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
  • H04N7/167—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

Definitions

• VIDEOTEX SYSTEM PROVIDED WITH INFORMATION ACCESS CONTROL MEANS VIDEOTEX SYSTEM PROVIDED WITH INFORMATION ACCESS CONTROL MEANS.
• the present invention relates to a videotex system provided with means for controlling access to information.
• the invention finds application in the transmission and display of information on television receivers for any purpose of entertainment, information, or teaching.
• the invention applies essentially to the so-called "ANTIOPE” system (Digital Acquisition and Televisualization of Images Organized in Writing Pages), and to the so-called “TITAN” system (Interactive Teletext Terminal with Call by Dialing).
• ANTIOPE Digital Acquisition and Televisualization of Images Organized in Writing Pages
• TITAN Interactive Teletext Terminal with Call by Dialing
• DIDON Digital Data Diffusion
• FIG. 1 very schematically recalls the essential elements of an ANTIOPE teletext system.
• Such a system comprises a transmission center 2 and receiver stations 4, 4 ′, etc.
• the transmission center receives information from one or more sources 5 and it includes:
• circuit 10 for storing the magazine in the form of digital signals grouped into bytes (8 binary elements);
• Each receiving station includes:
• circuit 14 for receiving and demodulating said television signal
• this channel comprising in particular a digital data decoder
• the flow of information from information depositors to dissemination centers has the following general characteristics.
• Source 5 which is a database of information, is, for example, a meteorological service, the Stock Exchange, an information agency mations, etc ...
• This bank feeds the composition means 6 which puts this information on page in ANTIOPE format.
• an interactive line connecting the broadcasting center to the information repository typically operates at 4800 b / s and that it is this difference in speed compared to broadcasting at 12800 b / s which explains the need for storage of information at the source of distribution.
• the bytes are divided into control bytes and data bytes.
• the command bytes indicate in particular headers and end of pages as well as headers and end of rows.
• the data bytes, inserted between command bytes, correspond to characters contained in the rows. All of these bytes, whether control or data, include a most significant bit element which is an evenness element.
• the set of codes, identified by such bytes, is organized according to a table which is as follows:
• a current page of information accessible to the user, takes the following form:
• FF is a code that indicates a new page
• NP 1 , NP 2 , NP 3 are codes indicating a page number from 001 to 999.
• C 1 , C 2 , C 3 are complementary codes
• RC LF complete the row.
• Row zero can also contain a service name, a. date, time and possibly charging details. This zero row does not convey information constituting the service. It is part of the procedure. 3) - After row zero, come rows of information first comprising a row header which consists of the codes (RC LF) US NR ⁇ NR 2 , where: RC LF end the previous row, US is a row flag,
• NR 1 , NR 2 constitute the row number which goes from 01 to 24.
• the data bytes d 1 , d 2 ... d n are inserted between the current row header and either an end of the row - the beginning of another row - or an end of page.
• These bytes d 1 , d 2 , ... d n represent the information constituting the service broadcast. The element of information in such a system is therefore the viewable row.
• Subscription-type taxation constitutes a flexible and lasting relationship between a service and its users. It is in diffusion especially that such a method of taxation finds its justification.
• Consumption-type taxation can also be used; this method of charging is fundamental for "interactive" systems (in which a dialogue is established between the subscriber and the information source, as is the case for TITAN); but it remains secondary in broadcast systems (in which information is transmitted unidirectionally to subscribers, as is the case for ANTIOPE).
• Intermediate systems known as “quasi-interactive” may arise, in which the content of the broadcasting source is constantly modified to meet the requests of users which are transmitted by a public data network.
• the advent of new very high capacity means of broadcasting will greatly develop this quasi-interactive mode, making it necessary to implement a system to control access to the information offered.
• the method of scrambling information and that of recovering the intelligibility of information must not penalize the performance of the system.
• the messages translated into the ANTIOPE language are characterized by significant redundancy, so that the impact of transmission errors on the intelligibility of the information disseminated is minimized.
• This is how alphabetical texts are inherently very redundant; like most semi-graphic designs; that the character display commands use escape characters; that the page and line numberings use Hamming codes; that all the bytes constituting a magazine are transmitted with imparity, etc ...
• No effort is therefore made to compress the information and the method of recovering the intelligibility of the information must therefore respect this redundancy and not propagate the harmful consequences of transmission errors, which are difficult to control during broadcasting.
• the means of recovering the intelligibility of previously locked information constitute a sort of "electronic lock", and only the use of an appropriate key makes it possible to recover the intelligibility of the locked information.
• the invention answers this question by proposing a lock which is attached to the service level.
• This procedure has several advantages. First of all, it respects the synchronization and non-propagation constraints of transmission errors. In addition, it is independent of the transport network used by videotex. Finally, it does not require any reorganization of existing ANTIOPE standards and will accommodate any changes to these standards.
• the information constituting an ANTIOPE magazine is locked at the level of the distribution source. More precisely, the locking means are located upstream of the DIDON multiplexer which, in the diagram in FIG. 1, bears the reference 12. A place having been assigned to the locking, remains the question of the object to which applies this lock.
• the invention answers this second question by proposing a means whose function is to exclusively lock the information conveyed in the viewable rows of ordinary magazine pages.
• the locking does not affect - the control codes listed in columns 0 and 1 of the code table indicated above and in particular, the codes ETX, FF, RS, RC, LF and US. It only affects the data codes d 1 , d 2 , etc.
• the invention proposes to solve a third problem which is that of respecting the impartiality of the bytes broadcast.
• a locking automaton which comprises a means for forming a series of encrypting bytes whose binary elements, denoted c 1 to c 8 are generated in the following manner :
• - c 1 , c 2 , c 3 , c 4 and c 5 are taken at the output of a pseudo-random sequence generator, reset at the start of each row viewable by a service key K and by the numbers on the page and of the row considered;
• the ciphering sequence obtained is composed of even bytes. These bytes are denoted C 1 , C 2 ... C n or, generically C j .
• the clear bytes constituting a row of information form a sequence noted d 1 , d 2 ... d n or generically d j .
• These bytes are odd and they are locked by the encrypting bytes according to the following rules: With each new clear byte in the displayable row, one byte is taken from the encrypting sequence. Two cases may arise:
• the diffuse bytes are odd, just like the clear bytes, which meets the requirement posed above.
• the "OR-exclusive" operation results in a substitution for the clear byte of a broadcast byte belonging to the same group of columns as the clear byte, namely: - the group of columns 2 and 3 which basically contains numbers and punctuation marks,
• the bytes belonging to columns 0 and 1 are not modified, in particular the bytes corresponding to the ETX, FF, RS, RC, LF and US codes which are transmitted as they are.
• the nullity of the 6 and 7 binary elements of the encrypting bytes there is no introduction of new bytes belonging to these columns. The desired transparency is therefore ensured.
• the service key K is advantageously modified randomly at determined and relatively short intervals (for example of the order of a few minutes). It then remains, at the reception, to unlock the information.
• the receiver must include a decrypting byte generator which delivers bytes formed as follows: - the 5 low-weight binary elements are taken from a quasi-random sequence obtained by a generator reset at each row header by the service key K, by the page number and by the row number considered; - the 6 th and 7 th binary elements are zero, and
• the unlocking rules are analogous to the locking rules: with each new received byte belonging to a locked row, a new decrypting byte is generated. Two cases can arise:
• Videotex system comprising an information transmission center and receiving stations, the transmission center comprising: - a means of composing a magazine consisting of pages organized in rows of characters, if this means is not already contained in the information source, - a circuit for storing the magazine in the form of digital signals grouped in bytes ( 8 binary elements), these bytes comprising control bytes and data bytes, the control bytes indicating in particular page end headers as well as headers and end of rows, the data bytes corresponding to characters contained in each row, all of these command and data bytes, comprising a most significant binary element which is an evenness element, the bytes having zero 6 and 7 binary elements being command bytes,
• each receiver station comprising: a circuit for receiving and demodulating said television signal
• the encryption means of the transmission center include: a) a generator delivering a digital signal representing a service key K, this key changing randomly at determined intervals, b) a locking automaton comprising: i) a comparator with an input connected to the magazine memorizing circuit, where it receives clear octets, said comparator being capable of distinguishing among these clear octets, those whose 7 th and 6 th bits are null, said comparator having two outputs, the first conveying these bytes has 7 and 6 null bits and which is connected to the broadcast multiplexer through the junction, and the second conveying the clear bytes d.
• the encryption means of the transmission center include: a) a generator delivering a digital signal representing a service key K, this key changing randomly at determined intervals, b) a locking automaton comprising: i) a comparator with an input connected to the magazine memorizing circuit, where it receives clear octets, said comparator being capable of distinguishing among these clear
• the decryption means of each receiving station include: d) a generator of a digital signal representing the service key K in progress in the transmission center, e) an unlocking machine comprising: i) a comparator with a connected input to the digital signal decoder of the receiving station from which it receives the encrypted bytes, this comparator being able to distinguish, among these encrypted bytes, those whose 7 th and 6 binary elements are zero, this comparator having two outputs, the first carrying these bytes of which the 7 th and 6 th binary elements are zero, this first output being connected directly to the display member, the second carrying the encrypted bytes D j of which the 7 th and / or 6 binary elements are not zero, ii) an OR-exclusive logic circuit with two inputs, one connected to the second output of the comparator from which it receives the encrypted bytes D j , this logic circuit having an output which conveys bytes decrypted d j then directed towards the display member; f) a generator of decrypting bytes controlled by the unlock
• Such locking and unlocking means make it possible to advantageously solve the problem of taxation mentioned above.
• the invention proposes to use, in addition to the service key, the role of which has just been defined, subscription keys which are generated randomly by a tax management center. These keys have a relatively long lifespan (from 1 to 12 months), compared to that of the service key (which is around a few minutes).
• a subscription scheme which would use four types of subscriptions: 1 month, 3 months, 6 months and a year.
• a subscription is characterized by its start month.
• the tax management center provides each distribution center with a list of 22 current subscription keys for each service. broadcast by this center. In addition, it provides subscription sales outlets with another list of 4 keys that will start the following month (one month, three months, six months and one year), for each service, with the subscription prices.
• a suitable machine installed in each point of sale, registers some of these keys in the form of blocks of subscriptions on supports provided for this purpose (for example smart cards of the "credit card” type). These cards are then introduced by the service users in their receiving station.
• a new key to service K is generated at random by each broadcasting center concerned.
• a few dozen service keys can follow one another.
• a broadcasting center As soon as a broadcasting center generates a new service key K, it calculates, for each current subscription key C i for this service, a message M. by an algorithm (K), the keys C i playing the role parameters .
• All the messages M i in force constitute the access control information associated with the service broadcast. This access control information is obviously not locked by the electronic lock.
• This particular system of subscription charges involving two keys, one subscription, the other service is the subject, in its essential elements, of French patent application No. EN 79 02995 filed on February 6 1979 and entitled "Information transmission system between a transmitting center and. Receiving stations, this system being provided with a means of controlling access to the information transmitted".
• a particular application of this system is provided in the context of the present invention, to videotex systems (ANTIOPE or TITAN).
• the messages M i are grouped in a special page, called the access control page, which is updated each time the service key is changed.
• the access control page is distributed cyclically, like the ordinary information pages constituting the service. However, it is not locked by the electronic lock.
• the access control page is systematically read by the receiver when contacting the service, then each time this page is updated, during consultation of the service, but it cannot be viewed.
• the messages are, in fact. Its primary lock synchronization patterns and these patterns can be interpreted by an algorithm providing the service key.
• This algorithm is of the form: (M i ), and it is developed by a playback circuit (which can also be part of the subscription medium, which already contains the subscription key C.) to whom the messages M i are supplied.
• This circuit therefore supplies the unlocking machine with the service key K, which enables it to unlock the information received.
• the subscription medium which contains, on the one hand, the subscription keys C i and which can, on the other hand, contain the circuit for restoring the service key K, it is the subject, in itself, from another French patent application No. EN 79 02996 filed on February 6, 1979 and entitled "Subscription card for videotex receiver and loading station for said card”.
• FIG. 2 shows the block diagram of a system according to the invention
• FIG. 3 represents the diagram of a circuit making it possible to materialize a particular primitive generator polynomial
• FIG. 4 shows a pseudo-random sequence generator consisting of a combination of three circuits of the type of the previous figure
• FIG. 5 shows the block diagram of a generator of encrypting bytes or decrypting bytes
• FIG. 6 shows a diagram illustrating the different states that a locking machine can take
• FIG. 7 illustrates the block diagram of a teletext system provided with access control means operating using subscription keys
• FIG. 8 shows the means used in the broadcasting center to lock the information
• FIG. 9 shows the block diagram of a receiver according to the prior art
• FIG. 10 shows the block diagram of the means to be inserted into the receiver of the type of the previous figure to perform the unlocking of information.
• the videotex system of the invention is represented, in the form it takes in the case of the ANTIOPE system, by the diagram in FIG. 2. This system comprises known elements already represented in FIG.
• the system further comprises: A) - in the transmission center 2: a) - a generator 22 delivering a digital signal representing a service key K, this key changing randomly at determined intervals which are for example, of the order of a few minutes b) a locking automaton 24 comprising i) a comparator 28 to an input connected to the circuit 10 for memorizing the magazine from which it receives clear bytes, this comparator is able to distinguish, among these clear octets, those whose 7th and 6th binary elements are zero; this comparator has two outputs 31 and 32, the first conveying these bytes with 7 and 6 null bits and which is connected to the broadcasting multiplexer 12 (through a junction 11 ′), and the second conveying the clear bytes d j whose 7 and / or 6 bits are not zero; ii) a logic circuit 34 of the OR-exclusive type with two inputs, one connected to the second output 32 of the comparator 28 from which it receives the clear bytes d j to
• each receiver station 4 d) a circuit 36 delivering a digital signal representing the service key K in progress in the station transmission, e) an unlocking automaton 38 comprising: i) - a comparator 42 at an input receiving the encrypted bytes; this comparator.
• this comparator having two outputs 43 and 44, the first conveying these bytes whose 7 th and 6 th binary elements are zero, this first output being connected to the display member 20, the second conveying the encrypted bytes D j of which the 7 th and / or 6 th binary elements are not zero, ii) a logic circuit 46 of the OR-exclusive type with two inputs, one connected to the output 44 of the comparator from which it receives the encrypted bytes D j , this logic circuit having an output which carries decrypted bytes d j , which are then directed to the display member 20.
• this decrypting byte generator has an output 41 which delivers, for each encrypted byte received, a decrypting byte
• the generator of encrypting (or decrypting) bytes uses a pseudo-random sequence generator, which can be of different types.
• the sequence thus obtained is periodic and of maximum length 2 17 -1, and we then say that the generator polynomial is primitive. If ⁇ denotes a root of this polynomial, we can show that the set 0, 1, ⁇ , ⁇ 2 , ⁇ 3 ..., has a structure of body: it is the body provided with laws of addition by OU-exclusive and of multiplication modulo the polynom of Galois of extension CG (2 17 ).
• the interface with the outside includes 4 connections: an input 54, an output 56, a clock connection
• the minimum time interval tmm. between two clock strokes is linked to the delay in the propagation of the signal in the gates and the flip-flops.
• t min 3 gate delays + 1 toggle delay.
• the delay obtained is 23 ns
• the delay obtained is 40 ns .
• the maximum clock frequency is then approximately 7 MHz.
• the circuit of Figure 3 operates as follows. A "reset" command is first issued to impose a known state; then, the circuit is initialized by presenting n binary elements on the input connection 54 in synchronism with n clock ticks on the clock connection 58. The generator is then ready to operate. It delivers a binary element each time it receives a new clock signal.
• the combination of polynomials in question is obtained using the circuit 61 of FIG. 4.
• the circuit 62 generates the polynomial T, the circuit 64 the polynomial R and the circuit 66 the polynomial S.
• the gates 68 and 70 are AND gates, the second being., connected to circuit 66 by an inverting gate 72; door 74 is an OU-exclusive door.
• the entire circuit has an input 76, an output 78, a clock connection 80 and a reset connection 82.
• It essentially comprises a pseudo-random sequence generator 61 such as that which has just been described in connection with FIG. 4, a set of eight flip-flops 84 of the type D, connected to a bus 86, and a sequencer 88 also connected to the bus 86 and to the generator 61 and which manages the clock ticks and the input-outputs of the circuit.
• the interface with the outside is made up of 16 connections respectively: - selection 91, read 92, write 93 and reset 94, in terms of control, - clock 95, encryption / decryption 96, power supply 97 and ground 98 in terms of implementation, and - eight data connections B 1 to B 8 for the outputs.
• the parity of the encrypted bytes is the same as that of the clear bytes and we know that these bytes are odd.
• the 6th and 7th scales are. forced to zero, the 8th flip-flop imposes the correct parity if one is in the "encryption” position, and it is forced to zero if one is in the "decryption” position for the reasons which have just been mentioned; c) - The "write" command results in the display, on the bus, of the states of the eight flip-flops 84.
• the byte generator is initialized using the service key (which is made up of 64 binary elements, i.e. 8 bytes denoted k 1 to k 8 ) of the row number (which varies from
• This initialization of the generator, of bytes is practiced at the beginning of each row of information, using 8 particular bytes, obtained from the eight bytes which define the service key and the five bytes defining the page number and the row number.
• These eight bytes are, for example: k 1 ⁇ NR 1 , k 2 ⁇ NR 2 , k 3 ⁇ NP 1 , k 4 ⁇ NP 2 , k 5 ⁇ NP 3 , k 6 ⁇ NP 3 , k 7 ⁇ NR 1 , k 8 ⁇ NR 2 .
• the byte generator undergoes the following operations:
• Encrypting bytes C 1 C 2 C 3 C 4 C 5 C 6 C 7 . ..
• the locking automaton receives, from circuit 10, a series of bytes which modify its situation each time. This situation is defined by three parameters, which respectively depend on the page number received (which varies between 001 and 999), the row number (which ranges from 00 to 24) and its "state", which can take six different forms. :
• - State 3 the automaton lets the row number pass (NR 1 NR 2 ) by registering it;
• - State 4 the PLC encrypts the row of information after resetting the byte generator;
• FIG. 6 illustrates the evolution of the automaton as a function of the nature of the bytes that it receives.
• the FF, RS, US notations have already been defined.
• the different states of the PLC are represented by circled numbers corresponding to the previous list (states 1 and 3 are in dashed lines to distinguish them from the others because they are passive states).
• the PLC is in state O (to the left of the diagram). If the byte received is different from RS, the PLC remains in this state O. Hence the arrow which starts from the 0 circled and which returns to it.
• the automaton enters state 1 and lets the row number pass by registering it; then it goes to state 2 where it waits for a row start, etc.
• the clear byte is a "US" (row flag): the PLC goes to state 3; - the clear byte is a "FF" (end of page); the PLC goes to state 0; - the clear byte is an "RS" (page flag); the PLC goes to state 1;
• FIG. 7 illustrates the block diagram of the system of the invention provided with these access control means. As shown, this system comprises, in addition to the elements which have already been described in connection with FIG. 2:
• A) - a subscription management center 100 which generates digital signals corresponding to the subscription keys C i , these keys changing randomly at long intervals of the order of the month and according to patterns similar to that which has been indicated above by way of example;
• B) - in the transmission center - a circuit 102 for forming messages M. which receives from circuit 100 the signals corresponding to said subscription keys C i and from generator 22 the signal corresponding to service key K. These messages are obtained using an algorithm (K) parameterized by C i , which will be explained later.
• the circuit 102 delivers as many messages M i as there are subscription keys C i , these messages changing with the service key K. All of these messages are organized in a special page 104 called the control page d 'access. This page is transmitted cyclically by the multiplexer 12, but is not not viewable; its structure will be indicated later;
• each receiving station i) a subscription medium 106 which contains a memory 108 in which is registered at least one subscription block representing one of the subscription keys C i ; j) a circuit 110 for restoring the service key K, connected, on the one hand, to the digital signal decoder of circuit 14 from which it receives all of the messages M i constituting the access control page, and on the other hand, to the memory 108 of the subscription medium from which it receives the subscription key C i .
• This circuit 110 for restoring the service key K connected, on the one hand, to the digital signal decoder of circuit 14 from which it receives all of the messages M i constituting the access control page, and on the other hand, to the memory 108 of the subscription medium from which it receives the subscription key C i .
• each of these stations is capable of temporarily receiving subscription media and of writing one of the subscription keys C i into their memory 108.
• the subscription keys are generated at the subscription management center 100 which supplies lists to the emission centers 2 and to the stations 112 for loading the cards. More specifically, the subscription management center provides:
• a subscription block is composed for example of four fields:
• a subscription block is therefore composed of 168 binary elements, or 21 bytes.
• Such a block can easily be written in a medium such as a "credit card” which would be provided with a PROM (Programmable Read Only Memory) with a capacity of 4096 binary elements usable for this purpose.
• PROM Program Read Only Memory
• Such a card could accommodate up to 24 subscription blocks having the indicated characteristics.
• the calculation of the messages from the subscription keys C i and the key K is carried out in the transmission center by the circuit 102 which is organized around a microprocessor.
• This circuit is programmed to implement an algorithm which is based on two Galois bodies having for characteristics the prime numbers of Mersenne 2 61 -1 and 2 127 -1.
• This algorithm uses the subscription keys C i (127 binary elements) and the service key K (56 binary elements), as follows:
• the structure of the access control page which collects such messages is as follows:
• Row zero begins with three complementary codes C 1 , C 2 and C 3 traditionally intended to allow the insertion of functional pages in magazines.
• the fourth binary element of C 2 is at 1.
• the zero row continues with a header block which includes the service code (16 binary elements), the current month (6 binary elements) and a cyclic redundancy code of 16 binary elements.
• a subscription block is characterized by a subscription index which consists of a code with 8 binary elements. Likewise, it was indicated that at any given time, there could be 22 subscription blocks in progress, if we retain the subscription scheme indicated above for 24 available rows.
• a row number extends over 2 bytes each having 4 useful binary elements (the other four constitute a Hamming code), or in total also 8 binary elements.
• the subscription index is possible to take the subscription index as the row number in the access control page. Consequently, in an advantageous variant, the number of a row on the access control page gives the index of the subscription to which the following access block relates.
• said access blocks they consist of two fields:
• a slow assembly 120 (constituted in practice by a suitably programmed microprocessor and interface) which includes a circuit 122 which ensures the control and management of the clocks (lifetime of the key of lock K, decision to insert pages access control) and a circuit 124, for the composition of the access control page, this circuit receiving the messages M i of the circuit 102 already mentioned.
• the circuits 122 and 102 are connected to a random generator 134.
• the operator supplies this set 120 with the operating time instructions one by one. connection 126 and the subscription blocks in progress at the start of each session of the service considered, by a connection 128.
• This slow assembly is interfaced by two memories: memory 130 which contains K, the service key, and memory 132 which contains the access control page. Unrepresented control connections make it possible to convey orders: lock-stop, insertion of the access control page, reading of K, acknowledgment at the end of the magazine page, acknowledgment at the end of the access control page and of course , reset.
• a fast assembly 134 (constituted by a wired logic allowing bit rates of the order of 20 k bytes / second) which includes the locking automaton 24 already described and the generator of encrypting bytes 26, the structure and operation have been explained above with reference to FIG. 5.
• the advantage of the assembly described is that the operator is master of the life of the service key K, and of the instants of insertion of the access control page in the locked magazine.
• the receiver illustrated in FIG. 9 comprises the large functional blocks already mentioned in FIGS. 1 and 2, namely: a reception and demodulation circuit 14, a channel 16 for processing image signals, a channel 18 for processing digital signals and a display means 20.
• the circuit 14 delivers, on the one hand, the sound to a loudspeaker 15, and on the other hand, the video signal to a color decoder and scanning generator 19.
• the color signals B 1 , V 1 and R 1 , as well as the luminance L 1 from the circuit 19 are transmitted to the tube 140 through a video switch 141.
• the receiver station illustrated comprises in the channel 18 for processing digital signals, a video splitter data 142 (which works according to the DIDON procedure to extract a sequence of bytes from the analog signal) whose input is connected to the video output of circuit 14.
• This separator has its output connected to a first selection circuit 143 (which functions nne also according to the DIDON procedure, so as to extract the bytes conveyed in a digital channel) similar to the terminal equipment described in patent application n ° EN 75/18319 already cited.
• the output of circuit 143 is connected by a junction 144 of the type described in French patent application no.
• the data are bytes structured in packets wrapped by a procedure of eight header bytes, including three bytes of channel number.
• the digital DIDON circuit 143 selects a digital channel, that is to say lets the useful data of the selected packets pass, according to their channel number.
• junction 144 does not play an essential role in the system of the invention, but is above all useful for facilitating physical separation at the transport level (DIDON) and at the service level (ANTIOPE).
• the page selection and the decoding of the selected pages are carried out in the circuit 145.
• This assembly decodes an information page, row by row, and comes to fill the page memory 146.
• This memory can have a capacity of 1001 words of 16 binary elements (25 rows of 40 characters plus a control word), each character being coded on 16 binary elements in form and display attributes.
• the decoding of the information pages by the circuit 145 does not pose any particular problem, because in its conventional design (described in the patent application already cited), this circuit is already aware of the page numbers and row. He is even aware of the zero row since he analyzes the complementary codes there. The page number is used to select the page, while the row number is used to position a pointer in page memory 146.
• the decoder 145 initializes the decrypting byte generator 26 ′, according to the process indicated above with respect to FIG. 5 and which uses nine successive orders .
• the circuit 145 has the programs allowing the analysis and the use of the access control pages.
• the circuit locates in memory 108 of the card 106, at the appropriate address, a valid subscription block from which it extracts the index of the subscription. Then it searches in the access page, the row corresponding to this subscription index (since, as we have seen, the rows are numbered by the indices). He retrieves the access block there and extracts the message M i . This message is transmitted to the circuit 110 which then calculates the key K using the subscription key C i appearing in the subscription block which has just been located in the card.
• the circuit 110 (which can be an integral part of the card and constitute the support 36) is programmed to develop an algorithm which is, as on the show, a double body algorithm.
• the operations are as follows:
• K having 56 useful binary elements, elements 57, 58, 59, 60 and 61 must be zero. Otherwise K is set to zero before continuing operations. 3)
• the 56 useful bits of K are then available in the form of eight odd bytes.
• the foregoing description relates to an ANTIOPE system in which information is transmitted by the DIDON procedure in the lines of a television signal.
• the invention is more general, since it does not presuppose a particular method of transporting information since, as was pointed out above, the locking takes place at the service level and not at the level of transport.
• ANTIOPE system was only taken as an embodiment and that the invention could be applied to other systems without difficulty for those skilled in the art, and in particular to the TITAN system or else to CEEFAX or ORACLE, or VIEWDATA or PRESTEL systems.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Television Systems (AREA)
• Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
• Lock And Its Accessories (AREA)
• Small-Scale Networks (AREA)
• Compression Or Coding Systems Of Tv Signals (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9221650

Family Applications (1)

Country Status (9)

Families Citing this family (144)

Citations (2)

Family Cites Families (7)

• 1979
  • 1979-02-06 FR FR7902994A patent/FR2448824A1/fr active Granted
• 1980
  • 1980-01-30 CA CA000344659A patent/CA1150820A/en not_active Expired
  • 1980-01-31 US US06/117,234 patent/US4337483A/en not_active Expired - Lifetime
  • 1980-02-04 EP EP80400169A patent/EP0014652B1/fr not_active Expired
  • 1980-02-04 DE DE8080400169T patent/DE3064785D1/de not_active Expired
  • 1980-02-05 WO PCT/FR1980/000019 patent/WO1980001636A1/fr unknown
  • 1980-02-05 ES ES488280A patent/ES8106994A1/es not_active Expired
  • 1980-02-05 JP JP55500389A patent/JPH0318396B2/ja not_active Expired
  • 1980-10-04 SU SU802990876A patent/SU1172456A3/ru active

Patent Citations (2)

Also Published As

Similar Documents

Legal Events