CA2182455C - Digital signal broadcasting - Google Patents
Digital signal broadcasting Download PDFInfo
- Publication number
- CA2182455C CA2182455C CA 2182455 CA2182455A CA2182455C CA 2182455 C CA2182455 C CA 2182455C CA 2182455 CA2182455 CA 2182455 CA 2182455 A CA2182455 A CA 2182455A CA 2182455 C CA2182455 C CA 2182455C
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- CA
- Canada
- Prior art keywords
- atm cells
- subscribers
- scrambling
- atm
- different
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
- H04N19/61—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding in combination with predictive coding
Abstract
A distribution network groups television program signals into service tiers. To provide these from unsynchronized MPEG streams without resynchronization, each stream, representing a single program signal is encapsulated into ATM cells with a virtual path(VP) identification of each ATM cell corresponding to the service tier and a virtual channel (VC) identification corresponding to the respective program signal. Payloads in cells having the same VP are scrambled using a scrambling key allocated to that VP and hence to the corresponding service tier, and are unscrambled by entitled subscribers using the scrambling key which is supplied to them individually using public/private encryption techniques.
Description
2182455 i~) DIGITAL SIGNAL BROADCASTING
This invention relates to digital signal IJluad~,a>Lillg, especiaUy of television signals.
RA- k.~rolmfl of ~hP I
It is well known to provide broadcast distribution of television signals for example via a cable television network, from a head end of the network to 5nhc~ihl rc The cable network operator constitntes a service provider~ to whom the television signals are typicaUy supplied by content praviders, each of whom may provide one or more television p}ogram signals. Typically, the service provider groups selected television program signals from different content providers into different service packages, or tiers, to which the subscribers can subscribe, each subscriber to a service tier being enabled to use all of the program signals within that service tier.
L~ asill~;ly~ digital sigllals are being used or proposed for use for c. " . .l, .~ l, ng television program signals from content providers io service providers, and from service -providers to s~ hc~rihPrg To facilitate this, the television program signals are .,o~ ,lldy CUIll,u~ into a digital bit stream in accordance with standards such as the MPEG(Moving Pictures Expens Group) standard MPEG-2. The resulting bit stream is referred to as an MPEG stream. The MPEG stream can also include arbitrary types of signal other than, and in addition to, television program signals, but for COII~ ,llce and simplicity only television program signals are discussed here, it being understood that the same comments apply equaUy to other signals.
An MPEG stream containing a television program signal comprises encoded, culll~Jlt.~ , program data with a time sequence providing timing (clocking) information to enable a decoder to reconstruct the program data to reproduce the television program signal. Where a content provider supplies a plurality of television program signals, it is desirable to do this in a single M[PEG stream using a time sequence that is common to aU
of the signals, thereby reducing the amount of ' that must be c, Similarly, for digital broadcast of a service tier from a service provider to snhc~rihPrs~ it is desirable for th~ service provider to provide a single MPEG stream which contains aU of the program data for the television program signals in the service tier, together with a time sequence that is common to aU of these signals, and entidement infnrmAti- n that enables only entided subscribers to recover dhe television program signals. However, because dhe television program signals in dhe service tier are generally supplied by different content providers that are ull~yll~lllul~i~,~l relative to one another, dlis grouping into a single MPEG stream for each service tier ~ a y~,luulli~lion of dhe television program signals at the service provider. This process is c~ ly very intensive and nn~lP.cirAhlP.
~ ~ 21 82455 An object of this invention is to provide a method of digital signal b uddua-D~ g that enables this diDadv ~ to be avoided or reduced.
Sllmm ~fv of the Tnvrn~irn According to one aspecl, this invention provides a method of b~udd~r~DLillg a S plurality of digital signals, each comprising a data strearn including data and timing , r"", . -~i...., to a ~- ne~twork for supply to a plurality of ' ' 1 comprising the steps of: allocating a virtual path gVP? i ~ l~ .1; l; l A l, u ~ l of ATM (~IDJ ~ transfer mode) cells to the plurality of digital signals and a respective virtual channel (VC) if lrn~ifirr~irn of the ATM cells lo each individual one of the plurality of digital signals;
10 . ,. ~ g the data stream of each of the plurality of digital signals in ATM cells having saidVP ' ~ rn andtherespectiveVCi.l~..tj~;, 1l,... scramblingthe~
datastreamineachATMcellhzLvingsaidVPi.1. ~I;..-I;....infl~ f upona scrambling key allocated to the 'v'P; and supplying the resulting ATM cells to the diDllilJuLion network.
Typically the plurality of digital signals can comprise television program signals in the form of an MPEG data stream.
The method UUII~. ~ 'y further includes the step of supplying the scrambling keyin encrypted form in ATM cells to subscribers via the distribution network. This can comprise the steps of encryptingr the scrambling key using different public keys for 20 different subscribers to produce different encrypted forms of the scrambling key for the different snhs~rihf rc~ and suppbling the different encrypted forms of Lhe scramb3ing key to the .li~l, ;l.~.n. ..- network for decryption by the respective subscribers using respective plivatf, keys of the 5nhcrrihf.r.c Another aspect of this invention relates to a method of providing a plurality of25 television program signals in se3vice tiers in a distribution network, each service tier comprising at least one of said t.,levision program signals, comprising the steps of:
providing each television program signal as a digital signal in ATM (r~D~IlulllùlluuD
transfer mode) cells with a virtual channel (vc) ~ -n~n of each ATM cell identifying therespectivetelevisionprogramsigna3andavirtua3path(VP);.1. ..;;li~ -n~...ofeachATM
cell identifying the service tier comprising the respective television program signal;
allocating different scrambling k.eys to different VPs and hence to different service tiers;
scrambling the digital signals in the ATM cells in il ~ upon the scrambling key allocated to the respective VPs of the ATM cells; and supplying the resulting ATM ceils to the dist3ibution network.
According to a furLher aspect, this invention provides subscriber apparatus for connection to a digital signal broadcast distribution network, the apparatus cr~mrrici-tg a selector for selecting from the notwork ATM (~D,~ ' transfer mode) cells having a virtual path (VP) ~ ~ .ulluD3!ul.dil.g to a group of one or more digital signal 2 1 82455 ~j channels on the network and having a virtual channel (VC) ' ' '~ g to an individual one of the digital signal channels of the group; a store for storing a key associated with said VP for l ' ' g scrambled contents of the selected ATM ceEls;
and a unit responsive to the selccted ATM cells and the key associated with said VP for 5 ~ . ~.., ,., ..1,1: 1, the contents of the selected ATM cells to produce said individual one of the digital signal channels for use at the subscriber apparatus.
The apparatus CO~ f.~ y includes a decryption unit responsive to a private key of the subscriber apparatus and to encrypted hlrulllld ~ in ATM cells on the network for producing said key associated with said VP for storage in the store.
10 Brief Description of the Drawin ~s The invention will be further understood from the following description with reference to the a~ulll~ y g drawings, in which:
Fig. 1 isablockdiagramillustratingadigitalsignallnud~a~Li.. g,................. ,,.. ~;.... ,lin accordance with the prior art; =
Fig. 2 is a block diagram illustrating a digital signal l ., ~ .g ,.. "... L,~ .. ,., I in accordance with the invention; ~und Fig. 3 is a block diagram illustrating subscriber apparatus in a digital signal bluàdcas~illg ~ a in acl~ordance with the invention.
D~ A lP~ n Refenring to Fig. 1, a digital signal broadcasting au~u~g~ llL in accordance with the prior art includes a service provider 10, shown within a dashed line box and for example in the fonm of a cable network operator, which is supplied with television program signals in the form of ]!~PEG strearns via c ~ ,, . ,.. ,.., .;, -~;/~nC paths 12 and 14 from content providers 16 and 18 .c~ ,Liv ~ , only two content providers being shown for 25 sirnplicity. The content provider 16 is assumed here to prc vide on the path 12 a plurality of television program signals ,.."l~ l in a single MPEG stream with a common time sequence. At the service provider 10 this is .1,, .. ,~ ,1 by an MPEG strearn .L ~ .. 20 into a pluralitv of separate MPEG streams, each with its own time sequence, on paths 22 two of w hich are shown. Each of the paths 22, and the path 14 which is assumed here to provi<le an individual television program signal and time sequence in an MPEG stream, constitutes a respective input to a unit 24. Other single or multiple program MPEG streams from other content providers are handled in a Cullc:,uululillg manner to provide multiple single-program MPEG streams, each widh its own time sequence, to the unit 24.
For each of one or morc service tiers, each typically comprising~a plurality of television prograrn signals. the unit 24 serves for selecting the respective-single-prograrn MPEG streams from the inputs of the unit 24, IC~ U..;~illg these, adding subscriber entidement inf~nn~ n supplied at the selvice provider by an entitlement generator 26, " ., .1~ ;. .g the signals into a muliti-program MPEG stream with a common timing sequence for all of the program signals, and supplying the resulting MPEG stream to a cable network 28 for broadcast distribution to subscIiber equipment connected to the cable network. As explained in the ba~,h~l~ ' of the invention, this requires very intensive S c~ u~ by the unit 24, which accu~ ,ly is complex and costly to provide. It is observed in this respect that the ' ' il ' ~ g provided by the unit 20 is much simpler than the lcDyll~luulli~ ull and ' il I g provided in the unit 24.
Fig. 2 illustrates a digital signal t ' ~ ,, n~ I in accordance with the invention, which is aJi, ' lly similhr to the ~ of Fig. 1 except that the service provider 10 includes a unit 30 instead of the unit 24, and the entitlement generator 26 is modified to operate C~ D;Dt~ Y with the description below. The unit 30 serves, like the unit 24 in Fig. 1, to select thie single-program signals from the input MPEG streams on the paths 14 and 22 to constitute the desired service tier, but handles these streams in a different mannér from the unit 24. This handling includes an, . ' of the MPEG
15 streams into ATM (hDyll ILliUllU JD transfer mode) cells, and encryption of the ceDi data, as described below.
As is well known, ATM cells each comprise a header of five bytes or octets and apayload of 48 bytes or octets. l'he header includes 24 bits which conventionally provide an 8-bit virtual path (VP) identii~ler and a 16-bit virtual channel ~VC) identifier which serve 20 as an address for the ATM ceDi. It is well known to use ATM ceDs for c~ g arbitrary types of data; for exhmple, ATM ceDis could be used on the paths 12 and 14 for .~ ~, .. : - l; .. g MPEG streams from the content providers 16 and 18 to the service provider 10. In this case, the VP hnd VC in each ceD header wouid identify the service provider 10 as the rc-cipient of the ATM ceD data. In an " in accordance with 25 the invention, ATM ceDs are also used for distribution of signals via the cable network 28, but the VP and VC are used in a! different manner from such Cu~ ' use in ATM
ceDis in the prior art.
More specificaDiy, in the v of Fig. 2 the cable network 28 is a broadcast ffihnfil~n network in which all signals are delivercd to aDi ' ' Accordingly, the 30 VP and VC in the ceD headers are not rc-quired to identify specific subscribers or rccipients of the cells. Instead, in the network 28 the VP is used to identify a service tier. Within that service tier, each individual television program signali is aDocated an individual, respective VC, and the single MPEG stream for that signal, comprising both the program data and the respcctive time seqlence, is c.-.. ;- ~1 in the payload of the ATM ceDis 35 identified by that VC. Thus the scrvice tier is uniquely identified by the~ VP, and each television program signal in thac service tier is uniquely identified by the respective VC
with that VP, whose ATM ceD payloads contain aD of the program data for that one ~ ~ 21 82455 -) s television program signal. There is therefore no ~ vluvlfiLaLvll or "i ' ~ ~ of MPEG streams in the unit 30 in the .1l I nl lv ~ of Fig. 2.
With this r~ b there can be an arbitrary number up to 255 (28, minus one VP for signaaing purposes) of ,service tiers, and an arbitrary number from 1 to 216 of 5 television program signals (each a single program MPEG stream).
In order to ensure that only subscribers entitled to receive the television program signals in the service tier can ploperly receive these signals, an encryption or scrambling key is allocated to the VP CUIIV~ " lv to the service tier, tbis is referred to as a service tier key. For each television prcgram signr~l~ and hence VC, within that service tier, the 10 entire payload of each ATM ce.ll is encrypted using the service tier key. cu~ ay, any subscriber supplied with the service tier key can use this to decrypt all of the television program signals in that se-rvice tier.
Distribution of the scrvice tier key to individual subscnbers can be performed in any known manner, using known security techniques. cu~ ay, a VC of the 15 signalling VP mentioned above is used for luluddvd~ lg entitlement ~ rullllavull to the subscribers to be uscd hlvliY ~ lly by each of them. Jn this case ,uubliv/~uliv key encryption can be used to ensure that the service tier key can only be received by each subscriber for which it is intended. This is explained further below.
Accordingly, for each television program signal on a path 14 or 22 incoming to the 20 unit 30 that is selected to be included in a par~cular service tier, the unit 30, the individual MPEG stream fo.r that program signal in the payload of ATM cells having a VC allocated to that program signal and having a VP allocated to that service tier, and encrypts the payload of each such ATM cell in accordance with a scrambling key that is allocated to that service tier. The ATM cells for all of the program signals in all of the 25 service tiers, together with AT~I cells contr,ining entitlement; " r. ,., . ~ i . ., . from the f nfiflrmf nt generator 26 as described above, are supplied to the cable network 28 for broadcast ~liefrihntinn ¢o all of the ' hf r.c Fig. 3 illustrates appara~.us at a subscriber to the digital signal bluàvvasLulg.... ~ .~;... ,., .1 of Fig. 2, including a splitter 32 that is connected to the cable network 28 and 30 scrves to separate entitlement inft~nn ~finn ATM cells fûr the subscriber and supply these to a luubliv~p~ iv key dccryption unit 34. In known manner, the unit 34 stores a private key 36 allocated to the individual subscriber, which perrnits or,ly this subscriber to decrypt ~ ""-~;,.,.encryptedusingapublickeyofthesubscribcr. F.nfiflfmfnf;l.~..,..."l;..~ in particular the service tier key for each service tier for which this subscriber is entitled, is 35 encrypted by the entitlement generator 26 at the service provider 10 using the public key of this subscriber and is distributevd via the network 28 as described abovev, with an address orother;~ ri~-l;n~ofthissubscriberforwhichitisintended~ Onlythissubscriberis able to decrypt this entitlement information, using the private key 36, to reproduce the ~ 21 82455 !--~
service tier key which is thereby ~ ~ ' securely to this subscriber. Service tier keys are similarly c~ ~ ' to other subscribers in a secure manner using their respective l~ublic/~liv~tc, keys. At each subscriber, each decrypted service tier key is stored as one of a set of working keys 38. It can be appreciatcd that this ,~
5 facilitates changing or updating of the service tier keys by the service provider 10 whenever desired.
The splitter 32 supplies other ATM cells, containing the television prograrn signals and with encrypted payloads as described above, to a VPIVC selector 40. A selection unit 42, which serves to select a particular television program in a manner equivalent to a 10 channel selector, supplies the VC of a desired television progratn signal, and the VP of the service tier in which that program signal is included, via a path 44 to the selector 40, which aw,uldill~;ly passes to its output path 46 only those ATM cells from the network 28 having that VP and VC and hence including the MPEG strearn of the desired television program signal. These cells.on the path 46 are supplied to an ATM cell decryption unit 15 48, which (assuming that this subscriber is entitled to receive programs in this service tier) decrypts the payload of each cel~. using the respective working key supplied from the set of working keys 38 via the selection unit 42 and a path 50.
The decrypted ATM cells from the unit 48 are supplied to an SAR (~.~;. . ,~"1,,1 ;", .
and ~ lbly) unit 52 of known form to reproduce the individual MPEG stream for the 20 television program signal, which is supplied to an MPEG decoder 54 also of known form for decoding the MPEG stream to reproduce the original television program signal for use.
Although a particular form of the invention has been described in detail, it can be that numerous, . "~ variations, and adaptations may be made without departing from the scope of the invention as defined in the claims.
This invention relates to digital signal IJluad~,a>Lillg, especiaUy of television signals.
RA- k.~rolmfl of ~hP I
It is well known to provide broadcast distribution of television signals for example via a cable television network, from a head end of the network to 5nhc~ihl rc The cable network operator constitntes a service provider~ to whom the television signals are typicaUy supplied by content praviders, each of whom may provide one or more television p}ogram signals. Typically, the service provider groups selected television program signals from different content providers into different service packages, or tiers, to which the subscribers can subscribe, each subscriber to a service tier being enabled to use all of the program signals within that service tier.
L~ asill~;ly~ digital sigllals are being used or proposed for use for c. " . .l, .~ l, ng television program signals from content providers io service providers, and from service -providers to s~ hc~rihPrg To facilitate this, the television program signals are .,o~ ,lldy CUIll,u~ into a digital bit stream in accordance with standards such as the MPEG(Moving Pictures Expens Group) standard MPEG-2. The resulting bit stream is referred to as an MPEG stream. The MPEG stream can also include arbitrary types of signal other than, and in addition to, television program signals, but for COII~ ,llce and simplicity only television program signals are discussed here, it being understood that the same comments apply equaUy to other signals.
An MPEG stream containing a television program signal comprises encoded, culll~Jlt.~ , program data with a time sequence providing timing (clocking) information to enable a decoder to reconstruct the program data to reproduce the television program signal. Where a content provider supplies a plurality of television program signals, it is desirable to do this in a single M[PEG stream using a time sequence that is common to aU
of the signals, thereby reducing the amount of ' that must be c, Similarly, for digital broadcast of a service tier from a service provider to snhc~rihPrs~ it is desirable for th~ service provider to provide a single MPEG stream which contains aU of the program data for the television program signals in the service tier, together with a time sequence that is common to aU of these signals, and entidement infnrmAti- n that enables only entided subscribers to recover dhe television program signals. However, because dhe television program signals in dhe service tier are generally supplied by different content providers that are ull~yll~lllul~i~,~l relative to one another, dlis grouping into a single MPEG stream for each service tier ~ a y~,luulli~lion of dhe television program signals at the service provider. This process is c~ ly very intensive and nn~lP.cirAhlP.
~ ~ 21 82455 An object of this invention is to provide a method of digital signal b uddua-D~ g that enables this diDadv ~ to be avoided or reduced.
Sllmm ~fv of the Tnvrn~irn According to one aspecl, this invention provides a method of b~udd~r~DLillg a S plurality of digital signals, each comprising a data strearn including data and timing , r"", . -~i...., to a ~- ne~twork for supply to a plurality of ' ' 1 comprising the steps of: allocating a virtual path gVP? i ~ l~ .1; l; l A l, u ~ l of ATM (~IDJ ~ transfer mode) cells to the plurality of digital signals and a respective virtual channel (VC) if lrn~ifirr~irn of the ATM cells lo each individual one of the plurality of digital signals;
10 . ,. ~ g the data stream of each of the plurality of digital signals in ATM cells having saidVP ' ~ rn andtherespectiveVCi.l~..tj~;, 1l,... scramblingthe~
datastreamineachATMcellhzLvingsaidVPi.1. ~I;..-I;....infl~ f upona scrambling key allocated to the 'v'P; and supplying the resulting ATM cells to the diDllilJuLion network.
Typically the plurality of digital signals can comprise television program signals in the form of an MPEG data stream.
The method UUII~. ~ 'y further includes the step of supplying the scrambling keyin encrypted form in ATM cells to subscribers via the distribution network. This can comprise the steps of encryptingr the scrambling key using different public keys for 20 different subscribers to produce different encrypted forms of the scrambling key for the different snhs~rihf rc~ and suppbling the different encrypted forms of Lhe scramb3ing key to the .li~l, ;l.~.n. ..- network for decryption by the respective subscribers using respective plivatf, keys of the 5nhcrrihf.r.c Another aspect of this invention relates to a method of providing a plurality of25 television program signals in se3vice tiers in a distribution network, each service tier comprising at least one of said t.,levision program signals, comprising the steps of:
providing each television program signal as a digital signal in ATM (r~D~IlulllùlluuD
transfer mode) cells with a virtual channel (vc) ~ -n~n of each ATM cell identifying therespectivetelevisionprogramsigna3andavirtua3path(VP);.1. ..;;li~ -n~...ofeachATM
cell identifying the service tier comprising the respective television program signal;
allocating different scrambling k.eys to different VPs and hence to different service tiers;
scrambling the digital signals in the ATM cells in il ~ upon the scrambling key allocated to the respective VPs of the ATM cells; and supplying the resulting ATM ceils to the dist3ibution network.
According to a furLher aspect, this invention provides subscriber apparatus for connection to a digital signal broadcast distribution network, the apparatus cr~mrrici-tg a selector for selecting from the notwork ATM (~D,~ ' transfer mode) cells having a virtual path (VP) ~ ~ .ulluD3!ul.dil.g to a group of one or more digital signal 2 1 82455 ~j channels on the network and having a virtual channel (VC) ' ' '~ g to an individual one of the digital signal channels of the group; a store for storing a key associated with said VP for l ' ' g scrambled contents of the selected ATM ceEls;
and a unit responsive to the selccted ATM cells and the key associated with said VP for 5 ~ . ~.., ,., ..1,1: 1, the contents of the selected ATM cells to produce said individual one of the digital signal channels for use at the subscriber apparatus.
The apparatus CO~ f.~ y includes a decryption unit responsive to a private key of the subscriber apparatus and to encrypted hlrulllld ~ in ATM cells on the network for producing said key associated with said VP for storage in the store.
10 Brief Description of the Drawin ~s The invention will be further understood from the following description with reference to the a~ulll~ y g drawings, in which:
Fig. 1 isablockdiagramillustratingadigitalsignallnud~a~Li.. g,................. ,,.. ~;.... ,lin accordance with the prior art; =
Fig. 2 is a block diagram illustrating a digital signal l ., ~ .g ,.. "... L,~ .. ,., I in accordance with the invention; ~und Fig. 3 is a block diagram illustrating subscriber apparatus in a digital signal bluàdcas~illg ~ a in acl~ordance with the invention.
D~ A lP~ n Refenring to Fig. 1, a digital signal broadcasting au~u~g~ llL in accordance with the prior art includes a service provider 10, shown within a dashed line box and for example in the fonm of a cable network operator, which is supplied with television program signals in the form of ]!~PEG strearns via c ~ ,, . ,.. ,.., .;, -~;/~nC paths 12 and 14 from content providers 16 and 18 .c~ ,Liv ~ , only two content providers being shown for 25 sirnplicity. The content provider 16 is assumed here to prc vide on the path 12 a plurality of television program signals ,.."l~ l in a single MPEG stream with a common time sequence. At the service provider 10 this is .1,, .. ,~ ,1 by an MPEG strearn .L ~ .. 20 into a pluralitv of separate MPEG streams, each with its own time sequence, on paths 22 two of w hich are shown. Each of the paths 22, and the path 14 which is assumed here to provi<le an individual television program signal and time sequence in an MPEG stream, constitutes a respective input to a unit 24. Other single or multiple program MPEG streams from other content providers are handled in a Cullc:,uululillg manner to provide multiple single-program MPEG streams, each widh its own time sequence, to the unit 24.
For each of one or morc service tiers, each typically comprising~a plurality of television prograrn signals. the unit 24 serves for selecting the respective-single-prograrn MPEG streams from the inputs of the unit 24, IC~ U..;~illg these, adding subscriber entidement inf~nn~ n supplied at the selvice provider by an entitlement generator 26, " ., .1~ ;. .g the signals into a muliti-program MPEG stream with a common timing sequence for all of the program signals, and supplying the resulting MPEG stream to a cable network 28 for broadcast distribution to subscIiber equipment connected to the cable network. As explained in the ba~,h~l~ ' of the invention, this requires very intensive S c~ u~ by the unit 24, which accu~ ,ly is complex and costly to provide. It is observed in this respect that the ' ' il ' ~ g provided by the unit 20 is much simpler than the lcDyll~luulli~ ull and ' il I g provided in the unit 24.
Fig. 2 illustrates a digital signal t ' ~ ,, n~ I in accordance with the invention, which is aJi, ' lly similhr to the ~ of Fig. 1 except that the service provider 10 includes a unit 30 instead of the unit 24, and the entitlement generator 26 is modified to operate C~ D;Dt~ Y with the description below. The unit 30 serves, like the unit 24 in Fig. 1, to select thie single-program signals from the input MPEG streams on the paths 14 and 22 to constitute the desired service tier, but handles these streams in a different mannér from the unit 24. This handling includes an, . ' of the MPEG
15 streams into ATM (hDyll ILliUllU JD transfer mode) cells, and encryption of the ceDi data, as described below.
As is well known, ATM cells each comprise a header of five bytes or octets and apayload of 48 bytes or octets. l'he header includes 24 bits which conventionally provide an 8-bit virtual path (VP) identii~ler and a 16-bit virtual channel ~VC) identifier which serve 20 as an address for the ATM ceDi. It is well known to use ATM ceDs for c~ g arbitrary types of data; for exhmple, ATM ceDis could be used on the paths 12 and 14 for .~ ~, .. : - l; .. g MPEG streams from the content providers 16 and 18 to the service provider 10. In this case, the VP hnd VC in each ceD header wouid identify the service provider 10 as the rc-cipient of the ATM ceD data. In an " in accordance with 25 the invention, ATM ceDs are also used for distribution of signals via the cable network 28, but the VP and VC are used in a! different manner from such Cu~ ' use in ATM
ceDis in the prior art.
More specificaDiy, in the v of Fig. 2 the cable network 28 is a broadcast ffihnfil~n network in which all signals are delivercd to aDi ' ' Accordingly, the 30 VP and VC in the ceD headers are not rc-quired to identify specific subscribers or rccipients of the cells. Instead, in the network 28 the VP is used to identify a service tier. Within that service tier, each individual television program signali is aDocated an individual, respective VC, and the single MPEG stream for that signal, comprising both the program data and the respcctive time seqlence, is c.-.. ;- ~1 in the payload of the ATM ceDis 35 identified by that VC. Thus the scrvice tier is uniquely identified by the~ VP, and each television program signal in thac service tier is uniquely identified by the respective VC
with that VP, whose ATM ceD payloads contain aD of the program data for that one ~ ~ 21 82455 -) s television program signal. There is therefore no ~ vluvlfiLaLvll or "i ' ~ ~ of MPEG streams in the unit 30 in the .1l I nl lv ~ of Fig. 2.
With this r~ b there can be an arbitrary number up to 255 (28, minus one VP for signaaing purposes) of ,service tiers, and an arbitrary number from 1 to 216 of 5 television program signals (each a single program MPEG stream).
In order to ensure that only subscribers entitled to receive the television program signals in the service tier can ploperly receive these signals, an encryption or scrambling key is allocated to the VP CUIIV~ " lv to the service tier, tbis is referred to as a service tier key. For each television prcgram signr~l~ and hence VC, within that service tier, the 10 entire payload of each ATM ce.ll is encrypted using the service tier key. cu~ ay, any subscriber supplied with the service tier key can use this to decrypt all of the television program signals in that se-rvice tier.
Distribution of the scrvice tier key to individual subscnbers can be performed in any known manner, using known security techniques. cu~ ay, a VC of the 15 signalling VP mentioned above is used for luluddvd~ lg entitlement ~ rullllavull to the subscribers to be uscd hlvliY ~ lly by each of them. Jn this case ,uubliv/~uliv key encryption can be used to ensure that the service tier key can only be received by each subscriber for which it is intended. This is explained further below.
Accordingly, for each television program signal on a path 14 or 22 incoming to the 20 unit 30 that is selected to be included in a par~cular service tier, the unit 30, the individual MPEG stream fo.r that program signal in the payload of ATM cells having a VC allocated to that program signal and having a VP allocated to that service tier, and encrypts the payload of each such ATM cell in accordance with a scrambling key that is allocated to that service tier. The ATM cells for all of the program signals in all of the 25 service tiers, together with AT~I cells contr,ining entitlement; " r. ,., . ~ i . ., . from the f nfiflrmf nt generator 26 as described above, are supplied to the cable network 28 for broadcast ~liefrihntinn ¢o all of the ' hf r.c Fig. 3 illustrates appara~.us at a subscriber to the digital signal bluàvvasLulg.... ~ .~;... ,., .1 of Fig. 2, including a splitter 32 that is connected to the cable network 28 and 30 scrves to separate entitlement inft~nn ~finn ATM cells fûr the subscriber and supply these to a luubliv~p~ iv key dccryption unit 34. In known manner, the unit 34 stores a private key 36 allocated to the individual subscriber, which perrnits or,ly this subscriber to decrypt ~ ""-~;,.,.encryptedusingapublickeyofthesubscribcr. F.nfiflfmfnf;l.~..,..."l;..~ in particular the service tier key for each service tier for which this subscriber is entitled, is 35 encrypted by the entitlement generator 26 at the service provider 10 using the public key of this subscriber and is distributevd via the network 28 as described abovev, with an address orother;~ ri~-l;n~ofthissubscriberforwhichitisintended~ Onlythissubscriberis able to decrypt this entitlement information, using the private key 36, to reproduce the ~ 21 82455 !--~
service tier key which is thereby ~ ~ ' securely to this subscriber. Service tier keys are similarly c~ ~ ' to other subscribers in a secure manner using their respective l~ublic/~liv~tc, keys. At each subscriber, each decrypted service tier key is stored as one of a set of working keys 38. It can be appreciatcd that this ,~
5 facilitates changing or updating of the service tier keys by the service provider 10 whenever desired.
The splitter 32 supplies other ATM cells, containing the television prograrn signals and with encrypted payloads as described above, to a VPIVC selector 40. A selection unit 42, which serves to select a particular television program in a manner equivalent to a 10 channel selector, supplies the VC of a desired television progratn signal, and the VP of the service tier in which that program signal is included, via a path 44 to the selector 40, which aw,uldill~;ly passes to its output path 46 only those ATM cells from the network 28 having that VP and VC and hence including the MPEG strearn of the desired television program signal. These cells.on the path 46 are supplied to an ATM cell decryption unit 15 48, which (assuming that this subscriber is entitled to receive programs in this service tier) decrypts the payload of each cel~. using the respective working key supplied from the set of working keys 38 via the selection unit 42 and a path 50.
The decrypted ATM cells from the unit 48 are supplied to an SAR (~.~;. . ,~"1,,1 ;", .
and ~ lbly) unit 52 of known form to reproduce the individual MPEG stream for the 20 television program signal, which is supplied to an MPEG decoder 54 also of known form for decoding the MPEG stream to reproduce the original television program signal for use.
Although a particular form of the invention has been described in detail, it can be that numerous, . "~ variations, and adaptations may be made without departing from the scope of the invention as defined in the claims.
Claims (13)
1. A method of broadcasting a plurality of digital signals, each comprising a data stream including data and timing information, to a distribution network for supply to a plurality of subscribers, comprising the steps of:
allocating a virtual path (VP) identification of ATM (asynchronous transfer mode) cells to the plurality of digital signals and a respective virtual channel (VC) identification of the ATM cells to each individual one of the plurality of digital signals;
encapsulating the data stream of each of the plurality of digital signals in ATM cells having said VP identification and the respective VC identification;
scrambling the encapsulated data stream in each ATM cell having said VP
identification in dependence upon a scrambling key allocated to the VP; and supplying the resulting ATM cells to the distribution network.
allocating a virtual path (VP) identification of ATM (asynchronous transfer mode) cells to the plurality of digital signals and a respective virtual channel (VC) identification of the ATM cells to each individual one of the plurality of digital signals;
encapsulating the data stream of each of the plurality of digital signals in ATM cells having said VP identification and the respective VC identification;
scrambling the encapsulated data stream in each ATM cell having said VP
identification in dependence upon a scrambling key allocated to the VP; and supplying the resulting ATM cells to the distribution network.
2. A method as claimed in claim 1 wherein the plurality of digital signals comprise television program signals.
3. A method as claimed in claim 1 or 2 wherein each data stream constituting one of the plurality of digital signals comprises an MPEG (Moving Pictures Experts Group) data stream.
4. A method as claimed in claim 1 or 2 wherein the step of supplying the resulting ATM cells to the distribution network comprises step of supplying the resulting ATM cells to a cable television distribution network.
5. A method as claimed in claim 1 or 2 and further including the step of supplying the scrambling key in encrypted form in ATM cells to subscribers via the distribution network.
6 . A method as claimed in claim 5 wherein the step of supplying the scrambling key in encrypted form in ATM cells lo subscribers comprises the steps of encrypting the scrambling key using different public keys for different subscribers to produce different encrypted forms of the scrambling key for the different subscribers, and supplying the different encrypted forms of the scrambling key to the distribution network for decryption by the respective subscribers using respective private keys of the subscribers.
7. A method of providing a plurality of television program signals in service tiers in a distribution network, each service tier comprising at least one of said television program signals, comprising the steps of:
providing each television program signal as a digital signal in ATM (asynchronous transfer mode) cells with a virtual channel (VC) identification of each ATM cell identifying the respective television program signal and a virtual path (VP) identification of each ATM
cell identifying the service tier comprising the respective television program signal;
allocating different scrambling keys to different VPs and hence to different service tiers;
scrambling the digital signals in the ATM cells in dependence upon the scrambling key allocated to the respective VPs of the ATM cells; and supplying the resulting ATM cells to the distribution network.
providing each television program signal as a digital signal in ATM (asynchronous transfer mode) cells with a virtual channel (VC) identification of each ATM cell identifying the respective television program signal and a virtual path (VP) identification of each ATM
cell identifying the service tier comprising the respective television program signal;
allocating different scrambling keys to different VPs and hence to different service tiers;
scrambling the digital signals in the ATM cells in dependence upon the scrambling key allocated to the respective VPs of the ATM cells; and supplying the resulting ATM cells to the distribution network.
8. A method as claimed in claim 7 wherein each digital signal comprises an MPEG
(Moving Pictures Experts Group) data stream.
(Moving Pictures Experts Group) data stream.
9. A method as claimed in claim 7 or 8 and further including the step of supplying the scrambling keys in encrypted form in ATM cells to subscribers via the distribution network.
10. A method as claimed in claim 9 wherein the step of supplying the scrambling keys in encrypted form in ATM cells to subscribers comprises the steps of selectivelyencrypting the scrambling keys using different public keys for different subscribers to produce different encrypted forms of selected scrambling keys for the different subscribers, and supplying the different encrypted forms of the selected scrambling keys to the distribution network for decryption by the respective subscribers using respective private keys of the subscribers.
11. Subscriber apparatus for connection to a digital signal broadcast distribution network, the apparatus comprising:
a selector for selecting from the network ATM (asynchronous transfer mode) cellshaving a virtual path (VP) identification corresponding to a group of one or more digital signal channels on the network and having a virtual channel (VC) identification corresponding to an individual one of the digital signal channels of the group;
a store for storing a key associated with said VP for unscrambling scrambled contents of the selected ATM cells; and a unit responsive to the selected ATM cells and the key associated with said VP for unscrambling the contents of the selected ATM cells to produce said individual one of the digital signal channels for use at the subscriber apparatus.
a selector for selecting from the network ATM (asynchronous transfer mode) cellshaving a virtual path (VP) identification corresponding to a group of one or more digital signal channels on the network and having a virtual channel (VC) identification corresponding to an individual one of the digital signal channels of the group;
a store for storing a key associated with said VP for unscrambling scrambled contents of the selected ATM cells; and a unit responsive to the selected ATM cells and the key associated with said VP for unscrambling the contents of the selected ATM cells to produce said individual one of the digital signal channels for use at the subscriber apparatus.
12. Apparatus as claimed in claim 11 and including a decryption unit responsive to a private key of the subscriber apparatus and to encrypted information in ATM cells on the network for producing said key associated with said VP for storage in the store.
13. Apparatus as claimed in claim 11 or 12 and including a decoder for decoding an MPEG (Moving Pictures Experts Group) data stream constituted by said individual one of the digital signal channels.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2182455 CA2182455C (en) | 1996-07-31 | 1996-07-31 | Digital signal broadcasting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2182455 CA2182455C (en) | 1996-07-31 | 1996-07-31 | Digital signal broadcasting |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2182455A1 CA2182455A1 (en) | 1998-02-01 |
| CA2182455C true CA2182455C (en) | 2000-08-15 |
Family
ID=4158691
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2182455 Expired - Lifetime CA2182455C (en) | 1996-07-31 | 1996-07-31 | Digital signal broadcasting |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2182455C (en) |
-
1996
- 1996-07-31 CA CA 2182455 patent/CA2182455C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2182455A1 (en) | 1998-02-01 |
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Effective date: 20160801 |