JP5231522B2 - Content distribution system, content distribution device, terminal device, content distribution program, and content distribution method - Google Patents

Description

  The present invention relates to a content distribution system having a content distribution device that distributes electronic content to a terminal device, a content distribution device, a terminal device, a content distribution program, and a content distribution method.

  In recent years, various electronic contents such as music contents, moving picture contents, and electronic book contents have been provided on the Internet, and users are increasingly purchasing these electronic contents using a terminal device such as a personal computer. .

  In general, encryption processing is performed on such electronic content so that only a purchased user can use the electronic content (for example, refer to Patent Document 1 for an electronic book).

JP 2009-163612 A

  However, the conventional encryption process has a problem that the load on the encryption process is large because the entire electronic content is to be encrypted.

  The present invention solves the problems of the prior art as described above, and an object thereof is to reduce the load on the encryption processing.

  Based on the above object, one aspect (1) of the present invention is a content distribution system including a content distribution device that distributes electronic content to a terminal device, wherein the content distribution device stores data constituting the electronic content as data A dividing unit that divides the first data including at least a part of the data configuration information that defines the configuration of the main body and the other second data; a generating unit that generates a user key corresponding to the user of the terminal device; Encryption means for encrypting the first data with the user key generated by the generation means; first data transmission means for transmitting the first data encrypted by the encryption means to the terminal device; Second data transmission means for transmitting second data to the terminal device, and user key transmission for transmitting the user key to the terminal device And the terminal device receives first encrypted data from the content distribution device, and second data reception means receives the second data from the content distribution device. A user key receiving means for receiving the user key from the content distribution device, a decrypting means for decrypting the encrypted first data with the user key, and a first decrypted by the decrypting means. A combining means for combining one data and the second data is provided.

  An aspect (13) of the present invention that grasps the above aspect (1) from the viewpoint of a method is a content distribution method for distributing electronic content from a content distribution device to a terminal device, wherein the electronic content is configured in the content distribution device. Dividing the data into first data including at least a part of data configuration information defining the configuration of the data body and other second data, generating a user key corresponding to the user of the terminal device, The first data is encrypted with a user key, the encrypted first data is transmitted to the terminal device, the second data is transmitted to the terminal device, and the user key is transmitted to the terminal device. The terminal device receives the encrypted first data from the content distribution device, and the second data is received from the content distribution device. Receiving from the distribution device, receiving the user key from the content distribution device, decrypting the encrypted first data with the user key, and combining the decrypted first data and the second data It is characterized by making it.

  One aspect (10) of the present invention, which captures the above aspect (1) from the content distribution apparatus side, is a content distribution apparatus that distributes electronic content to a terminal device. A dividing unit that divides the first data including at least a part of the data configuration information to be defined and other second data; a generating unit that generates a user key corresponding to a user of the terminal device; and the generating unit An encryption unit that encrypts the first data with the generated user key; a first data transmission unit that transmits the first data encrypted by the encryption unit to the terminal device; and the second data. A second data transmission unit configured to transmit to the terminal device; and a user key transmission unit configured to transmit the user key to the terminal device. To.

  One aspect (11) of the present invention, which captures the aspect (1) from the terminal device side, is the terminal device that acquires the electronic content transmitted from the content distribution device according to the aspect (10). A first data receiving means for receiving one data from the content distribution apparatus; a second data receiving means for receiving the second data from the content distribution apparatus; and a user key reception for receiving the user key from the content distribution apparatus. Means, decrypting means for decrypting the encrypted first data with the user key, and combining means for combining the first data decrypted by the decrypting means and the second data. It is characterized by that.

  According to the present invention, in the content distribution device, the data constituting the electronic content is divided into the first data including at least a part of the data configuration information defining the configuration of the data body and the other second data. Dividing and encrypting the first data with the user key. As described above, it is difficult to restore the electronic content by encrypting the data configuration information. On the other hand, only a part of the information constituting the electronic content needs to be encrypted. The load on processing can be reduced. Moreover, since the data configuration information often has a small amount of data, the load on the encryption process can be effectively reduced.

  Also, the terminal device receives the encrypted first data and the unencrypted second data, decrypts the first data, and combines the second data with the electronic data to restore the electronic content. Therefore, only the decryption process needs to be performed on a part of the information constituting the electronic content, so that the load on the decryption process can be reduced. In addition, since decryption can be performed only by the user key, the possibility that the electronic content is acquired and reproduced by another user can be reduced.

  According to another aspect (9) of the present invention, in a content distribution device that distributes electronic content to a terminal device, at least a part of data configuration information that defines a configuration of a data main body is used for data constituting the electronic content. A dividing unit that divides the first data including the second data; a generating unit that generates a user key corresponding to a user of the terminal device; and the first data generated by the user key generated by the generating unit. Encryption means for encrypting, first data transmission means for transmitting the first data encrypted by the encryption means to the terminal device, and second data transmission for transmitting the second data to the terminal device Means, user key transmitting means for transmitting the user key to the terminal device, and a program transmitter for transmitting a predetermined program to the terminal device The predetermined program includes a terminal device, a first data receiving unit that receives the encrypted first data from the content distribution device, and a second data that receives the second data from the content distribution device. Data receiving means, user key receiving means for receiving the user key from the content distribution device, decryption means for decrypting the encrypted first data with the user key, and decryption by the decryption means. It is made to function as a coupling | bonding means which couple | bonds 1 data and said 2nd data.

  Another aspect (12) of the present invention that grasps the above aspect (9) from the viewpoint of a computer program is a content distribution program for causing a computer to execute a process for distributing electronic content to a terminal device. Is divided into first data including at least a part of data configuration information defining the configuration of the data body and other second data, and a user key corresponding to the user of the terminal device is generated, and the user key To encrypt the first data, transmit the encrypted first data to the terminal device, transmit the second data to the terminal device, transmit the user key to the terminal device, and The computer is caused to execute a process for transmitting the program to the terminal device. Receiving encrypted first data from the computer, receiving the second data from the computer, receiving the user key from the computer, and decrypting the encrypted first data by the user key And causing the terminal device to execute a process of combining the decrypted first data and the second data.

  According to the present invention, in the content distribution apparatus, the data constituting the electronic content is divided into the first data including at least a part of the data configuration information defining the configuration of the data body and the other second data. Dividing and encrypting the first data with the user key. As described above, it is difficult to restore the electronic content by encrypting the data configuration information. On the other hand, only a part of the information constituting the electronic content needs to be encrypted. The load on processing can be reduced. In addition, the terminal device receives the encrypted first data and the unencrypted second data based on the program transmitted from the content distribution device, decrypts the first data, and then combines the second data. To restore the electronic content. Therefore, since it is only necessary to decrypt only a part of the information constituting the electronic content, the load on the decryption process can be reduced.

  According to another aspect (2) of the present invention, in any one of the above aspects, the content distribution device uses the image generation means for generating data of the digital watermark image and the data of the digital watermark image by the user key. Image encrypting means for encrypting the encrypted digital watermark image and image transmitting means for transmitting the encrypted digital watermark image data to the terminal device, wherein the terminal device stores the encrypted digital watermark image data An image receiving means for receiving, an electronic watermark image decoding means for decoding the encrypted digital watermark image data with the user key, and the electronic watermark image superimposed on the electronic content restored by the combining means Display control means for displaying on the display means is provided.

  According to the present invention, when an image of electronic content displayed on the display means is captured, a digital watermark image is superimposed on the image. Therefore, for example, even when the captured image is released on the network, the outflow source of the captured image can be easily specified.

  According to another aspect (3) of the present invention, in any one of the above aspects, the data constituting the electronic content includes a plurality of data files and the data configuration information including information on the plurality of data files. It is characterized by that.

  According to the present invention, it is possible to make it difficult to read a plurality of data files by encrypting the first data including at least a part of the data configuration information, and the electronic content is acquired and reproduced by another user. The possibility of being reduced can be reduced.

  According to another aspect (4) of the present invention, in any one of the above aspects, the first data includes at least a part of the data configuration information and a part of the data file.

  According to the present invention, reading of a data file can be made more difficult, and the possibility that electronic content is acquired and reproduced by another user can be further reduced.

  According to another aspect (5) of the present invention, in any one of the above aspects, the content distribution device includes means for bit-shifting the data file included in data constituting the electronic content in a predetermined direction, The terminal device includes means for bit-shifting the data file in a direction opposite to the predetermined direction.

  According to the present invention, reading of a data file can be made more difficult, and the possibility that electronic content is acquired and reproduced by another user can be further reduced.

  According to another aspect (6) of the present invention, in any one of the above aspects, the storage unit stores a user ID and the user key in association with each other, and a unit that acquires the user ID from the terminal device, The encryption unit reads the user key corresponding to the acquired ID from the storage unit and encrypts the first data.

  According to the present invention, since the user key can be selected based on the user ID, it is not necessary to generate the user key every time, and the first data can be encrypted quickly.

  According to another aspect (7) of the present invention, in any one of the above aspects, the generation unit generates the user key based on a user ID acquired from the terminal device.

  According to the present invention, since the user key is generated based on the user ID, it is possible to generate a unique user key corresponding to the user ID, and electronic content can be acquired and reproduced by other users. Can be further reduced.

  According to another aspect (8) of the present invention, in any one of the above aspects, the terminal device includes the encrypted first data received by the first data receiving unit, and the second data receiving unit. Storage means for storing the second data received by the user key and the user key received by the user key receiving means, and a selection means for selecting electronic content to be displayed on the display means, the decoding means Obtains the encrypted first data corresponding to the selected electronic content from the storage means and decrypts it with the user key, and the combining means selects the first data corresponding to the selected electronic content. Two data is acquired from the storage means, and the second data is combined with the decoded first data.

  According to the present invention, the electronic content information is stored in the terminal device in a partially encrypted state, and the electronic content is restored when played back. Therefore, the electronic content is acquired and played by another user. The possibility can be further reduced.

  According to the present invention, it is possible to reduce the load on the encryption process.

FIG. 1 is a schematic diagram of a content distribution system according to an embodiment of the present invention. FIG. 2 is a configuration diagram of a content distribution system according to an embodiment of the present invention. FIG. 3 is a block diagram of the content distribution apparatus (during download distribution). FIG. 4 is a diagram illustrating an example of a data configuration of electronic book content. FIG. 5 is an explanatory diagram of a data format of electronic book content. FIG. 6 is a block diagram (during streaming distribution) of the content distribution apparatus. FIG. 7 is a block diagram of the terminal device (during download distribution). FIG. 8 is a block diagram of the terminal device (during streaming distribution). FIG. 9 is a flowchart showing the processing procedure of the content distribution apparatus. FIG. 10 is a flowchart showing the content distribution processing procedure shown in FIG. FIG. 11 is a flowchart illustrating a processing procedure of the terminal device.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings.

[1. Overview of content distribution system]
First, an outline of a content distribution system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of a content distribution system according to an embodiment of the present invention.

  As shown in FIG. 1, the content distribution system according to this embodiment includes a content distribution device 10 and a terminal device 20, and the content distribution device 10 and the terminal device 20 are connected via a network such as the Internet, for example. It is connected so that it can communicate.

  The content distribution device 10 transmits electronic content corresponding to the request from the terminal device 20 to the terminal device 20. The electronic content transmitted and received in this way is electronic book content, and includes a data body including data of a plurality of data files and data configuration information as shown in FIG. The electronic book content is composed of binary data.

  The data configuration information is data for recognizing a plurality of data files constituting the data body. For example, when the electronic book content is provided in the Zip format, the central directory corresponds to the data configuration information.

  When transmitting the electronic book content to the terminal device 20, the content distribution device 10 encrypts a part of data constituting the electronic book content. Specifically, the content distribution apparatus 10 performs the following process.

  First, the content distribution apparatus 10 divides the data constituting the electronic book content into first data including at least part of the data configuration information and other second data (step S1). In the example shown in FIG. 1, the data configuration information is divided into first data and the data body is divided into second data.

  Next, the content distribution device 10 performs an encryption process for encrypting the first data using the user key corresponding to the user of the terminal device 20 as an encryption key (step S2). In such encryption processing, for example, a known secret key cryptosystem such as DES (Data Encryption Standard) or AES (Advanced Encryption Standard) can be used.

  The user key is a key generated for each user of the terminal device 20, and is generated by the content distribution device 10 when the terminal device 20 acquires electronic book content from the content distribution device 10 for the first time, for example.

  The user key generated in this way is stored in the content distribution device 10 in association with the user ID corresponding to the user of the terminal device 20. The user key is transmitted from the content distribution apparatus 10 to the terminal apparatus 20 (step S3) and stored in a storage unit in the terminal apparatus 20.

  Next, the content distribution device 10 transmits the first data encrypted in step S2 (hereinafter also referred to as “encrypted first data”) and the second data to the terminal device 20 (step S4). The terminal device 20 receives the encrypted first data and the second data transmitted from the content distribution device 10 in this way, and stores them in the internal storage means (step S5).

  As described above, the electronic book content is divided into the first data and the second data and stored in the storage unit of the terminal device 20, and the first data necessary for recognizing the data body is stored in the terminal device 20. This is a state encrypted with a user key corresponding to the user. Therefore, even if the electronic book content stored in the storage means in this way is passed to a third party, the third party cannot browse the electronic book content.

  In addition, since it is not necessary to encrypt the entire electronic book content on the content distribution apparatus 10 side, the processing time required for encryption can be reduced, and the processing load on the content distribution apparatus 10 can be reduced. .

  Moreover, since it is not necessary to encrypt the entire electronic book content when transmitting the electronic book content, the processing time required for the encryption can be reduced, and the electronic book content is quickly transmitted to the terminal device 20. It becomes possible.

  Returning to FIG. 1, the description will be continued. After the terminal device 20 stores the encrypted first data and the second data in the storage unit, the terminal device 20 starts a reproduction process of the electronic book content in accordance with a user operation.

  In this reproduction process, first, the terminal device 20 reads the encrypted first data and the user key from the storage unit, and performs a decryption process for decrypting the encrypted first data using the user key as a decryption key (step S6). .

  Next, the terminal device 20 reads the second data from the storage unit, and performs a combining process for combining with the first data decoded in step S6 (step S7). Accordingly, the electronic book content is restored based on the data obtained by encrypting the divided part.

  After restoring the electronic book content in this way, the terminal device 20 reproduces the restored electronic book content. Specifically, the terminal device 20 displays an image of the electronic book content on the display unit.

  In the above description, an example in which the electronic book content is received in the download distribution format and the terminal device 20 receives and reproduces the content from the content distribution device 10 has been described. The present invention can also be applied to the case of receiving and reproducing from In this case, when the encrypted first data is received, it is immediately decrypted, combined with the second data, the electronic content is restored, and reproduction is performed.

  In addition, in FIG. 1, the data configuration information is described as the first data, and the example in which the data body is divided as the second data is described. However, the first data only needs to include at least part of the data configuration information. This makes it difficult to recognize the data body.

  By making all of the data configuration information the first data, it becomes more difficult to recognize the data body, and further, by including a part of the data body in the first data, the reproduction becomes more difficult.

  In the content distribution system according to the present embodiment, as will be described later, it is difficult to recognize the second data by bit-shifting the data file that constitutes the data body. Content can be prevented from being viewed by a third party.

[2. Specific configuration of content distribution system]
Next, the content distribution system according to the present embodiment will be described in detail with reference to FIGS.

  First, the configuration of the content distribution system according to the present embodiment will be described. FIG. 2 is a diagram illustrating a configuration of the content distribution system according to the present embodiment.

As shown in FIG. 2, the content distribution system according to the present embodiment includes a content distribution device 10 and a plurality of terminal devices 20 _{1 to} 20 _n . The content distribution device 10 and each of the terminal devices 20 _{1 to} 20 _n are connected to a network 30 such as the Internet, for example.

Then, each of the terminal devices 20 _{1 to} 20 _n accesses the content distribution device 10 and acquires the electronic book content from the content distribution device 10. E-book content to retrieve from the content distribution device 10, has a viewable by a dedicated viewer program, to the terminal device 20 ₁ ~20 _n, a dedicated viewer program that you downloaded from the content distribution device 10 is installed .

In each of the terminal devices 20 _{1 to} 20 _n , the electronic book content is acquired from the content distribution device 10 by a dedicated viewer program, and an image corresponding to the electronic book content is displayed on the display unit so as to be viewable. Each of the terminal devices 20 _{1 to} 20 _n can acquire the electronic book content from the content distribution device 10 in either a download distribution format or a streaming distribution format.

  Regarding the content distribution system configured as described above, first, the configuration of the content distribution apparatus 10 will be described in detail.

[2.1. Configuration of content distribution apparatus]
As described above, the content distribution apparatus 10 may transmit the electronic book content to the terminal apparatus 20 in the download distribution format and may transmit the electronic book content to the terminal apparatus 20 in the streaming distribution format. The configuration of the content distribution apparatus 10 will be described.

(During download delivery)
First, the configuration when transmitting to the terminal device 20 in the download distribution format will be described in detail. FIG. 3 is a block diagram of the content distribution apparatus 10 (during download distribution).

  As shown in FIG. 3, the content distribution apparatus 10 includes a communication interface (I / F) 11, a storage unit 12, and a control unit 13.

  The communication I / F 11 is an interface for enabling the content distribution device 10 to be connected to the terminal device 20 via the network 30 and includes, for example, an Ethernet (registered trademark) adapter. If the network 30 is the Internet, the content distribution apparatus 10 is connected to the network 30 via a router or the like.

  The storage unit 12 includes a storage area 12a for storing user information, a storage area 12b for storing electronic book content, a storage area 12c for storing a viewer program, and a storage area 12d for storing a shared key. . The storage unit 12 includes, for example, a nonvolatile storage device (nonvolatile semiconductor memory, hard disk device, optical disk device, etc.), a randomly accessible storage device (for example, SRAM (Static Random Access Memory), DRAM (Dynamic Random Access Memory)) Consists of.

  In the storage area 12a, information for each user who uses the content distribution service is stored as user information. Specifically, as user information, a user ID and a user key are associated with each other and stored in the storage area 12a for each user.

  A plurality of electronic book contents are stored in the storage area 12b. In the following, as an electronic book content stored in the storage area 12b, an electronic book content conforming to an electronic book file format standard called ePUB will be described as an example. However, the format is not limited to this, and other formats are also available. It can also be applied to electronic book content.

  FIG. 4 shows the data file structure of the ePUB format electronic book content stored in the storage area 12b. As shown in the figure, the ePUB format electronic book content is composed of a metafile and a book body.

  The metafile includes data files such as “mimetype”, “book name.ncx”, “book name.opf”, “container.xml”, and the like. On the other hand, the book body is composed of data files such as an HTML (HyperText Markup Language) file, a CSS (Cascading Style Sheets) file, and an image file, and is stored in a directory having a directory name “OBEPS”. Note that a directory with a directory name “images” is stored in the directory “OBEPS”, and an image file is stored in the directory “images”.

  As described above, since the ePUB electronic book contents are composed of data files such as HTML files, CSS files, and image files, the same work as web page creation is possible if only metafiles can be prepared. Can be created.

  “Mimetype” is a data file for specifying that the electronic book content is in the ePUB format, and is designated to be at the head of the file after ZIP conversion. “Book name.ncx” is a table of contents file, and associates the ID of the table of contents item specified in this file with the HTML file included in the book body. “Book name.opf” is a data file that is the core of the ePUB file, and specifies the title of the electronic book content, meta information of the author, the path of each data file included in the book body, and the setting of the table of contents. “Container.xml” is a file for designating the path of the opf file (book name.opf) that is the core of the ePUB file.

  The electronic book content in the ePUB format has the above-described data configuration, and is formed by converting a metafile, a book body, etc. into one ZIP file format. Here, a data format of the electronic book content will be described. FIG. 5 is an explanatory diagram of a data format of electronic book content.

  As shown in FIG. 5, a data body 50 that is archive data is included as data constituting the electronic book content. The data body 50 is composed of a plurality of file entries. Each file entry includes a local file header 51 and file data 52. The file data 52 is a data file or directory shown in FIG.

  In addition, a central directory 60 is arranged at the end of the data constituting the electronic book content, that is, behind the data body 50. The central directory 60 is data configuration information that defines the configuration of the data body 50, and includes file headers 61, 61,... Corresponding to local file headers 51, 51,.

  In order to read the file data 52, 52,... Stored in the electronic book content, it is first necessary to access the central directory 60 and read the file headers 61, 61,. And each file data 52, 52, ... is read based on each read file header 61, 61, ... information.

  Since the electronic book content is defined in such a data format, it is difficult to read the data body 50 by encrypting the central directory 60 that is the data configuration information.

  Returning to the description of FIG. A viewer program is stored in the storage area 12 c of the storage unit 12. This viewer program is a viewer for browsing electronic book content on the terminal device 20. This viewer program incorporates a storage key to be described later. A shared key is stored in the storage area 12 d of the storage unit 12.

  The control unit 13 is a control unit that performs overall control of the content distribution apparatus 10. The control unit 13 includes a reception unit 13a, a user key presence / absence determination unit 13b, a user key generation unit 13c, a data acquisition unit 13d, a bit shift unit 13e, a division unit 13f, an encryption unit 13h, a digital watermark Image generation means 13g and transmission means 13i are further provided.

  FIG. 3 shows a functional configuration of the control unit 13. The control unit 13 is physically configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). ). The CPU reads out the program from the ROM and executes it using the RAM as a work area, thereby functioning as the above-described means 13a to 13i.

  The receiving unit 13a receives various information transmitted from the terminal device 20 via the communication I / F 11. For example, the receiving unit 13a receives a request signal for requesting transmission of electronic book content, a request signal for requesting transmission of a user key, and the like.

  The user key presence / absence determination unit 13b acquires the user ID transmitted from the terminal device 20, and determines whether the user key corresponding to the acquired user ID exists in the storage area 12a of the storage unit 12. When the user key corresponding to the acquired user ID does not exist in the storage area 12a, the user key presence / absence determination unit 13b makes a user key generation request to the user key generation unit 13c. On the other hand, when a user key corresponding to the acquired user ID exists in the storage area 12a, the user key presence / absence determination unit 13b transmits the user key from the transmission unit 13i to the terminal device 20.

  When a user key generation request is received from the user key presence / absence determination unit 13b, the user key generation unit 13c generates a user key corresponding to the user ID acquired by the user key presence / absence determination unit 13b. Here, the user key is a value obtained by calculating the user ID using a hash function, but the method for generating the user key is not limited to this. For example, a value obtained by calculating the user ID with a function other than the hash function can be used as a user key, or a value obtained by performing predetermined processing on the user ID can be used as a user key.

  The user key generation unit 13c stores the generated user key in the storage area 12a in association with the corresponding user ID, and transmits the generated user key to the terminal device 20 from the transmission unit 13i.

  When the receiving unit 13a receives a request signal for requesting transmission of electronic book content from the terminal device 20, the data acquisition unit 13d reads the electronic book content corresponding to the request signal from the storage area 12b of the storage unit 12, and performs bit shift. Output to means 13e. Further, when the receiving unit 13a receives the request signal for requesting the transmission of the catalog from the terminal device 20, the data acquiring unit 13d reads the catalog data from the storage unit 12, and the catalog data is transmitted from the communication unit 13i to the terminal device. 20 to be transmitted.

  The bit shift means 13e bit-shifts the image file in a predetermined direction (first direction) among the data constituting the electronic book content acquired from the storage unit 12 by the data acquisition means 13d. This bit shift makes it difficult to reproduce the image file. Note that not only image files but also HTML files may be bit-shifted.

  The dividing unit 13f divides the electronic book content obtained by bit-shifting the image file by the bit shift unit 13e into first data and second data. The first data is information including at least a part of the central directory 60 that is data configuration information, and the second data is data excluding the first data.

  The dividing unit 13f can also use the entire central directory 60, which is data configuration information, as the first data, and can also use the entire central directory 60 and a part of the data body 50 as the first data. Further, the dividing unit 13f can also use a part of the central directory 60 and a part of the data body 50 as the first data. In this case, all or part of the central directory 60 constituting the first data and part of the data body 50 do not have to be continuous.

  The digital watermark image generation unit 13 g generates digital watermark image data based on the user ID transmitted from the terminal device 20. This digital watermark image is generated so that the user ID can be specified.

  For example, the digital watermark image generation unit 13g can generate a digital watermark image as dots that constitute characters, symbols, and the like that cannot be visually recognized by the user. The digital watermark image may be identification information itself such as a user ID or a terminal ID, or may be information based on the identification information. For example, based on ASCII (American Standard Code for Information Interchange), a binary number is used. You may display by a decimal number, a hexadecimal number, etc. In a more specific example, the identification information can be indicated in binary by filling one square with a 2 × 2 dot area as one unit. For example, based on ASCII, t can be indicated by a binary number “01110100” and a can be indicated by a binary number “01100001”. By using this, the user ID “ta” can be represented in binary. By using one of these 2 × 2 dot areas as a unit and painting one of the squares and making the other three squares transparent, it is possible to create an electronic watermark image that cannot be visually recognized by the user.

  Since the terminal device 20 displays an electronic watermark image superimposed on the image of the electronic book content, for example, a function (so-called capture function) for saving a display on a display such as a print screen or a screen shot as an image is used. In this case, an electronic watermark image is stored in the image saved by this function. Therefore, by analyzing the digital watermark image, it is possible to specify the user who saved the image of the electronic book content and provided it to other users based on the identification information.

  The encryption unit 13h reads the user key corresponding to the user ID of the user who requested transmission of the electronic book content from the storage area 12a of the storage unit 12, and reads the first data output from the dividing unit 13f from the storage area 12a. Encrypt the read user key as an encryption key. The encryption unit 13h does not encrypt the second data.

  In addition, when the electronic book content requested to be transmitted is for browsing, the encryption unit 13h reads a common key common to all the terminal devices 20 from the storage area 12d of the storage unit 12, and from the division unit 13f. The output first data is encrypted using the shared key read from the storage area 12d as an encryption key.

  If only important file data 52 in the data main body 50 needs to be difficult to read, only a part of the central directory 60 may be encrypted as the first data by the encryption unit 13h. For example, when a metafile may be read out of electronic book content, only the central directory 60 corresponding to the book body is set as the first data. By doing in this way, the time and load concerning an encryption process can be reduced.

  Moreover, the restoration of the electronic book content can be made more difficult by using the first data including a part of the data body 50. In this case, the first data does not include the file data 52 but includes one or more local file headers 51, thereby suppressing an increase in the data amount of the first data to be encrypted.

  The encryption unit 13h encrypts the data of the digital watermark image output from the digital watermark image generation unit 13g using the user key read from the storage area 12a as the encryption key, like the first data.

  The transmission unit 13 i functions as a first data transmission unit that transmits the first data encrypted by the encryption unit 13 h to the terminal device 20. The transmission unit 13 i functions as a second data transmission unit that transmits the second data output from the dividing unit 13 f to the terminal device 20.

  Further, the transmission unit 13 i functions as a user key transmission unit that transmits the user key generated by the user key generation unit 13 c to the terminal device 20. The transmission unit 13 i functions as a digital watermark image transmission unit that transmits data of the digital watermark image generated by the digital watermark image generation unit 13 g and encrypted by the encryption unit 13 h to the terminal device 20.

(Streaming delivery)
Next, the configuration when transmitting to the terminal device 20 in the streaming distribution format will be described in detail. FIG. 6 is a block diagram of the content distribution apparatus 10 (during streaming distribution).

  The block diagram shown in FIG. 6 has the same configuration except for a part of the block diagram shown in FIG. 3 (during download distribution), and here, the description will focus on parts different from the download distribution format.

  When transmitting to the terminal device 20 in the streaming distribution format, the content distribution device 10 separates the image file and sets the electronic book content in which the link destination of the image file is changed in the HTML file as the first distribution target to the terminal device 20, The image file is transmitted in response to a request from the terminal device 20.

  In order to realize such a function, the data acquisition unit 13d ′ reads the electronic book content corresponding to the request signal from the terminal device 20 from the storage area 12b of the storage unit 12, and then uses the data constituting the electronic book content. Separate image files. For example, when the electronic book content has the file configuration shown in FIG. 4, the content distribution apparatus 10 separates the image files whose file names are “image1.jpg” and “image2.jpeg” from the electronic book content.

  In addition, the data acquisition unit 13d ′ includes, in the HTML data constituting the electronic book content read from the storage unit 12, the link destination information of the image file from the link destination information indicating that the electronic book content is in the electronic book content. Change to link information indicating that

  For example, when the electronic book content has the file configuration shown in FIG. 4, the HTML file (“book name.html”) is, for example, “/ image / image1” as the link destination information of the image file “image1.jpg”. .Jpeg "is described.

  In such a case, the data acquisition unit 13d 'changes "/image/image1.jpg" described as the link destination information to, for example, "network address / book name / image1.jpg". The “network address” is an address of the content distribution apparatus 10 on the network 30 and corresponds to a domain name when the network 30 is the Internet.

  In this way, the electronic book content obtained by separating the image file and changing the link destination information of the image file is output from the data acquisition unit 13d 'to the division unit 13f. The data acquisition unit 13d 'outputs the separated image file to the bit shift unit 13e'.

  Upon acquiring the image file from the data acquisition unit 13d ', the bit shift unit 13e' bit-shifts the image file in a predetermined direction (first direction) and stores it in the storage area 12b of the storage unit 12.

  The electronic book content from which the image file has been removed is separated into the first data and the second data by the dividing unit 13f as in the case of download distribution. The first data is encrypted by the encryption unit 13h and transmitted from the transmission unit 13i to the terminal device 20. The second data is output from the dividing unit 13f to the transmitting unit 13i and transmitted to the terminal device 20 by the transmitting unit 13i.

  On the other hand, the bit-shifted image file is read from the storage area 12 b of the storage unit 12 in response to a request from the terminal device 20 and transmitted to the terminal device 20. Specifically, when the request signal requesting transmission of the image file is received by the receiving unit 13a, the data acquisition unit 13d ′ reads the image file corresponding to the request signal from the storage area 12b of the storage unit 12, and transmits the transmission unit 13i. To the terminal device 20 from the transmission means 13i.

  As described above, when the electronic book content is transmitted to the terminal device 20 in the streaming distribution format, the content distribution device 10 separates the image file from the electronic book content out of the data constituting the electronic book content and describes it in the HTML file. Change the link information of the image file.

  Then, the content distribution device 10 bit-shifts the image file separated from the electronic book content, stores the image file in the storage area 12b of the storage unit 12, and performs the bit shift according to the request from the terminal device 20. The file is transmitted to the terminal device 20.

[2.2. Configuration of Terminal Device 20]
Next, the configuration of the terminal device 20 will be described in detail. As described above, the terminal device 20 may receive the electronic book content from the content distribution device 10 in the download distribution format, and may receive the electronic book content from the content distribution device 10 in the streaming distribution format. In the following, the configuration of the terminal device 20 will be described separately for each case.

(During download delivery)
First, a configuration in the case of receiving information on electronic book content from the content distribution device 10 in the download distribution format will be described in detail. FIG. 7 is a block diagram of the terminal device 20 (during download distribution).

  As illustrated in FIG. 7, the terminal device 20 includes a communication interface (I / F) 21, a display unit 22, an operation unit 23, a storage unit 24, and a control unit 25.

  The communication I / F 21 is an interface for enabling the terminal device 20 to be connected to the content distribution device 10 via the network 30 and includes, for example, an Ethernet (registered trademark) adapter. If the network 30 is the Internet, the terminal device 20 is connected to the network 30 via a router or the like.

  The display unit 22 is configured by a display device such as an LCD (Liquid Crystal Display) or an organic EL (Electoro Luminescence), and displays an image in response to a request from the control unit 25.

  The operation unit 23 has keys to which various functions such as a power key, a numeric key, a character key, a direction key, and an enter key are assigned, and when these keys are operated by the user, A signal corresponding to the operation content is generated, and the generated signal is input to the control unit 25 as a user instruction. The operation unit 23 functions as a selection unit that selects electronic content to be displayed on the display unit 22.

  The storage unit 24 includes storage areas 24a to 24d. The storage unit 24 includes, for example, a nonvolatile storage device (nonvolatile semiconductor memory, hard disk device, optical disk device, etc.), a randomly accessible storage device (eg, SRAM, DRAM), or the like.

  The storage area 24a stores user ID, user key, and digital watermark image data as user information.

  Information on the electronic book content acquired from the content distribution device 10 is stored in the storage area 24b. The stored electronic book content information includes encrypted first data and second data. The encrypted first data and the second data are stored in the storage area 24b in association with each other.

  In the storage area 24c, a storage key uniquely assigned to the terminal device 20 is stored. This storage key is generated when the viewer program provided from the content distribution apparatus 10 is first activated. In the storage area 24d, a common key that is common to all the terminal devices 20 is stored. This shared key is stored in the storage unit 24 when the viewer program is first started.

  The control unit 25 is a control unit that performs overall control of the terminal device 20. The control unit 25 further includes a receiving unit 25a, a request processing unit 25b, a decoding unit 25c, a combining unit 25d, a bit shift unit 25e, a display control unit 25f, and a transmission unit 25g.

  7 shows a functional configuration of the control unit 25. The control unit 25 physically includes a CPU (Central Processing Unit), a flash memory, and a RAM (Random Access Memory). ).

  The CPU reads out the program from the flash memory and executes it using the RAM as a work area, thereby functioning as the above-described means 25a to 25g. Note that the program stored in the flash memory is a viewer program transmitted from the content distribution apparatus 10.

  The receiving unit 25a receives various information transmitted from the content distribution apparatus 10 via the communication I / F 21. Specifically, the receiving unit 25 a functions as a first data receiving unit that receives the encrypted first data from the content distribution apparatus 10. The receiving unit 25 a functions as a second data receiving unit that receives the second data from the content distribution device 10.

  Furthermore, the receiving unit 25a functions as a user key receiving unit that receives a user key from the content distribution apparatus 10. The receiving unit 25 a functions as an image receiving unit that receives encrypted digital watermark image data from the content distribution apparatus 10.

  When receiving the encrypted first data and the second data, the receiving unit 25a stores the information as electronic book content information in the storage area 24b of the storage unit 24. In addition, when receiving the encrypted digital watermark image data, the receiving unit 25a stores the data in the storage area 24a of the storage unit 24 in association with the user ID.

  In addition, when receiving the user key, the receiving unit 25a reads the storage key stored in the storage area 24c of the storage unit 24, and encrypts the user key using this storage key. The receiving unit 25a stores the user key encrypted in this way (hereinafter referred to as an encrypted user key) in the storage area 24a of the storage unit 24.

  The request processing unit 25 b performs processing based on a user operation on the operation unit 23. For example, when the operation on the operation unit 23 requests a catalog of electronic book content, the request processing unit 25b transmits a request signal for requesting a catalog transmission from the transmission unit 25g to the content distribution apparatus 10. . In response to this request, when the request processing unit 25b acquires catalog data from the content distribution device 10 via the receiving unit 25a, an image based on the acquired data (an electronic book content catalog image) is displayed on the display unit 22. Display.

  In addition, when a catalog image is displayed on the display unit 22 and any of the electronic book contents listed in the catalog is selected by an operation on the operation unit 23, the request processing unit 25b transmits the transmission unit 25g. A request signal for transmitting the selected electronic book content to the content distribution apparatus 10 is transmitted. At this time, if the user key is not stored in the storage area 24a of the storage unit 24, the request processing unit 25b transmits a request signal for requesting transmission of the user key to the content distribution apparatus 10 from the transmission unit 25g. To do.

  In addition, when the operation on the operation unit 23 is an operation of selecting information on the electronic book content stored in the storage area 24b of the storage unit 24, the request processing unit 25b restores the selected electronic book content. Then, the decoding unit 25c and the combining unit 25d are operated.

  Based on the request from the request processing means 25b, the decryption means 25c, the encrypted first data stored in the storage area 24b of the storage unit 24, the encrypted user key stored in the storage area 24a, and the storage area 24c The stored key stored in is read. Then, the decryption means 25c decrypts the encrypted user key using the stored key as a decryption key, and acquires the user key. Further, the decryption means 25c decrypts the encrypted first data using the user key as a decryption key, and acquires the first data.

  In addition, when the electronic book content requested by the request processing unit 25b is for browsing, the decryption unit 25c reads the shared key stored in the storage area 24d of the storage unit 24. Then, the decryption means 25c decrypts the encrypted first data using the shared key as a decryption key, and acquires the first data.

  The combining unit 25d combines the first data decoded by the decoding unit 25c and the second data output from the receiving unit 25a.

  The bit shift means 25e bit-shifts the image data included in the data combined by the combining means 25d in the second direction opposite to the first direction to restore the electronic book content. The bit shift means 25e outputs the electronic book content restored in this way to the display control means 25f.

  When the display control unit 25f acquires the electronic book content from the bit shift unit 25e, the display control unit 25f reads the encrypted digital watermark image data and the user key from the storage area 24a of the storage unit 24, and encrypts it using the user key as a decryption key. The digital watermark image data is decoded. In this way, the display control unit 25f functions as a digital watermark image decoding unit that decrypts data of a digital watermark image encrypted using the user key as a decryption key.

  Then, the display control unit 25f outputs image data in which the digital watermark image is superimposed on the image of the electronic book content acquired from the bit shift unit 25e to the display unit 22, and displays the electronic book content in which the digital watermark image is superimposed on the display unit. 22 is displayed.

  The transmission unit 25 g transmits the user ID stored in the storage area 24 a of the storage unit 24 to the content distribution device 10. Further, the transmission unit 25g transmits a request signal for requesting transmission of electronic book content to the content distribution apparatus 10.

  Thus, in the terminal device 20, the information of the electronic book content acquired from the content distribution device 10 is stored in the storage unit 24 in a state before being restored. That is, since the first data is encrypted and stored in the storage unit 24 with the user key unique to the user, it is possible to prevent the electronic book content from being browsed by the terminal device 20 of another user.

  In addition, since the encryption of the electronic book content is performed on the data configuration information having a relatively small amount of data compared to the data body, the processing time and processing load for encryption can be reduced, and the electronic book content It is possible to display an image based on the information more quickly.

  Furthermore, since the user key for restoring the electronic book content is encrypted with a storage key unique to each user and stored in the storage unit 24, the electronic book content is browsed by the terminal device 20 of another user. This can be prevented more firmly.

  In addition, since an electronic watermark image corresponding to the user is superimposed on the image of the electronic book content displayed on the display unit 22, for example, when the image displayed on the display unit 22 is captured and copied. In addition, it is possible to easily grasp from which user the image has flowed out.

(Streaming delivery)
Next, a detailed description will be given of a configuration in the case of receiving electronic book content information from the content distribution device 10 in a streaming distribution format. FIG. 8 is a block diagram of the terminal device 20 (at the time of streaming distribution).

  The block diagram shown in FIG. 8 has the same configuration except for a part of the block diagram shown in FIG. 7 (during download distribution), and here, the description will focus on the parts different from the download distribution format.

  The information on the electronic book content transmitted from the content distribution device 10 to the terminal device 20 in the streaming distribution format is information on the electronic book content in which the image file is separated and the link destination of the HTML file is changed (the encrypted first data and the encrypted data). Second data).

  The terminal device 20 decrypts the encrypted first data in the received information of the electronic book content, combines it with the second data, and displays an image based on the restored electronic book content on the display unit 22. The image displayed on the display unit 22 is information based on an HTML file included in the electronic book content.

  That is, the terminal device 20 acquires image file data from the content distribution device 10 that is a link destination described in the HTML file, and displays an image based on the acquired image file at the position and size specified in the HTML file. It is displayed on the display unit 22.

  In order to realize such a function, when receiving means 25a receives encrypted first data from content distribution apparatus 10, receiving means 25a outputs the encrypted first data to decryption means 25c, and from content distribution apparatus 10 receives second data. When data is received, the second data is output to the combining means 25d. Note that the decryption unit 25c and the combination unit 25d perform the same processing as during download distribution. In addition, when receiving the image file data from the content distribution apparatus 10, the receiving unit 25a outputs the image file data to the bit shift unit 25e '.

  Upon acquiring the electronic book content from the combining unit 25d, the display control unit 25f 'reads the encrypted digital watermark image data from the storage area 24a of the storage unit 24 and decrypts it in the same manner as during download distribution. In addition, the display control unit 25 f ′ makes an image file transmission request to the link destination (content distribution device 10) described in the HTML file included in the acquired electronic book content, and acquires the image file.

  The display control means 25f ′ outputs information of an image obtained by further superimposing a digital watermark image on the image based on the acquired electronic book content and the image file to the display unit 22, and displays the electronic book content superimposed with the digital watermark image. To display.

  Next, a specific operation of the content distribution apparatus 10 according to the present embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a flowchart illustrating an outline of a processing procedure executed by the control unit 13 of the content distribution apparatus 10. This process is started when a predetermined request is received from the terminal device 20.

  These processes are executed (implemented) by a microcomputer (CPU) constituting the control unit 13 based on a program, but the relationship with the functional blocks shown in FIGS. 3 and 6 is easily understood. Therefore, for the sake of convenience, description will be made using the expression that each functional block is executed.

  As shown in FIG. 9, in the content distribution apparatus 10, the receiving unit 13a determines whether or not the received request signal is a signal requesting transmission of a user key (step S10). In this process, if it is determined that the signal is a signal requesting transmission of a user key (step S10, Yes), the user key presence / absence determining unit 13b determines that the user key corresponding to the user ID included in the request signal is stored in the storage unit 12. It is determined whether or not it exists in the storage area 12a (step S11).

  When the user key presence / absence determination unit 13b determines that the user key does not exist (No in step S11), the user key generation unit 13c generates a user key corresponding to the user ID acquired by the user key presence / absence determination unit 13b ( Step S12). The generated user key is associated with the user ID by the user key generating unit 13c and stored in the storage area 12a of the storage unit 12.

  And the transmission means 13i transmits a user key to the terminal device 20 which transmitted the request signal (step S13). That is, when the user key exists in the storage area 12 a of the storage unit 12, the user key presence / absence determination unit 13 b reads out the user key stored in the storage area 12 a and transmits it to the terminal device 20. On the other hand, when the user key does not exist in the storage area 12 a of the storage unit 12, the user key generation unit 13 c transmits the generated user key to the terminal device 20.

  In step S10, if the receiving unit 13a determines that the received request signal is not a signal requesting transmission of a user key (No in step S10), whether or not the received request signal is a transmission request for electronic book content. Is determined (step S14).

  In this process, if it is determined that the received request signal is a request for transmitting electronic book content (step S14, Yes), a content distribution process for transmitting the electronic book content is performed (step S15). The content distribution process is a process of steps S30 to S38 shown in FIG. 10, and will be described in detail later.

  In step S14, if the receiving means 13a determines that the received request signal is not an electronic book content transmission request (No in step S14), it determines whether or not the received request signal is an image file transmission request. (Step S16).

  In this process, when it is determined that the request is an image file transmission request (step S16, Yes), the data acquisition unit 13d reads the image file according to the request from the storage area 12b of the storage unit 12. Then, the data acquisition unit 13d transmits the read image file from the transmission unit 13i to the terminal device 20 that has transmitted the request signal (step S17).

  If it is determined in step S16 that the received request signal is not an image file transmission request (No in step S16), the receiving unit 13a determines whether or not the received request signal is a digital watermark image transmission request. (Step S18).

  In this process, if it is determined by the receiving unit 13a that the transmission request is a digital watermark image (Yes in step S18), the digital watermark image generating unit 13g is based on the user ID transmitted from the terminal device 20. Image data is generated and encrypted with the user key. Then, the digital watermark image generation unit 13g transmits the encrypted digital watermark image data from the transmission unit 13i to the terminal device 20 that has transmitted the request signal (step S19).

  If it is determined in step S18 that the request is not a digital watermark image transmission request (No in step S18), the receiving unit 13a performs other processing according to the received request signal (step S20).

  Here, the content distribution processing in step S15 will be specifically described with reference to FIG. FIG. 10 is a flowchart illustrating an outline of a content distribution processing procedure executed by the control unit 13 of the content distribution apparatus 10.

  In this content distribution process, first, the receiving means 13a determines whether or not the request from the user of the terminal device 20 is in the download distribution format (step S30). When it is determined that the request from the user is in the download distribution format (step S30, Yes), the data acquisition unit 13d reads the electronic book content requested by the user from the storage area 12b of the storage unit 12, and the bit shift unit It outputs to 13e (step S31).

  The bit shift unit 13e bit-shifts the image file in a predetermined direction among the data constituting the electronic book content acquired from the storage unit 12 by the data acquisition unit 13d (step S32). Thereafter, the dividing unit 13f divides the data constituting the electronic book content processed by the bit shift unit 13e into first data and second data (step S33).

  Subsequently, the encryption unit 13h encrypts the first data (step S34). When the electronic book content requested to be transmitted is purchase content, the encryption unit 13h reads a user key corresponding to the user ID of the user who requested transmission of the electronic book content from the storage area 12a of the storage unit 12. Then, the encryption unit 13h encrypts the first data using the user key read from the storage area 12a as the encryption key.

  On the other hand, when the electronic book content requested to be transmitted is for browsing, the encryption means 13h reads the shared key from the storage area 12d of the storage unit 12, and uses the shared key read from the storage area 12a as the encryption key to Encrypt data.

  The transmission means 13i transmits the encrypted first key and second key to the terminal device 20 that has requested transmission of the electronic book content (step S35). The transmitting unit 13i can transmit the encrypted first key and the second key separately, and can also transmit them together.

  If it is determined in step S30 that the request from the user is not the download distribution format but the streaming distribution format (No in step S30), the data acquisition unit 13d ′ stores the electronic book content requested by the user in the storage unit. The data is read from the 12 storage areas 12b (step S36).

  Then, the data acquisition unit 13d 'separates the image file from the data constituting the electronic book content and outputs it to the bit shift unit 13e'. The bit shift unit 13e 'bit shifts the image file acquired from the data acquisition unit 13d' and stores it in the storage area 12b of the storage unit 12 (step S37).

  Further, the data acquisition unit 13d 'converts the link information of the image file in the read electronic book content, and outputs it to the dividing unit 13f (step S38). Thereafter, the processes of steps S33 to S35 are performed.

  Next, a specific operation of the terminal device 20 according to the present embodiment will be described with reference to FIG. FIG. 11 is a flowchart illustrating an outline of a processing procedure executed by the control unit 25 of the terminal device 20. This process is performed repeatedly.

  These processes are executed (implemented) by a microcomputer (CPU) constituting the control unit 25 based on a program, but the relationship with the functional blocks shown in FIGS. 7 and 8 is easily understood. Therefore, for the sake of convenience, description will be made using the expression that each functional block is executed.

  As illustrated in FIG. 11, in the terminal device 20, the request processing unit 25 b determines whether or not an acquisition request operation for requesting acquisition of an electronic book content has been performed by a user operation on the operation unit 23 (Step S <b> 51). ). In this process, if it is determined that the acquisition request operation has been performed (step S51, Yes), the request processing unit 25b requests the content distribution apparatus 10 to transmit the electronic book content that is the target of the acquisition request operation. Is transmitted (step S52).

  Subsequently, the request processing unit 25b determines whether or not the user key is stored in the storage area 24a of the storage unit 24 (step S53). If it is determined that the user key is not stored in the storage area 24a (No at Step S53), the request processing unit 25b transmits a request signal for requesting transmission of the user key to the content distribution apparatus 10. Thereby, the user key transmitted from the content distribution apparatus 10 is received by the receiving means 25a and stored in the storage area 24a of the storage unit 24 (step S54).

  When the user key is acquired in step S54, or when it is determined in step S53 that the user key is stored in the storage area 24a (step S53, Yes), the process proceeds to step S55. In step S55, the receiving means 25a determines whether or not the information of the electronic book content transmitted from the content distribution device 10 to the terminal device 20 in response to the request in step S52 is a download distribution format (step S55).

  In this process, if it is determined that the download distribution format is selected (step S55, Yes), the receiving unit 25a stores the received information on the electronic book content in the storage area 24b of the storage unit 24 (step S56).

  On the other hand, when it is determined that the information of the electronic book content is not in the download distribution format (No at Step S55), the decryption means 25c decrypts the encrypted first data among the information of the electronic book content ( Step S57).

  Subsequently, the combining unit 25d combines the first data decrypted by the decrypting unit 25c and the second data of the information on the electronic book content, restores the electronic book content, and displays the display control unit 25f ′. (Step S58). In step S61, the display control unit 25f 'causes the display unit 22 to display an image corresponding to the electronic book content output from the combining unit 25d. In this case, the display control unit 25 f ′ acquires an image file from the content distribution device 10 based on the HTML file included in the electronic book content.

  On the other hand, if it is determined in step S51 that the acquisition request operation has not been performed (No in step S51), the receiving unit 25a determines whether an image file has been received from the content distribution apparatus 10 (step S59). ).

  If it is determined that the image file has been received (step S59, Yes), the bit shift means 25e 'bit-shifts the data of the image file received by the reception means 25a and outputs it to the display control means 25f' (step). S60). In step S61, the display control unit 25f 'causes the display unit 22 to display an image based on the image file acquired from the bit shift unit 25e' based on the HTML file included in the electronic book content.

  If it is determined in step S59 that the image file has not been received (step S59, No), the request processing means 25b determines whether or not there has been a request for reproduction of the electronic book content (step S63). Specifically, the request processing unit 25b determines whether or not there has been an operation for selecting information on the electronic book content stored in the storage area 24b of the storage unit 24 by the user's operation on the operation unit 23.

  If it is determined that there is a request for reproduction of the electronic book content (Yes in step S63), information on the electronic book content requested for reproduction is read by the decryption means 25c and the combining means 25d (step S64). The decryption unit 25c decrypts the encrypted first data in the information of the electronic book content requested to be reproduced, and outputs the decrypted first data to the combining unit 25d (step S65).

  The combining unit 25d combines the first data decrypted by the decrypting unit 25c and the second data of the information on the electronic book content requested to be reproduced, and outputs the combined data to the bit shift unit 25e (step S66). ). The bit shift means 25e bit-shifts the image data included in the data output from the combining means 25d in the second direction, restores the electronic book content, and outputs it to the display control means 25f (step S67). In step S61, the display control unit 25f causes the display unit 22 to display an image corresponding to the electronic book content output from the combining unit 25d.

  When the processes of steps S56 and S61 are completed, or when it is determined in step S63 that there is no electronic book content reproduction request (step S63, No), this process is terminated.

  As described above, the content distribution apparatus 10 divides the data constituting the electronic book content into the first data including at least a part of the data configuration information and the other second data. The first data is encrypted by the user key and transmitted to the terminal device 20, and the second data is transmitted to the terminal device 20 without being encrypted.

  Therefore, since it is not necessary for the content distribution apparatus 10 to encrypt the entire electronic book content, the processing time required for encryption can be reduced, and the processing load on the content distribution apparatus 10 can be reduced.

  On the other hand, the terminal device 20 acquires the encrypted first data, the second data, and the user key from the content distribution device 10, decrypts the encrypted first data with the user key, Join.

  Therefore, it is not necessary to decrypt the entire electronic book content, the processing time required for the decryption can be reduced, and the processing load on the terminal device 20 can be reduced. In addition, since decryption can be performed only by the user key, the possibility that the electronic content is acquired and reproduced by another user can be reduced.

  As described above, by making the first data to be encrypted all of the data configuration information, it becomes more difficult to reproduce the electronic book content, and further by including even part of the data body, the electronic book content Becomes more difficult to play.

  Therefore, for example, when the internal processing load in the content distribution apparatus 10 is small, more data is included in the first data, while when the processing load is large, the data included in the first data is reduced. It may be.

  In addition, for example, in a time zone in which the transmission request of the electronic book content from the terminal device 20 is small, more data is included in the first data, while in a time zone in which the transmission request is high, it is included in the first data. Data may be reduced.

  Also, the data included in the first data may be changed according to the type of electronic book content (for example, newspaper, monthly magazine, weekly magazine, or novel). Further, the data included in the first data may be changed according to the number of electronic book contents distributed and the expected number. Further, the encryption method may be changed according to the type of electronic book content.

  In the above description, the first data and the second data are divided from a certain position. However, the present invention is not necessarily limited to this. For example, the first data may be constituted by the head portion of the data constituting the electronic book content and the data configuration information, and the remaining portion may be the second data.

  In the above description, the example in which the data configuration information exists in the footer portion of the data constituting the electronic book content has been described, but the data configuration information may be any location. For example, when the data configuration information exists in the header portion of the data constituting the electronic book content, the content distribution device 10 may encrypt at least a part of the data configuration information in the header portion as the first data. .

  In the above description, the digital watermark image data corresponding to the user ID is generated. However, the terminal ID is assigned to the terminal device 20, and the user ID and the terminal ID can be grasped by the digital watermark image generation unit 13g. Such a digital watermark image may be generated. If only the terminal ID needs to be specified, the digital watermark image data can be generated based on the terminal ID.

  In the above description, the electronic book content has been described as an example of the electronic content. However, the electronic book content can be applied to any electronic content as long as the electronic content has data configuration information. For example, the present invention can be applied to various electronic contents such as moving picture contents, music contents, and game contents.

  Further, in the above description, an example in which an image file is bit-shifted has been described.

  Further, in the above description, the content distribution apparatus 10 performs the encryption process of the electronic book content when the transmission request of the electronic book content is received from the terminal apparatus 20. However, the transmission request from the terminal apparatus 20 is received. Encryption processing may be performed prior to being stored in the storage unit 12. Thereby, it is possible to quickly transmit the electronic book content requested to be transmitted from the terminal device 20.

  When the number of users is large, it is necessary to increase the storage capacity of the storage unit 12 if all electronic book contents are encrypted in advance for all users. Therefore, when the number of users is large, it is desirable that only electronic book content satisfying a predetermined condition is encrypted in advance and stored in the storage unit 12, thereby reducing the storage capacity. For example, the official version of the electronic book content corresponding to the browsing electronic book content browsed by the user is encrypted in advance, and the others are encrypted when there is a transmission request. Since the electronic book content for browsing is encrypted with the shared key, it may be stored in the storage unit 12 by performing the encryption process before the transmission request from the terminal device 20 is received. desirable.

  Further, in the content distribution apparatus 10, the first data and the digital watermark image are combined into one package, and the package is encrypted using the user key as an encryption key. Watermark image) may be transmitted to the terminal device 20. In this way, the encryption process is only required once, and the processing load can be reduced.

  As described above, some of the embodiments of the present invention have been described in detail with reference to the drawings. However, these are merely examples, and various embodiments can be made based on the knowledge of those skilled in the art including the aspects described in the section of the disclosure of the invention. The present invention can be implemented in other forms that have been modified or improved.

DESCRIPTION OF SYMBOLS 10 Content delivery apparatus 12 Storage part of content delivery apparatus 13 Control part of content delivery apparatus 13a Receiving means 13b User key presence determination means 13c User key generation means 13d, 13d 'Data acquisition means 13e, 13e' Bit shift means 13f Dividing means 13g Digital watermark image generation means 13h Encryption means 13i Transmission means 20 Terminal apparatus 22 Display section 23 Operation section 24 Terminal apparatus storage section 25 Terminal apparatus control section 25a Receiving means 25b Request processing means 25c Decoding means 25d Coupling means 25e, 25e 'Bit shift means 25f, 25f' Display control means 25g Transmission means

Claims (13)

In a content distribution system including a content distribution device that distributes electronic content to a terminal device,
The content distribution device includes:
Dividing means for dividing the data constituting the electronic content into first data including at least part of data configuration information defining a data configuration of a data body and other second data;
Generating means for generating a user key corresponding to a user of the terminal device;
Encryption means for encrypting the first data with the user key generated by the generation means;
First data transmission means for transmitting the first data encrypted by the encryption means to the terminal device;
Second data transmitting means for transmitting the second data to the terminal device;
User key transmission means for transmitting the user key to the terminal device,
The terminal device
First data receiving means for receiving the encrypted first data from the content distribution device;
Second data receiving means for receiving the second data from the content distribution device;
User key receiving means for receiving the user key from the content distribution device;
Decryption means for decrypting the encrypted first data with the user key;
Combining means for combining the first data decoded by the decoding means and the second data ;
The electronic content includes a plurality of data files as the data body, and is data in one file format.
The first data includes at least a part of the data configuration information and a part of the data file, and a part of the data file is a header added to the data file. Content distribution system. The content distribution device includes:
Image generation means for generating digital watermark image data;
Image encryption means for encrypting the data of the digital watermark image by the user key;
Image transmitting means for transmitting the encrypted digital watermark image data to the terminal device,
The terminal device
Image receiving means for receiving data of the encrypted digital watermark image;
Digital watermark image decrypting means for decrypting the encrypted digital watermark image data with the user key;
2. The content distribution system according to claim 1, further comprising display control means for superimposing the digital watermark image on the electronic content restored by the combining means and displaying the image on the display means. The generating means includes
The content distribution system according to claim 1 or 2, wherein the data amount of the first data is changed according to a load state or a time zone of the content distribution device. The electronic content includes electronic book content for browsing and electronic book content for purchase,
The encryption means includes
When the electronic content separated by the dividing means is the electronic book content for purchase, the first data is encrypted by the user key generated by the generating means, and the electronic content separated by the dividing means is In the case of the electronic book content for browsing, the first data is encrypted with a common key common to all the terminal devices,
The terminal device
A shared key storage means for storing the shared key;
The decoding means includes
When the encrypted first data is data of the electronic book content for purchase, the encrypted first data is decrypted with the user key, and the encrypted first data is used for browsing The encrypted first data is decrypted with the shared key stored in the shared key storage means when the data is the electronic book content data of The content distribution system according to any one of claims . The content distribution device includes:
Separating means for separating a predetermined data file from the electronic content;
Link destination changing means for changing the link destination information of the predetermined data file included in the electronic content from link destination information indicating that it is in the electronic content to link destination information indicating that it is in the content distribution device; With
The dividing means includes
The data constituting the electronic content after the predetermined data file is separated by the separating means and the link destination information of the predetermined data file is changed by the link destination changing means is the first data and the data Divided into the second data other than
The terminal device
File acquisition means for acquiring the predetermined data file from the content distribution device based on the link destination information included in the electronic content generated by combining by the combining means.
The content distribution system according to claim 1, wherein the content distribution system is a content distribution system. The content distribution device includes:
Means for bit-shifting the data file included in the data constituting the electronic content in a predetermined direction;
The terminal device
The content distribution system according to any one of claims 1 to 5, further comprising means for bit-shifting the data file in a direction opposite to the predetermined direction. Storage means for storing a user ID and the user key in association with each other;
Means for obtaining a user ID from the terminal device,
The encryption means includes
The content distribution system according to any one of claims 1 to 6 , wherein a user key corresponding to the acquired ID is read from the storage unit and the first data is encrypted. The generating means includes
The content distribution system according to claim 7 , wherein the user key is generated based on a user ID acquired from the terminal device. The terminal device
The encrypted first data received by the first data receiving means, the second data received by the second data receiving means, and the user key received by the user key receiving means Storage means for storing;
Selecting means for selecting electronic content to be displayed on the display means,
The decoding means includes
Obtaining the encrypted first data corresponding to the selected electronic content from the storage means and decrypting it with the user key;
The coupling means includes
It claims 1-8, characterized in that to obtain the second data corresponding to electronic content wherein selected from the memory means is coupled to the first data the second data is the decoded The content distribution system according to item 1. In a content distribution device that distributes electronic content to a terminal device,
Dividing means for dividing the data constituting the electronic content into first data including at least part of data configuration information defining a data configuration of a data body and other second data;
Generating means for generating a user key corresponding to a user of the terminal device;
Encryption means for encrypting the first data with the user key generated by the generation means;
First data transmission means for transmitting the first data encrypted by the encryption means to the terminal device;
Second data transmitting means for transmitting the second data to the terminal device;
User key transmitting means for transmitting the user key to the terminal device;
Program transmitting means for transmitting a predetermined program to the terminal device,
The electronic content includes a plurality of data files as the data body, and is data in one file format.
The first data includes at least a part of the data configuration information and a part of the data file, and a part of the data file is a header added to the data file,
The predetermined program includes a terminal device,
First data receiving means for receiving the encrypted first data from the content distribution device;
Second data receiving means for receiving the second data from the content distribution device;
User key receiving means for receiving the user key from the content distribution device;
Decryption means for decrypting the encrypted first data with the user key;
A content distribution apparatus that functions as a combining unit that combines the first data decrypted by the decrypting unit and the second data. In a content distribution device that distributes electronic content to a terminal device,
Dividing means for dividing the data constituting the electronic content into first data including at least part of data configuration information defining a data configuration of a data body and other second data;
Generating means for generating a user key corresponding to a user of the terminal device;
Encryption means for encrypting the first data with the user key generated by the generation means;
First data transmission means for transmitting the first data encrypted by the encryption means to the terminal device;
Second data transmitting means for transmitting the second data to the terminal device;
User key transmission means for transmitting the user key to the terminal device ,
The electronic content includes a plurality of data files as the data body, and is data in one file format.
The first data includes at least a part of the data configuration information and a part of the data file, and a part of the data file is a header added to the data file. Content distribution device. In a content distribution program for causing a computer to execute processing for distributing electronic content to a terminal device,
Dividing the data constituting the electronic content into first data including at least a part of data configuration information defining a data configuration of a data body and other second data;
Generating a user key corresponding to the user of the terminal device;
Encrypting the first data with the user key;
Transmitting the encrypted first data to the terminal device;
Transmitting the second data to the terminal device;
Transmitting the user key to the terminal device;
Causing the computer to execute a process of transmitting a predetermined program to the terminal device;
The electronic content includes a plurality of data files as the data body, and is data in one file format.
The first data includes at least a part of the data configuration information and a part of the data file, and a part of the data file is a header added to the data file,
The predetermined program is
Receiving the encrypted first data from the computer;
Receiving the second data from the computer;
Receiving the user key from the computer;
Decrypting the encrypted first data with the user key;
A content distribution program that causes the terminal device to execute a process of combining the decrypted first data and the second data. In a content distribution method for distributing electronic content from a content distribution device to a terminal device,
The content distribution device is
Wherein the data constituting the electronic content is divided into a first data including at least a portion of the data structure information that defines the data structure of the data body and the other of the second data,
It generates a user key corresponding to the user of the terminal device,
Encrypting said first data by said user key,
Transmitting a first data the encrypted to the terminal device,
Transmitting said second data to said terminal device,
Transmitting the user key to said terminal device,
The electronic content includes a plurality of data files as the data body, and is data in one file format.
The first data includes at least a part of the data configuration information and a part of the data file, and a part of the data file is a header added to the data file,
The terminal device is
Receiving the first data the encrypted from the computer,
Receiving the second data from the computer,
Receiving the user key from the computer,
The first data said encrypted decrypted by said user key,
Content distribution method is characterized that you couple the second data and the first data obtained by the decoding.

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