JP2004240952A - Content use management system, content use management method and client equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content delivery system for delivering a content in a delivery form according to the attribute of the content. <P>SOLUTION: The content delivery system 200 delivers a content key and content use condition for controlling the use of the content in client equipment 110 from a multicast delivery server 122 or a unicast delivery server 123. A content delivery management server determines the delivery method of delivering the content key and content use condition of each content according to the attribute of the content (compression format, compression ratio, content holder, etc.). An encrypted content delivery server 124 delivers only an encrypted content with unicasted content key and content use condition, and a multicast delivery server 122 multicasts an encrypted content with superposed content key and content use condition. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a content usage management system, a content usage management method, and a client device that include a server and a client device that distribute digital content such as music data and video data.

In a content distribution system via a network, content to be distributed is encrypted, and an encrypted content and a decryption key (hereinafter abbreviated as a content key) of the encrypted content are distributed to a user terminal.
There are the following two types of content key distribution methods. The unicast distribution distributes the content key one-to-one only to the client devices that have requested the use of the content, and the multicast distribution distributes the content key all at once to the client devices that do not request the use of the content. Conventionally, in one content distribution system, the content key is distributed by the same distribution method regardless of the type of content (see Patent Document 1).
Japanese Patent Laid-Open No. 11-312175

  However, the number of clients that distribute the content key varies depending on the content. When there are many client devices that use content, unicast distribution distributes the content key after communicating with each client device, so that the server load is lower when performing multicast distribution than with unicast distribution. On the other hand, in unicast distribution, information such as which content key has been distributed to which client device can be recorded in a log, so that higher security than multicast distribution can be ensured in protecting copyright. In the prior art, the content key is distributed by either one of the distribution methods regardless of the content. Depending on the content, it is possible to reduce the server load by distributing the content key by the multicast distribution method. Is distributed in a high format. Moreover, although higher security is desired depending on the content, the content is distributed in a low-security manner.

  Accordingly, in view of the above problems, the present invention has an object to provide a content use management system capable of selectively distributing content decryption keys while reducing the communication load in the system or ensuring security. And

  The content usage management system according to the present invention is a content usage management system that distributes usage control data for controlling usage of content in a client device via a network, and transmits the usage control data to a plurality of client devices. One or more distribution servers that distribute according to different distribution methods, and a distribution management server that determines in which distribution method the usage control data of each content is distributed according to the attribute of the content, Any one of them is characterized in that the use control data is distributed according to the determined distribution method.

The content attribute may be a content compression format, and the distribution management server may determine a distribution method of the usage control data according to the compression format of each content.
The attribute of the content may be a content provider who provides the content, and the distribution management server may determine a distribution method of the usage control data according to the content provider of each content.

The content attribute may be a content compression rate, and the distribution management server may determine a distribution method of the usage control data according to the compression rate of each content.
The content attribute may be a content usage condition, and the distribution management server may determine a distribution method of the usage control data according to each content usage condition.

  The one or more distribution servers include a unicast distribution unit that distributes the usage control data according to a unicast distribution method that distributes data in response to a request from a client device, and a plurality of client devices at a predetermined distribution time. However, it may be provided with at least one of multicast distribution means for distributing the usage control data by a multicast distribution method for distributing data simultaneously.

The distribution management server refers to a distribution method determination rule holding unit that holds a distribution method determination rule indicating a rule for determining the distribution method, and the distribution method determination rule corresponding to the attribute of the content. And a distribution method determining means for determining the distribution method according to the distribution method determination rule.
In addition, the distribution server including the unicast distribution unit can further confirm that the client device is a pre-registered client device through communication with each client device, and the client device as a valid user. An authentication unit that is recognized as being present may be provided, and the unicast distribution unit may distribute the usage control data only to a client device that is recognized as a valid user by the authentication unit.

  The usage control data includes a decryption key for decrypting the encrypted content, and the client device acquires usage control data corresponding to each content from any of the distribution servers. Obtaining means, extracting the decryption key from the obtained usage control data, decrypting the content corresponding to the usage control data using the extracted decryption key, and reproducing the decrypted content Reproducing means may be provided.

The usage control data further includes usage conditions indicating conditions for using the content, and the client device further extracts the usage conditions from the acquired usage control data and is extracted. Reproduction control means for controlling the reproduction means so that the reproduction is performed within a range in which usage conditions are satisfied may be provided.
Furthermore, the content usage management method according to the present invention is a content usage management method for a server that distributes usage control data for controlling usage of content in a client device via a network, according to content attributes. A distribution method determining step for determining in which distribution method the usage control data for each content is distributed, and distribution for distributing the usage control data in a determined distribution method among a plurality of different distribution methods And a step.

In the content usage management method, a distribution method determination rule indicating a rule for determining the distribution method is stored in advance, and in the distribution method determination step, the distribution method determination rule corresponding to the attribute of the content is stored. The distribution method may be determined by referring to the distribution method determination rule.
Further, the client device according to the present invention is a client device in a content usage management system that distributes usage control data for controlling usage of content in the client device via a plurality of different distribution methods, Content request means for requesting content distribution to the content server that distributes the content, and usage control data corresponding to the requested content according to success or failure of acquisition of the content from the content server A distribution method determination unit that determines a distribution method, and a usage control data acquisition unit that acquires the usage control data from a distribution server that distributes the usage control data by the determined distribution method.

  In addition, from a content server that distributes content, a client device in a content usage management system that distributes usage control data for controlling the usage of content in a client device via a plurality of different distribution methods. Content acquisition means for acquiring content including information indicating a distribution method of usage control data corresponding to each content, information indicating the distribution method is extracted from the acquired content, and based on the extracted information The usage control data acquisition means for acquiring the usage control data from a distribution mode identifying means for identifying a distribution mode of usage control data corresponding to the content and a distribution server for distributing the usage control data in the identified distribution mode. Means.

  Further, the client device in the content usage management system that distributes the usage control data for controlling the usage of the content in the client device via a plurality of different distribution methods, the distribution method of the usage control data being A method information acquisition unit for acquiring information indicating a distribution method of each usage control data from a server to be determined, and a distribution method for identifying a distribution method of the usage control data corresponding to the content based on the information indicating the distribution method An identification unit and a usage control data acquisition unit that acquires the usage control data from a distribution server that distributes the usage control data by the identified distribution method may be provided.

  The present invention can be realized not only as such a content usage management system, but also as a content distribution management server, a user management server, an encrypted content distribution server, and a unicast distribution server constituting these content usage management systems. It can be realized as a stand-alone device such as a multicast distribution server and a client device, or can be realized as a content usage management method with the characteristic operations in these content usage management systems as a step, It can also be realized as a program that is executed by a computer. Needless to say, the program can be distributed via a computer-readable recording medium such as a CD-ROM or a transmission medium such as the Internet.

  As described above, according to the content usage management system of the present invention, the content usage management system includes the distribution server that distributes the usage control data by a plurality of different distribution schemes. By switching, it becomes possible to distribute the usage control data by an optimal distribution method from the viewpoint of ensuring the load on the distribution server and ensuring security.

  As described above, according to the client device of the present invention, the usage control data distribution method can be determined on the client device side even when the usage control data to be distributed by multicast is superimposed on the content. . As a result, even when the distribution method of the usage control data differs depending on the content, the usage control data can be acquired and the content can be used without any problem.

  In addition, according to another client device of the present invention, even when information indicating a distribution method of usage control data is superimposed on content, the distribution method of usage control data can be identified on the client device side. As a result, even when the distribution method of the usage control data differs depending on the content, the usage control data can be acquired and the content can be used without any problem.

  According to still another client device of the present invention, even when information indicating the distribution method of each usage control data is acquired from the server that determines the distribution method of the usage control data, the usage control data is obtained on the client device side. Can be identified. As a result, even when the distribution method of the usage control data differs depending on the content, the usage control data can be acquired and the content can be used without any problem.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 shows a conceptual diagram of a moving image content distribution service system according to an embodiment. The client device 110 is connected to a content distribution management server 121, a multicast distribution server 122, a unicast distribution server 123, an encrypted content distribution server 124, and a user management server 120 through a communication path 130 such as the Internet. The content distribution management server 121 is connected to the multicast distribution server 122, the unicast distribution server 123, the encrypted content distribution server 124, and the user management server 120 through a communication path 130 such as the Internet. The multicast distribution server 122 and the unicast distribution server 123 are collectively referred to as a content key distribution server.

The moving image content distribution service using this system is a service that provides an environment in which a user who has registered in advance can reproduce moving image content via the communication path 130 such as the Internet using the client device 110.
The content distributed to the user is encrypted by the content holder, and is once registered in the multicast distribution server 122 or the encrypted content distribution server 124 via the content distribution management server 121.

  The user acquires the encrypted content from the multicast distribution server 122 or the encrypted content distribution server 124. A key for decrypting the content (hereinafter referred to as a content key) and a content usage condition are distributed from either the multicast distribution server 122 or the unicast distribution server 123. Content for which the content key is unicast is registered in the encrypted content distribution server 124, and content for which the content key is multicast is registered in the multicast distribution server 122.

  The content use condition is a restriction item when the user uses the content, and the number of reproducible times, the reproducible period, the reproducible time and the like are set. The client device 110 decrypts the acquired encrypted content with the content key and reproduces it according to the content usage conditions. The reproducible number of times is a limit on the number of times the content is used, and the number of times decreases each time the content is used. The reproducible period is a period during which the content can be used, and can be used only when the date and time when the content is used is within the period. The reproducible time is the remaining time during which the content can be used, decreases by the time the content is used, and becomes unavailable when it reaches zero.

The components of this system will be described.
The client device 110 is a device on which a user reproduces content. The client device 110 has a client ID that is an identifier for uniquely identifying the device. The client ID is set at the time of factory shipment and is not changed by the user after the shipment. Note that the client device 110 can confirm by the client ID that it can receive the distribution of this system by the unicast distribution and the multicast distribution.

  The user management server 120 manages users who subscribe to the content distribution service using this system. The user management server 120 includes a user management database (hereinafter abbreviated as “DB”) 180. The user management DB 180 holds and manages a user ID for uniquely identifying a user, a user name, a password for authenticating the user, a client ID of the client device 110 used by the user, and the like.

An example of data held and managed by the user management DB 180 is shown in FIG.
In FIG. 2, the user name “User1” is set with the user ID “User — 1111” and the password “aaabbccc”, and indicates that the client device 110 with the client ID “123_abc” is owned. The user ID is assigned by the user management server at the time of user registration, and the password is set by the user himself.

  The content distribution management server 121 has a function of receiving a content distribution request from a content holder and determining a distribution method of a content key and content usage conditions. It also manages content holders and distribution methods for each content. The content distribution management server 121 includes a content holder management DB 140, a content distribution method management DB 141, and a distribution method determination rule DB 142. In the content holder management DB 140, in order to hold and manage information related to a content holder that receives a content distribution request, the content holder management DB 140 holds a content holder ID for uniquely identifying the content holder, a content holder name, a password for authentication, and the like. FIG. 3 shows an example of data held and managed by the content holder management DB 140.

FIG. 3 shows that, for example, the content holder name “C_HOLDER_1” is set with the content holder ID “Holder — 1111” and the password “abcrst”.
In the content distribution method management DB 141, a content ID for uniquely identifying a content, a content name, a content holder ID of a content holder that provides the content, a content compression format, a content key and a content usage condition distribution method, and content reproduction Maintain and manage time, data size of encrypted content, etc. FIG. 4 shows an example of data held and managed by the content distribution method management DB 141.

In FIG. 4, for example, the content name “Mountain Range of the World” is represented by the content ID “CONT — 0001” and is owned by the content holder ID “Holder — 1111”, the compression format is “MPEG-2”, and the distribution method is “ This indicates that the “unicast method”, the reproduction time “60 minutes”, and the data size “1,500 MB”.
The distribution method determination rule DB 142 holds and manages rules for determining a distribution method according to content. Details of data held and managed by the distribution method determination rule DB 142 will be described later.

  The multicast distribution server 122 distributes the content key and the content usage condition to the client device 110 owned by the user managed by the user management server 120 every day by IP multicast at a preset time. The multicast distribution server 122 includes a distribution schedule DB 150 and a multicast content DB 151. The distribution schedule DB 150 holds and manages the time for distributing the content key by multicast, the content ID of the content that can be reproduced with the distributed content key, the distributed content key, the content usage conditions, and the like. The multicast content DB 151 stores encrypted content data only for content for which content keys are distributed by multicast distribution. FIG. 5 is a diagram showing an example of a delivery schedule table held and managed by the delivery schedule DB 150.

  As shown in FIG. 5A, the content with the content ID “CONT — 0001” is encrypted with the content key “0xaaa ... aaaa”. In the content usage condition of the content ID “CONT — 0001”, a restriction “3 times of reproduction” is set, and the content key is set to be distributed at “12:00”. In addition to this, the distribution schedule table describes a file path indicating the storage location of each content in the multicast content DB 151.

  The unicast distribution server 123 is a server that distributes content keys and content usage conditions when requested by a user managed by the user management server 120. The unicast distribution server 123 includes a distribution data management DB 160. The distribution data management DB 160 holds and manages the content ID of content that can be reproduced with the content key to be distributed, the content key to be distributed, and the content usage conditions. An example of data managed by the distribution data management DB 160 is shown in FIG. In FIG. 6, the content with the content ID “CONT — 0001” is encrypted with the content key “0x1111... 1111”. The content usage condition of the content ID “CONT — 0001” indicates that a restriction of “reproduction count 3” is set.

  The encrypted content distribution server 124 is a server for the user to download encrypted content. The encrypted content distribution server 124 includes an encrypted content management DB 170 and a unicast content DB 171. The encrypted content management DB 170 holds and manages the content ID, the data size of the encrypted content, the file path where the encrypted content data is stored, and the like. The unicast content DB 171 stores encrypted content data for content for which content keys are distributed by unicast. FIG. 7 shows an example of data held and managed by the encrypted content management DB 170. In FIG. 7, the size of the encrypted content data of the content ID “CONT — 0001” is “1,500 MB”, the content key distribution method is unicast distribution, and the encrypted content data is “C: "\ Content \ cont_0001.enc".

  FIG. 8A and FIG. 8B show the difference in data structure between the encrypted content stored in the multicast content DB 151 and the encrypted content stored in the unicast content DB 171. FIG. 8A is a diagram showing a data structure of encrypted content stored in the unicast content DB 171 shown in FIG. FIG. 8B shows the data structure of the encrypted content stored in the multicast content DB 151 shown in FIG. As shown in FIG. 8A, the content to which the content key is distributed by unicast is composed of a content ID and encrypted content data. On the other hand, as shown in FIG. 8B, the content to which the content key is distributed by multicast includes a content ID, a content key, content usage conditions, encrypted content data, and the like. That is, a content key and a content usage condition are further superimposed on the content shown in FIG. The content key and the content usage condition data are protected by using a function that limits the client device 110 that can use the received data, so that only the specific client device 110 can be used. Specifically, it is assumed that the content key and content usage conditions that are superimposed and multicast on the content are encrypted in advance. The encrypted content key and the decryption key for decrypting the content usage conditions are distributed only to the user who has registered as a user. As a method for distributing the decryption key, a method for distributing the client device 110 in which the decryption key is previously written in a non-volatile memory such as a ROM (Read Only Memory) to a registered user, or a record in which the decryption key is recorded. There are methods for distributing media to registered users. As a result, the client device 110 of the user who has registered as a user can read the decryption key from the ROM, the distributed recording medium, or the like, and decrypt the content key and content usage conditions superimposed on the multicast content. . Using the decrypted content key, the client device 110 can decrypt the encrypted content and then use the content in accordance with the decrypted content usage conditions. Note that the decryption key for decrypting the encrypted content key does not necessarily have to be recorded and distributed in the ROM or the recording medium, as long as it is distributed in advance to the user who has registered by secure communication. Good. This encryption method is described in detail in Non-Patent Literature: Nakano et al., “Key Management Method for Digital Content Protection”, 2001 Cipher and Information Security Symposium Proceedings, 5A-5, 2001. Note that the method of making the multicast content key and content usage conditions available only to registered users is not limited to the digital content protection key management method, and may be another method. The encrypted content having such a data structure may be generated by the content distribution management server 121 and stored in the multicast content DB 151, or may be generated by the multicast distribution server 122 and stored in the multicast content DB 151.

The content registration terminal 100 is a terminal used when a content holder registers content to be distributed to the content distribution management server 121. Content registration will be described later.
Hereinafter, each process in the service will be described in order of registration of a distribution content by a content holder, a method for determining a distribution method, user registration by a user, and use of the user's content.

First, distribution content registration by a content holder will be described.
The content holder makes a content registration request to the content distribution management server 121 using the content registration terminal 100. FIG. 9 shows a flowchart of content registration processing by the content holder.
The content distribution management server 121 authenticates the content holder before receiving a distribution content registration request from the content holder. In the present embodiment, the content holder needs to be registered in the content holder management DB 140 in advance. The content holder transmits the content holder ID and password to the content distribution management server 121 via the communication path 130 using the content registration terminal 100 when a distribution content registration request is made. The content distribution management server 121 determines the success or failure of login by referring the received set of content holder ID and password to the data registered in the content holder management DB 140 (S901).

  After the content holder successfully logs in the content distribution management server 121 (S902), the content holder sends a registration request for the content to be distributed to the content distribution management server 121 (S903). At this time, the content holder transmits the encrypted content, the content key, the content usage condition, and the content metadata. In the present embodiment, the content compression format is MPEG-2, and the content is encrypted by AES (Advanced Encryption Standard) using a 128-bit key. For details on MPEG-2, see ISO / IEC 13818, and for AES, see FIPS-197.

  The metadata describes “content ID”, “content name”, “content holder name”, “compression format”, “playback time”, and “data size of encrypted content” that uniquely identify the content. Yes. FIG. 10 shows an example of metadata. In FIG. 10, the content name of the content with the content ID “CONT — 0001” is “World Mountain Range”, and the content holder that provides this content is “Content Holder_ABC”. The compression format is “MPEG-2”, the reproduction time is “60 minutes”, and the data size of the encrypted content is “1,500 MB”. The metadata may include “production year”, compression rate “average rate of CBR (Constant Bit Rate), VBR (Variable Bit Rate)”, and the like.

The content distribution management server 121 determines a content key distribution method to be registered from the content compression format in the metadata received by the content registration request from the content holder and the distribution method determination rule DB 142 (S904). The content key distribution method determination method will be described later.
When it is determined to be unicast distribution (S905), the content distribution management server 121 registers the content key, content usage conditions, metadata, and content distribution conditions in the unicast distribution server 123 (S906). At the same time, the content distribution management server 121 registers the encrypted content data in the encrypted content distribution server 124. Data stored and managed in the distribution data management DB 160 of the unicast distribution server 123 uses the data shown in FIG.

  When it is determined that multicast distribution is to be performed (S905), the content distribution management server 121 registers the content key, content usage conditions, metadata, and encrypted content data in the multicast distribution server 122 (S907). The multicast distribution server 122 stores the newly registered encrypted content data in the multicast content DB 151, adds the distribution schedule of the newly registered content at the time when the distribution schedule is available, and updates the distribution schedule DB 150. .

  FIG. 5 shows how the distribution schedule DB 150 is updated. As shown in FIG. 5A, the content ID “CONT — 0002”, the content key “0xbbbb... Bbb (128 bits)”, and the content usage condition “number of times of playback” are stored in the distribution schedule DB 150 before the update. Consider the case of adding a delivery schedule. Since the distribution schedule of “13:00” is vacant before the update, if the time is set as the distribution schedule of the content to be added and the distribution schedule DB 150 is updated, the post-update distribution shown in FIG. It will be in the state of schedule DB.

  The content distribution management server 121 registers the encrypted content in which the content key is unicast distributed to the encrypted content distribution server 124 after registering the content key and the content use condition in each distribution server according to the determined distribution method (S908). The process is terminated.

Details of the content key distribution method determination method in step S904 shown in FIG. 9 will be described with reference to FIG.
After receiving the content metadata from the content holder, the content distribution management server 121 determines the distribution method of the content key and the content usage conditions. Specifically, first, the content distribution management server 121 acquires a content key distribution method determination rule from the distribution method determination rule DB 142 (S1001).
In the present embodiment, it is assumed that the number of users who use the content changes depending on the content compression format, and the content compression format described in the content metadata is determined based on the content key and content usage condition distribution method determination. Parameter.

  FIG. 12A shows an example of data (distribution method determination rule) held and managed in the distribution method determination rule DB 142 of the present embodiment. In this rule, the compression format in the metadata of the content to be registered is used as a parameter for determining the distribution method. Using the parameters, the distribution method is determined according to the distribution method determination rule (S1002). In this case, when the compression format is MPEG-2 or AVI (Audio, Video, still Images), unicast distribution is selected, and when the compression format is MPEG-4, multicast distribution is selected. MPEG-4 is detailed in ISO / IEC 14496.

Hereinafter, another example of data (distribution method determination rule) managed by the distribution method determination rule DB 142 will be described.
FIG. 12B shows an example of a distribution method determination rule when a content holder ID is set as a parameter for determining the content distribution method, assuming that there is a request to change the distribution method according to the content holder. . In the case of the content holder IDs “Holder — 1111” and “Holder — 3333”, the unicast distribution is set. In the case of the content holder ID “Holder — 2222”, the multicast distribution is selected.

  FIG. 12 (c) shows an example of a distribution method determination rule when the number of users who use the content varies depending on the image quality of the content, and the parameter for determining the content distribution method is set to the average rate of CBR and VBR. . Here, multicast distribution is set when the average rate of CBR and VBR is less than 500 kbps, and unicast distribution is set when 500 kbps or more and less than 15 Mbps, and when 15 Mbps or more.

  FIG. 12 (d) assumes that there is a request to change the distribution method according to the elapsed time since the content was first distributed, and determines the distribution method when the parameter for determining the content distribution method is the content usage condition. An example of a rule is shown. When the content usage condition is “3 times of playback” and “Playback period 2003/01/01 to 2003/01/31”, unicast distribution, “No limit of playback” and “Playback period 2003/02” In the case of / 01 to 2003/02/28 ", it is set to select the multicast distribution.

Next, the user registration operation will be described with reference to FIG.
When using the content, the user registers in advance in the user management server 120. More specifically, first, the user uses the client device 110 to make a registration request to the user management server 120. Next, the user name, password, and client ID of the client device 110 used by the user are transmitted to the user management server (S1201). However, the client ID of the client device 110 may be manually input by the user together with the user name and password. However, the client device 110 automatically attaches the client ID to the user name and password input by the user and transmits them. Is common. Upon receiving the user registration request, the user management server 120 assigns a user ID (S1202), adds data to the user management DB 180 (S1203), notifies the client device 110 of the end of user registration, and ends.

Next, the user's content use operation will be described with reference to FIG.
The content use service is provided only to registered users, and needs to be authenticated by the user management server 120 once. Therefore, transmission / reception of data necessary for authentication is performed between the client device 110 and the user management server 120 (S1301). The client device 110 determines the success or failure of the authentication, and can perform the subsequent processing only when the authentication is successful (S1302).

When using the content, the user acquires information regarding the content currently being distributed from the content distribution management server 121 (S1303).
As shown in FIG. 4, content information includes content ID, content name, content holder name (or content holder ID) that provides content, compression format, content key distribution method, content playback time, encrypted content Data size etc. are included. The client device 110 generates a content list for requesting content distribution based on the information regarding the content acquired from the content distribution management server 121, and displays it to the user.

  The user selects content to be used from the content list (S1304). The client device 110 transmits a distribution request for the content selected from the content list to the encrypted content distribution server 124. The encrypted content distribution server 124 distributes the encrypted content only when the content key of the requested content is unicasted. If the client device 110 can obtain the encrypted content from the encrypted content distribution server 124, the client device 110 determines that the content key distribution method is unicast distribution (S1305). On the other hand, when the encrypted content cannot be acquired from the encrypted content distribution server 124, the client device 110 determines that the content key distribution method is multicast distribution.

Hereinafter, the content key of the selected content and the distribution method of the content usage conditions will be described.
A case where the content key of the selected content and the content usage condition are unicast distribution will be described. When it is determined that the content key of the selected content is distributed by unicast distribution, the client device 110 further checks whether or not the content key of the selected content is held in the client device 110. (S1306). When the client device 110 already holds the content key of the selected content, the reproduction processing on the client device 110 is performed using the held content key (S1311). If the client device 110 does not hold the content key of the selected content, authentication is performed between the user's client device 110 and the unicast distribution server 124, and communication with confidentiality / tamper resistance is ensured. (S1307). In this embodiment, no particular method is described for such a communication method, but SSL (Secure Sockets Layer) or the like is used. For SSL, see A. Frier et al., “The SSL 3.0 Protocol”, Netscape Communications Corp. Nov. Details on 18, 1996. Note that the authentication between the client device 110 and the unicast distribution server 123 may be an authentication using a PKI method or a common key method. Through the above-described communication, the client device 110 acquires the content key and the content usage condition from the unicast distribution server 123 (S1308). If the authentication with the unicast distribution server 123 fails in step S1307, the client device 110 ends the process.

  A case where the content key of the selected content and the content usage condition are multicast distribution will be described. When it is determined that the content key of the selected content is distributed by multicast distribution, the client device 110 checks whether or not the content key of the selected content is held inside the client device 110 (S1309). . When the client device 110 already holds the content key of the selected content, the reproduction processing on the client device 110 is performed using the held content key (S1311). When the client device 110 does not hold the content key of the selected content, the client device 110 receives content key distribution from the multicast distribution server 122. In the case of multicast distribution, the multicast distribution server 122 multicasts content, content keys, and content usage conditions based on a preset distribution schedule. Since the content key and the content usage condition are not held in the client device 110, the client device 110 waits for the next multicast distribution (S1310). The client device 110 can acquire the multicast distribution schedule from the multicast distribution server 122. The multicast distribution method in the present embodiment needs to be distributed only to the client device 110 used by the user managed by the user management server 120, and thus has a function of limiting the client device 110 that can use the received data. Realize with the delivery system provided. The specific implementation method is described in detail in Non-Patent Document: Nakano et al., “Key Management Method for Digital Content Protection,” 2001 Encryption and Information Security Symposium Proceedings, 5A-5, 2001.

In each distribution process, after acquiring the content, the content key, and the content use condition, a reproduction process is performed in the client device 110 (S1311).
Next, details of the reproduction processing inside the client device 110 in step S1311 of FIG. 14 will be described using FIG. 15 and FIG. FIG. 15 is a functional block diagram showing the configuration of the client device 110. FIG. 16 is a flowchart showing an operation of content reproduction processing in the client device 110 in step S1311 of FIG.

The client device 110 includes a communication unit 1401, a use condition determination unit 1402, an encrypted content storage unit 1403, a content decryption unit 1404, a content decoding unit 1405, a client ID storage unit 1406, a content key storage unit 1407, an input unit 1408, and request processing. A section 1409, a distribution method determination section 1410, and a screen output section 1411.
The communication unit 1401 is a function processing unit for communicating with various servers. The use condition determination unit 1402 is a function processing unit that determines whether a new use of content satisfies the content use condition. The encrypted content storage unit 1403 is a storage unit and function processing unit that stores encrypted content. The encrypted content acquired in step S1305 or step S1308 in FIG. 14 is stored in the encrypted content storage unit 1403. The content decryption unit 1404 is a function processing unit that decrypts encrypted content using a content key.

  The content decoding unit 1405 is a functional processing unit that decodes content according to the content compression format and outputs video and audio data. The client ID accumulation unit 1406 is a storage unit and a function processing unit that accumulates client IDs. When the client ID needs to be transmitted in communication with the server, the communication unit 1401 acquires the client ID from here. The content key storage unit 1407 is a storage unit and a function processing unit that store content keys and content usage conditions. The content key and content usage conditions acquired in step S1308 in FIG. 14 are stored in the content key storage unit 1407. An input unit 1408 is a function processing unit that inputs a request from a user. The request processing unit 1409 is a function processing unit that performs processing in response to a request input from the input unit 1408. The distribution method determination unit 1410 determines whether the content key of the content selected by the user is distributed by multicast or unicast. The screen output unit 1411 is a function processing unit that draws moving images to be reproduced and information from the server and presents them to the user.

  After the client device 110 acquires the content key stored in the content key storage unit 1407 and the content usage condition, the usage condition determination unit 1402 determines that the new usage of the content at the current time is the acquired content usage. It is confirmed whether or not the conditions indicated in the conditions are satisfied (S1501). For example, it is confirmed whether the reproducible number is not 0 or whether the date and time when the content is reproduced is within the reproducible period. When the content usage condition is satisfied, the usage condition determination unit 1402 transmits the content key stored in the content key storage unit 1407 to the content decryption unit 1404 (S1501). The content decryption unit 1404 acquires the encrypted content from the encrypted content storage unit 1403 and decrypts it using the content key acquired from the use condition determination unit 1402 (S1502). The decrypted data is transmitted to the content decoding unit 1405. The content decoding unit 1405 decodes the content according to the compression format, outputs video and audio data (S1503), and ends the process.

  As described above, according to the content distribution system 200 of the present embodiment, on the side that distributes content, content keys, and the like, the distribution method of content keys and content usage conditions is switched according to the attributes of each content. can do. Thereby, for example, when it is predicted that the distribution request of the content key and the content usage condition will be flooded with respect to the same content, the content key and the content usage condition are distributed by multicast, and the content distribution system 200 Server load can be reduced. In addition, when content copyright protection is given priority over the server load of the content distribution system 200, the content key and the content usage conditions are distributed by unicast to improve copyright safety. it can. On the client device 110 side, the internal distribution method determination unit 1410 can determine the distribution method of the content key and the content usage conditions, so that the content key and content usage conditions distributed by different distribution methods for each content can be determined. , Can be obtained without hindrance. As a result, the desired content can be used without any problem.

The content distribution management server 121, the multicast distribution server 122, the unicast distribution server 123, the encrypted content distribution server 124, and the user management server 120 are not independent, and one server may also function as another server.
Note that multicast distribution does not have to be performed every day.
In addition to the content compression format, the parameter for determining the content key distribution method may be a content holder ID, an average rate of CBR and VBR, a content usage condition, or the like.

In addition, the parameter that determines the distribution method of the content key may be specified to the content distribution management server 121 when the content holder registers the content, or the content distribution management server 121 may specify the content distribution system. It may be determined dynamically according to the load of each server at 200.
Note that the encrypted content acquisition method may be distribution by media or distribution by broadcast such as broadcast.

  In the embodiment described above, the client device 110 determines the content key distribution method by requesting the encrypted content distribution server 124 to distribute desired content. That is, the content key and content usage conditions distributed by multicast are superimposed on the content and distributed from only the multicast distribution server 122, but the present invention is not limited to this. For example, the client device 110 may determine the content key distribution method by reading information superimposed on the content. That is, information indicating the distribution method of the content key and the content usage condition may be superimposed on the content instead of the substance of the content key and the content usage condition. FIG. 17 is a diagram illustrating an example of a data structure of content when information indicating a content key distribution method is superimposed on encrypted content data. As shown in the figure, information indicating the distribution method of the content ID, the content key, and the content usage conditions is superimposed on the encrypted content data.

  In this case, after determining the distribution method of the content key and the content usage condition for each content, the content distribution management server 121 superimposes information indicating the determined distribution method on each content and registers it in the encrypted content distribution server 124. To do. Accordingly, the content is centrally distributed from the encrypted content distribution server 124 regardless of the distribution method of the content key and the content usage conditions. The content distribution management server 121 determines the content key and the content use condition distribution method for each content, and then determines the content key and the content use condition according to the determined distribution method, the unicast distribution server 123 and the multicast distribution server. 122 is registered.

  Correspondingly, in the client device 110, when the user intends to use the content, first, the encrypted content is acquired from the encrypted content distribution server 124. Thereafter, the distribution method determination unit 1410 determines the distribution method of the content key and the content usage condition from the information superimposed on the acquired encrypted content, and the content key and the content usage condition from the corresponding server according to the determination result. To get. That is, when it is determined that the distribution method of the content key and the content usage condition is multicast, the distribution key 122 waits for the content key and the content usage condition to be distributed from the multicast distribution server 122, and distributes the content key and the content usage condition. If it is determined that the method is unicast, the unicast distribution server 123 is requested to distribute the content key and the content usage conditions. Hereinafter, the content reproduction processing in the client device 110 is as already described with reference to FIG.

  Further, the client device 110 may acquire information for specifying the distribution method of the content key and the content usage condition from the server. Specifically, the client device 110 requests information related to the content from the content distribution management server 121 in the process of step S1303 shown in FIG. In response to a request from the client device 110, the content distribution management server 121 reads the data (information regarding the content) illustrated in FIG. 4 from the content distribution method management DB 141 and transmits the data to the client device 110. The client device 110 refers to the information about the content acquired from the content distribution management server 121, determines the content key distribution method, and acquires the content key and the content usage condition from the server corresponding to the determined distribution method.

According to this method, it is not necessary for the client device 110 to acquire the content before the content key and the content usage condition, and even if the content is acquired after acquiring the content key and the content usage condition, there is no problem. Content can be used.
Note that the encrypted content may have the data structure shown in FIG. 8A regardless of the distribution method of the content key, and the encrypted content distribution server 124 may manage and distribute it centrally. Of course, as in the above embodiment, only the content whose content key is distributed by unicast is distributed from the encrypted content distribution server 124 with the data structure shown in FIG. 8A, and the content key is distributed by multicast. The content may be distributed from the multicast distribution server 122 with the data structure shown in FIG. Further, although the load on the unicast distribution server 123 increases, the encrypted content distribution server 124 is eliminated, and the unicast distribution server 123 and the multicast distribution server 122 instead have the data structure shown in FIG. Content may be distributed.

  Note that the content distribution management server 121 does not have to transmit the information regarding the content in the list as shown in FIG. 4 in response to the request from the client device 110. For example, the client device 110 may inquire about the distribution method of the content key and the content usage conditions for each content to be used. On the other hand, the content distribution management server 121 may return the distribution method of the content key and the content usage conditions only for the inquired content. In this way, the processing load on the content distribution management server 121 increases, but the processing load for determining the distribution method in the client device 110 decreases.

  Further, instead of the content distribution management server 121 transmitting the information about the content in response to the request from the client device 110, the information about the content may be distributed to the client device 110 in advance by broadcasting or multicasting.

  The client device of the present invention is useful as a content playback device having a communication function, a personal computer, a PDA (Personal Digital Assistant), a mobile phone, an STB (Set Top Box), and the like.

It is a conceptual diagram of the content delivery service system in this invention. It is a figure which shows an example of the management data of user management DB. It is a figure which shows an example of the management data of content holder management DB. It is a figure which shows an example of the management data of content delivery system management DB. (A) is a figure which shows an example before the update of the delivery schedule table hold | maintained by delivery schedule DB. (B) is a figure which shows an example after the update of the delivery schedule table hold | maintained by delivery schedule DB. It is a figure which shows an example of the management data of distribution data management DB. It is a figure which shows an example of the management data of encryption content management DB. (A) is a figure which shows the data structure of the encryption content stored in unicast content DB shown in FIG. (B) is a figure which shows the data structure of the encrypted content stored in multicast content DB shown in FIG. It is a flowchart of the registration of the content by a content holder. It is a figure which shows an example of the metadata of content. It is a flowchart of the determination method of the delivery method of a content key and usage conditions. (A) is a figure which shows an example of the management data of the delivery system determination rule DB in case a parameter is a compression format of a content. (B) is a figure which shows an example of the management data of the delivery system determination rule DB in case a parameter is content holder ID. (C) is a figure which shows an example of the management data of distribution system decision rule DB in case a parameter is the average rate of CBR and VBR. (D) is a figure which shows an example of the management data of the delivery system determination rule DB in case a parameter is content usage conditions. It is a flowchart of user registration. It is a flowchart until content utilization. It is a functional block diagram which shows the structure of a client apparatus. It is a flowchart which shows the reproduction | regeneration processing in a client apparatus. It is a figure which shows an example of the data structure of a content in case the information which shows the delivery method of a content key is superimposed on encryption content data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Content registration terminal 110 Client device 120 User management server 121 Content distribution management server 122 Multicast distribution server 123 Unicast distribution server 124 Encrypted content distribution server 130 Communication path 140 Content holder management DB
141 Content distribution method management DB
142 Distribution method decision rule DB
150 Delivery schedule DB
151 Multicast content DB
160 Distribution data management DB
170 Encrypted content management DB
171 Unicast Content DB
180 User management DB
200 Content Distribution System 1401 Communication Unit 1402 Usage Condition Determination Unit 1403 Encrypted Content Storage Unit 1404 Content Decryption Unit 1405 Content Decoding Unit 1406 Client ID Storage Unit 1407 Content Key Storage Unit 1408 Input Unit 1409 Request Processing Unit 1410 Distribution Method Determination Unit 1411 Screen Output section

Claims (43)

A content usage management system that distributes usage control data for controlling usage of content in a client device via a network,
One or more distribution servers for distributing the usage control data to a client device by a plurality of different distribution methods;
A distribution management server that determines in which distribution method the distribution control data of each content is distributed according to the attribute of the content;
Any one of the distribution servers executes distribution of the usage control data according to the determined distribution method. The content attribute is a content compression format,
The content usage management system according to claim 1, wherein the distribution management server determines a distribution method of the usage control data in accordance with a compression format of each content. The attribute of the content is a content provider that provides the content,
The content usage management system according to claim 1, wherein the distribution management server determines a distribution method of the usage control data according to a content provider of each content. The attribute of the content is a compression rate of the content,
The content usage management system according to claim 1, wherein the distribution management server determines a distribution method of the usage control data according to a compression rate of each content. The attribute of the content is a usage condition of the content,
The content usage management system according to claim 1, wherein the distribution management server determines a distribution method of the usage control data in accordance with usage conditions of each content. The one or more distribution servers are:
Unicast distribution means for distributing the usage control data by a unicast distribution method for distributing data in response to a request from a client device;
The apparatus according to claim 1, further comprising at least one of a multicast distribution unit that distributes the usage control data by a multicast distribution method that distributes data simultaneously to a plurality of client devices at a predetermined distribution time. Content usage management system. The delivery management server
A distribution method determination rule holding means for holding a distribution method determination rule indicating a rule for determining the distribution method;
The content usage management system according to claim 6, further comprising: a distribution method determination unit that refers to the distribution method determination rule corresponding to the attribute of the content and determines the distribution method according to the distribution method determination rule. The content use management system further includes:
A content server for distributing content to the client device;
The distribution management server further includes:
Method information generating means for generating information indicating the determined distribution method;
A method information transmitting means for transmitting the generated information indicating the distribution method to the content server in association with content;
The content use management system according to claim 7, wherein the content server distributes content including information indicating the distribution method. The client device is
Content acquisition means for acquiring content from the content server;
A distribution method identifying means for extracting information indicating the distribution method from the acquired content and identifying a distribution method of usage control data corresponding to the content based on the extracted information;
The content usage management system according to claim 8, further comprising usage control data acquisition means for acquiring the usage control data from any one of the distribution servers according to the identified distribution method. When the identified distribution method is a unicast distribution method, the usage control data acquisition unit requests the unicast distribution unit to distribute the usage control data corresponding to the acquired content, and is identified. The content use management system according to claim 9, wherein when the delivery method is a multicast delivery method, the system waits until a delivery time at which usage control data corresponding to the content is delivered. The distribution management server further includes:
Method information generating means for generating information indicating the determined distribution method;
A method information transmitting means for transmitting the generated information indicating the distribution method to the client device;
The client device is
Method information acquisition means for acquiring information indicating the distribution method from the distribution management server;
A distribution method identifying means for identifying a distribution method of usage control data corresponding to the content based on information indicating the distribution method;
The content usage management system according to claim 7, further comprising usage control data acquisition means for acquiring the usage control data from any of the distribution servers according to the identified distribution method. When the identified distribution method is a unicast distribution method, the usage control data acquisition unit requests the unicast distribution unit to distribute the usage control data corresponding to the acquired content, and is identified. The content use management system according to claim 11, wherein when the delivery method is a multicast delivery method, the system waits until a delivery time at which usage control data corresponding to the content is delivered. The distribution server comprising the unicast distribution means further includes
When it is confirmed that the client device is a pre-registered client device through communication with each client device, the authentication device recognizes the client device as a valid user,
The content usage management system according to claim 6, wherein the unicast distribution unit distributes the usage control data only to a client device that is recognized as a valid user by the authentication unit. The content use management system according to claim 13, wherein the authentication unit authenticates the client device by a PKI method. The content use management system according to claim 13, wherein the authentication unit authenticates the client device by a common key method. A distribution server comprising the multicast distribution means,
Multicast content storage means for storing multicast content including content and usage control data corresponding to the content,
The content usage management system according to claim 6, wherein the multicast distribution unit distributes the multicast content as the usage control data. The content use management system further includes:
A user management server that distributes a predetermined decryption key only to users registered in advance,
The distribution management server includes control data encryption means for encrypting the usage control data determined to be distributed by a multicast distribution method using a key corresponding to the predetermined decryption key,
The content usage management system according to claim 16, wherein the multicast content storage unit stores the multicast content including the encrypted usage control data. The content use management system further includes:
A content server that distributes only the content determined to be distributed by the unicast distribution method to the client device;
The content usage management system according to claim 16, wherein the unicast distribution means distributes only usage control data of each content distributed by the content server. The client device is
Content requesting means for requesting the content server to distribute content and acquiring the content;
A distribution method determination means for determining a distribution method of usage control data corresponding to the requested content in accordance with success or failure of acquisition of the content from the content server;
The content usage management system according to claim 18, further comprising usage control data acquisition means for acquiring the usage control data from any of the distribution servers according to the determination result. The distribution method determining means (1) determines that the usage control data is distributed by a unicast distribution method when the acquisition is successful, and (2) if the acquisition fails, the usage control data is multicast It is determined that it will be delivered by the delivery method,
The usage control data acquisition means: (1) When it is determined that the usage control data is distributed by a unicast distribution method, the usage control data acquisition means makes the content that has been successfully acquired to the distribution server distributed by the unicast distribution method. (2) When it is determined that the usage control data is distributed by the multicast distribution method, wait until the distribution time at which the multicast content including the content that has failed to be acquired is distributed. The content use management system according to claim 19, wherein: The multicast content includes encrypted usage control data;
The client device further includes:
Control data decryption key holding means for holding in advance a control data decryption key for decrypting the encrypted use control data;
Control data separating means for separating the usage control data from the acquired multicast content when it is determined that the usage control data is distributed by a multicast distribution method;
21. The content usage management system according to claim 20, further comprising: control data decryption means for decrypting the separated usage control data using the held control data decryption key. The usage control data includes a decryption key for decrypting the encrypted content,
The client device is
Usage control data acquisition means for acquiring usage control data corresponding to each content from any of the distribution servers;
Decryption means for extracting the decryption key from the acquired usage control data, and decrypting the content corresponding to the usage control data using the extracted decryption key;
The content use management system according to claim 1, further comprising: a reproducing unit that reproduces the decrypted content. The usage control data further includes usage conditions indicating conditions for using the content,
The client device further includes:
The reproduction control means for extracting the usage condition from the acquired usage control data and controlling the reproduction means so that the reproduction is performed within a range where the extracted usage condition is satisfied. Item 23. The content use management system according to Item 22. A content usage management method for a server that distributes usage control data for controlling usage of content in a client device via a network,
A distribution method determining step for determining in which distribution method the usage control data of each content is distributed according to the attribute of the content;
A distribution step of distributing the usage control data by a determined distribution method among a plurality of different distribution methods. In the content usage management method, a distribution method determination rule indicating a rule for determining the distribution method is stored in advance,
The content usage management method according to claim 24, wherein, in the distribution method determination step, the distribution method is determined according to the distribution method determination rule with reference to the distribution method determination rule corresponding to the attribute of the content. The content attribute is a content compression format,
26. The content usage management method according to claim 25, wherein, in the distribution method determination step, the distribution method of the usage control data is determined with reference to the distribution method determination rule corresponding to the compression format of each content. The attribute of the content is a content provider that provides the content,
26. The content usage management method according to claim 25, wherein, in the distribution method determination step, the distribution method of the usage control data is determined with reference to the distribution method determination rule corresponding to the content provider of each content. The attribute of the content is a compression rate of the content,
26. The content usage management method according to claim 25, wherein, in the distribution method determination step, the distribution method of the usage control data is determined with reference to the distribution method determination rule corresponding to the compression rate of each content. The attribute of the content is a usage condition of the content,
26. The content usage management method according to claim 25, wherein, in the distribution method determination step, the distribution method of the usage control data is determined with reference to the distribution method determination rule corresponding to the usage condition of each content. A client device in a content usage management system that distributes usage control data for controlling usage of content in a client device via a plurality of different distribution methods,
Content request means for requesting content distribution to a content server for distributing content and acquiring the content;
A distribution method determination means for determining a distribution method of usage control data corresponding to the requested content in accordance with success or failure of acquisition of the content from the content server;
A client device comprising: usage control data acquisition means for acquiring the usage control data from a distribution server that distributes the usage control data by the determined distribution method. The distribution method determining means (1) determines that the usage control data is distributed by a unicast distribution method in which a server distributes data in response to a request from a client device when the acquisition is successful. 2) When the acquisition fails, it is determined that the usage control data is distributed by a multicast distribution method in which the server distributes data to a plurality of client devices at a predetermined distribution time,
The usage control data acquisition means: (1) When it is determined that the usage control data is distributed by a unicast distribution method, the usage control data acquisition means makes the content that has been successfully acquired to the distribution server distributed by the unicast distribution method. The distribution of the corresponding usage control data is requested, and (2) when it is determined that the usage control data is distributed by the multicast distribution method, the content that failed to be acquired and the usage control data corresponding to the content are included. The client device according to claim 30, wherein the client device waits until a distribution time at which multicast content is distributed. The usage control data includes a decryption key for decrypting the encrypted content,
The client device further includes:
Decryption means for extracting the decryption key from the acquired usage control data, and decrypting the content corresponding to the usage control data using the extracted decryption key;
31. The client device according to claim 30, further comprising: a reproducing unit that reproduces the decrypted content. The usage control data further includes usage conditions indicating conditions for using the content,
The client device further includes:
The reproduction control means for extracting the usage condition from the acquired usage control data and controlling the reproduction means so that the reproduction is performed within a range where the extracted usage condition is satisfied. Item 33. The client device according to Item 32. A client device in a content usage management system that distributes usage control data for controlling usage of content in a client device via a plurality of different distribution methods,
Content acquisition means for acquiring content including information indicating a distribution method of usage control data corresponding to each content from a content server for distributing the content;
A distribution method identifying means for extracting information indicating the distribution method from the acquired content and identifying a distribution method of usage control data corresponding to the content based on the extracted information;
Client equipment comprising: usage control data acquisition means for acquiring the usage control data from a distribution server that distributes the usage control data by the identified distribution method. When the identified distribution method is a unicast distribution method in which a server distributes data in response to a request from a client device, the usage control data acquisition unit distributes the usage control data by a unicast distribution method. Multicast in which distribution server requests distribution of usage control data corresponding to acquired content, and the identified distribution method distributes data to a plurality of client devices all at once at a predetermined distribution time 35. The client device according to claim 34, wherein the client device waits until a distribution time at which usage control data corresponding to the content is distributed. A client device in a content usage management system that distributes usage control data for controlling usage of content in a client device via a plurality of different distribution methods,
Method information acquisition means for acquiring information indicating a distribution method of each usage control data from a server that determines the distribution method of the usage control data;
A distribution method identifying means for identifying a distribution method of usage control data corresponding to the content based on information indicating the distribution method;
Client equipment comprising: usage control data acquisition means for acquiring the usage control data from a distribution server that distributes the usage control data by the identified distribution method. When the identified distribution method is a unicast distribution method in which a server distributes data in response to a request from a client device, the usage control data acquisition unit distributes the usage control data by a unicast distribution method. Multicast in which distribution server requests distribution of usage control data corresponding to acquired content, and the identified distribution method distributes data to a plurality of client devices all at once at a predetermined distribution time 37. The client device according to claim 36, wherein when the method is a distribution method, the client device waits until a distribution time at which usage control data corresponding to the content is distributed. A server that distributes usage control data for controlling usage of content in a client device via a network,
A distribution method determining means for determining in which distribution method the usage control data of each content is distributed according to the attribute of the content;
A server comprising: a distribution unit that distributes the usage control data using a determined distribution method among a plurality of different distribution methods. The server further includes:
A distribution method determination rule holding means for holding in advance a distribution method determination rule indicating a rule for determining the distribution method;
39. The content usage management method according to claim 38, wherein the distribution method determination means refers to the distribution method determination rule corresponding to the content attribute and determines the distribution method according to the distribution method determination rule. A program for a server that distributes usage control data for controlling the usage of content on a client device to a client device via a network. The usage control data for each content is sent to the computer according to the content attribute. A distribution method determining step for determining which distribution method to distribute,
A program for executing a distribution step of distributing the usage control data in a determined distribution method among a plurality of different distribution methods. A program for a client device in a content usage management system that distributes usage control data for controlling usage of content in a client device via a plurality of different distribution methods, and distributes the content to a computer A content requesting step for requesting content distribution to the content server and acquiring the content;
A distribution method determination step of determining a distribution method of usage control data corresponding to the requested content according to success or failure of acquisition of the content from the content server;
A program for executing a usage control data acquisition step of acquiring the usage control data from a distribution server that distributes the usage control data by the determined distribution method. A program for a client device in a content usage management system that distributes usage control data for controlling usage of content in a client device via a plurality of different distribution methods, and distributes the content to a computer A content acquisition step of acquiring content including information indicating a distribution method of usage control data corresponding to each content from the content server;
A distribution method identifying step of extracting information indicating the distribution method from the acquired content, and identifying a distribution method of usage control data corresponding to the content based on the extracted information;
A program for executing a usage control data acquisition step of acquiring the usage control data from a distribution server that distributes the usage control data by the identified distribution method. A program for a client device in a content usage management system that distributes usage control data for controlling usage of content in a client device via a plurality of different distribution methods, the computer controlling the usage control data A method information acquisition step of acquiring information indicating a distribution method of each usage control data from a server that determines the distribution method;
A distribution method identifying step for identifying a distribution method of usage control data corresponding to the content based on information indicating the distribution method;
A program for executing a usage control data acquisition step of acquiring the usage control data from a distribution server that distributes the usage control data by the identified distribution method.

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