JP2008187691A - Content distribution system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content distribution system in which content data in a plurality of forms can be distributed and can be reproduced by a user terminal while suppressing the load on a server. <P>SOLUTION: In the content distribution system, a content distribution server 10 includes a transmission section 122 for transmitting encrypted content data Enc (Kci:Ci) which have been encrypted by content key data Kci different for each item of content data Ci, to a user terminal 30 in a streaming (ST) form or a download (DL) form. A key transmission server 20 is equipped with an encryption section 221 which encrypts the content key data Kci using a user key Kus for ST different for each user and generates encrypted content key data Enc (Kus:Kci) for ST. Furthermore, the encryption section 221 encrypts the content key data Kci using user key data Kud for DL different for each user and generates encrypted content key data Enc (Kud:Kci) for L. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a content distribution system and a content distribution method for distributing encrypted content data in response to a request from a user terminal held by a user.

  In recent years, in addition to terrestrial television, AM, FM broadcasting, and the like, data is received by a communication terminal connected to a communication network such as the Internet, and contents of digital information such as music and video are viewed.

  Here, when viewing content, the following two formats are roughly used.

  The first format is a download format (hereinafter referred to as “DL”). In the DL format, the user can view the content after completing reception of the entire content data at the user terminal.

  The second format is a streaming (hereinafter referred to as “ST”) format. In the ST format, the user can view the received content at the same time while receiving the content data at the user terminal.

  And since the content data which is digital information can be easily copied, a measure is taken to encrypt the content data to be distributed. For example, in Patent Document 1, content data is encrypted using a double key encryption method.

However, in general, contracts are often different between the DL format and the ST format. In this case, different key data (content key data) is used even though the same content data is distributed in the DL format and the ST format. Therefore, the data amount of the encryption key stored in the server increases, and the load on the server increases.
JP 2006-020154 A

  An object of the present invention is to provide a content distribution system that enables distribution of content data in a plurality of formats and reproduction by a user terminal while suppressing the load on the server.

  In order to achieve the above object, a content distribution system according to an aspect of the present invention includes a user terminal held by a user, and encrypts the content data with content key data in response to a request for content data from the user terminal. A content distribution server that distributes the encrypted content data, and a key distribution server that distributes the content key data for decrypting the encrypted content data to the user terminal. A first transmission unit configured to transmit the encrypted content data encrypted with different content key data for each content data to the user terminal, wherein the key distribution server includes the encrypted content data having a first format; Corresponding content key data for each user The first encrypted content key data is encrypted by using different first user key data to generate the first encrypted content key data, and the content key data corresponding to the encrypted content data having the second format is changed by the second user key data that is different for each user. An encryption unit that encrypts and generates second encrypted content key data; and a second transmission unit that transmits the first encrypted content key data or the second encrypted content key data to the user terminal, The user terminal decrypts the received first encrypted content key data with the first user key data to generate the content key data, decrypts the encrypted content data with the generated content key data, and The content data having the format 1 is generated and the received second encrypted content key Decrypting data with the second user key data to generate the content key data, and decrypting the encrypted content data with the generated content key data to generate the content data having the second format It comprises a part.

  The content distribution method according to one aspect of the present invention is the content distribution method for distributing encrypted content in response to a request from a user terminal held by a user, wherein the content key data encrypted with content key data that differs for each content data A first transmission step of transmitting encrypted content data to the user terminal; and first encrypting the content key data corresponding to the encrypted content data having the first format with different first user key data for each user. Encrypted content key data is generated, or the content key data corresponding to the encrypted content data having the second format is encrypted with different second user key data for each user, and the second encrypted content key data is An encryption step to be generated; and the first encrypted content key data, A second transmission step of transmitting the second encrypted content key data to the user terminal; and decrypting the received first encrypted content key data with the first user key data to generate the content key data, The encrypted content data is decrypted with the generated content key data to generate the content data having the first format, or the received second encrypted content key data is decrypted with the second user key data A decrypting step of generating the content key data and decrypting the encrypted content data with the generated content key data to generate the content data having the second format.

  According to the present invention, it is possible to provide a content distribution system that enables distribution of content data in a plurality of formats and reproduction by a user terminal while suppressing the load on the server.

  First, an example of an encrypted double key method employed in MQbic (registered trademark) will be described with reference to FIG. FIG. 13 is a schematic diagram showing a configuration of an SD card and a user terminal corresponding to the encryption double key method adopted in the MQbic. Here, the SD card SDq is an example of a secure storage medium that securely stores data, and includes a system area 1, a hidden area 2, a protected area 3, a user data area ( User Data Area) 4 and encryption / decryption unit 5, and data is stored in each of the areas 1 to 4.

  Specifically, in such an SD card SDq, the system area 1 stores key management information MKB (Media Key Block) and a media identifier IDm, the secret area 2 stores a media unique key Kmu, and a protection area. 3 stores an encrypted user key Enc (Kmu: Ku), and the user data area 4 stores an encrypted content key Enc (Ku: Kc). Note that the notation Enc (A: B) means data B encrypted with data A in this specification. Here, the user key Ku is an encryption / decryption key for the content key Kc, and is commonly used for a plurality of encrypted content keys Enc (Ku: Kc1), Enc (Ku: Kc2),. Can be done. The subscript q of the SD card SDq indicates that it corresponds to MQbic (registered trademark).

  Here, the system area 1 is an area that is read-only and accessible from the outside of the SD card. The secret area 2 is a read-only area that is referred to by the SD card itself, and cannot be accessed from outside. The protected area 3 is an area that can be read / written from the outside of the SD card when authentication is successful. The user data area 4 is an area that can be freely read / written from the outside of the SD card. The encryption / decryption unit 5 performs authentication, key exchange, and encryption communication between the protection area 3 and the outside of the SD card, and has an encryption / decryption function.

  For such an SD card SDq, the user terminal 10q for reproduction operates logically as follows. That is, in the user terminal 10q, the key management information MKB read from the system area 1 of the SD card SDq is subjected to MKB processing with a preset device key Kd (ST1) to obtain a media key Km. Next, the user terminal 10q performs a hash process on the media key Km and the media identifier IDm read from the system area 1 of the SD card SDq (ST2) to obtain a media unique key Kmu.

  Thereafter, the user terminal 10q performs authentication and key exchange (AKE: Authentication Key Exchange) processing with the encryption / decryption unit 5 of the SD card SDq based on the media unique key Kmu (ST3), and the SD card. The session key Ks is shared with SDq. Note that the authentication and key exchange processing in step S3 succeeds when the media unique key Kmu in the secret area 2 referred to by the encryption / decryption unit 5 matches the media unique key Kmu generated in the user terminal 10a. The session key Ks is shared.

  Subsequently, when the user terminal 10q reads the encrypted user key Enc (Kmu: Ku) from the protected area 3 via encrypted communication using the session key Ks (ST4), the encrypted user key Enc (Kmu: Ku) is read out. ) Using the media unique key Kmu (ST5) to obtain the user key Ku.

  Finally, when the user terminal 20q reads the encrypted content key Enc (Ku: Kc) from the user data area 4 of the SD card SDq, the user terminal 20q decrypts the encrypted content key Enc (Ku: Kc) with the user key Ku. (S5q), the content key Kc is obtained. Finally, when the user terminal 10a reads the encrypted content Enc (Kc: C) from the memory 11q, the encrypted content Enc (Kc: C) is decrypted with the content key Kc (ST6). The content C is reproduced. In the above example, the encrypted content is stored in the memory 11q in the user terminal 20q. However, the encrypted content may be stored in an external storage medium.

  Next, an embodiment of a content distribution system according to the present invention will be described with reference to FIGS. Note that the content distribution system of this embodiment uses MQbic (registered trademark), which is the above-described encrypted double key method. In the encrypted double key system of the present system, encrypted content data Enc (Kci: Ci) obtained by encrypting content data Ci based on content key data Kci is used. Further, in this system, the content key data Kci is encrypted with the DL encrypted content key Enc (Kud: Kci) encrypted with the DL user key Kud, or the ST encryption encrypted with the ST user key Kus. Content key Enc (Kud: Kci) is used.

[First embodiment]
(Configuration of the first embodiment)
With reference to FIG. 1, the structure of the content delivery system which concerns on 1st Embodiment of this invention is demonstrated. As shown in FIG. 1, the content distribution system according to the first embodiment mainly includes a content distribution server 10 that distributes content, a key distribution server 20 that distributes various keys, and a user terminal 30 that is managed by the user. It is comprised by. The content distribution server 10, the key distribution server 20, and the user terminal 30 are connected via a communication network 40 such as the Internet. The user key data is separate (Kud, Kus) in the DL format and ST format, but the content key data Kci is common.

  Although FIG. 1 shows a configuration in which the content distribution server 10, the key distribution server 20, and the user terminal 30 are arranged one by one, the present invention is not limited to this configuration. For example, a plurality of content servers 10 and key distribution servers 20 may be arranged. Further, the content server 10 and the key distribution server 20 may be integrated. Further, the user terminal 30 may be a mobile phone or the like other than a personal computer, and is not limited to those owned by the user, but is a terminal that is arranged in an Internet cafe, a convenience store, a gas station, etc. and is shared among the public. Also good.

  The content distribution server 10 includes a storage unit 11 such as an HDD (Hard Disc Drive) and a control unit 12 such as a CPU (Central Processing Unit). The function of the control unit 12 is realized by a program read from the storage unit 11.

  The storage unit 11 includes a content data DB 111, a content metadata DB 112, and a content identification information DB 113. In addition, the storage unit 11 stores the aforementioned programs and the like. Note that “DB” indicates a database.

  The content data DB 111 stores plaintext content data Ci and encrypted content data Enc (Kci: Ci) obtained by encrypting the content data Ci with content key data Kci.

  The content metadata DB 112 stores information related to content (content metadata). Information related to content includes bibliographic information such as content name, type, and genre.

  The content identification information DB 113 includes CID (content identification information) that is information for uniquely specifying the content key data Kci for decrypting each encrypted content data Enc (Kci: Ci). The CID corresponding to the encrypted content Enc (Kci: Ci) in the ST format is different from the CID corresponding to the encrypted content data Enc (Kci: Ci) in the DL format.

  The control unit 12 includes an encryption unit 121, a transmission unit 122, and a CID giving unit 123.

  The encryption unit 121 encrypts the content data Ci stored in the content data DB 111 with the content key data Kci, and generates encrypted content data Enc (Kci: Ci). The encryption unit 121 stores the encrypted content data Enc (Kci: Ci) in the content data DB 111. Content key data KCi (Kc1, Kc2,..., Kcn) is provided in a one-to-one correspondence with content data Ci (C1, C2,..., Cn).

  The transmission unit 122 transmits the encrypted content data Enc (Kci: Ci) to the user terminal 30 via the network 40 in response to a request from the user terminal 30. The distribution of the encrypted content data Enc (Kci: Ci) is performed in the ST format or the DL format. The content key data Kci is distributed in one of the DL / ST formats, but is commonly used for the corresponding content data Ci regardless of the DL / ST format.

  The CID adding unit 123 transmits encrypted content data Enc (Kci: Kci: Kci: Kci: Ci), which is information for uniquely specifying the content key data Kci for decrypting the encrypted content data Enc (Kci: Ci). Ci).

  The key distribution server 20 includes a storage unit 21 such as an HDD and a control unit 22 such as a CPU. The function of the control unit 22 is realized by a program read from the storage unit 21.

  The storage unit 21 includes a content key data DB 211 and a user data DB 212.

  The content key data DB 211 stores content key data Kci.

  The user data DB 212 is a personal information of each user, an ST user key Kus for decrypting the ST encrypted content key data Enc (Kus: Kci), and a DL for decrypting the DL content key data Enc (Kud: Kci). The user key Kud is stored. The ST user key data Kus and the DL user key data Kud are generated based on different user IDs (individual identification information) for each user.

  The control unit 22 includes an encryption unit 221 and a transmission unit 222.

  The encryption unit 221 encrypts the content key data Kci based on the ST user key Kus or the DL user key Kud, and encrypts the ST encrypted content key data Enc (Kus: Kci) or DL. Encrypted content key data Enc (Kud: Kci) is generated. That is, the content key data Kci is commonly used for one content data Ci regardless of the DL format or the ST format. On the other hand, the user key, DL format and ST format are different (Kud, Kus).

  The transmission unit 222 transmits the DL encrypted content key data Enc (Kud: Kci) or the ST content key data Enc (Kus: Kci) to the user terminal 30 via the network 40 in response to a request from the user terminal 30. To do.

  The user terminal 30 includes a display control unit 31, an input / output (I / O) unit 32, a RAM 33, a control unit 34 such as a CPU, and a storage unit 35 such as an SD card.

  The control unit 34 includes a transmission / reception unit 341 and a DL content generation unit 342. The configuration of the control unit 34 is realized by executing a program stored in the storage unit 35.

  The transmission / reception unit 341 transmits / receives content data and the like to / from the outside. The DL content generation unit 342 generates DL format content data Enc (Kci: Ci) based on the ST format encrypted content data Enc (Kci: Ci).

  In the storage unit 35, the system area 351 stores key management information MKB (Media Key Block) and the media identifier IDm, the secret area 352 stores the media unique key Kmu, and the protection area 353 stores the DL encrypted user. Key data Enc (Kmu: Kus) and ST encrypted user key data Enc (Kmu: Kus) are stored, and DL encrypted content key data Enc (Kud: Kci) and ST data are stored in the user data area 4. Encrypted content key data Enc (Kus: Kci) is stored. The encrypted content data Enc (Kci: Ci) may be stored in the user data area 354 or may be stored in another storage medium (not shown). Here, the ST user key Kus is an encryption / decryption key for the ST encrypted content key data Kci, and includes a plurality of encrypted content keys Enc (Ku: Kc1), Enc (Ku: Kc2),. Also, it can be used in common. The same applies to the DL user key Kud.

  Here, the system area 351 is an area that is read-only and accessible from the outside of the storage unit 35. The secret area 352 is a read-only area that is referenced by the storage unit 35 and cannot be accessed from the outside. The protected area 353 is an area that can be read / written from the outside of the SD card when authentication is successful. The user data area 354 is an area that can be freely read / written from the outside of the SD card. The encryption / decryption unit 355 performs authentication, key exchange, and encrypted communication between the protection area 353 and the storage unit 35, and has an encryption / decryption function.

(Configuration of encrypted content data according to the first embodiment)
Next, an overview of the configuration of the encrypted content according to the first embodiment will be described with reference to FIGS. The ST distribution of the encrypted content data Enc (Kci: Ci) according to the first embodiment is performed in the TS (Transport Streaming) format.

  FIG. 2 is a diagram illustrating a TS format hierarchy. As shown in FIG. 2, in the TS format, a network information table (NIT) and a program allocation table (PAT) are located at the top. NIT indicates all channel information and frequency information in the network. The PAT indicates PID (Packet ID) of all PMT (Program Map Table) in the TS format.

  The PAT includes a plurality of PMTs (PMT1, PMT2,...). Each PMT (PMT1, PMT2, etc.) includes Video ES (Video Elementary Stream), Audio ES (Audio Elementary Stream), and PCR (Program Clock Reference). Here, Video ES includes video information. Audio ES includes audio information. PCR is information including the reference time (such as presentation timing) of the transmission unit 122.

  FIG. 3 is a diagram showing the structure of the MPEG TS Packet format. As shown in FIG. 3B, the transmitted information is composed of a plurality of continuous TS Packets (188 bytes).

  In the header of this TS packet, as shown from the left side of FIG. 3A, “Sync byte” (8 bits), “Transport error Indicator” (1 bit), “Payload unit start Indicator” (1 bit), “Trans Priority” (1 bit), “PID” (13 bits), “Transport Scrambling Control” (2 bits), “Adaptation Filed Control” (2 bits), and “Continuity Counter (4 bits)”.

  The MPEG TS Packet format has a configuration shown in FIG. 3C, following the header of the TSPacket. As shown from the left side of FIG. 3C, “Adaptation field length” (8 bits), “Discontinuity Indicator” (1 bit), “Random Access Indicator” (1 bit), “Elementary Stream Priority” (1 bit), “Flags” , “Optional Adaptation Fields”, “Stuffing bytes 0xFF”, and “Packet Payload (PES or PSI data) Start code 0x000001yy”. The encrypted content (video information, audio information, etc.) is included in “Packet Payload (PES (Packetized Elementary Stream) or PSI (Program Specific Information) data) Start code 0x000001yy”.

  In addition, no “CID” is assigned to “Packet Payload” shown in FIG. That is, the TS packet is identified only by the PID. This “Packet Payload” is encrypted with the content key data. “Packet Payload” is composed of a plurality of elementary streams, and each stream is given a unique PID. The CID is assigned to each program unit. Therefore, a plurality of elementary streams constituting the program correspond to the same CID.

  In addition, the “Optional Adaptation Fields” in FIG. 3C described above includes “PCR” (42 + 6res), “OPCR (Original Clock Reference)” (42 + 6res) as shown from the left side of FIG. , “Splice countdown” (8 bits), “TS private data” (variable), and “Adaptation field ext.”.

  Next, the configuration of the PAT will be described with reference to FIG. As shown in the upper left of FIG. 4, the PAT is “Table Identifier '0x00'” (8 bits), “Section syntax indicator“ 1 ”” (1 bit), “Reserved future use” (1 bit), “Reserved '11'”. (2 bits), “Section length” (12 bits), “Transport stream identifier” (16 bits), “Reserved“ 11 ”” (2 bits), “Version number” (5 bits), “Current next indicator” (1 bit), “Section” "number" (8bits), "Last section number" (8bits), "Section number" (8bits), "Last section number" (8bits), "repeat", "CRC (cyclic redundancy check)" (32bits) Including.

  Here, for example, “Table Identifier“ 0x00 ”” illustrated in FIG. 4 indicates the table ID of the PAT, and “Transport stream identifier” indicates the ID of the TS including the PAT. “Repeat” indicates processing to be repeated, and “Broadcasting program number identifier =“ 0 ”” (16 bits), “Reserved“ 111 ”” (3 bits), “Network PID“ 0x0010 ”” (13 bits), Includes information on “Broadcasting program number identifier <>“ 0 ”” (16 bits), “Reserved“ 111 ”” (3 bits), and “Program map PID” (13 bits). Here, “Network PID“ 0x0010 ”” indicates the PID of the NIT, and “Program map PID” indicates the PID of the PMT.

  Next, the configuration of the PMT will be described with reference to FIG. As shown in the upper left of FIG. 5, the PMT adds a TS packet header to the head T. Subsequently, the PMT consists of “Table Identifier '0x02'” (8 bits), “Section syntax indicator“ 1 ”” (1 bit), “Reserved future use“ 0 ”” (1 bit), “Reserved“ 11 ”” (2 bits) , “Section length” (12 bits), “Transport stream identifier” (16 bits), “Reserved“ 11 ”” (2 bits), “Version number” (5 bits), “Current next indicator” (1 bit), “Section number” ( 8bits), "Last section number" (8bits), "Reserved" 111 "" (3bits), "PCR_PID" (13bits), "Reserved" 1111 "" (4bits), "Program information length" (12bits), "Descriptors It contains information on “field1” (8 * Nbits), “repeat”, and “CRC” (32bits).

  Here, for example, “Table Identifier“ 0x02 ”” illustrated in FIG. 5 indicates the table ID of the PMT, and “Transport stream identifier” indicates the ID of the TS including the PMT. Further, “repeat” indicates a process to be repeated, and “Stream type identifier” (8 bits), “Reserved“ 111 ”” (3 bits), “Elementary stream PID” (13 bits), “Reserved“ 1111 ”” ( 4 bits), “ES information length”, and “Descriptors field 2” (8 * Nbits) information.

  In the first embodiment, the CID providing unit 123 describes the CID in “Descriptors field 2”. Thereby, PID and CID can be matched.

(Content data generation operation of the first embodiment)
Next, the content data generation operation of the first embodiment will be described with reference to FIG. 6 and FIG. FIG. 6 shows a content data generation operation in which the content data Ci is generated in the ST format, and FIG. 7 shows a content data generation operation in which the content data Ci is generated in the DL format.

  First, a case where content data Ci is generated in ST format will be described with reference to FIG. As shown in FIG. 6, first, in the user terminal 30, the transmission / reception unit 341 receives input from a keyboard or mouse (not shown) connected to the I / O 32, and distributes content data Ci in ST format as content. A request is made to the distribution terminal 10 (step S101).

  Subsequently, in the content distribution server 10, the transmission unit 122 reads out the encrypted content data Enc (Kci: Ci) corresponding to the content data Ci requested from the user terminal 30 from the content data DB 111 (step S102). Next, the transmission unit 122 requests the key distribution server 20 to transmit the ST encrypted content key data Enc (Kus: Kci) corresponding to the encrypted content data Enc (Kci: Ci) to the user terminal 30. (Step S103). Then, the transmission unit 122 reads out the CID corresponding to the encrypted content data Enc (Kci: Ci) read out from the content identification information DB 113, and sends the CID and encrypted content data Enc (Kci: Ci) to the user terminal 30. Distribute in the form (step S104).

  The encryption unit 121 encodes a video signal and an audio signal, and subsequently converts the signal into an ES (Elementary Stream) and then a PES (Packetized Elementary Stream). The encryption unit 121 encrypts the video signal and the audio signal when the PES is used. Further, the encryption unit 121 generates PSI (various arrangement information) based on the presentation timing and the signal format.

  The encryption unit 121 multiplexes the PES video information, the PES audio information, and the PSI, and distributes the scrambled data.

  On the other hand, in the key distribution server 20, the transmission unit 222 reads the content key data Kci from the content key data DB 211 (step S105). Subsequently, the transmitting unit 222 encrypts the content key data Kci with the ST user key Kus, and generates ST encrypted content key data Enc (Kus: Kci) (step S106). Here, the encrypted content key data for ST Enc (Kus: Kci) generated in step S106 is assumed to have a type that does not have a usage rule. Then, the transmission unit 222 transmits the generated encrypted content key data for ST Enc (Kus: Kci) to the user terminal 30 (step S107).

  Next, in the user terminal 30, the transmission / reception unit 341 receives ST encrypted content key data Enc (Kus: Kci) (step S108). Next, the encryption / decryption unit 355 reads the ST encrypted user key data Enc (Kmu: Kus) (step S109), decrypts it with the media unique key data Kmu, and generates the ST user key data Kus (step S109). S110).

  Subsequently, the encryption / decryption unit 355 decrypts the ST encrypted content key data Enc (Kus: Kci) using the generated ST user key data Kus, and generates content key data Kci (step S111). The transmission / reception unit 341 receives the encrypted content data Enc (Kci: Ci) and CID in the ST format (step S112), decrypts the encrypted content data Enc (Kci: Ci) with the content key data Kci, Content data Ci is generated (step S113). Thus, the series of processes shown in FIG.

  Here, the process of step S112 and step S113 is demonstrated concretely. First, the transmission / reception unit 341 acquires a TS packet with “PID = 0” (PAT acquisition). Subsequently, the transmission / reception unit 341 analyzes the PAT and acquires the PID of the TS packet that transmits the PMT. Next, the transmission / reception unit 341 acquires the PMT, performs PMT analysis, and acquires the PIDs of the bitstreams constituting each program. Then, the transmission / reception unit 341 selects a PID and acquires a media TS packet.

  Next, the encryption / decryption unit 355 first returns the received scrambled information to the original unscrambled information. Subsequently, the encryption / decryption unit 355 extracts the PSI from the encrypted content in the TS format, and selects a packet based on the PSI. Then, the encryption / decryption unit 355 extracts the PES using the selected packet. The encryption / decryption unit 355 decrypts the encrypted content when the PES is extracted. Subsequently, the encryption / decryption unit 355 converts the extracted PES into an ES, encodes it, and finally returns it to a video signal and an audio signal.

  Next, the case where the encrypted content data Enc (Kci: Ci) is distributed in the DL format will be described with reference to FIG. As shown in FIG. 7, first, in the user terminal 30, the transmission / reception unit 341 receives input from a keyboard or mouse connected to the I / O 32 and distributes the content data Ci in DL format to the content distribution terminal 10. A request is made (step S201).

  Subsequently, in the content distribution server 10, the transmission unit 122 reads out the encrypted content data Enc (Kci: Ci) corresponding to the content data Ci requested from the user terminal 30 from the content data DB 111 (step S202). Next, the transmission unit 122 requests the key distribution server 20 to transmit the DL encrypted content key data Enc (Kud: Kci) corresponding to the encrypted content data Enc (Kci: Ci) to the user terminal 30. (Step S203). Then, the transmission unit 122 reads the CID corresponding to the encrypted content data Enc (Kci: Ci) read from the content identification information DB 113, and DLs the CID and the encrypted content data Enc (Kci: Ci) to the user terminal 30. Distribute (step S204).

  On the other hand, in the key distribution server 20, the transmission unit 222 reads the content key data Kci from the content key data DB 211 (step S205). Subsequently, the transmission unit 222 encrypts the content key data Kci with the DL user key Kud, and generates DL encrypted content key data Enc (Kud: Kci) (step S206). Here, the DL encrypted content key data Enc (Kud: Kci) generated in step S206 uses a type having a usage rule. In the DL encrypted content key data Enc (Kud: Kci), the usage period is described. Then, the transmission unit 222 transmits the generated DL encrypted content key data Enc (Kud: Kci) to the user terminal 30 (step S207).

  Next, in the user terminal 30, the transmission / reception unit 341 receives the DL encrypted content key data Enc (Kud: Kci) (step S208). Next, the encryption / decryption unit 355 reads the DL encrypted user key data Enc (Kmu: Kud) (step S209), decrypts it with the media unique key data Kmu, and generates DL user key data Kud (step S209). S210).

  Subsequently, the encryption / decryption unit 355 decrypts the DL encrypted content key data Enc (Kud: Kci) with the generated DL user key data Kud, and generates content key data Kci (step S211). Then, the transmitting / receiving unit 341 receives the encrypted content data Enc (Kci: Ci) and CID in the ST format (step S212).

  Subsequently, the DL content generation unit 342 separates the received encrypted content data Enc (Kci: Ci) into content identification information, meta information, and the content (video, audio, etc.) of the encrypted content data (step S213). ). Subsequently, the DL content generation unit 342 generates the CID of the DL format content data from the CID of the ST format data based on a predetermined generation rule (step S214). Then, the DL content generation unit 343 generates DL-format encrypted content data Enc (Kci: Ci) based on the CID of the DL-format content, meta information, and the contents (video, audio, etc.) of the encrypted content data ( Step S215).

  Then, the encryption / decryption unit 355 decrypts the generated DL-format encrypted content data Enc (Kci: Ci) with the content key data Kci to generate content data Ci (step S216).

  According to such an operation, the content distribution server 10 further encrypts the content key data corresponding to each encrypted content Enc (Kci: Ci) with different keys for ST and DL, and sends them to the user terminal 30. Can be sent. That is, viewing of content data by the user terminal 30 can be restricted according to the format of content data distributed to each user terminal 30. For example, the administrator of the content distribution server 10 can distribute the ST format content data and the DL format content data with different set charges.

  Further, according to the operation as described above, even the encrypted content data Enc (Kci: Ci) distributed in the ST format can be stored in the DL format in the user terminal 30. That is, the user can view the content viewed in the ST format using the user terminal 30 again as DL format content data encrypted with the DL user key data Kud, and then view the content at any time. .

[Second Embodiment]
(Content generation operation of the second embodiment)
Next, a content distribution system according to the second embodiment will be described with reference to FIG. The content distribution system according to the second embodiment is different from the first embodiment in the operation of generating content data Ci in the DL format in the user terminal 30. Note that the configuration of the content distribution system according to the second embodiment and the generation operation of the content data Ci in the ST format are the same as those in the first embodiment, and thus description thereof is omitted.

  In FIG. 8, the processing from step S301 to step S315 shows the same processing as the DL format content generation operation (step S201 to step S215) in the first embodiment. Therefore, description of the process of step S301-step S315 is abbreviate | omitted.

  Subsequent to step S315, in the content distribution server 10, the DL content generation unit 124 decrypts the encrypted content data Enc (Kci: Ci) received as the TS packet with the content key data Kci, and generates content data Ci. (Step S316). Then, as shown in FIG. 9, the encryption / decryption unit 355 collectively encrypts “Payload (PES)” and “TS Header” of the decrypted content data Ci with the content key data Kci ′, Content data Enc (Kci ′: Ci + header) is generated (step S317).

  That is, in the processing of step S316 and step S317, as shown in FIG. 9, only “Payload (PES)” is encrypted (encrypted area [1]), “Payload (PES)” and This is a process of converting “TS Header” into an encrypted one (encrypted area [2]).

  According to the above operation, for example, encrypted content data Enc (Kci ′: Ci + header) can be stored in accordance with a storage standard such as an SD card.

[Third embodiment]
Next, a content distribution system according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a diagram illustrating a schematic configuration of a content distribution system according to the third embodiment, and FIG. 11 is a flowchart illustrating a DL content generation operation according to the third embodiment.

(Configuration of Content Distribution System of Third Embodiment)
First, the configuration of the content distribution system according to the third embodiment will be described with reference to FIG. As shown in FIG. 10, in the content distribution system according to the third embodiment, the configurations of the control unit 12 ′ of the content distribution server 10 ′ and the control unit 34 ′ of the user terminal 30 ′ are the first and second embodiments. And different. In addition, since the structure of the content delivery system of 3rd Embodiment is the same as that of 1st Embodiment and 2nd Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits the description.

  The control unit 12 ′ of the content distribution server 10 ′ is obtained by adding a DL content generation unit 124 to the control unit 12 of the first and second embodiments. The DL content generation unit 124 generates DL-format encrypted content data based on the ST-format encrypted content.

  The user terminal 30 ′ has a configuration in which the DL content generation unit 342 of the first embodiment is omitted.

(Content data generation operation of the third embodiment)
Next, the DL format content data generation operation in the third embodiment will be described with reference to FIG. As shown in FIG. 11, steps S401 to S403 in the third embodiment are the same as steps S201 to S203 in the first embodiment. Further, Steps S408 to S414 of the third embodiment are the same as Steps S205 to S211 of the first embodiment. Therefore, description of the process of step S401 to step S403 and step S408 to step S414 of the third embodiment is omitted.

  Subsequent to step S403 of the third embodiment, in the content distribution server 10 ′, the DL content generation unit 124 converts the ST-format encrypted content data Enc (Kci: Ci) into content identification information, meta information, and encrypted content data. (Step S404). Subsequently, the DL content generation unit 124 generates the CID of the DL format content data from the CID of the ST format data Ci based on a predetermined generation rule (step S405). Then, the DL content generation unit 124 generates DL-format encrypted content data Enc (Kci: Ci) based on the CID of the DL-format content, meta information, and the contents (video, audio, etc.) of the encrypted content data ( Step S406), and transmits it to the user terminal 30 ′ (step S407).

  Subsequent to step S414 of the third embodiment, in the user terminal 30 ', the transmission / reception unit 341 receives the encrypted content data Enc (Kci: Ci) in DL format (step S415). Then, the transmission / reception unit 341 decrypts the encrypted content data Enc (Kci: Ci) with the content key data Kci to generate content data Ci (step S416). Note that the DL content generation unit 124 receives the DL-format encrypted content data Enc (Kci: Ci) generated in the processes of Steps S404 to S406 and the CID of the DL-format content data Ci as the content data DB 111. To store.

  According to the operation as described above, the content distribution server 10 ′ can generate DL-format content data Ci in parallel with the ST-format content data distribution. For example, the content distribution server 10 ′ can broadcast live broadcasts and the like, and can generate DL-format content data Ci.

[Fourth Embodiment]
Next, a content distribution system according to a fourth embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 12, in the content distribution system according to the fourth embodiment, the configuration of the control unit 34 "of the user terminal 30" is different from that of the third embodiment. In addition, since the structure of the content delivery system of 4th Embodiment is the same as that of 3rd Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits the description.

  The control unit 34 ″ has a configuration obtained by adding a digital watermark superimposing unit 343 to the configuration of the control unit 34 ′ of the third embodiment.

  In any of the first to third embodiments described above, decryption is finally performed in any case, and plaintext content data Ci is generated. In the user terminal 30 ″ of the third embodiment, the digital watermark superimposing unit 343 superimposes and outputs the digital watermark on the content data Ci based on the user ID (individual identification information) determined for each user.

  In this way, by superimposing the digital watermark on the plaintext content data Ci and outputting it, it is possible to prevent copying of the content data Ci and protect the copyright. The digital watermark superimposing unit 343 may be configured to superimpose the digital watermark on the content data Ci based on the identification information of the DL user key Kud or the ST user key Kus and output the result. In addition, the digital watermark superimposing unit 343 may be configured to superimpose the digital watermark on the CID together with the content data Ci and output it.

  As mentioned above, although embodiment of invention was described, this invention is not limited to these, A various change, addition, substitution, etc. are possible within the range which does not deviate from the meaning of invention. For example, in the above embodiment, each time the user terminal 30 requests content, the encrypted content key data Enc for ST (Kus: Kci) or the encrypted content key data for DL Enc (Kud: Kud: Kci) is received. In contrast to this, before requesting the content data Ci, the user terminal 30 previously stores the ST encrypted content key data Enc (Kus: Kci) or the DL encrypted content key data Enc (Kud) from the key distribution server 20. : Kci) may be received.

1 is a schematic diagram of a content distribution system according to a first embodiment of the present invention. It is a figure which shows the hierarchy of TS format. It is a figure which shows the structure of an MPEG TS Packet format. It is a figure which shows the structure of PAT. It is a figure which shows the structure of PMT. It is a flowchart which shows the content production | generation operation | movement of 1st Embodiment which produces | generates content data in ST format. It is a flowchart which shows the content production | generation operation | movement of 1st Embodiment which produces | generates content data in DL format. It is a flowchart which shows the content delivery operation | movement of 2nd Embodiment which produces | generates content data in DL format. It is a figure which shows the area | region which performs encryption in step S316 and step S317 of FIG. It is the schematic of the content delivery system which concerns on 3rd Embodiment of this invention. It is a flowchart which shows the content production | generation operation | movement of 3rd Embodiment which produces | generates content data in DL format. It is the schematic of the content delivery system which concerns on 4th Embodiment of this invention. It is a figure explaining an example of the encryption double key system employ | adopted in MQbic (trademark).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,10 '... Content delivery server, 11 ... Memory | storage part, 111 ... Content data DB, 112 ... Content metadata DB, 113 ... CIDDB, 12, 12' ... Control part, 121 ... Encryption part, 122 ... Transmission part, 123: CID giving unit, 124 ... DL content generation unit, 20 ... key distribution server, 21 ... storage unit, 211 ... master content key data DB, 212 ... user data DB, 22 ... control unit, 221 ... encryption unit, 222: Transmitter, 30, 30 ', 30' '... User terminal, 31 ... Display controller, 32 ... Input / output (I / O) unit, 33 ... RAM, 34, 34', 34 '' ... Controller, 341 ... Transmission / reception unit, 342 ... DL content generation unit, 343 ... Digital watermark superimposition unit, 35 ... Storage unit, 355 ... Encryption / decryption unit.

Claims (13)

A user terminal held by a user, a content distribution server that distributes encrypted content data obtained by encrypting the content data with content key data in response to a request for content data from the user terminal, and decrypting the encrypted content data In a content distribution system having a key distribution server for distributing the content key data to be converted to the user terminal,
The content distribution server includes a first transmission unit that transmits the encrypted content data encrypted with content key data different for each content data to the user terminal,
The key distribution server
The content key data corresponding to the encrypted content data having the first format is encrypted with different first user key data for each user to generate first encrypted content key data, and the second format has the second format An encryption unit that encrypts the content key data corresponding to the encrypted content data with second user key data different for each user to generate second encrypted content key data;
A second transmission unit that transmits the first encrypted content key data or the second encrypted content key data to the user terminal;
The user terminal is
The received first encrypted content key data is decrypted with the first user key data to generate the content key data, and the encrypted content data is decrypted with the generated content key data to have the first format. Generate the content data, decrypt the received second encrypted content key data with the second user key data, generate the content key data, and decrypt the encrypted content data with the generated content key data A content distribution system comprising: a decrypting unit configured to generate the content data having the second format. Content identification information included in the encrypted content data decrypted based on the first encrypted content key data is content included in the encrypted content data decrypted based on the second encrypted content key data. The content distribution system according to claim 1, wherein the content distribution system is different from the identification information. The content distribution server is
In the first transmitting unit, the encrypted content data encrypted based on the first encrypted content key data is transmitted in a streaming format,
The content distribution system according to claim 1 or 2, wherein the first transmission unit transmits the encrypted content data encrypted based on the second encrypted content key data in a download format. . The content distribution server is
A first download content generating unit that generates encrypted content data in a download format using the encrypted content data in the streaming format and adds content identification information to the generated encrypted content data in the download format; The content distribution system according to claim 3, wherein: The content distribution server is
In the first transmitting unit, the encrypted content data encrypted based on the first encrypted content key data is transmitted in a streaming format,
The user terminal is
The content distribution system according to claim 1, further comprising: a second download content generation unit configured to accumulate the encrypted content data in the streaming format and generate the encrypted content data in the download format. The content distribution system according to claim 1, wherein the streaming format is a Transport Stream (TS) format. The content distribution according to claim 6, wherein a program map table (PMT) indicating a correspondence between the content identification information and a packet identifier (PID) included in the information in the TS format is multiplexed with the streaming in the TS format. system. The user terminal is
The content distribution system according to claim 6 or 7, further comprising a re-encryption unit that encrypts the content data decrypted by the decryption unit together with the TS header. The user terminal is
The content distribution system according to any one of claims 1 to 8, further comprising: a digital watermark superimposing unit that superimposes and outputs a digital watermark on the decrypted content based on the individual identification information. The content distribution system according to claim 9, wherein the digital watermark superimposing unit superimposes the digital watermark on the content identification information based on individual identification information. The key distribution server
The first encrypted content key data or the second encrypted content key data is transmitted to the user terminal before the encrypted content data is transmitted. The content distribution system according to claim 1. The key distribution server
11. The first encrypted content key data or the second encrypted content key data is transmitted to the user terminal every time the encrypted content data is transmitted. 11. The content distribution system according to item 1. In a content distribution method for distributing encrypted content in response to a request from a user terminal held by a user,
A first transmission step of transmitting the encrypted content data encrypted with different content key data for each content data to the user terminal;
The content key data corresponding to the encrypted content data having the first format is encrypted with the first user key data different for each user to generate the first encrypted content key data, or has the second format An encryption step of encrypting the content key data corresponding to the encrypted content data with second user key data different for each user to generate second encrypted content key data;
A second transmission step of transmitting the first encrypted content key data or the second encrypted content key data to the user terminal;
The received first encrypted content key data is decrypted with the first user key data to generate the content key data, and the encrypted content data is decrypted with the generated content key data to have the first format. The content data is generated, or the received second encrypted content key data is decrypted with the second user key data to generate the content key data, and the encrypted content data is generated with the generated content key data. A content distribution method comprising: a decrypting step of decrypting and generating the content data having the second format.

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