`Guillou
`
`[11]
`
`[45]
`
`4,337,483
`Jun. 29, 1982
`
`[75]
`
`[54] TEXT VIDEO-TRANSMISSION SYSTEM
`PROVIDED WITH MEANS FOR
`CONTROLLING ACCESS TO THE
`INFORMATION
`Inventor: Louis C. Guillou, Bourgbarre-Saint
`Erb1on, France
`[73] Assignees: Etablissement Public de Diffusion dit
`"Telediffusion de France",
`Montrouge; L'Etat Francais,
`represente par le Secretaire d'Etat
`aux Poste et Telecommunications
`(Centre National d'Etudes des
`Telecommunications), Issy les
`Moulineaux, both of France
`[21] Appl. No.: 117,234
`[22] Filed:
`Jan. 31, 1980
`[30)
`Foreign Application Priority Data·
`Feb. 6, 1979 [FR]
`France ................................ 79 02994
`Int. CJ,3 ......................... H04N 7/16; H04K 1/00
`[51]
`[52] U.S. Cl ..................................... 358/114; 340/706;
`358/147; 340/825.54; 340/825.5
`[58] Field of Search ...................... 455/2; 358/86, 114;
`340/147 LP, 149 A, 149 R, 152 R, 152 T, 706;
`178/22.08
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,934,079 1!1976 Barnhart ............................... 358/86
`3,956,615 5/1976 Anderson et al. .............. 340/152 R
`3,997,718 12/1976 Ricketts .......... : ....................... 455/2
`
`4,081,132 3/1978 Sherman ............................. 358/122
`4,214,230 7/1980 Fak et al. ........................ 340/149 A
`Primary Examiner-Howard A. Birmiel
`[57]
`ABSTRACT
`A text video-transmission system comprising an infor(cid:173)
`mation emitting center and receiving stations, the emit(cid:173)
`ting center comprising encryption means using an oper(cid:173)
`ating key, each receiving station comprising decryption
`means using the operating key, wlherein in this system,
`the encryption means of the emitting center comprise: a
`generator delivering a numerical signal representing an
`operating key K, this key changing randomly at prede(cid:173)
`termined intervals; an automatic encryption means
`comprising: a discriminator with an input connected to
`a magazine memorizing circuit from which it receives
`clear octets, this discriminator being capable of distin(cid:173)
`guishing, among these clear octets, those wherein the
`7th and 6th binary elements are zero, an OR-exclusive
`logic circuit connected to the discriminator from which
`it receives octets wherein the 6tlh and/or 7th binary
`elements are not zero, this logic circuit having an output
`which carries encrypted octets; a generator of encoding
`octets, the decoding means of each receiving station
`comprising: a generator of a numerical signal represent(cid:173)
`ing the operating key K in use in the emitting center,
`automatic decryption means comprising: a discrimina(cid:173)
`tor adapted to distinguish, among the encrypted octets,
`those wherein the 7th and 6th binary elements are zero,
`an OR-exclusive logic circuit connected to the discrimi(cid:173)
`nator; and a generator for decoding octets.
`
`11 Claims, 10 Drawing Figures
`
`OISCRIMNAlOR
`
`42
`jlt~ _L.::_=_t==~
`JB I
`,-1---'--.
`DIG!~ I
`I
`L_
`
`I.I'IE
`
`APPLE EX. 1006
`Page 1
`
`
`
`U.S. Patent
`
`Jun. 29, 1982
`
`Sheet 1 of 9
`
`4,337,483
`
`INFORMATION
`SOURCE
`.
`
`FIG. 1
`
`RECEIVING / ;
`STATIONS
`·
`'24
`
`RECEIVING
`C CT
`
`~~-
`
`____..------4-..
`
`14
`
`VIDEO
`LINE
`
`1.§
`
`DIGITAL
`LINE ~_,.--,-
`I
`I
`I~__.
`I
`I
`I
`I
`L ____ _j
`
`APPLE EX. 1006
`Page 2
`
`
`
`U.S. Patent
`
`Jun. 29, 1982
`
`Sheet 2 of 9
`
`4,337,483
`
`INFORMATION
`SOURCE
`
`5
`
`22
`
`GENERATOR
`
`__,.........\. I
`EMITTING
`l
`CENTER _____.-
`DISCRIMINATOR I
`24 I
`ENCRYPTION""
`MEANS
`
`FIG. 2
`
`APPLE EX. 1006
`Page 3
`
`
`
`U.S. Patent
`
`Jun. 29, 1982
`
`Sheet 3 of 9
`
`4,337,483
`
`APPLE EX. 1006
`Page 4
`
`
`
`U.S. Patent
`
`Jun. 29, 1982
`
`Sheet 4 of 9
`
`4,337,483
`
`7G
`
`78
`
`FIG. 4
`
`BUS r~ _ _ _ _ _ _ ___:_
`
`.Ba 8 7 13>6 · Bs B4 B..3 B-< 8 1
`
`I •~~~~~~~
`
`sEauENCER
`
`84FLIP(cid:173)
`YFLOPS
`
`I
`I
`I
`I
`I
`I
`I
`I
`1.___.---1--1
`~
`I
`I
`I
`CONNECTIONS
`L - - - - - - - - - - - ~---_j
`FIG. 5 GENERATOR._..2,G' ( 2{)')
`
`APPLE EX. 1006
`Page 5
`
`
`
`U.S. Patent
`
`Jun. 29, 1982
`
`Sheet 5 of 9
`
`4,337,483
`
`FF
`j
`:j; R$
`us
`RS--0:)
`
`·~~*1&i ~00
`~Rs~--0::)
`FF
`I
`=/:- R/$
`us
`
`FF
`
`Fin
`
`FIG. 6
`
`APPLE EX. 1006
`Page 6
`
`
`
`U.S. Patent
`
`Jun. 29, 1982
`
`Sheet 6 of 9
`
`4,337,483
`
`INFORMATION
`SOURCE
`
`EMITTING
`
`ENCRYPTION
`MEANS----
`SUBSCRIPTION
`CENTER
`
`MESSAGE
`FORMING
`CIRCUIT
`
`I c.i.:
`
`I
`I
`I
`I
`
`I
`I
`I
`I
`I
`
`STATION
`
`FIG. 7
`
`APPLE EX. 1006
`Page 7
`
`
`
`128
`
`MEMORY
`
`•·
`
`c .
`Cl'1 .
`
`Cl
`
`COMPOSITION OF
`THE ACCESS CONTROL
`PAGE
`
`MESSAGES I
`I
`FORMING
`CCT
`
`SLOW
`ASSEMBLY
`
`. . .
`i
`:
`:
`-- _____ i ____ j _____ t__7
`:
`~
`·.
`12
`/
`\,.._ ·------:-· ________ .,
`! \!/
`l . .
`. .
`:
`..........
`
`\
`
`l
`
`APPLE EX. 1006
`Page 8
`
`
`
`LOUDSPEAKER
`
`, - - - - -~----16'
`I
`15 I
`I
`I L ___ _
`r-= -.. -.: - - -- - CO-LOR DECOD-ER A-N-D -
`I
`142
`I
`VIDEO-DATA
`I
`~..,--, ....... .......,,...,....,,.... SEPARATOR
`I
`
`_ _j
`
`SCANNING GENERATOR
`
`-
`
`I
`I
`I
`L
`
`-
`
`-
`
`-
`
`-
`
`-
`
`FIG. 9
`
`JUNCTION
`144
`
`PAGE
`MEMORY
`
`f---.___
`I 18
`j
`\
`- - , '--,.----
`I rnGtTAL
`I
`147
`I PROCESSING
`\....KEYBOARD
`I
`~ ~ ~ ~ 1----------.....J LINE
`I
`I
`0000
`0000
`L ________ - - __ _j
`
`c .
`en .
`
`-\0
`
`00
`N
`
`00
`0
`~
`\0
`
`APPLE EX. 1006
`Page 9
`
`
`
`U.S. Patent
`
`Jun. 29, 1982
`
`Sheet 9 of 9
`
`4,337,483
`
`DECODING
`CIRCUIT
`
`J~~TION
`
`DISCRIMINATOR
`
`~2
`
`146
`-LPA.GE: ______ _j
`MEMORY
`
`46 OR-EXCL.
`-GATE
`
`KEYBOARD
`
`0 0 0 0
`0000
`0000
`0000
`
`Mi
`
`K
`
`147
`
`Ci I I MEMORY
`I 1os
`106 ~
`
`I
`
`L-~-J l
`
`c3G
`
`OPERATING
`K SUPPLY
`
`FIG. 10
`
`APPLE EX. 1006
`Page 10
`
`
`
`1
`
`4,337,483
`
`TEXT VIDEO-TRANSMISSION SYSTEM
`PROVIDED WITH MEANS FOR CONTROLLING
`ACCESS TO THE INFORMATION
`
`20
`
`BACKGROUND OF THE INVENTION
`The present invention relates to a text video-transmis(cid:173)
`sion system provided with means for controlling access
`to the information.
`It can be used in the transmission and display of infor- 10
`mation on television receivers for purposes ofentertain(cid:173)
`ment, information or education. The invention applies
`essentially to a broadcase system (i.e. unidirectional) by
`means of which alphanumerical information organised 15
`into pages and magazines can be put into television lines
`·and to interactive system (i.e. two-directional) affording
`access to data bases (general information, directories,
`etc.) and to interactive services (transactions, messages,
`education) through the telephone system.
`In the first system, the distribution of information is
`effected by a method of distribution in bundles, compat(cid:173)
`ible with the distribution of the television signal.
`These systems have already been described in numer(cid:173)
`ous articles or patent applications. Reference is made 25
`hereinafter essentially to the so-called ANTIOPE sys(cid:173)
`tem, a detailed description of which can be found par(cid:173)
`ticularly in the following documents:
`the article by Y. GUINET entitled: "Etude compara(cid:173)
`tive des systeines de
`te!etexte en radiodiffusion. 30
`Quelques avantages de Ia diffusion des donnees par
`paquets appliquee au teletexte" which appeared in the
`U.E.R. Cahier Technique, no. 165, October 1977, pages
`242 to 253;
`the article by B. MARTI and M. MAUDUIT entitled 35
`"ANTIOPE, service de telt~texte", which appeared in
`the journal "Radiodiffusion Television", 9th year, no.
`40. November-December 1975, 5/5, pages 18 to 23;
`the "Specification du Systeme de teletexte ANTI(cid:173)
`OPE", edited by the Centre Commun d'Etudes de THe- 40
`vision et Telecommunications (CCETT);
`French patent application no. 75 18319, filed on June
`6th 1975 and entitled "Data distribution system";
`French patent application Peg. no. 76 27212, filed on
`Sept. 6th 1976 and entitled "System for the numerical 45
`transmission and displaying of text on a television
`screen";
`French patent application no. 76 29034, filed on Sept.
`22nd 1976 and entitled "Improvements to systems for
`the numerical transmission and displaying of texts on a so
`television screen";
`the French application for a certificate of addition no.
`77 17625, filed on June 3rd 1977 and entitled "Data
`distribution system".
`As this video-transmission system is thus widely 55
`known, it will not be described in detail here. Only the
`essential principles will be mentioned, to make the in(cid:173)
`vention easier to understand. For any details of design
`or construction, reference can be made to the docu(cid:173)
`ments cited above which in turn refer to others, and all 60
`these documents should be regarded as incorporated in
`this description.
`FIG. 1 shows, in highly diagrammatic form, the es(cid:173)
`sential elements of such a system. Such a system com(cid:173)
`prises an emitting centre 2 and receiving stations 4, 4', 65
`etc.
`The emitting centre receives information from one or
`more sources 5 and comprises:
`
`2
`means 6 for composing a magazine consisting of
`pages organised into lines of characters, if the supplier
`of the information has not already composed it in this
`way;
`a magazine memorising circuit 10 in the form of 'nu(cid:173)
`merical signals grouped into octets (8 binary elements);
`a junction 11 connected to the circuit 10,
`a distribution multiplexer 12 serving to form bundles
`of octets and insert information in the lines of a televi(cid:173)
`sion signal, this device using the procedure mentioned
`above.
`Each receiving station comprises:
`a circuit 14 for receiving and demodulating said tele(cid:173)
`vision signal;
`a line 16 for processing the video picture signals;
`a line 18 for processing numerical signals, this line
`comprising notably a numerical data decoder, and fi(cid:173)
`nally
`display means 20.
`In a system of this kind, the flux of information from
`the suppliers of information to the distribution. centres
`has the following general characteristics.
`The source 5, which is an information-supplying data
`bank, is, for example, a meteorological service,. the
`Stock Exchange, an information agency, etc. This bank
`supplies the composing means 6 which puts the infor(cid:173)
`mation into pages of the suitable format. ·
`To indicate the size scales involved, it can be stated
`that, in the case of an experimental magazine produced
`for share values, there may be about 80 pages containing
`on average 800 octets, i.e, a total of 64000 octets. A
`shares magazine of this kind uses a resource of 10 lines
`per frame. A television line lasts 64 I-tS and can carry 32
`useful octets, and there are 50 frames per second .. Thus,
`the resource of a line/frame makes it possible to trans(cid:173)
`mit 50 X 32 X 8 = 12800 b/s (binary elements per sec(cid:173)
`ond). The entire magazine is thus transmitted in
`
`64 X 8
`12.8 X 10
`
`<II seconds,
`
`which means that the magazine is transmitted cyclically
`with a periodicity of 4 seconds.
`It will be noted that an interactive line connecting the
`distribution centre to the information supplier typically
`operates at 4800 b/s and this difference in speed relative
`to the speed of broadcasting at 12800 b/s explains the
`need to memorise the information at the distribution
`source.
`In such system, the octets carrying the information
`are traditionally marked as fo]]ows:
`
`bs
`Odd-numbered
`
`High weight
`
`Low weight
`
`wherein the binary element b8 is an odd-numbered ele(cid:173)
`ment, in other words an element wherein the total num(cid:173)
`ber of "l" appearing in the octet is odd.
`the octet
`Thus, according
`to
`this notation,
`U/k)=(4/7) corresponds to the octet 11000111.
`The octets are divided into control octets and data
`octets. The control octets indicate, in particular, the
`beginnings and ends of pages and the beginnings and
`ends of lines. The data octets, inserted between the
`control octets, correspond to the characters contained
`
`APPLE EX. 1006
`Page 11
`
`
`
`4,337,483
`
`3
`in the lines. All these octets, both control and data oc(cid:173)
`tets, comprise a heavy weight binary element which is
`an odd-numbered element.
`All the codes, identified by such octets, are organised
`into a table as follows:
`
`0
`0
`I
`
`0
`1
`0
`
`b7
`b6
`bs
`
`j
`
`0
`0
`0
`
`0
`
`1
`0
`I
`
`1
`0
`0
`
`4
`
`0
`I
`2
`3
`4
`15
`
`b4
`0
`0
`0
`0
`0
`I
`
`b3
`0
`0
`0
`0
`I
`I
`
`b2
`0
`0
`I
`I
`0
`I
`
`bi
`0
`I
`0
`I
`0
`I
`
`15
`
`Now that these points regarding the general system
`have been mentioned, we can deal with the problem
`which the invention sets out to solve.
`The advent of the new services above mentioned
`raises the question of how to charge for them, i.e. how
`to implement a system for identifying and controlling
`the audiences. This question arises more generally for
`any broadcast service which tends to make the broad(cid:173)
`casting networks more profitable by making better use
`10 of the resources.
`Taxation of the subscription type constitutes a both
`flexible and durable relationship between a service and
`its users. Such a method of taxation is particularly justi(cid:173)
`fied in broadcasting.
`Taxation of the type based on consumption may also
`be used; this method of taxation is fundamental for "in(cid:173)
`teractive" systems (where there is a dialogue between
`the subscriber and the information source; however, it is
`of secondary value in broadcasting systems (in which
`information is transmitted in one direction to the sub(cid:173)
`scribers).
`There may be intermediate systems known as "quasi-
`interactive" systems wherein the content of the distribu(cid:173)
`tion source is continuously modified to meet the re(cid:173)
`quirements of the users, which are transmitted via a
`public data network. The advent of new distribution
`means with a very large capacity, such as satellites, will
`develop this quasi-interactive mode considerably, thus
`making it necessary to implement a system for control-
`30 ling access to the information provided.
`This problem of access control raises above all the
`problems of encrypting the information when it is
`broadcast and decrypting when it is received. Natu(cid:173)
`rally, these problems must be resolved in accordance
`with the specificity of the teletext system which is to be
`controlled. In particular, the method of scrambling the
`information and restoring the intelligibility of the infor(cid:173)
`mation should not harm the performance of the system.
`Now, it is known that messages translated into the
`40 suitable language are characterised by a substantial
`redundancy so that the incidence of transmission errors
`on the intelligibility of the information broadcast is
`minimised. Thus, alphabetic texts are intrinsically very
`redundant, as are the majority of semi-graphic draw(cid:173)
`ings; the character display controls use escapement
`characters; the page and line numbering uses Hamming
`codes; all the octets constituting a magazine are trans(cid:173)
`mitted with imparity, etc .... Thus, there is no attempt
`to compress the information and the method of recover(cid:173)
`ing the intelligibility of the information must therefore
`respect this redundancy and not propagate the deleteri-
`ous consequences of transmission errors, which are
`difficult to monitor in broadcasting.
`The means for recovering the intelligibility of infor-
`55 mation which has been locked up beforehand consti(cid:173)
`tute, to some extent, an "electronic lock", and the intel(cid:173)
`ligibility of the locked up information can only be re(cid:173)
`covered by the use of a suitable key.
`The first question which arises is therefore the room
`60 to be allotted to this electronic lock in the system to be
`monitored. In fact, in the case of the teletext system,
`two procedures are used: the transporting procedure
`and the operating procedure. At what level of the pro(cid:173)
`cedure should this lock be placed?
`
`25
`
`In this table,
`the columns 0 and l which correspond to the octets 20
`wherein the 6th and 7th binary elements are zero
`(b6=b7=0); contain control octets;
`col1.1mns 2 and 3 contain essentially numbers and
`punctuation marks;
`column& 4 and 5 contain essentially capital letters,
`columns 6 and 7 chiefly contain lower case letters.
`As an example, a current page of information accessi-
`ble to tpe user is in the following form:
`(l) First, it contains a page heading, which is made up
`of the control codes (ETX) FF RS NP1 NP2 NP3:
`wherein:
`ETX is a code which terminates the preceding page,
`FF is a code indicating a new page,
`RS is a page flag,
`NP1, NP2, NP3 are codes indicating a page number 35
`from 001 to 999.
`(2) After the page heading there is a "zero" line: US
`00 C1 C2 C3 ........ RC LF,
`wherein:
`US is a line flag,
`00 indicates the zero line,
`C1. Cz, C3 are supplementary codes,
`RC LF terminate the line.
`The zero line may also contain an operating name, a
`date, a time and optionally information on charges. This 45
`zero line does not carry any information which consti(cid:173)
`tutes the service. It is part of the procedure.
`(3) After the zero line come the information lines
`comprising first of all a line heading which is made up of
`the codes (RC LF) US NR1 NRz, wherein:
`RC LF terminate the previous line,
`US is a line flag,
`NR1 NR2 constitute the line number, which goes
`from 01 to 24.
`Then come the data octets d1, dz ... dn. These octets are
`inserted between the start of the current line and either
`a line end-start of new line - or the end of a page.
`These octets d1. dz, ... dn represent the information
`constituting the service being broadcast. Thus the infor(cid:173)
`mation element in a system ofthis kind is the displayable
`line.
`There are also other pages in addition to these current
`pages of information. They are functionally accessible
`by means of the supplementary codes C1, Cz, C3 con(cid:173)
`tained in the zero line. These are, for example, cover 65
`sheets and warning pages. All these pages are part of the
`procedure. Finally, there is a page of summary which
`can be regarded as part of the data.
`
`so
`
`BRIEF SUMMARY OF THE INVENTION
`The invention answers this question by proposing a
`lock which is attached to the operating level. This
`
`APPLE EX. 1006
`Page 12
`
`
`
`4,337,483
`
`25
`
`5
`method has a number of advantages. First, it respects all
`the constraints of synchronisation and non-propagation
`of the transmission errors. Furthermore, it is indepen(cid:173)
`dent of the transporting network used by the system.
`Finally, it does not require any adjustment of the exist(cid:173)
`ing standards and will accommodate any future devel(cid:173)
`opment of these standards.
`In other words, and according to a first feature of the
`invention, the encryption of the information constitut(cid:173)
`ing a magazine is carried out at the distribution source. 10
`More precisely, the encryption means are located up(cid:173)
`stream of the multiplexer, which has reference numeral
`12 in the plan in FIG. 1.
`Now that room has been found for the encryption
`means, there is still the question of the object to which 15
`these means are applied.
`The invention an~wers this second question by pro(cid:173)
`posing means whose function is to encrypt up only the
`information carried in the displayable lines of the ordi(cid:173)
`nary pages of the magazine. In other words, the encryp- 20
`tion does not affect the control codes appearing in col(cid:173)
`umns 0 and 1 of the table of codes given hereinbefore
`and, in particular, the codes ETX, FF, RS, RC, LF and
`US. It affects only the data codes d1, d2, etc. This is the
`second feature of the invention.
`Finally, the invention sets out to solve a third prob(cid:173)
`lem, that of respecting the imparity of the octets broad(cid:173)
`cast.
`All these aims are achieved by the use, according to
`the invention, of automatic encryption means which 30
`comprise means for forming a succession of encoding
`octets wherein the binary elements marked CJ to cs are
`generated as follows:
`CJ. c2, c3, c4and csare taken at the output of a pseudo(cid:173)
`random series generator which is reset at the start of 35
`each displayable line by an operating key K and by the
`page and line numbers in question;
`C6 and C7 are at zero, and
`cs is an even-numbered element.
`Thus, the coding series obtained is made up of even 40
`octets. These octets are marked C1, C2 ... Cn or, generi(cid:173)
`cally, Cj. The clear octets constituting a line of informa(cid:173)
`tion form a series marked db d2 ... dn or, generi(cid:173)
`cally, dj. These octets are odd-numbered and are
`locked up by the encoding octets in accordance with 45
`the following rules:
`At each new clear octet of the displayable line, an
`octet is taken from the encoding series. There are two
`possibilities:
`If the clear octet belongs to columns 0 and 1 of the 50
`table of codes (b6=b7=0) the clear octet is transmitted
`as it stands, and the encoding octet is not used;
`If the clear octet does not belong to column 0 or 1,
`then the clear octet and the encoding octet are com(cid:173)
`bined by an "OR-exclusive" logic circuit to form a 55
`broadcast octet: Dj=dj$Cj, where the symbol EEl repre(cid:173)
`sents the "OR-exclusive" logic operation.
`Because of the parity of the encoding octets, the
`broadcast octets are odd, like the clear octets, thus
`satisfying the requirement mentioned above.
`Moreover, the "OR-exclusive" operation is mani(cid:173)
`fested by the substitution of the clear octet by a broad(cid:173)
`cast octet belonging to the same group of columns as
`the clear octet, namely:
`the group of columns 2 and 2 which contains essen- 65
`tially the numbers and punctuation marks,
`the group of columns 4 and 5 which contains mainly
`capital letters,
`
`6
`and the group of columns 6 and 7 which contains
`mainly lower case letters.
`Finally, the octets belonging to columns 0 and 1 are
`not modified, particularly the octets corresponding to
`the codes ETX, FF, RS, RC, LF and US, which are
`transmitted as they stand. Moreover, owing to the fact
`that the 6th and 7th binary elements of the encoding
`octets are zero, no new octets belonging to these col-
`umns are introduced. Thus the desired transparency is
`ensured.
`In this way, all the aims listed albove are attained with
`the locking means used according to the invention.
`To reinforce the inviolability of the lock thus formed,
`the operating key K is advantageously modified at ran(cid:173)
`dom at predetermined, relatively short intervals (of the
`order of a few minutes, for example).
`It then remains to decrypt the information when it is
`received. To do this, the receiver should comprise a
`generator of decoding octets which delivers octets
`formed as follows:
`the low weight 5th binary elements are taken from a
`quasi-random series obtained from a generator reset at
`each start of a line by the operating key K, by the page
`and line numbers in question;
`the 6th and 7th binary elements are zero, and
`the 8th binary element is forced to zero.
`The rules for decryption are analogous to the rules
`for encryption; at each new octet received, belonging to
`an encrypted line, a new decoding octet is generated.
`There are two possibilities:
`If the octet received belongs to columns 0 and 1, it is
`transmitted as it stands to the interpreting circuits;
`If the octet received does not belong to columns 0
`and 1 (because its 6th and/or 7th binary elements are
`not zero) it is combined by an OR-exclusive circuit with
`the decoding octet before interpretation is carried out.
`Interpretation of the language is thus closely inter(cid:173)
`connected to the encryption of the lines of information,
`and the robustness of the structure of the language
`broadcast is not affected by the encryption operations.
`Now that these general comments have been made
`regarding the invention, the precise definition of the
`object of the invention can then be worded as follows:
`Transmission system comprisi111g an information emit(cid:173)
`ting centre and receiving stations, the emission centre
`comprising:
`means 6 for composing a magazine consisting of
`pages organised into lines of characters, if such means
`are not already contained in the information source,
`a circuit 10 for memorising the magazine in the form
`of numerical signals grouped i111 octets (8 binary ele(cid:173)
`ments), these octets comprising control octets and data
`octets, the control octets indicating in particular the
`beginnings and ends of pages and the beginnings and
`ends of lines, the data octets corresponding to the char(cid:173)
`acters contained in each line, all these control and data
`octets comprising a binary element of high weight
`which is an odd-numbered element, the octets wherein
`the 6th and 7th binary elements are zero being control
`60 octets,
`a junction 11 connected to the circuit 10, and
`a distribution multiplexer 12 serving to insert infor-
`mation in the lines of a television signal, this emitting
`centre also comprising means for encoding the informa(cid:173)
`tion using an operating key, each receiving station com(cid:173)
`prising:
`a circuit 14 for receiving and demodulating said tele(cid:173)
`vision signal,
`
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`7
`a line 16 for processing the video picture signals,
`a line 18 for processing numerical signals, containing
`in particular a numerical signal decoder, and
`display means 20, each receiving station further com(cid:173)
`prising means for decoding the coded information using
`said operating key, the system being characterised in
`that:
`(A) the encoding means of the emission centre com(cid:173)
`prise:
`(a) a generator 22 delivering a numerical signal repre- 10
`senting an operating key K, this key changing randomly
`at predetermined intervals,
`(b) automatic encryption means 24 comprising:
`(i) a discriminator with an input connected to the
`magazine memorising circuit from which it receives 15
`clear octets, this discriminator being adapted to distin(cid:173)
`guish, among these clear octets, those wherein the 7th
`and 6th binary elements are zero, this discriminator
`having two outputs, the first carrying these octets
`wherein the 7th and 6th binary elements are zero, and 20
`connected to the distribution multiplexer through the
`junction, and the second carrying the clear octets dj
`wherein the 7th and/or 6th binary elements are not
`zero,
`(ii) an OR-exclusive logic circuit with two inputs, one 25
`of which is connected to the second output of the dis(cid:173)
`criminator from which it receives the clear octets dj
`wherein the 6th and/or 7th binary elements are not
`zero, this logic circuit having an output which carries
`odd-numbered coded octets Dj, the coded octets then 30
`being directed towards the distribution multiplexer
`through the junction;
`(c) a generator of encoding octets controlled by the
`automatic encryption means from which it receives
`octets indicating the page and line numbers of the data 35
`to be transmitted and the signal corresponding to the
`operating key, this generator of octets delivering, for
`each data octet dj of a displayable line, an encrypted
`octet Cj, this octet having an even-numbered 8th binary
`element and 7th and 6th binary elements of zero, this 40
`octet being applied to the other input of the logic cir(cid:173)
`cuit,
`(B) the decoding means of each receiving station
`comprise:
`(d) a generator of a numerical signal representing the 45
`current operating key K in the emitting centre,
`(e) automatic decryption means comprising:
`(i) a discriminator with an input connected to the
`numerical signal decoder of the receiving station, from
`which it receives. the coded octets, this discriminator SO
`being adapted to distinguish, among these coded octets,
`those wherein the 7th and 6th binary elements are zero,
`this discriminator having two outputs, the first carrying
`these octets wherein the 7th and 6th binary elements are
`zero, this first output being directly connected to the 55
`display means, the second carrying the coded octets Dj
`wherein the 7th and/or 6th binary elements are not
`zero,
`(ii) an OR-exclusive logic circuit with two inputs, one
`connected to the second output of the discriminator 60
`from which it receives the coded octets Dj, this logic
`circuit having an output which carries decoded octets
`dj which are then directed towards the display means;
`(f) a generator of decoding octets controlled by the
`automatic decryption means which transmits to it the 65
`octets indicating the page and line numbers of the data
`transmitted and the signal corresponding to the current
`operating key K, this generator of decoding octets
`
`8
`having an output which delivers, for each encrypted
`octet received, a decoding octet Cj having a high
`weight binary element which is forced to zero and 7th
`and 6th binary elements of zero.
`Encryption and decryption means of this kind pro(cid:173)
`vide an advantageous solution to the problem of charg(cid:173)
`ing mentioned hereinbefore. For this purpose, the in(cid:173)
`vention proposes that in addition to the operating key
`whose function has been defined above, subscribers'
`keys should be used, which are generated randomly by
`a charge administration centre. These keys have a rela(cid:173)
`tively long service life (from 1 to 12 months), compared
`with the operating key (which is of the order of a few
`minutes).
`To illustrate the functioning of this double key sys(cid:173)
`tem, one could take the example of a subscription plan
`using four types of subscription:.! month, 3 months, 6
`months and one year. In addition to its duration, a sub(cid:173)
`scription is characterised by the month in which it be(cid:173)
`gins. With a plan of this kind, in a given month and for
`a given service, there are thus 22 subscribers' keys liable
`to be used by the users: a monthly key, three three(cid:173)
`monthly keys, six six-monthly keys and twelve yearly
`keys.
`.
`Each month, the charge administration centre pro(cid:173)
`vides each distribution centre with a list of 22 subscrib(cid:173)
`ers' keys in use for each service distributed by this cen(cid:173)
`tre. It also provides the subscription sales points with
`another list of 4 keys which are to start in the following
`month (one month, three months, six months and a
`year), for each service, with the prices of the subscrip(cid:173)
`tions.
`A suitable machine installed in each sales point re(cid:173)
`cords some of these keys, in the form of subscription
`blocks, on holders provided for this purpose (for exam(cid:173)
`ple, information-bearing· cards of the credit card type).
`These cards are then inserted by the users of the service
`in the receiver.
`For each chargeable service, approximately every
`five minutes, a new operating key K is generated at
`random, by each distribution centre concerned. Thus, in
`the course of a session of a service (one or more hours),
`several dozen operating keys may succeed On\!. another.
`As soon as a distribution centre generates a new oper(cid:173)
`ating key K, it calculates, for each current subscribers'
`key in use Ci for this service, a message Mi by means of
`an algorithm Mi=Fci (K), with the keys Ci acting as
`parameters.
`Thus, for a service using the subscription plan de(cid:173)
`scribed above, there are 22 different messages in force at
`any one time. The duration of a message is equal to that
`of the operating key K, and for a given service, at any
`one time, there are as many messages as there are sub(cid:173)
`scribers' keys in use.
`All the messages Mi in force together constitute the
`information for access control associated with the ser(cid:173)
`vice being broadcast. This access control information is
`obviously not locked up by the electronic lock.
`A particular application of this system is envisaged
`within the scope of the present invention. In this in(cid:173)
`stance, the messages Mi are grouped in a special page,
`known as the access control page, which is updated
`each time the operating key is changed. The access
`control page is distributed cyclically, like the ordinary
`pages of information constituting the service. However,
`it is not locked up by the electronic lock. The access
`control page is read systematically by the receiver
`when it is put into contact with the service, then each
`
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`9
`time this page is updated, during the period of consulta(cid:173)
`tion of the service, but it is not displayable.
`The messages are therefore, in fact, motifs of primary
`synchronisation of the lock and these motifs can be
`interpreted by an algorithm supplying the operating
`key. This algorithm is in the form: K=GCi(M;), and is
`developed by a restoring circuit (which may also be
`part of the subscription holder which already contains
`the subscribers' key C;) to which the messages M; are
`supplied. This circuit therefore provides the automatic 10
`unlocking means with the o