JP3579202B2 - Receiving device and receiving method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a broadcasting system for distributing a literary work having the same content to a plurality of parties, a receiving apparatus and a receiving method in the broadcasting system.
[0002]
[Prior art]
Digitization of communication and broadcasting for homes and end users is being promoted. As a result, conventional televisions and radios can provide a variety of information, and new services such as video on demand (VOD) are becoming possible.
[0003]
On the other hand, digitalization of video and audio media has made it possible to copy copyrighted works with little deterioration. While this benefits the user, it poses a threat to the creator of the copyrighted work from infringing copyright by copying.
[0004]
As a conventional technique for solving this problem, there is a method of putting a "sign" on a work to indicate that the work belongs to a copyright holder. For example, there is a method in which the name of the distributor or the name of the broadcasting station to be broadcast is put in the corner of the screen of the movie to be broadcast. However, this method not only hinders appreciation of the work, but also may be judged to be a modification of the work. On the other hand, in this method, it is difficult to remove the signature without damaging the copyrighted work, so that the protection of the copyrighted work is high.
[0005]
Another method is to provide an additional signal to the copyrighted work, which describes information about the copyright owner or whether copying is possible or not. In audio media, DAT and MD are used. The problem with this scheme is that additional signals can be removed relatively easily without damaging the copyrighted work. Once the additional signal has been removed, a pirated copy that is exactly the same as the original will be freely available.
[0006]
Here, disabling the identification information in the form of a “watermark” that is invisible to the user in the content of the work does not prevent viewing of the work and is effective as a means for preventing copying (for example, "Cryptology for Digital TV Broadcasting", Benoit M. Macq, and Jean-Jacques Quisquater, Proceedings of the IEEE, 83 (6): 944, 1995.
[0007]
The use of the “watermark” includes a display of a right holder of a work or a copy prohibition function when the right holder is set. For tape or disk distribution, the serial number is also included and can be used to identify the source of the pirated copy.
[0008]
By adding identifying information, such as a serial number, to copyrighted work, copyright owners can identify the source of a large number of pirated copies and prevent damage by using legal measures. . The advantage of adding an identifier is that it can protect the rights of the author without limiting the rights of the user for private copying.
[0009]
In recent years, the concept of shareware has become widespread in software. This means that anyone can use the software freely because there are no restrictions on the use of the software itself, but pay a corresponding price for use beyond a certain standard. This concept can be applied to a wider range of general works, and if you want to create a video clip that uses a part of a movie, you must obtain the movie's permission in advance if copying is completely prohibited. However, if you are free to copy privately, you can create a video clip by quoting a movie and then get permission to sell it. This has the effect of promoting the distribution of multimedia contents.
[0010]
However, in the past, the same literary work was distributed to a plurality of users in broadcasting or video-on-demand, and it was not possible to add separate identification information to each user.
[0011]
[Problems to be solved by the invention]
As a means of balancing the rights of the user with the rights of the copyright holder, it is effective to add identification information indicating to whom the copyrighted work is granted the right to use. In particular, it is desirable from the viewpoint of copyright protection to add in the form of a “watermark” that cannot be known to the user and cannot be removed.
[0012]
However, conventionally, in a broadcasting system or video-on-demand, since the same literary work is distributed to a plurality of users, there has been a problem that separate identification information cannot be added to them. Further, it is necessary to prevent a signal to be added from being modified by a malicious user.
[0013]
Further, it is desirable that the copyright protection be performed at each stage of the copy distribution of the copyrighted work. For that purpose, it is necessary to add the identification information in a plurality of times. For example, a stage of copying from a copyright holder to a broadcasting station and a stage of copying from a broadcasting station to a user who is an end user. Thus, it is necessary to prevent the identification information added a plurality of times from deteriorating the discriminability of each other in reading, and preventing the quality of the work from being degraded.
[0014]
The present invention has been made in view of the above circumstances, and when a broadcast signal broadcast to a limited plurality of subscribers is received and copied to a medium, a copy subject of the broadcast signal can be specified. It is an object of the present invention to provide a receiving device, a broadcasting system, and a receiving method.
[0015]
[Means for Solving the Problems]
The present invention (claim 1) provides a receiving device installed on a subscriber side for receiving a broadcast signal broadcasted to a registered subscriber, wherein at least the broadcast signal is added to the received broadcast signal. Means for adding an additional signal including the received information identifying the subscriber.
[0016]
According to the present invention, in a broadcasting system limited to subscribers in which the same copyrighted work is distributed to a plurality of users such as a broadcasting system or video-on-demand, a receiving device installed on the subscriber side includes: By adding a signal specifying a subscriber (recipient) to the signal output from, separate identification information can be added for each subscriber.
[0017]
This prevents illegal distribution and sale of a copy of the work, and can identify the source even if the broadcast work is copied and distributed.
[0018]
According to the present invention (claim 2), a receiver receives and decodes a broadcast signal that is broadcast with its contents encrypted for a registered subscriber, and the reception corresponding to the subscriber is managed by a broadcast station side. The apparatus further comprises means for adding, to the received and decoded broadcast signal, an additional signal including at least information specifying the subscriber corresponding to the receiving apparatus that has received the broadcast signal.
[0019]
According to the present invention, in a broadcasting system limited to subscribers in which the same copyrighted work is distributed to a plurality of users such as a broadcasting system or video-on-demand, a receiving device installed on the subscriber side includes: By adding a signal specifying a subscriber (recipient) to the signal output from, separate identification information can be added for each subscriber.
[0020]
As a result, it is possible to prevent a third party other than the subscriber from acquiring the work and distributing an illegal copy of the work to which the identification information is not added.
According to a third aspect of the present invention, in the receiving device according to the first or second aspect, a broadcast station identification signal including information for specifying the broadcast station is added to a broadcast signal broadcast from the broadcast station. The means for adding the additional signal includes a signal addition format used for adding the additional signal from a plurality of predetermined signal addition formats based on the signal addition format of the broadcast station identification signal. Is selected.
[0021]
According to the present invention, signals including information specifying a subject (broadcasting station and subscriber) involved in delivery of a copyrighted work, which are added a plurality of times, interfere with each other and impair the mutual discrimination in reading. That is, it is possible to prevent the quality of the copyrighted work from deteriorating.
[0022]
According to a fourth aspect of the present invention, in the receiving apparatus according to the third aspect, the signal addition method of the additional signal is based on a time-domain or space-domain spread spectrum method using a specific codeword. The means for adding the additional signal selects, as the codeword used for adding the additional signal, a codeword in which the broadcast station identification signal and the codeword used for the additional signal are codewords orthogonal to each other. .
[0023]
According to the present invention, the information included in each of the added signals is selected by selecting an appropriate format for the additional signal added in the receiving device based on the format of the broadcast station identification signal added to the broadcast signal. Can be prevented from deteriorating the discriminability of each other and lowering the quality of the copyrighted work.
[0024]
According to a fifth aspect of the present invention, in the receiving device according to any one of the first to fourth aspects, an identification information storage unit storing device identification information capable of identifying the own device from another device; A means for preventing three parties from accessing the apparatus from outside and acquiring the apparatus identification information stored in the identification information storage unit, and a broadcasting station that broadcasts the broadcast signal. When transmitting predetermined authentication information generated based on the device identification information stored in the identification information storage unit to the outside of the device in order to authenticate the validity of the device, Means for intercepting the transmitted predetermined authentication information and disabling acquisition of the apparatus identification information, and a third party accessing the apparatus from outside and receiving the broadcast signal received by the apparatus. Take the one in which the additional signal has not been added yet. Characterized by comprising a means for disabling that.
[0025]
Here, means for disabling a third party from accessing the apparatus from outside and obtaining the apparatus identification information stored in the identification information storage unit and a means for preventing the third party from accessing the apparatus from outside are provided. Means for disabling acquisition of the broadcast signal received by the own device and in a state where the additional signal has not been added is, for example, using a device housing having a tamper-resistant property. It can be realized with.
[0026]
Further, in order to authenticate the validity of the apparatus itself with a broadcasting station that broadcasts the broadcast signal, a predetermined authentication generated based on the apparatus identification information stored in the identification information storage unit. Means for disabling a third party from intercepting the transmitted predetermined authentication information and acquiring the apparatus identification information when transmitting the information to the outside of the apparatus is, for example, a method in which the receiving apparatus is connected to the broadcast station side. This can be realized by using a zero-knowledge proof method in a procedure for proving that a device has a valid device identifier.
[0027]
ADVANTAGE OF THE INVENTION According to this invention, the illegal distribution of the work to which identification information is not added can be prevented by acting on the receiving device of the subscriber side or by using the unauthorized receiving device.
[0028]
The present invention (claim 6) provides a transmission system on a broadcast station side that broadcasts a broadcast signal by encrypting the contents for a registered subscriber, and a broadcast system in which the broadcast station manages information of each subscriber. In a broadcasting system including a management system and a receiving device installed on each subscriber side for receiving and decoding the broadcast signal, the broadcast management system includes information for identifying a subscriber, and information installed on the subscriber side. Means for managing the correspondence with the specified information for identifying the receiving device, means for performing authentication of the receiving device with each receiving device, and the receiving device determined to be legitimate by this authentication. First designation information for designating a decryption key to be used for decryption, and a signal to be added to the broadcast signal received on the receiving device side, at least corresponding to the receiving device that has received the broadcast signal. Identify subscriber Means for transmitting identification information including identification information including the information to be transmitted to the broadcast management system, wherein the receiving apparatus authenticates the apparatus with respect to the broadcast management system; Means for receiving the first designation information and the second designation information transmitted from the broadcast management system, and using the decryption key received by the own device and designated by the first designation information Means for adding an additional signal including identification information specified by second specification information to the decoded broadcast signal.
[0029]
According to a seventh aspect of the present invention, there is provided a receiving method of a receiving device installed on a subscriber side for receiving a broadcast signal broadcasted to a registered subscriber, the method comprising: And adding an additional signal including at least information specifying the subscriber who has received the broadcast signal.
[0030]
According to the present invention (claim 8), a receiver receives and decodes a broadcast signal broadcasted with its contents encrypted for a registered subscriber. The reception corresponding to the subscriber is managed by a broadcast station side. In the receiving method of the apparatus, an additional signal including at least information specifying the subscriber corresponding to the receiving apparatus that has received the broadcast signal is added to the received and decoded broadcast signal.
It should be noted that the invention according to each device is also realized as an explanation related to a method.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the invention will be described with reference to the drawings.
FIG. 1 shows an example of a configuration of a broadcasting / receiving system according to an embodiment of the present invention. In the figure, 9 is a system in the subscriber's house. Reference numeral 2 denotes a connection to a CATV or a telephone / data communication network, 3 denotes a satellite broadcast receiving antenna, and 4 denotes a terrestrial broadcast receiving antenna.
[0032]
The broadcast management system 8 is installed for each broadcasting station (or one for a predetermined number or all the broadcasting stations), and performs device authentication, decryption key of the receiving device 1 with the receiving device 1 at each subscriber's house. Delivery, collection of billing information, and exchange of other necessary information.
[0033]
In the present embodiment, it is assumed that the receiving device 1 installed in each subscriber's house is assigned a device identifier capable of specifying the device. Also, it is assumed that each subscriber is assigned subscriber identification information such as a subscriber number capable of specifying each subscriber. It is assumed that the correspondence between the identification information of the subscriber and the device identifier of the receiving device 1 installed in the subscriber's home is managed by the broadcast management system 8.
[0034]
The receiving device 1 installed at the subscriber home has at least one broadcast input. The broadcast input may be any of, for example, terrestrial broadcasting (VHF / UHF), satellite broadcasting, cable TV, and broadcasting through a communication network. FIG. 1 shows an example in which one receiving device 1 supports a plurality of broadcast inputs, but the number and combinations of broadcast formats are arbitrary. Of course, there may be one having an input of any one broadcast format.
[0035]
In addition, the receiving device 1 has communication means capable of performing bidirectional communication with the broadcast management system 8 in addition to the broadcast input. When a cable TV is used as a transmission medium for broadcasting, it is preferable that the communication means use a bidirectional communication function with the broadcasting station side system of the cable TV itself for cost reduction. In this case, the cable is shared with the transmission of the broadcast wave. On the other hand, in the case of satellite broadcasting or terrestrial broadcasting, a communication medium other than the broadcasting transmission medium, for example, a telephone network may be used as the communication means. This communication means is used for, for example, authenticating the receiving device, charging, and delivering a key used for decrypting the encrypted broadcast content.
[0036]
The receiving device 1 decodes an encrypted signal (or a compressed and encrypted signal) broadcast from a broadcasting station such as CATV, satellite broadcasting, or terrestrial broadcasting and received via a network or an antenna. (Or decryption and decompression processing) and further add an identification signal containing information capable of specifying the subscriber (recipient), and reproduce the subscriber's playback device such as a TV 5, VTR 6, or personal computer (PC) 7. Output to
[0037]
As information that can identify a subscriber, first, it is conceivable to use subscriber identification information. If the subscriber identification information and the device identifier of the receiving device 1 have a one-to-one correspondence, the device identifier may be used. Further, both the subscriber identification information and the device identifier of the receiving device 1 may be used.
[0038]
The output of the receiving device 1 is a VHF band modulated signal using an existing TV cable, NTSC video, or a digitized TV or VCR interface (IEEE 1934: “IEEE P1394 Standard for High Performance Serial Bus Draft 8”). .3v1 ", IEEE, 1996) or a combination thereof.
[0039]
Here, the broadcasting station and the broadcasting management system according to the present embodiment are not limited to a specific transmission system such as a radio wave or a cable TV and a form for the purpose of producing and providing a program. This includes services in general services distributed to companies. For example, an interactive broadcasting service in which the transmission means is not limited to one type, or an interactive service in which a service is performed in response to a request from a user without taking the form of a program that broadcasts according to a predetermined schedule. This includes image search and provision services.
[0040]
FIG. 2 shows a basic configuration of the receiving apparatus 1 according to the present embodiment.
Schematically, this receiving apparatus 1 is intended for broadcasts that are encrypted in order to prohibit eavesdropping on broadcasts of non-subscribers, and uses a decryption key for encryption as a valid subscriber (registered subscribers). ) Has a communication function to make it available only to the receiving device 1, and has a function of decoding a received broadcast signal, adding an identification signal to the received broadcast signal, and outputting it.
[0041]
In FIG. 2, an encrypted broadcast signal is input from an input line 14 and is decoded by a decoding unit 11. An identification signal including identification information for identifying a subscriber is added to the decoded signal by an identification signal adding unit 12, and output from an output line 15. The key used for decryption and information added as an identification signal are obtained by the decryption key / subscriber information management unit 13 from the broadcast management system 8 on the broadcast station side via the communication line 16. As described above, the input line 14 and the communication line 16 may be physically the same transmission medium.
[0042]
The identification signal includes, for example, additional information such as the identification number of the subscriber, the device identifier of the receiving device 1, the title of the broadcast content, and the broadcast time.
This identification signal is added in a form that cannot be removed without deteriorating the quality of the original signal. This is described, for example, in "Cryptology for Digital TV Broadcasting", Benoit M. Macq, and Jean-Jacques Quisquater, Proceedings of the IEEE, 83 (6): daisag, Diesal, ltg. Boney et al., Proceedings of International Conference on Multimedia Computing and Systems, IEEE, 1996 ".
[0043]
For this reason, even if a broadcasted program is duplicated and distributed, it can be known by examining the identification signal when and to whom the program was distributed, and copyright and broadcasting stations are required to comply with relevant laws. And take appropriate action.
[0044]
However, if a malicious third party steals the broadcast content used by a certain subscriber and duplicates and sells it, the suspicion of the content duplication will depend on the legitimate subscriber.
[0045]
In order to prevent this, it is desirable that transmission means from the receiving device 1 to the reproduction / storage device is provided with a means for preventing access by a malicious third party. In the present embodiment, the use of the transmission means is limited to the delivery of a program in a home. Therefore, since a malicious third party generally does not easily enter the home, unnecessary radiation may be prevented by using, for example, an optical fiber as the transmission means.
[0046]
In addition, the broadcast signal that has been encrypted exists in the receiving device 1 in a state where the broadcast signal is decrypted by the decryption unit 11. From the standpoint of the broadcasting station, there is a risk that the original signal to which the identification signal is not added by the malicious subscriber is read out and copied. This is because the duplication of the original signal to which the identification signal is not added cannot be prohibited as described above. Therefore, it is desirable to take a measure to prohibit the reading of signals from outside the receiving device.
[0047]
Means for prohibiting unauthorized access to such a device or reading of internal information by destructive means can be realized by using a technique already known as a tamper-resistant device (for example, Mori, R. et al. , Kawahara, M: "Superdistribution: The Concept and the Architecture", IEICE transaction 73 (7), 1990).
[0048]
In addition to the tamper resistance described above, the receiving device 1 on the subscriber side confirms that its own device has correctly implemented the tamper resistance, charging, and other functions in accordance with the specifications determined by the broadcast station. It is desirable to prove by communication with the system 8. In this case, for example, the receiving device 1 certifies its own identification number to the broadcast management system 8. It is needless to say that it is impractical to perform this proof by a method such as an inspection by a supervisor instead of communication, in terms of labor costs.
[0049]
In this case, a device identifier stored in the receiving device 1 used for certification is also prohibited from being accessed from outside due to tamper resistance or the like.
The procedure for proving that the receiving apparatus 1 has a valid apparatus identifier on the broadcast station side uses a zero-knowledge certifying method that enables authentication of the content of the data without passing the data itself. Is desirable. Regarding the zero-knowledge proof method, for example, Fit Shamir's zero-knowledge proof method is described in “Fiat, A., Shamir, A .:“ How to probe your self-selling: applica- tional agreement proof-of-principation proof-of-principation proof-of-principle proof-of-principle proof-of-principle proof-of-principle proof-of-principle proof-of-principation and proof-of-consultation. Verlag, Berlin, 1987 ".
[0050]
When certifying to the broadcasting station that the receiving device 1 has a certain device identifier p, a method of encrypting and transmitting the identifier p may be used instead of using the zero-knowledge proof method. An example of the procedure is shown below.
[0051]
The partner broadcasting station has a secret key e and a public key f, and the receiving device 1 knows the public key f. The receiving device 1 encrypts the identifier p with the public key f and transmits the key to the broadcasting station. The broadcasting station can directly obtain the identifier p using the secret key e corresponding to the public key f. On the other hand, since the third party does not know the secret key e, even if the data of the identifier p encrypted by the public key f can be intercepted, the identifier p cannot be directly obtained from the intercepted data. Also, obtaining a corresponding identifier p from the public key f and the intercepted data requires a very large amount of calculation, and it can be considered virtually impossible to obtain the identifier p.
[0052]
Many such techniques already exist, one of which is well known is the RSA encryption. The RSA encryption is described in, for example, “RL Rivest, A. Shamir, and LM Adelman,“ A method for observing digital signatures and public-key cryptosystems, two-way cryptosystems, two-dimensional cryptosystems, two-dimensional cryptosystems, two-dimensional cryptosystems, two-dimensional cryptosystems, two-dimensional cryptosystems, two-dimensional cryptosystems, two-dimensional cryptosystems, two-dimensional cryptosystems, and two-dimensional cryptosystems. ".
[0053]
However, if a malicious third party has misrepresented the broadcasting station, this method may leak the secret of the identifier, so that the broadcasting station must be proved in advance to the receiving device. A reverse authentication procedure is required.
[0054]
As another method, a method using a Diffy-Hellman key sharing protocol may be considered.
Hereinafter, some receiving devices having the basic configuration as described above will be described in detail.
[0055]
FIG. 3 shows an example of the configuration of the receiving device 1 according to the present embodiment.
Here, it is assumed that the broadcast signal to be broadcast has been compressed and encrypted.
[0056]
14-1 to 14-n represent input lines 1 to n, respectively. These correspond to inputs such as terrestrial broadcasting (VHF / UHF), satellite broadcasting, and cable TV. The receiving apparatus 1 includes tuning / demodulation circuits 21-1 to 21-n, a decoding unit 22, an expansion coding unit 23, an identification signal adding unit 24, a compression unit 25, an output circuit 26, a decoding key / subscriber information. The management device 27 includes a device identifier 28.
[0057]
The tuning / demodulation circuits 21-1 to 21-n are tuning / demodulation circuits corresponding to inputs modulated by a unique frequency / modulation method, respectively, where the input signal is converted into a digital signal. It is to be noted that how many types of tuning / demodulation circuits corresponding to which system are provided is arbitrary.
[0058]
The decryption unit 22 decrypts the encrypted digital signal obtained by tuning and demodulation. As a result, a compression-coded signal is obtained. In FIG. 3, the decoding function is treated as a single function, but there are a plurality of methods, and a functional block may be divided for each method.
[0059]
The decompression encoding unit 23 performs decompression encoding on the compression-encoded signal obtained by decoding to obtain an original signal.
The identification signal adding unit 24 adds an identification signal to a signal obtained by decoding and decompression.
[0060]
The compression unit 25 compression-encodes the signal to which the above-described identification signal has been added in the encoding format of the output interface.
The output circuit 26 outputs the compression-encoded signal to the broadcast line 15.
[0061]
Then, this output is transmitted to the playback device of the subscriber, and playback is performed.
Here, the output interface assumes digital modulation. If analog output is performed, it is not necessary to perform compression encoding, and the compression unit 25 is omitted.
[0062]
The decryption key / subscriber information management device 27 performs a procedure for certifying to the broadcast management system 8 via the communication line 16 that the device itself has the correct device identifier 28 and obtaining the decryption key and identification information to be added to the program. Do. The decryption key is notified to the decryption unit 22 and the identification information is notified to the identification information adding unit 24.
[0063]
In this configuration, the tamper resistance is required because the decoding unit 22, the decompression encoding unit 23, the identification information adding unit 24, the decoding key / subscriber information managing unit 27 indicated by the hatched portion 29 , The device identifier 28 and the connection between those blocks. Of course, other parts may be mounted in a form having tamper resistance.
[0064]
Here, one of the reasons why the decompression encoding is performed once before the addition of the identification signal is that the input and output may have different compression formats. For example, this corresponds to the case where the broadcasting station uses MPEG2 encoding and the output side uses the DV format.
[0065]
Another reason is a technique of using information such as a frequency spectrum of an original signal in a method of adding identification information (for example, “Digital Watermarks for Audio Signals”, L. Bonuey et al., Proceedings of International Conference, International Education, International Education, International Communications, and International Education, International Communication, International Communication, and International Communication, International Communication, and International Education , 1996), it is sometimes difficult to add identification information to these compression-encoded signals as they are due to a reduction in image quality or the like.
[0066]
As long as the input and output encoding formats are the same, and an additional format of the identification signal that does not have the above-described problems such as deterioration of image quality is available, compression without expansion and compression encoding is performed. By employing a configuration in which the identification signal is directly added to the encoded original signal, it is possible to reduce the size and cost of the system.
[0067]
Next, FIG. 4 shows another example of the configuration of the receiving device 1 according to the present embodiment.
Here, it is assumed that the signal to be broadcast has been compressed and encrypted.
This configuration example corresponds to the case where the compression encoding is not performed after the identification signal is added, and is the same as the case of FIG. 3 except that the compression encoding unit 25 of FIG. 3 is not provided. The output may be either digital modulation or analog modulation such as NTSC. In the present configuration, a portion requiring tamper resistance is indicated by a hatched region 29.
[0068]
Next, FIG. 5 shows another example of the configuration of the receiving device 1 according to the present embodiment.
Here, it is assumed that the signal to be broadcast has been compressed and encrypted.
This configuration example corresponds to a case where an identification signal is added and output without performing expansion coding, and the expansion coding unit 23 and the compression coding unit 25 are omitted from the configuration of FIG. . However, in this case, the identification information adding unit 24 uses a method capable of adding an identification signal to a compression-encoded signal as it is without deterioration in image quality. In this configuration, a portion where tamper resistance is required is indicated by a region 29.
[0069]
In the following, a procedure for viewing a program with the above-described receiving device will be described.
FIG. 6 shows an example of this procedure.
[0070]
The viewing of the program is started by a user's request for viewing the program (step S31). The program viewing request is input from a remote control device or a timer reservation device attached to the receiving device 1 by a user operation, or from a connected reproducing / recording device or communication interface 16. When the communication interface 16 is used, since there is a possibility of access by a third party other than the subscriber, it is desirable to take appropriate security measures such as authentication using encryption or a password.
[0071]
Upon receiving the program viewing request, the receiving device 1 performs a procedure for proving that the receiving device 1 is a legitimate device with the broadcast management device 8 on the broadcast station side (step S32). After the proof is issued, the program is requested to the broadcast management device 8 (step S33), and a corresponding decryption key is obtained. For a program request, channel information is used in the case of being broadcast on an existing channel, and information of the program is used in a broadcast service started by a user request such as VOD. The data exchange between the receiving device 1 and the broadcast management device 8 is not only performed by delivering the decryption key but also other procedures are encrypted by an appropriate method to protect the privacy of the individual. Should not be able to know its contents.
[0072]
The receiving device 1 that has obtained the decryption key executes a process of receiving an instruction from the broadcast station for information to be added to the identification signal in addition to the identification number as information to be included in the identification signal to be added to the broadcast signal (step S34). . The identification signal includes, for example, broadcast station identification information, subscriber device identification information, subscriber identification information (when a plurality of viewers exist in a single subscriber device), program identification information, and a predetermined reference time. Information such as the absolute time and the elapsed time from the start of the program is included. From the viewpoint of preventing the distribution of unauthorized copies, it is desirable that the subscriber information (subscriber device information) and the program identification information be unique worldwide. If the broadcast station identification information is unique all over the world, this can be realized by setting the identification information uniquely in the subscriber device of each broadcast station.
[0073]
Furthermore, in order to show that the information belongs to the broadcasting station that broadcasts the information, the information is encrypted with the private key of the broadcasting station and decrypted with the corresponding public encryption key. It is desirable to add an authenticator that can be read correctly by doing so. If this is not done, a malicious third party with the original signal of a program can add the identification information of any broadcast station to the signal, thereby pretending that the program was broadcast by that broadcast station. This is because it may be possible.
[0074]
Next, the receiving device 1 sends a reproducible signal to the reproducing device (step S35).
Note that the decryption key of the broadcast signal is changed every certain period in order to prevent damage due to leakage of key information. For example, a program unit or a fixed time unit. However, it is needless to say that the longer the interval is, the higher the possibility of leaking the key information is, and the shorter the interval is, the greater the overhead of distributing the key information is.
[0075]
Further, the change of the key information and the charging for viewing the broadcast need not always correspond. For example, even when the key information is changed once a day, the broadcast viewing unit may be managed by a time unit smaller than one day. In this case, the receiving device 1 does not decrypt the broadcast even if the subscriber has the key information at a time when the subscriber does not want to view, and does not charge for that time. In this case, in step S35, charging starts at the same time as the start of the process of sending a reproducible signal to the reproducing device. On the other hand, in the case where the change of the key information is made to correspond to the charge for viewing the broadcast, the charge is started in step S34. In addition, various methods can be applied to billing.
[0076]
Also, regarding the viewing time of the program and the elapsed time from the start of the program, the receiving device 1 has a clock for managing the information without receiving the information from the broadcast management system 8, thereby reducing the use of the communication line. be able to. The information indicating the viewing time and the elapsed time from the start of the program may be based on a signal accompanying the broadcast.
[0077]
In the above, description has been given of adding an identification signal to a work distributed by a broadcasting station through broadcasting.
When the copyright holder distributes the work to the broadcasting station, such an identification signal may naturally be added. Different identification signals are added at the stage of copying from the copyright holder to the broadcasting station and at the stage of copying from the broadcasting station to the user who is the end user. Even when the identification information is added a plurality of times as described above, it is necessary to prevent the reading of the identification information from deteriorating the mutual identification and the quality of the work. The method will be described below.
[0078]
FIG. 7 shows a procedure in a case where a change of the identification signal adding method is included. The difference from the procedure of FIG. 6 is that the format of the identification information added to the broadcast signal is obtained in step S44 for obtaining information from the broadcasting station, and the format of the identification information previously obtained in step S45. Is to change the format of the identification information added in the receiving device 1 based on the
[0079]
For example, the work is voice, and the identification signal is a signal obtained by modulating an information sequence related to the work with a codeword based on the M sequence and spectrally spreading the audio signal in the audio frequency band. Consider the case where signal addition is performed by taking The identification signal is added with an intensity that is suppressed by human auditory characteristics by the original signal and cannot be heard. It is known that there is such a signal strength threshold in human auditory characteristics.
[0080]
The decoding of the identification signal can be performed by demodulating the difference S'-S between the two, where S is the original signal and S 'is the signal to which the identification signal is added. That is, the identification signal can be reproduced from the output signal S ′ of the receiving device 1 by using the original signal.
[0081]
Here, the identification signal added at the time of transmission from the broadcasting station is referred to as identification signal 1, and the identification signal added in the receiving device is referred to as identification signal 2.
Even when the identification signal is added a plurality of times, if the power spectrum of the sum of the identification signal 1 and the identification signal 2 is equal to or less than a threshold value which is perceptually suppressed with respect to the original signal, the addition of the signal is not performed. It does not impair the quality of the copyrighted work.
[0082]
The reproduction of the identification signal is performed by demodulating the sum signal of the two signals. However, when the identification signal 1 and the identification signal 2 use codes orthogonal to each other, there is no problem because they do not interfere with each other. This can be realized by using a set of codes called an M-sequence when the periods of the code words are the same. It is also known that, even when the same codeword is used, a plurality of identifiers can be reproduced without interfering with each other by shifting the modulation period by a certain relative period called a bit (“Spread Spectrum Systems”). ", R. Dixon, 1976).
[0083]
Therefore, a set after orthogonal codes is determined in advance, and in step S44, the broadcasting station notifies the receiving apparatus 1 of the code word of the identification information added to the work, so that the receiving apparatus 1 Can be selected. Instead of directly transmitting the codeword of the identification information, an identifier for identifying the codeword in a set of codewords may be determined in advance, and the identifier corresponding to the codeword may be transmitted.
[0084]
Further, when the receiving apparatus 1 has only a signal adding means based on one kind of code, the receiving apparatus obtains information indicating a code phase relationship of the identification signal 1 so that the receiving apparatus can perform identification for an appropriate period. By shifting the phase of the signal, interference between the identification signal 1 and the identification signal 2 can be prevented.
[0085]
In the above description, only one type of identifier is added at the time of transmitting a signal from a broadcast station. However, a plurality of identifiers may be provided corresponding to a plurality of stages of distribution.
The present invention is not limited to the above-described embodiment, and can be implemented with various modifications within the technical scope thereof.
[0086]
【The invention's effect】
According to the present invention, in a broadcasting system limited to subscribers in which the same copyrighted work is distributed to a plurality of users such as a broadcasting system or video-on-demand, a receiving device installed on the subscriber side includes: By adding a signal specifying a subscriber (recipient) to the signal output from, separate identification information can be added for each subscriber.
[0087]
This prevents illegal distribution and sale of a copy of the work, and can identify the source even if the broadcast work is copied and distributed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a system according to an embodiment of the present invention.
FIG. 2 is a diagram showing a basic configuration of a receiving apparatus according to the embodiment;
FIG. 3 is a diagram showing a configuration example of a receiving apparatus according to the embodiment;
FIG. 4 is a diagram showing another configuration example of the receiving apparatus according to the embodiment;
FIG. 5 is a diagram showing still another configuration example of the receiving apparatus according to the embodiment;
FIG. 6 is a flowchart showing an example of a program viewing procedure according to the embodiment;
FIG. 7 is a flowchart showing another example of the program viewing procedure according to the embodiment;
[Explanation of symbols]
1. Receiving device
2. External network
3: Satellite broadcast receiving antenna
4: Terrestrial broadcast receiving antenna
5 ... TV
6 VTR
7. Personal computer
8. Broadcast management system
9. Subscriber home system
11, 22... Decoding part
12, 24 ... identification signal adding section
13, 27: decryption key / subscriber information management unit
14, 14-1 to 14-n ... input lines
15 ... Output line
16 Communication line
21-1 to 21-n: tuning / demodulation circuit
23 ... Decompression coding unit
25 ... Compression unit
26 ... Output circuit
28 Device identifier

Claims (4)

A receiving device for receiving a broadcast signal broadcast from a broadcast station,
The broadcast signal is obtained by modulating an identification signal including at least information for identifying the broadcast station using a specific codeword, performing spectrum spreading in a time space or a space domain, and adding the same to the original signal, and adding the identification signal. Compression and encryption of the original signal
Decoding means for decoding the received broadcast signal;
Additional means for adding an additional signal including information specifying at least the subscriber corresponding to the receiving device that has received the broadcast signal to the original signal so that the original signal is not deteriorated;
Compression means for compressing the original signal to which the additional signal is further added;
Output means for outputting a signal compressed by the compression means;
And the additional means comprises:
Decompression means for decompressing the signal obtained by decoding by the decoding means to obtain the original signal to which the identification signal is added,
A means for selecting a codeword that is orthogonal to the codeword used when modulating the identification signal, based on the codeword or the identifier used when modulating the identification signal, transmitted from the broadcast station. ,
The additional signal is modulated using the selected codeword so that the additional signal does not interfere with the identification signal, and the power spectrum of the sum of the identification signal and the additional signal does not cause a human to feel deterioration of the original signal. Means to spread the spectrum in time space or space domain so as to be equal to or less than the threshold value, and to add the additional signal to the original signal to which the identification signal obtained by the expansion means is added,
A receiving device comprising: A receiving device for receiving a broadcast signal broadcast from a broadcast station,
The broadcast signal is obtained by modulating an identification signal including at least information for identifying the broadcast station using a specific codeword, performing spectrum spreading in a time space or a space domain, and adding the same to the original signal, and adding the identification signal. Compression and encryption of the original signal
Decoding means for decoding the received broadcast signal;
Additional means for adding an additional signal including information specifying at least the subscriber corresponding to the receiving device that has received the broadcast signal to the original signal so that the original signal is not deteriorated;
Output means for outputting an original signal to which the additional signal is further added;
And the additional means comprises:
Decompression means for decompressing the signal obtained by decoding by the decoding means to obtain the original signal to which the identification signal is added,
A means for selecting a codeword that is orthogonal to the codeword used when modulating the identification signal, based on the codeword or the identifier used when modulating the identification signal, transmitted from the broadcast station. ,
The additional signal is modulated using the selected codeword so that the additional signal does not interfere with the identification signal, and the power spectrum of the sum of the identification signal and the additional signal does not cause a human to feel deterioration of the original signal. Means to spread the spectrum in time space or space domain so as to be equal to or less than the threshold value, and to add the additional signal to the original signal to which the identification signal obtained by the expansion means is added,
A receiving device comprising: An identification signal broadcast from a broadcasting station and containing at least information for identifying the broadcasting station is modulated using a specific codeword, spectrum-spread in time space or a spatial domain and added to the original signal, and the identification signal In a receiving apparatus that receives a broadcast signal obtained by compressing and encrypting the added original signal, an additional signal including at least information specifying a subscriber corresponding to the receiving apparatus that has received the broadcast signal is converted into an additional signal of the original signal. A method of receiving the broadcast signal for adding to the original signal so that there is no deterioration,
The received broadcast signal is decoded and decompressed to obtain the original signal to which the identification signal has been added, and a codeword transmitted from the broadcasting station and used for modulating the identification signal or its identifier is used. A codeword that is orthogonal to the codeword used to modulate the identification signal is selected, and the additional signal is modulated using the selected codeword so as not to interfere with the identification signal. Then, the power spectrum of the sum of the identification signal and the additional signal is spectrally spread in the time space or the spatial domain so that the degradation of the original signal is equal to or less than a predetermined threshold at which the human does not perceive the deterioration of the original signal. Receiving the original signal to which the additional signal is added, and then compressing and outputting the original signal to which the additional signal is further added. An identification signal broadcast from a broadcasting station and containing at least information for identifying the broadcasting station is modulated using a specific codeword, spectrum-spread in time space or a spatial domain and added to the original signal, and the identification signal In a receiving apparatus that receives a broadcast signal obtained by compressing and encrypting the added original signal, an additional signal including at least information specifying a subscriber corresponding to the receiving apparatus that has received the broadcast signal is converted into an additional signal of the original signal. A method of receiving the broadcast signal for adding to the original signal so that there is no deterioration,
The received broadcast signal is decoded and decompressed to obtain the original signal to which the identification signal has been added, and a codeword transmitted from the broadcasting station and used for modulating the identification signal or its identifier is used. A codeword that is orthogonal to the codeword used to modulate the identification signal is selected, and the additional signal is modulated using the selected codeword so as not to interfere with the identification signal. Then, the power spectrum of the sum of the identification signal and the additional signal is spectrally spread in the time space or the spatial domain so that the degradation of the original signal is equal to or less than a predetermined threshold at which the human does not perceive the deterioration of the original signal. Receiving the original signal to which the additional signal is added, and thereafter outputting the original signal to which the additional signal is further added.

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