitted to end users.
`[0054] The SMS 3004 also transmits messages to the
`SAS 3002 which imply no modifications or creations of
`EMMs but imply only a change in an end user's state
`(relating to the authorization granted to the end user
`when ordering products or to the amount that the end
`user will be charged).
`
`Entitlement Management Messages and Entitlement
`Control Messages
`
`ECMs or Entitlement Control Messages are
`[0055]
`encrypted messages embedded in the data stream of a
`transmitted program and which contain the control word
`necessary for descrambling of part or all of a program.
`Authorisation of a given receiver/decoder is controlled
`by EMMs or Entitlement Management Messages, trans-
`mitted on a less frequent basis and which supply an
`authorised receiver/decoder with the exploitation key
`necessary to decode the ECM.
`[0056] An EMM is a message dedicated to an individ-
`ual end user (subscriber), or a group of end users. A
`group may contain a given number of end users. This
`organisation as a group aims at optimising the band-
`width; that is, access to one group can permit the reach-
`ing of a great number of end users.
`[0057] Various specific types of EMM may be used.
`Individual EMMs are dedicated to individual subscrib-
`ers, and are typically used in the provision of Pay Per
`View services. So-called << Group >> subscription
`EMMs are dedicated to groups, of say, 256 individual
`users, and are typically used in the administration of
`some subscription services. This EMM has a group
`identifier and a subscribers' group bitmap
`For security reasons, the control word CW
`[0058]
`embedded in an encrypted ECM changes on average
`every 1 0 seconds or so. In contrast, the exploitation key
`Cex used by the receiver to decode the ECM is changed
`every month or so by means of an EMM. The exploita-
`tion key Cex is encrypted using a personalised key cor-
`responding to the identity of the subscriber or group of
`subscribers recorded on the smart card. If the sub-
`scriber is one of those chosen to receive an updated
`exploitation key Cex, the card will decrypt the message
`using its personalised key to obtain that month's exploi-
`tation key Cex.
`[0059] The operation of EMMs and ECMs will be well-
`known to one skilled in the art and will not be described
`here in any more detail.
`
`Receiver/Decoder Structure
`
`Referring to Figure 3, the elements of a
`[0060]
`receiver/decoder 2020 or set-top box for use in a digital
`broadcast system and adapted to be used in the
`present invention will now be described. As will be
`understood, the elements of this decoder are largely
`conventional and their implementation will be within the
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`capabilities of one skilled in the art.
`[0061] As shown, the decoder 2020 is equipped with
`several interfaces for receiving and transmitting data, in
`particular an MPEG tuner and demultiplexer 2040 for
`receiving broadcast MPEG transmissions, a serial inter-
`face 2041 , a parallel interface 2042, and a modem 2028
`for sending and receiving data via the telephone net-
`work. In this embodiment, the decoder also includes a
`first and second smart card reader 2030 and 2031 , the
`first reader 2030 for accepting a subscription smart card
`containing decryption keys associated with the system
`and the second reader 2031 for accepting bank and
`other cards. As will be described, the use of a two-slot
`decoder, adapted to read bank cards, is an important
`is aspect in the implementation of the gaming system of
`Figure 4.
`[0062] The decoder also includes a receiver 2043 for
`receiving infra-red control signals from the handset
`remote control 2044 and a Peritel output for sending
`20 audiovisual signals to a television 2022 connected to
`the decoder. In certain cases it may be desired that the
`infra-red signals transmitted from the handset 2044 to
`receiver 2043 are subject
`to a simple scram-
`bling/descrambling process to ensure that no useful
`information may be obtained by any third party monitor-
`ing the transmission.
`Such algorithms will not be described in any
`[0063]
`detail, but may comprise, for example a symmetric algo-
`to both handset 2044 and
`rithmic key known
`receiver/decoder 2020. This may be varied fro