JP2007336234A - Stream receiver and stream transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stream receiver which reproduces only currently transmitted video and audio signals of the digital broadcast, relating to a stream transmission system which transmits a digital broadcast through an IP network. <P>SOLUTION: The stream receiver 100 comprises a communication interface 111 which receives an encoded stream; an intrinsic information extractor 117 which acquires the intrinsic information of the stream from it; an intrinsic information validater 118 which controls whether to permit decoding of stream or not, by validating the fact that the received stream is currently in service based on the intrinsic information; and a decoder 115 which decodes the encoded stream when decoding is permitted by the intrinsic information validater 118. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a stream receiving apparatus that receives and displays a distribution service such as video and audio using an IP (Internet Protocol) network, and a stream transmission system having the same.

  In the field of digital broadcasting such as satellite digital broadcasting and terrestrial digital broadcasting, a mechanism for enabling only authorized receivers to view digital broadcasting, or enabling only contracted receivers to view specific programs As a mechanism for this, a conditional access system called CAS (Conditional Access System) is used. For example, in Japan, a method called B-CAS is used.

  A limited reception system in digital broadcasting is disclosed in Patent Document 1. A conventional stream receiving apparatus described in Patent Document 1 that receives digital broadcasting will be described below with reference to FIG.

  The tuner 121 receives a radio wave of digital broadcasting and outputs it as a TS (Transport Stream) stream. The TS stream includes encrypted video / audio data and an ECM (Entitlement Control Message) for decrypting the encryption of the video / audio data, and is transmitted after being divided into fixed-length packets called TS packets.

  The demultiplexing unit 112 extracts video / audio data and ECM from the TS packet, outputs the video / audio data to the encryption / decryption unit 113, and outputs the ECM to the key information extraction unit 196.

  In the key information extraction unit 196, viewing conditions indicating conditions of programs that can be viewed on the stream receiving device 109 are set in advance by another means. The viewing conditions include identifiers of programs that can be viewed. The key information extraction unit 196 decrypts the ECM with the key acquired in advance, extracts program information and key information from the ECM, and determines that the program information satisfies viewing conditions, the encryption information decryption unit 113 Set to.

  The encryption / decryption unit 113 decrypts the video / audio data using the key information set by the key information extraction unit 196 and outputs the decrypted video / audio data to the video / audio decoding unit 114. The video / audio decoding unit 114 decodes MPEG2-Video or MPEG2-AAC audio.

The key information extraction unit 196 does not set the key information in the encryption / decryption unit 113 when the program information included in the ECM does not satisfy the viewing condition. Therefore, the encryption of the video / audio data is not decrypted, and the video / audio is not correctly decrypted and displayed. In this way, the conventional stream receiving apparatus 109 performs viewing restriction based on viewing conditions.
JP-A-11-341467

  When a broadband IP (Internet Protocol) network called broadband becomes widespread, digital broadcasts can be retransmitted using the IP network in the same form as CATV. However, unlike broadcasting using radio waves, broadcasting over an IP network has the feature that broadcasting data can be easily captured using a personal computer (hereinafter referred to as “PC”), and the conventional conditional access system is used. There is a problem that the broadcast cannot be sufficiently protected by simply applying it to the IP network as it is. For example, if a stream retransmitted from a transmitter is captured as an IP packet by a PC or the like, temporarily stored in a hard disk or the like, and transmitted from the PC to the receiver at another time, even the stream once stored is received. The machine cannot be distinguished from the original broadcast, and decrypts the stream and reproduces video and audio in the same way as when receiving the original broadcast. Such reproduction is a copyright issue.

  The present invention aims to solve the above problems, and provides a stream receiving apparatus and a stream transmission system that limit viewing of a stream that is not currently being retransmitted.

  The stream reception device of the present invention includes a communication interface that receives an encrypted stream, a unique information extraction unit that acquires unique information of the stream from the stream, and the received stream is currently based on the unique information. By verifying whether the stream is in service, a unique information verification unit that controls whether or not to permit the decryption of the stream; and when the decryption is permitted by the unique information verification unit, the encryption of the stream And a decoding unit for decoding. This prevents unauthorized decoding of a stream that is not currently in service.

  The unique information verification unit transmits the unique information extracted by the unique information extraction unit via the communication interface to a server that holds a list of unique information of a stream that is currently in service. A determination result as to whether or not the stream is currently in service may be received, and decoding by the decoding unit may be permitted when the stream is currently in service. Thereby, since it is possible to request verification of the unique information from a reliable server, the verification can be performed safely.

  The stream receiving device further includes a unique information list receiving unit that receives a unique information list including a list of unique information of a stream that is currently in service, and the unique information verification unit is configured to extract the unique information extraction unit. When the unique information is included in the unique information list, decoding by the decoding unit may be permitted. Thereby, the load of the server for providing the confirmation information of specific information can be reduced.

  The unique information list further includes a transmission time of the unique information list, and the unique information verification unit determines whether or not a difference between the transmission time and the current time is within a preset valid period range. However, when it is determined that it is within the valid period, the decoding by the decoding unit may be permitted. As a result, it is possible to reliably perform confirmation based on information on the stream currently being serviced. For example, it is possible to prevent fraud by means such as temporarily storing the unique information list in a PC or the like and transmitting the unique information list from the PC to the stream receiving device at another time.

  The stream includes encryption key information obtained by encrypting key information for decrypting the cipher of the stream, and the unique information extraction unit uses the encryption key information as all or part of the stream as the unique information. May be extracted from Thereby, it is possible to prevent the stream from being illegally received by rewriting the stream and falsifying the unique information.

  The stream includes encryption key information obtained by encrypting key information for decrypting the encryption of the stream, and the unique information extraction unit extracts all or a part of the encryption key information from the stream. The data may be converted by a one-way function, and the converted data may be output as the unique information. Thereby, the size of the unique information of the stream can be reduced and the communication amount can be reduced.

  The unique information verification unit may verify whether or not the decryption by the decryption unit is permitted when the encryption key information is updated. Accordingly, it is possible to further improve safety by verifying the unique information even during the stream reception.

  The unique information verification unit may count the number of updates of the encryption key information, and determine a frequency of performing verification using the unique information based on the number of updates and a random number. Thereby, it is possible to reduce the concentration of access to the server for confirming the unique information when updating the encryption key information.

  The unique information verification unit may determine a time from when the encryption key information is updated to when verification with the unique information is performed using a random number. Thereby, it is possible to reduce the concentration of accesses to the server for confirming the unique information when updating the encryption key information.

  The stream may be in an MPEG2 transport stream format, and the encryption key information may be ECM. As a result, in a service using an MPEG2 transport stream, it is possible to prevent illegal reception of a stream that is not currently in service.

  The decryption unit extracts, from the stream, encrypted key information obtained by encrypting key information for decrypting the cipher of the stream, decrypts the key information, and outputs the key information; and the key information And an encryption / decryption unit that decrypts the cipher of the stream, and a video / audio decoding unit that decodes the stream output from the encryption / decryption unit into video / audio, and the unique information verification unit includes: In addition, it is possible to control whether or not at least one of the key information extraction unit, the encryption / decryption unit, and the video / audio decoding unit is permitted to decrypt the stream.

  The stream transmission system of the present invention has a stream transmission device that transmits an encrypted stream, a list of unique information of the stream that is currently transmitted by the stream transmission device, and receives an inquiry about the unique information Determining whether the specific information is currently being transmitted, receiving the specific information server that outputs the determination result, the stream output from the stream transmitting device, and receiving the stream from the stream A stream that acquires unique information, transmits the unique information to the unique information server, and decrypts the cipher of the stream only when a determination result indicating that the unique information is a stream currently being transmitted is received from the unique information server And a receiving device. As a result, it is possible to prevent the stream receiving apparatus from illegally reproducing a stream that is not currently being serviced by the stream transmitting apparatus.

  Another stream transmission system includes a stream transmission device that transmits an encrypted stream, a unique information server that transmits a unique information list including a list of unique information of a stream that the stream transmission device is currently transmitting, and the stream A stream receiving device that receives the stream and the unique information list, obtains the stream unique information from the stream, and decrypts the cipher of the stream only when the obtained unique information is included in the unique information list; Have. As a result, it is possible to prevent the stream receiving apparatus from illegally reproducing a stream that is not currently being serviced by the stream transmitting apparatus.

  The stream receiving apparatus and the stream transmission system of the present invention can determine whether or not the received stream is currently in service, and can restrict viewing of streams that are not currently in service. For this reason, it is possible to limit an action that becomes a loophole in copy protection, such as once the stream is accumulated and viewed at another time.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment specifically showing the best mode for carrying out the invention will be described with reference to the drawings.

Embodiment 1
[Configuration of stream receiver]
FIG. 1 shows the configuration of a stream receiving apparatus capable of receiving broadcasts over an IP network according to Embodiment 1 of the present invention. The stream receiving apparatus 100 according to the present embodiment includes a communication interface 111 that receives a digital broadcast IP packet and extracts a TS stream from the IP packet. The communication interface 111 performs bi-directional communication using the IP protocol with the outside using an interface such as Ethernet, wireless LAN, or CATV modem.

  The stream receiving apparatus 100 includes a demultiplexing unit 112 that separates video / audio data included in the TS stream and an ECM (Entitlement Control Message), and a unique information extraction unit 117 that extracts unique information of the TS stream from the ECM. Based on the specific information, it is determined whether the digital broadcast is currently in service, and the specific information verifying unit 118 that controls whether or not to permit the decoding of the stream based on the determination result, and the specific information verifying unit 118 perform the decoding. It further has a decoding unit 115 for decoding the video / audio data when permitted.

  The decryption unit 115 decrypts the ECM and extracts the key information, the key information extraction unit 116 decrypts the video / audio data using the key information, and the video / audio data decrypts the video / audio data. The audio decoding unit 114 is included.

  The key information extraction unit 116 according to the present embodiment is different from the prior art in that it switches whether or not to set key information in the encryption / decryption unit 113 according to the determination result of the unique information verification unit 118. The key information extraction unit 116 according to the present embodiment extracts program information and key information from the ECM received from the demultiplexing unit 112, the program information satisfies the preset viewing conditions, and the unique information verification unit 118 reads “ Only when “decryption is possible” is notified, the key information is set in the encryption / decryption unit 113.

[Structure of TS stream]
FIG. 2 shows an outline of the format of the TS stream included in the IP packet received by the communication interface 111. The TS stream 700 is in the MPEG2 standard TS (Transport Stream) format, and is transmitted by being divided into 188-byte fixed-length packets called TS packets 701. Each TS packet 701 has a header part 710 and a payload part 720.

  The header portion 710 includes an identifier called PID (Packet ID) for identifying the type of each TS packet. The PID is assigned a different value for each type of video, audio, or each control data. Note that the PID value of each data is determined in advance by the standard, or is indirectly specified from data having the determined PID.

  In the TS stream 700, control data such as encryption key information obtained by encrypting key information for decrypting the stream is multiplexed in addition to video / audio data, and each data has an appropriate size. And is mapped to the payload area 720 of the TS packet 701. The video data is compressed and encoded in the MPEG2-Video format, and the audio data is compressed and encoded in the MPEG2-AAC format and mapped to the payload 720 of the TS packet 701. Video / audio data is encrypted.

  Key information for decrypting the encryption of the video / audio data is encrypted in the payload portion 720 of the TS packet 701 having a specific PID in a data format called ECM, and is periodically transmitted. The ECM includes program information such as a program identifier in addition to the key information.

[Configuration of stream transmission system]
FIG. 3 shows an outline of an IP retransmission system that retransmits digital broadcasts using radio waves over an IP network as an example of a stream transmission system including the stream receiver of this embodiment. The stream transmission system of the present embodiment receives the broadcast by radio waves via the stream receiver 100 shown in FIG. 1, the digital broadcast transmission station 800 that transmits the broadcast by radio waves via the transmission antenna 802, and the reception antenna 202, Specific information including a list of specific information of an IP broadcast transmitting station 200 that converts the IP packet into an IP packet and transmits the IP packet to the stream receiving apparatus 100 via the IP network 300 and a TS stream currently retransmitted by the IP broadcast transmitting station 200 A unique information server 400 having a list 410 is included.

[Operation of stream transmission system]
In FIG. 3, the digital broadcast transmitting station 800 broadcasts the TS stream 700 shown in FIG. The IP broadcast transmitting station 200 receives the broadcast by the radio wave transmitted from the digital broadcast transmitting station 800 by the receiving antenna 202, takes out the TS stream 700, divides it into an appropriate size, and stores it in the IP packet. The IP packet is transmitted to the stream receiving apparatus 100 via the 300.

  In the stream receiving apparatus 100, the communication interface 111 receives the IP packet sent from the IP broadcast transmitting station 200, extracts the TS stream 700 therefrom, and passes it to the demultiplexing unit 112.

  The demultiplexing unit 112 refers to the PID included in the header portion 710 of each TS packet 701 of the TS stream 700 to separate the video / audio data and the ECM from the TS stream 700, and converts the video / audio data into the video / audio data. The data is output to the encryption / decryption unit 113, and the ECM is output to the unique common use extraction unit 117 and the key information extraction unit 116.

  The unique information extraction unit 117 generates unique information of the TS stream 700 by calculating the hash value of the ECM as data that is the basis of the unique information. The ECM separated by the demultiplexing unit 112 is obtained by encrypting a part of the area including key information for decrypting the encryption of the video / audio data, and the unique information extracting unit 117 remains encrypted. A hash value is obtained from the ECM.

  The unique information verification unit 118 outputs the ECM hash value obtained by the unique information extraction unit 117 to the communication interface 111 as unique information of the TS stream 700. The communication interface 111 transmits unique information to the unique information server 400 via the IP network 300 shown in FIG. Communication between the communication interface 111 and the unique information server 400 is performed on a communication path protected by an SSL (Secure Socket Layer) protocol. In SSL, it is possible to authenticate that a communication partner is a correct partner by using a certificate, and since communication is performed in an encrypted manner, it is possible to prevent an illegal act due to impersonation of the unique information server 400.

  The unique information server 400 compares the unique information transmitted from the stream receiving apparatus 100 with the unique information list 410 of the stream currently being retransmitted, determines whether there is a match, and determines the determination result as the stream receiving apparatus. Return to 100.

  The communication interface 111 of the stream receiving apparatus 100 transfers the determination result from the unique information server 500 to the unique information verification unit 118. When the unique information server 400 returns that the unique information is included in the list 410, the unique information verification unit 118 sets “decryption is possible”, otherwise “decryption is impossible” to the key information extraction unit 116. Notice.

  The key information extraction unit 116 decrypts the ECM, extracts program information and key information, and determines whether the program information satisfies a preset viewing condition. The key information extraction unit 116 sets the key information in the encryption / decryption unit 113 only when the viewing condition is satisfied and “decryption is possible” is notified from the unique information verification unit 118.

  The encryption / decryption unit 113 decrypts the encryption of the video / audio data using the key information set by the key information extraction unit 116, and the video / audio decoding unit 114 decodes the MPEG2-Video or MPEG2-AAC audio I do.

  As described above, in this embodiment, the ECM hash value is used as unique information of the TS stream 700. The ECM includes a content key that is key information for decrypting the encryption of the TS stream 700 in an encrypted form, and the content key is operated so that a different value is used for each TS stream as much as possible for security reasons. Therefore, the ECM is effective as unique information of the TS stream.

  In addition, hash calculation is a kind of one-way function, and a method is selected such that the probability that the same hash value is obtained becomes extremely small when the original data is partially different. Therefore, if the hash values match, it can be estimated that the probability that the original data matches is high. Therefore, the hash value of ECM is also effective as unique information of the TS stream. In addition, since the hash value can generally be smaller than the original data, it is more effective in reducing the amount of communication than when the ECM itself is sent as the unique information. As a hash calculation method, MD-5, SHA-1, SHA-256, or the like can be used, but the method is not limited to these methods.

  Further, if the ECM of the TS stream 700 is tampered, the content key for decrypting the TS stream 700 cannot be obtained correctly. Therefore, using the ECM or its hash value as the unique information of the stream means that the stream is rewritten and the unique information It is also effective in preventing unauthorized viewing by falsifying In addition, since the encrypted ECM or its hash value is used instead of the key information itself, even if the data is transmitted to the unique information server 400, the encryption security is not impaired.

  As described above, the stream receiving apparatus 100 according to the present embodiment decrypts the encryption only when the received TS stream 700 is confirmed to be a TS stream currently being broadcast by the IP broadcast transmitting station 200. Thus, unauthorized viewing of TS streams other than those currently being broadcast can be prevented.

[Operation of stream receiving apparatus when updating ECM]
The ECM is data including key information. In digital broadcasting and the like, the operation of updating the key information at regular intervals to increase the encryption strength is common.

  When the demultiplexing unit 112 detects that the ECM has been updated, the demultiplexing unit 112 notifies the unique information extracting unit 117 of the new ECM, and the unique information extracting unit 117 obtains new unique information by performing a hash calculation of the new ECM. The unique information verification unit 118 checks the unique information verification server 400 to check whether new unique information is included in the unique information list 410.

  By confirming the unique information verification server 400 every time the ECM is updated, safety can be improved as compared with a mode in which confirmation is performed only at the start of stream reception. As a result, the stream receiving device 100 is allowed to receive a regular TS stream that is currently being broadcast only at the start of stream reception, and after confirming with the specific information server 400, an illegal TS stream that is not currently being broadcast. By switching and transmitting to the stream receiving apparatus 100, the problem that the stream receiving apparatus 100 decodes an illegal TS stream can be solved.

  Furthermore, by using a value that changes every certain time as the unique information, it is possible to improve the safety against fraud in which the TS stream 700 is rewritten and the unique information is falsified.

  When the TS stream 700 is broadcast in the broadcast mode as in the present embodiment, since many receivers detect ECM updates all at once, the stream receiver 100 detects the ECM update and immediately becomes unique. When the information server 400 is confirmed, the load is concentrated on the specific information server 400 at the timing of ECM update. Therefore, the unique information verification unit 118 checks the unique information server 400 after waiting for a random time determined by the random number after detecting the update of the ECM. In this way, the timing of access to the unique information server 400 can be distributed.

  In the present embodiment, the stream receiving apparatus 100 confirms the unique information with the unique information server 400 each time an ECM update is detected. However, it is not always necessary to confirm the ECM update. The unique information may be confirmed when the update is detected a plurality of times. In this case, if the frequency of confirmation is determined by random numbers, the load on the server can be further distributed.

<< Embodiment 2 >>
FIG. 4 shows a stream receiving apparatus according to the second embodiment of the present invention. In addition to the configuration of the first embodiment, the stream receiving apparatus 101 according to the present embodiment includes a unique information list receiving unit 120 that receives the unique information list 410 illustrated in FIG. It further has between information verification part 128.

  In the present embodiment, the configuration of the stream transmission system including the stream receiving apparatus 101 is the same as that in FIG. 3 of the first embodiment. However, in the present embodiment, the unique information server 400 differs from the first embodiment in that the unique information list 410 including the list of unique information of the TS stream 700 currently transmitted by the IP broadcast transmission station 200 is stored in the IP Broadcast on the network 300 by multicast protocol. The unique information server 400 writes the transmission time in the unique information list 410, and further sends the unique information list 410 with an electronic signature to prove that the unique information list 410 is authentic.

  The unique information list receiving unit 120 of the stream receiving apparatus 102 verifies the signature of the received unique information list 410 and only determines that the unique information list 410 is the proper unique information list 410. hand over.

  The unique information verification unit 128 compares the unique information extracted by the unique information extraction unit 117 with the unique information list 410 received by the unique information list reception unit 120, thereby verifying the unique information as follows. The unique information verification unit 128 is preset with a valid period of the unique information list (for example, about several seconds), and the transmission time of the unique information list 410 passed from the unique information list receiving unit 120 is compared with the current time. If the difference between the transmission time and the current time is within the valid period, it is determined whether or not the unique information extracted by the unique information extraction unit 117 exists in the unique information list 410. The key information extraction unit 116 is notified of “decryption is possible” and “decryption is impossible” otherwise. If the expiration date of the unique information list 410 has expired, the unique information verification unit 128 notifies the key information extraction unit 116 of “decryption is impossible”. As a result, the unique information list 410 is received and accumulated by a PC or the like, and the unique information list 410 is transmitted from the PC to the stream receiving apparatus 101 at another time, and the unique information verification unit 128 sets “decoding is possible”. It is possible to prevent fraud such as output.

  When the ECM in the TS stream is updated, the unique information server 400 updates and distributes the content of the unique information list 410. The unique information list receiving unit 120 of the stream receiving apparatus 101 receives the new unique information list 410 and passes it to the unique information verification unit 128. Each time the demultiplexing unit 112 detects that the ECM of the received TS stream has been updated, the demultiplexing unit 112 notifies the unique information extracting unit 117, and the unique information extracting unit 117 verifies the unique information as the stream unique information using the hash value of the new ECM. The unique information verification unit 128 compares the new unique information with the new unique information list. As described above, by confirming the unique information every time the ECM is updated, it is possible to prevent an illegal TS stream from being viewed for the same reason as in the first embodiment.

  According to the present embodiment, since the unique information server 400 distributes the unique information list 410 in accordance with the multicast protocol, the load on the unique information server 400 can be reduced compared to the case of the first embodiment.

  In the present embodiment, the unique information server 400 distributes the unique information list 410 in accordance with the multicast protocol. However, the stream reception apparatus 101 may obtain the unique information list 410 to the unique information server 400. . In this case, as in the first embodiment, the stream receiving apparatus 101 randomly controls the time from detection of an ECM update until acquisition of the unique information list 410 using a random number, The load on the unique information server 410 is distributed by randomly controlling the number of times until the unique information list 410 is acquired by counting the number of updates, using random numbers.

  In Embodiments 1 and 2, the hash value of the entire ECM is used as the unique information of the TS stream 700. However, all or a part of the ECM itself may be used, or a hash of a part of the ECM is used. A value may be used. Alternatively, the information is not limited to this as long as the information is unique to the TS stream. For example, a transport stream ID (identified by a PAT (Program Association Table) multiplexed in the TS stream) for identifying the TS stream ( transport_stream_id), service ID (service_id (also referred to as program_number)) that is a program identifier included in PMT (Program Map Table), or the like may be used.

  In Embodiments 1 and 2, the key information extraction unit 116 controls whether or not to set key information in the encryption / decryption unit 113 according to the result of the unique information verification unit 128. The operation of the unit 113 and the operation of the video / audio decoding unit 114 may be controlled.

  Further, the system for retransmitting the digital broadcast transmitted from the digital broadcast transmission station 800 via the IP network 300 has been described. However, the present invention is not limited to this. For example, the IP broadcast transmission station 200 in FIG. The stream held in the stream may be transmitted directly to the stream receiving apparatus 100. The present invention can also be applied to a case where the IP broadcast transmitting station 200 relays a stream obtained via another IP network.

  The stream receiving apparatus of the present invention is useful as a receiver in a stream transmission system that transmits a digital broadcast including an encrypted stream via an IP network.

1 is a schematic configuration diagram of a stream receiving apparatus according to Embodiment 1 of the present invention. The figure which shows the outline of TS stream used with digital broadcasting The figure which shows the structure of the stream transmission system of Embodiment 1 and Embodiment 2. Schematic configuration diagram of a stream receiving apparatus according to Embodiment 2 of the present invention. Schematic configuration diagram of a conventional stream receiver

Explanation of symbols

100, 101, 109 Stream receiving device 111 Communication interface 112 Demultiplexing unit 113 Encryption / decryption unit 114 Video / audio decoding unit 116, 196 Key information extraction unit 117 Specific information extraction unit 118, 128 Specific information verification unit 120 Specific information list reception unit 121 Tuner 200 IP Broadcasting Transmitter 202 Receiving Antenna 300 IP Network 400 Specific Information Server 800 Digital Broadcasting Transmitting Station 802 Transmitting Antenna 700 TS Stream 701 TS Packet 710 Header Portion 720 Payload Portion

Claims (13)

A communication interface for receiving the encrypted stream;
A unique information extraction unit that acquires unique information of the stream from the stream;
A unique information verification unit that controls whether to permit decoding of the stream by verifying whether the received stream is currently in service based on the unique information;
A decryption unit for decrypting the cipher of the stream when decryption is permitted by the unique information verification unit;
A stream receiving apparatus comprising:   The unique information verification unit transmits the unique information extracted by the unique information extraction unit via the communication interface to a server that holds a list of unique information of a stream that is currently in service. The stream reception according to claim 1, wherein a determination result of whether or not the stream is currently in service is received, and decoding by the decoding unit is permitted when the stream is currently in service. apparatus. A unique information list receiving unit for receiving a unique information list including a list of unique information of streams currently in service;
The stream receiving device according to claim 1, wherein the unique information verification unit permits decoding by the decoding unit when the unique information extracted by the unique information extraction unit is included in the unique information list. . The unique information list further includes a transmission time of the unique information list,
The unique information verification unit determines whether or not the difference between the transmission time and the current time is within a preset valid period, and determines that the difference is within the valid period, the decoding unit 4. The stream receiving apparatus according to claim 3, wherein decoding according to claim 3 is permitted. The stream includes encryption key information obtained by encrypting key information for decrypting the encryption of the stream,
The stream reception according to any one of claims 1 to 4, wherein the unique information extraction unit extracts all or part of the encryption key information as the unique information from the stream. apparatus. The stream includes encryption key information obtained by encrypting key information for decrypting the encryption of the stream,
The unique information extraction unit extracts all or a part of the encryption key information from the stream, converts it by a one-way function, and outputs the converted data as the unique information. The stream receiving device according to any one of claims 1 to 4.   The stream according to claim 5 or 6, wherein, when the encryption key information is updated, the unique information verification unit verifies whether or not the decryption by the decryption unit is permitted. Receiver device.   8. The stream reception according to claim 7, wherein the unique information verification unit counts the number of updates of the encryption key information, and determines a frequency of performing verification based on the unique information based on the number of updates and a random number. apparatus.   The stream reception according to claim 7 or 8, wherein the unique information verification unit determines a time from when the encryption key information is updated to when verification with the unique information is performed using a random number. apparatus.   The stream receiving apparatus according to any one of claims 5 to 9, wherein the stream is in an MPEG2 transport stream format, and the encryption key information is ECM. The decryption unit extracts, from the stream, encrypted key information obtained by encrypting key information for decrypting the cipher of the stream, decrypts the key information, and outputs the key information;
An encryption / decryption unit that decrypts the encryption of the stream using the key information;
A video / audio decoding unit that decodes the stream output from the encryption / decryption unit into video / audio;
Have
The unique information verification unit controls whether at least one of the key information extraction unit, the encryption / decryption unit, and the video / audio decoding unit is permitted to decrypt the stream. The stream receiving device according to claim 1. A stream transmitting device for transmitting an encrypted stream;
Having a list of unique information of the stream currently transmitted by the stream transmitting device, and receiving the inquiry of the unique information, it is determined whether or not the unique information is currently being transmitted, and the determination A unique information server that outputs the results;
Receiving the stream output from the stream transmitting device, obtaining the unique information of the stream from the stream, transmitting the unique information to the unique information server, and currently transmitting the unique information from the unique information server A stream receiving device that decrypts the cipher of the stream only when a determination result indicating that the stream is
A stream transmission system comprising: A stream transmitting device for transmitting an encrypted stream;
A unique information server that transmits a unique information list including a list of unique information of a stream that the stream transmitting device is currently transmitting;
Stream reception that receives the stream and the unique information list, acquires the unique information of the stream from the stream, and decrypts the cipher of the stream only when the acquired unique information is included in the unique information list Equipment,
A stream transmission system comprising:

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