JP2011055310A - Content reproduction management device and receiver - Google Patents

Abstract

The present invention provides a technique for managing reproduction of content that has already been distributed to a receiving apparatus.
A content playback management device 3 stores a storage means 31 for storing a plurality of public keys and secret keys, a playback request receiving means 34 for receiving a playback request signal for content, and a right processing flag when it is not completed. Is a reproduction management determination unit 35a that determines to manage reproduction of distributed content, a key information acquisition unit 36 that acquires key information from the storage unit 31, and a key information encryption that encrypts key information using a user secret key. A key information transmitting means 39 for transmitting key information, a reproduction number updating means 40, and a message transmitting means 41.
[Selection] Figure 5

Description

  The present invention relates to content copyright protection, and more particularly, to a technique for managing reproduction of content distributed to a receiving device.

  In recent years, a book use service for sharing digital contents, such as books, that are subject to copyright protection on a network has been studied. Consider a case where such a book use service is applied to a broadcast service, for example. In general, in many business models for direct or indirect content distribution by content holders, copyright right processing is performed before content distribution, and content distribution is enabled after all right processing is completed. However, the enormous number of content broadcasts in the past has a large number of rights holders, and there are many cases where it is not easy to contact the rights holder. ing.

  Therefore, for example, the invention described in Patent Document 1 has been proposed for copyright protection on the content holder side when the content holder performs content distribution. In the invention described in Patent Document 1, the distribution device distributes the encrypted content including the copyright protection program, and performs mutual authentication between the copyright protection program received by the reception device and the built-in media player. Do. In the invention described in Patent Document 1, the receiving apparatus decrypts the encrypted content using a copyright protection program and reproduces it on the media player. As a result, the invention described in Patent Document 1 allows different copyright protection policies to be flexibly changed.

JP 2008-187421 A

  On the other hand, some of the above-described book use services adopt a post-approval method in which content distribution is performed without performing right processing, and when profit is generated, it is returned to the right holder. If this concept is applied to content distribution, all content including content for which rights processing has not been completed will be distributed. At the same time, when the right processing is advanced and the reproduction of the content is prohibited according to the request of the right holder, a means that the content holder can stop the distribution of the content and can also prohibit the reproduction of the distributed content of the receiving device is desired. become. However, in the invention described in Patent Literature 1, it is not possible to manage the reproduction of content that has already been distributed to the receiving device.

  Therefore, an object of the present invention is to solve the above-described problems and to provide a technique for managing reproduction of content even after the content has been distributed to a receiving device.

  The inventors of the present application examined a mechanism for distributing content that does not require copyright-related rights processing, completed content, and content that has not been rights-processed to the receiving device, regardless of the status of rights processing for each content. In this case, a mechanism for controlling the copyright processing regardless of the status of these rights processing is required. In particular, processing of a license agreement with the copyright owner is important for content that has not been subjected to right processing. Specifically, it is assumed that the content processing is not completed on the content holder side even after the content is distributed. When the right processing is confirmed, the result of the right processing must be applicable to the content already distributed to the receiving terminal. For example, when the reproduction of the content is prohibited as a result of the right processing, it is necessary to perform control so that the content cannot be reproduced even for the content already distributed to the receiving device.

  Here, when the content is scrambled and distributed, this mechanism cannot be supported if the receiving device continues to hold the key information distributed to the receiving device in order to release the scramble. At this time, even if the content is distributed to the receiving device, if the content cannot be reproduced, it can be considered that the right of the right holder is not infringed. For this reason, in the present invention, it is necessary to prevent the content from being played unconditionally using the control information (content key) already acquired by the receiving apparatus.

  As described above, the content reproduction management device according to the first invention of the present application provides the receiving device that uses the content key for decrypting the encrypted content that is the encrypted content, the first control information for encrypting the content key, A content reproduction management device that transmits second control information for decrypting a content key encrypted with the first control information, and manages at least reproduction of content distributed to the receiving device, comprising: storage means; A reproduction request receiving unit, a reproduction management determination unit, a control information management unit, a control information acquisition unit, a control information encryption unit, a control information transmission unit, and a reproduction number update unit are provided.

  According to this configuration, the content reproduction management apparatus stores a plurality of first control information and second control information by the storage unit. Further, the content reproduction management device receives a reproduction request signal for requesting reproduction of the content from the reception device by the reproduction request receiving means. The content reproduction management device determines that reproduction of the distributed content is managed by the reproduction management determination unit when the right processing flag added in advance to the content is incomplete, and the right processing flag is completed or If it is unnecessary, it is determined not to manage the reproduction of the distributed content.

  In the content reproduction management device, the control information management unit stores information indicating that the first control information and the second control information are transmitted to the reception device, together with information indicating the reception device, in the storage unit. The content reproduction management device, when it is determined by the control information acquisition means to manage the reproduction of the distributed content in the reproduction management determination means, the first control information different from the first control information transmitted last time; Second control information corresponding to the first control information transmitted to the receiving device in response to the previous reproduction request signal is acquired from the storage means. Then, the content reproduction management device encrypts the first control information and the second control information acquired by the control information acquisition unit by using the user secret key that is different for each reception device by the control information encryption unit. . Further, the content reproduction management apparatus transmits the first control information and the second control information encrypted by the control information encryption unit by the control information transmission unit.

  Here, a right processing flag indicating whether right processing is unnecessary, completed, or incomplete is added to the content before distribution. The content reproduction management device, when requested to reproduce the content distributed to the receiving device with respect to the content for which the right processing flag is incomplete, includes first control information and second control for managing the reproduction of the content. Information to the receiving device. Thereafter, every time the content reproduction is requested, the receiving apparatus manages the content reproduction using the first control information and the second control information. In this way, the content reproduction management device can manage the reproduction of the distributed content in the receiving device.

  In the content reproduction management apparatus according to the second invention of the present application, the storage means includes the first control information that is a public key in a public key cryptosystem and the second key that is a secret key in the public key cryptosystem. Control information is stored, the control information acquisition means, the public key and the secret key that is a key pair for the public key transmitted to the receiving device in response to the previous reproduction request signal, It is obtained from the storage means.

  Here, a secret key (second control information) transmitted to the receiving apparatus in response to a reproduction request signal of a certain content, and a public key (first control information) transmitted to the receiving apparatus in response to the previous reproduction request signal. And become a key pair. That is, the content reproduction management device transmits different first control information and second control information to the receiving device every time content reproduction is requested. Then, after receiving the first control information and the second control information, the receiving device decrypts the content key using the second control information, and uses the first control information different from the previous one to use the content key. Is encrypted and stored, and the content is reproduced after being stored. As a result, the content reproduction management device cannot continue to store the content key encrypted with the same key in the receiving device, and can prevent a situation in which the encrypted content key is decrypted and the content is reproduced.

  In the content reproduction management device according to the third invention of the present application, the storage means stores the first control information and the second control information, which are common keys in a common key cryptosystem. .

  Here, the common key (second control information) transmitted to the receiving apparatus in response to a reproduction request signal of a certain content, and the common key (first control information) transmitted to the receiving apparatus in response to the previous reproduction request signal. Corresponds. That is, the content reproduction management device transmits different first control information and second control information to the receiving device every time content reproduction is requested. Then, after receiving the first control information and the second control information, the receiving device decrypts the content key using the second control information, and uses the first control information different from the previous one to use the content key. Is encrypted and stored, and the content is reproduced after being stored. As a result, the content reproduction management device cannot continue to store the content key encrypted with the same key in the receiving device, and can prevent a situation in which the encrypted content key is decrypted and the content is reproduced.

  In addition, the content reproduction management device according to the fourth invention of the present application prohibits reproduction of the content when the preset reproduction prohibition flag indicates prohibition in the content to which the right processing flag indicating incomplete is added. A playback prohibition determining unit that determines that the content is to be transmitted; and a message transmission unit that transmits a playback prohibition message that prohibits playback of the content when the playback prohibition determination unit determines that the playback of the content is prohibited. It is characterized by.

  Further, the content reproduction management device according to the fifth invention of the present application determines whether or not a rights protection period preset for each content has expired, and the right processing flag indicating the incomplete is added. For content that has been determined that the right protection period has expired, further comprises a playback permission determination means for determining that the playback of the content is permitted, and the message transmission means is configured to allow the playback permission determination means to When it is determined that reproduction is permitted, a reproduction permission message for permitting reproduction of the content is further transmitted.

  In addition, the content reproduction management device according to the sixth invention of the present application determines whether or not the right protection period has expired, and the right protection period of the content to which the right processing flag indicating the completion is added. Reproduction condition output determination means for determining that the content reproduction condition is to be transmitted for those determined not to have expired, and the message transmission means transmits the content reproduction condition by the reproduction condition output determination means. If it is determined, information indicating a reproduction condition of the content is further transmitted.

  According to the content reproduction management apparatus according to the fourth to sixth inventions of the present application, it is possible to manage the reproduction of the content in the receiving apparatus according to the status of the content right processing.

  The receiving device according to the seventh invention of the present application uses a content key for decrypting encrypted content that is encrypted content, and includes first control information for encrypting the content key, and first control information. A receiving device that receives second control information for decrypting the encrypted content key from the content reproduction management device and manages at least reproduction of the distributed content; a storage unit; a reproduction request transmission unit; The control information receiving means, the control information decrypting means, the content key decrypting means, the reproducing means, and the control information updating means are provided.

  According to this configuration, the receiving device stores the encrypted content and the encrypted content key that is the content key encrypted with the first control information, by the storage unit. In addition, the reception device transmits a reproduction request signal for requesting reproduction of the content to the content reproduction management device by the reproduction request transmission unit. Then, the receiving device receives the first control information encrypted using a user secret key that is different for each receiving device by the control information receiving means, and the first playback information received from the content playback managing device according to the previous playback request signal. 2nd control information corresponding to 1 control information is received from a content reproduction | regeneration management apparatus. Further, the receiving apparatus decrypts the first control information and the second control information received by the control information receiving unit by using the user secret key by the control information decrypting unit.

  In addition, the receiving apparatus decrypts the encrypted content key stored in the storage unit into the content key by using the second control information decrypted by the control information decrypting unit by the content key decrypting unit. Then, the receiving device uses the content key decrypted by the content key decrypting unit to decrypt the encrypted content and reproduce the content by the reproducing unit. Further, the receiving apparatus encrypts the content key by the control information update unit using the first control information decrypted by the control information decryption unit, and stores the encrypted content key in the storage unit.

  That is, the receiving device encrypts the content key that can decrypt the content by using different first control information every time the content is reproduced. The content key encrypted using the first control information can be decrypted only with the second control information corresponding to the first control information. As a result, the content reproduction management device can manage the reproduction of the distributed content in the reception device, and thus the reception device can receive the content before the right processing is determined.

  Further, in the receiving apparatus according to the eighth invention of the present application, the control information receiving means includes the first control information that is a public key in a public key cryptosystem and the second key that is a secret key in the public key cryptosystem. Control information is received.

  Here, the secret key (second control information) transmitted to the receiving apparatus in response to a certain reproduction request signal and the public key (first control information) transmitted to the receiving apparatus in response to the previous reproduction request signal are It becomes a key pair. That is, the content reproduction management device transmits different first control information and second control information to the receiving device every time content reproduction is requested. Then, when the reproduction of the content is finished, the receiving device encrypts and stores the content key using the first control information different from the previous one, and when the content is reproduced next, the second device received at that time The content key is decrypted using the control information. As a result, the receiving device does not continue to store the content key encrypted with the same key, and can prevent a situation in which the encrypted content key is decrypted and the content is reproduced.

  The receiving apparatus according to the ninth aspect of the present invention is characterized in that the control information receiving means receives the first control information and the second control information, which are a common key in a common key cryptosystem. .

  Here, the common key (second control information) transmitted to the receiving apparatus in response to a certain reproduction request signal and the common key (first control information) transmitted to the receiving apparatus in response to the previous reproduction request signal are Correspond. That is, the content reproduction management device transmits different first control information and second control information to the receiving device every time content reproduction is requested. Then, when the reproduction of the content is finished, the receiving device encrypts and stores the content key using the first control information different from the previous one, and when the content is reproduced next, the second device received at that time The content key is decrypted using the control information. As a result, the receiving device does not continue to store the content key encrypted with the same key, and can prevent a situation in which the encrypted content key is decrypted and the content is reproduced.

According to the present invention, the following excellent effects can be obtained.
According to the first and seventh aspects of the present invention, since the reproduction of the content distributed in the receiving device can be managed, the content can be distributed to the receiving device before the right processing is determined.
According to the second, third, eighth, and ninth inventions of the present application, the receiving device does not continue to store the content key encrypted with the same key, and the encrypted content key is decrypted and the content is reproduced. Can be prevented.
According to the fourth to sixth inventions of the present application, in the receiving device, the reproduction of the content can be managed according to the status of the content right processing.

It is a block diagram explaining the outline of the content delivery system in this invention. It is a figure explaining the reproduction | regeneration management method of the content in this invention, (a) is a sequence diagram which shows the operation | movement at the time of the 1st reproduction | regeneration request | requirement, (b) shows the state of the content key and content in a receiver. FIG. It is a figure explaining the reproduction | regeneration management method of the content in this invention, (a) is a sequence diagram which shows the operation | movement at the time of the (n-1) th reproduction | regeneration request | requirement, (b) is the content key and content state in a receiver FIG. It is a figure explaining the reproduction | regeneration management method of the content in this invention, (a) is a sequence diagram which shows the operation | movement at the time of the nth reproduction | regeneration request | requirement, (b) shows the content key and content state in a receiving device. FIG. It is a block diagram which shows the structure of the content reproduction management apparatus of FIG. It is a figure which shows the data structure of the key information table which the memory | storage means of FIG. 1 memorize | stores. It is a figure which shows the data structure of the content management table which the memory | storage means of FIG. 5 memorize | stores. It is a figure which shows the data structure of the user private key table which the memory | storage means of FIG. 5 memorize | stores. It is a flowchart which shows operation | movement of the content reproduction | regeneration management apparatus of FIG. 10 is a flowchart showing the reproduction management process of FIG. 9. (A) is a flowchart showing the reproduction prohibition process of FIG. 9, (b) is a flowchart showing the reproduction permission process of FIG. 9, and (c) is a flowchart showing the reproduction condition output process of FIG. It is a block diagram which shows the structure of the receiver of FIG. 13 is a flowchart showing a reproduction request transmission process by the receiving apparatus of FIG. 13 is a flowchart showing content reproduction processing by the receiving apparatus of FIG. It is a block diagram which shows the structure of the receiver which concerns on 2nd Embodiment of this invention. FIG. 16 is a flowchart showing an operation of the receiving apparatus of FIG. 15. FIG. FIG. 16 is a flowchart showing an operation of the receiving apparatus of FIG. 15. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In each embodiment, means having the same function are denoted by the same reference numerals and description thereof is omitted.

(First embodiment)
[Outline of content distribution system]
The outline of the content distribution system according to the present invention will be described with reference to FIG. The content distribution system 1 distributes the content to the receiving device 5 regardless of the status of right processing, and manages whether or not to reproduce the content when the content is requested to be reproduced. Here, as shown in FIG. 1, the content distribution system 1 includes a content distribution device 2, a content reproduction management device 3, and a reception device 5.

  For example, the content distribution device 2 stores one or more content, encrypts the content, and distributes the encrypted content to the reception device 5 via the broadcast wave H. Note that the method for distributing content is not particularly limited, and the content distribution device 2 may distribute the content via the network N (not shown).

A content ID, a right processing flag, and a right protection period are added in advance to the content.
The content ID is an identifier that uniquely identifies the content.
The right processing flag is information indicating whether the right processing is incomplete, completed or unnecessary for the content.
The right protection period is information indicating the last day of the right protection period for the content.
The encrypted content is content that is encrypted so that it can be decrypted with a content key Kc described later.

  The content reproduction management device 3 manages the reproduction of the content distributed to the receiving device 5. Specifically, the content reproduction management device 3 stores a key information table (see FIG. 6), a content management table (see FIG. 7), and a secret key table (see FIG. 8) which will be described later. Also, the content reproduction management device 3 refers to these tables and transmits key information (public key Kp and secret key Ks) to the reception device 5 in response to a reproduction request signal from the reception device 5. Details of the content reproduction management device 3 will be described later.

The reproduction request signal is a signal for requesting reproduction of content, and includes, for example, a user ID and a content ID.
The user ID is an identifier that uniquely identifies the user. In the content distribution system 1, a player ID or a device ID may be used instead of the user ID.

  The number of reproductions indicates the number of times that the same user has requested reproduction of the same content. For example, if the reproduction request is the second time, the number of reproductions is 2, and if the reproduction request is n (n is an integer of 2 or more), the number of reproductions is n. Hereinafter, when the number of times of reproduction is n, the number of times of reproduction is n, and when the number of times of reproduction is the first time, it is referred to as initial reproduction.

The content key Kc is a key for decrypting encrypted content, for example, a key generated by a common key encryption method.
The user secret key Km is used for encryption and decryption of key information in the receiving device 5 and is a key that is different for each user. The user secret key Km is, for example, a key generated by a common key encryption method, but may be a key generated by a public key encryption method.

The public key Kp is a key for encrypting the content key Kc in the receiving device 5, and is a key generated by a public key cryptosystem. Below, the public key Kp corresponding to the reproduction number of times n and the public key Kp _n. The public key Kp corresponds to the first control information described in the claims.

The secret key Ks is a key for decrypting the content key Kc in the receiving device 5, and is a key generated by a public key cryptosystem. Hereinafter, the secret key Ks corresponding to the reproduction count n is referred to as a secret key Ks _n-1 . The secret key Ks corresponds to the second control information described in the claims.

  The receiving device 5 is a device that allows a user to view content. Specifically, the receiving device 5 stores an encrypted content in which the content is encrypted and an encrypted content key SKc in which the content key Kc is encrypted. Further, the receiving device 5 stores a user secret key Km unique to the user of the receiving device 5 in the tamper resistant device. Then, the reception device 5 transmits a reproduction request signal to the content reproduction management device 3, and decrypts the encrypted content key SKc and the encrypted content by using the key information transmitted in response to the reproduction request signal. Play. Further, each time the content is reproduced, the receiving device 5 encrypts the content key Kc using the key information. In FIG. 1, three receivers 5 are illustrated, but the number is not particularly limited.

[Content playback management method]
Hereinafter, a method for managing content reproduction in the content distribution system 1 will be described with reference to FIGS. 2 to 5 (see FIG. 1 as appropriate). In FIG. 2, the receiving device 5 stores the encrypted content in the external storage unit 54b (see FIG. 12) in advance. Furthermore, the content reproduction management device 3 stores a unique user secret key Km for each user, and the receiving device 5 stores a unique user secret key Km for each user.

  2A, 3A, and 4A show sequence diagrams of the content reproduction management device 3 and the reception device 5. FIG. 2 (b), 3 (b), and 4 (b) show the state of the content key Kc and the state of the encrypted content in the receiving device 5, as shown in FIGS. a) and FIG. 4A are shown correspondingly. That is, in FIG. 2B, FIG. 3B, and FIG. 4B, the content key Kc and the content are not stored in the temporary storage means 54a or the external storage means 54b, which will be described later, in the broken line portion. In the double line portion, it shows a state where it is encrypted and stored in the temporary storage means 54a or the external storage means 54b. In the solid line portion, it is encrypted in the temporary storage means 54a or the external storage means 54b. It shows the state that is stored without. That is, the broken line portion and the double line portion indicate that the content key Kc and the content are unavailable, and the solid line portion indicates that the content key Kc and the content are available. Indicates.

  First, when the user wants to reproduce the content stored in the receiving device 5, the user operates the receiving device 5 to input a reproduction request. Then, the receiving device 5 transmits a first playback request (playback request signal) to the content playback management device 3 (step S1).

Subsequent to the processing in step S1, the content reproduction management device 3 searches the content management table for the number of reproductions using the user ID and content ID included in the reproduction request signal transmitted in step S1 as search conditions. Further, the content reproduction management device 3 retrieves the content key Kc and the public key Kp ₁ by searching the key information table using the user ID, the content ID, and the retrieved number of reproductions as retrieval conditions. Then, the content reproduction management device 3 encrypts the content key Kc and the public key Kp ₁ with the user secret key Km, and transmits it as key information (content key Kc and public key Kp ₁ ) to the receiving device 5 (step S2). Thereafter, the content reproduction management device 3 updates (increments) the content management table.

  Following the processing in step S2, the receiving device 5 decrypts the key information input in step S2 with the user secret key Km (step S3). Here, for example, the receiving device 5 stores the content key Kc included in the decrypted key information in the temporary storage unit 54a that is an area that can be referred to only by the reproducing unit 60 described later (see FIG. 12).

Following the processing in step S3, the receiving device 5 copies the content key Kc, encrypts it with the public key Kp ₁ , and stores it as the encrypted content key SKc (step S4). Here, for example, the receiving device 5 stores the encrypted content key SKc in the external storage unit 54b which is an area that can be referred to from the outside. Note that the receiving device 5 deletes the public key Kp ₁ because it is not necessary in the subsequent processing.

  Subsequent to the processing in step S4, the receiving device 5 reads the encrypted content stored in the external storage unit 54b and copies it to the temporary storage unit 54a (step S5).

  Following the processing in step S5, the receiving device 5 decrypts the encrypted content copied to the temporary storage unit 54a with the content key Kc stored in the temporary storage unit 54a, and reproduces the content (step S6). Here, for example, the receiving device 5 may partially read the encrypted content from the external storage unit 54b and reproduce the read encrypted content while decrypting it with the content key Kc.

  Subsequent to the processing in step S6, the receiving device 5 deletes the content key Kc and the content stored in the temporary storage means 54a after the reproduction of the content is completed (step S7).

  Hereinafter, with reference to FIG. 3, a method of managing content reproduction at the (n-1) th time will be described (see FIGS. 1 and 2 as appropriate). First, the receiving device 5 transmits an (n-1) th playback request (playback request signal) to the content playback management device 3 (step S11).

Subsequent to the processing in step S11, the content reproduction management device 3 encrypts the key information (secret key Ks _n-2 and public key Kp _n-1 ) retrieved by searching the key table with the user secret key Km and receives it. It transmits to the apparatus 5 (step S12). Thereafter, the content reproduction management device 3 updates (increments) the content management table.

Subsequent to the processing in step S12, the receiving device 5 decrypts the key information input in step S12 with the user secret key Km (step S13). The receiving device 5 reads the encrypted content key SKc stored in the external storage unit 54b (step S14). The receiving device 5 decrypts the encrypted content key SKc read out in step S14 with the secret key Ks _n−2 decrypted in step S13 (step S15). Here, for example, the receiving device 5 stores the decrypted content key Kc in the temporary storage unit 54a.

Following the processing of step S15, the receiving device 5 copies the content key Kc stored in the temporary storage unit 54a, encrypts it with the public key Kpn _-1 , and stores it in the external storage unit 54b as the encrypted content key SKc. (Step S16). At this time, the encrypted content key SKc previously stored in the external storage unit 54b is overwritten or deleted. Note that the receiving device 5 deletes the secret key Ks _n−2 and the public key Kp _n−1 because they are not necessary in the subsequent processing.

  Subsequent to the processing in step S16, the receiving device 5 reads the encrypted content stored in the external storage unit 54b and copies it to the temporary storage unit 54a (step S17). The receiving device 5 decrypts the encrypted content copied to the temporary storage unit 54a with the content key Kc stored in the temporary storage unit 54a, and reproduces the content (step S18).

  Subsequent to the processing in step S18, the receiving device 5 deletes the content key Kc and the content stored in the temporary storage means 54a after the reproduction of the content is completed (step S19).

  Hereinafter, a method of managing content reproduction at the nth time will be described with reference to FIG. 4 (see FIGS. 1 and 2 as appropriate). First, the receiving device 5 transmits an n-th playback request (playback request signal) to the content playback management device 3 (step S21).

Following the processing of step S21, the content reproduction management device 3 encrypts the read key information by searching the key table (secret key Ks _n-1 and a public key Kp _n) at the user's private key Km, the receiving apparatus 5 (Step S22). Thereafter, the content reproduction management device 3 updates (increments) the content management table. Note that the secret key Ks _n−1 transmitted in step S22 constitutes a key pair with the public key Kpn ₋₁ transmitted in step S12 of FIG.

Following the processing in step S22, the receiving device 5 decrypts the key information input in step S22 with the user secret key Km (step S23). The receiving device 5 reads the encrypted content key SKc stored in the external storage unit 54b (step S24). The receiving device 5 decrypts the encrypted content key SKc read out in step S24 with the secret key Ks _n−1 decrypted in step S23 (step S25). Here, for example, the receiving device 5 stores the decrypted content key Kc in the temporary storage unit 54a.

Following the processing of step S25, the receiving device 5, encrypted with the public key Kp _n by copying the stored contents key Kc in the temporary storage 54a, and stores in the external storage unit 54b as the encrypted content key SKc ( Step S26). At this time, the encrypted content key SKc previously stored in the external storage unit 54b (that is, the encrypted content key SKc encrypted with the public key Kpn _-1 ) is overwritten or deleted. And The receiving device 5, since the secret key Ks _n-1 and a public key Kp _n is unnecessary in subsequent processing, to remove it.

  Subsequent to the process of step S26, the receiving device 5 reads the encrypted content stored in the external storage unit 54b and copies it to the temporary storage unit 54a (step S27). Further, the receiving device 5 decrypts the encrypted content copied to the temporary storage unit 54a with the content key Kc stored in the temporary storage unit 54a, and reproduces the content (step S28).

  Subsequent to the processing in step S28, the receiving device 5 deletes the content key Kc and the content stored in the temporary storage means 54a after the reproduction of the content is completed (step S29).

  As shown in FIGS. 2 to 4, the receiving device 5 does not continue to store the decrypted content and the content key Kc in a usable state. Then, only when the user wants to play back the content, the receiving device 5 uses the key information transmitted from the content playback management device 3 to decrypt the encrypted content key SKc and the encrypted content.

As described above, the secret key Ks _n-1 and the public key Kpn _-1 constitute a key pair. That is, the content key Kc encrypted with the public key Kpn _-1 included in the key information transmitted in response to the (n-1) th reproduction request signal is key information transmitted in response to the nth reproduction request signal. Can be decrypted only with the private key Ks _n−1 included in the. In other words, in the content distribution system 1, the content key Kc is encrypted with a different public key Kp every time the content is reproduced. For this reason, at the time of the n-th of reproduction, even as a secret key Ks _n-1 from the key information that has been transmitted from the content reproduction management unit 3 has been stolen, there after the content key Kc has been encrypted with the public key Kp _n For example, at that time, the encrypted content key SKc cannot be decrypted and acquired, and the content cannot be reproduced.

[Configuration of Content Playback Management Device]
Hereinafter, the configuration of the content reproduction management apparatus 3 will be described with reference to FIG. As shown in FIG. 5, the content reproduction management apparatus 3 includes a storage unit 31, a key information generation unit 32, a communication unit 33, a reproduction request reception unit 34, a determination unit 35, a key information acquisition unit (control information). Acquisition means) 36, user secret key acquisition means 37, key information encryption means (control information encryption means) 38, key information transmission means (control information transmission means) 39, and reproduction count update means (control information management). Means) 40 and message transmission means 41.

The storage unit 31 is, for example, a memory or a hard disk that stores a key information table, a content management table, and a user secret key table.
The key information generation unit 32 generates a public key Kp and a secret key Ks and registers them in the key information table, generates a content key Kc and registers it in the content management table, generates a user secret key Km, and Register in the private key table. Hereinafter, these tables will be sequentially described.

<Key information table>
The key information table, as shown in FIG. 6, the content ID, for each user ID and play times, which is a table for storing key information (the public key Kp _n and the secret key Ks _n-1). In FIG. 6, the public key Kp _n shown as "Kp _n _ user ID", was shown the secret key Ks _n-1 as "Ks _n-1 _ user ID". For example, in FIG. 6, when “content ID = 0001”, “user ID = 003”, and “number of times of reproduction = 2”, “Kp ₂ _003” corresponds to “Ks ₁ _003”.

  In the case of “number of times of reproduction = 1”, since it is not necessary to transmit the secret key Ks, this portion is left blank as shown in FIG. In this case, the content reproduction management device 3 transmits the content key Kc instead of the secret key Ks. In FIG. 6, the key information of “number of times of reproduction = 1” is the key information at the time of the first reproduction.

  Here, the key information generation unit 32 generates a plurality of key pairs of the public key Kp and the secret key Ks using, for example, an RSA (Rivest Shamir Adleman) encryption method as a public key encryption method. Specifically, the key information generation means 32 generates two prime numbers p and q using a pseudo random number generator (not shown), and obtains a value N obtained by multiplying them. Further, the key information generating unit 32 obtains the least common multiple L of the prime number p-1 and the prime number q-1. Then, the key information generating unit 32 obtains a value E that is larger than 1 and smaller than the least common multiple L and whose greatest common divisor with the least common multiple L is 1. Further, the key information generating unit 32 obtains a value D that is larger than 1 and smaller than the value E and satisfies the following formula (1). Through the above calculation, the key information generating unit 32 generates the public key Kp (E, N) and the secret key Ks (D, N) that are key pairs.

  E × D mod L = 1 Expression (1)

Then, the key information generation unit 32 repeats this calculation, generates a plurality of key pairs of public key Kp _n and the secret key Ks _n. Further, the key information generating means 32 includes the public key Kpn _-1 in the key information transmitted in response to the (n-1) th reproduction request signal and the key information transmitted in response to the nth reproduction request signal. These are registered in the key information table so that the secret key Ks _n-1 becomes a key pair.

<Content management table>
As shown in FIG. 7, the content management table includes, for each content ID, a content key Kc for encrypting and decrypting the content, a right processing flag for the content, a right protection period for the content, and reproduction of the content. It is a table for storing prohibition flags. In addition, the content management table stores the number of times content is reproduced for each content ID and user ID.

  In FIG. 7, the content key Kc is illustrated as “Kc_content ID”, the right processing flag is illustrated as “right processing”, the right protection period is illustrated as “protection period”, and the reproduction prohibition flag is set as “reproduction prohibition”. " For example, in FIG. 7, the content key Kc of “content ID = 0001” is “Kc_0001”.

  The reproduction prohibition flag is information indicating whether or not the content is prohibited from being reproduced by the receiving device 5. For example, the reproduction prohibition flag indicates that reproduction is prohibited, and “permission” indicates that reproduction is possible. Note that the playback prohibition flag is registered as “prohibited” by the operator of the content distribution system 1 when, for example, the initial value is “permitted” and the right processing of the content is confirmed and the playback of the content is prohibited. The

  Here, the key information generation means 32 generates the same number of content keys Kc as the content by the common key encryption method such as DES (Data Encryption Standard), Triple DES, AES (Advanced Encryption Standard), etc., and stores it in the content management table. Register each.

  The number of reproductions indicates the number of reproductions of content corresponding to the content ID for each content ID and user ID. For example, in FIG. 7, the number of reproductions of “content ID = 0001” and “user ID = 001” is 4. In FIG. 7, “reproduction count = 1” is the first reproduction. Note that the number of reproductions of the content management table is information indicating that the first control information and the second control information in the claims are transmitted to the receiving device. The user ID of the content management table is information indicating the receiver in the claims.

<User private key table>
As shown in FIG. 8, the user secret key table is a table that stores user secret keys Km of all users for each user ID. In FIG. 8, the user secret key Km is illustrated as “Km_user ID”. For example, in FIG. 8, the user secret key Km of “user ID = 001” is “Km — 001”.

  Here, the key information generating means 32 generates user secret keys Km for all users by a common key encryption method such as DES, triple DES, AES, etc., and registers them in the user secret key table.

  In addition, the key information generation unit 32 may use a public key based on a public key cryptosystem such as RSA as the user secret key Km used by the content reproduction management device 3. In this case, needless to say, the receiving device 5 uses a secret key that is a key pair as the public key as the user secret key Km in the receiving device 5.

Hereinafter, returning to FIG. 5, the description of the configuration of the content reproduction management apparatus 3 will be continued.
The communication unit 33 performs communication control with the receiving device 5 via the network N (see FIG. 1). Specifically, the communication unit 33 outputs the reproduction request signal from the receiving device 5 to the reproduction request receiving unit 34. Further, the communication means 33 receives the key information (secret key Ks and public key Kp) from the key information transmission means 39 and various messages (reproduction prohibition message, reproduction permission message and reproduction condition message) from the message transmission means 41. Transmit to the receiving device 5.

  The reproduction request receiving unit 34 receives a reproduction request signal from the receiving device 5 via the communication unit 33. Then, the reproduction request receiving unit 34 extracts the user ID and content ID included in the reproduction request signal and outputs them to the determination unit 35.

  The determination unit 35 searches the content management table using the content ID from the reproduction request reception unit 34 as a search condition. The determination unit 35 determines whether the following determination conditions (1) to (4) are satisfied based on the right processing flag, right protection period, and reproduction prohibition flag in the searched content management table.

  Here, the determination unit 35 includes a reproduction management determination unit 35a, a reproduction prohibition determination unit 35b, a reproduction permission determination unit 35c, and a reproduction condition output determination unit 35d. Then, the reproduction management determination unit 35a performs the following determination (1), and the reproduction prohibition determination unit 35b performs the following determination (2). Further, the reproduction permission determination unit 35c performs the following determination (3), and the reproduction condition output determination unit 35d performs the following determination (4).

Judgment result: Judgment condition (1) Reproduction management: When the right processing flag is not completed (2) Reproduction prohibition: When the right processing flag is incomplete and the reproduction prohibition flag is prohibited (3) Reproduction permission: Rights processing flag Is not completed and the rights protection period has expired (4) Playback condition output: Rights processing flag is completed and within the rights protection period

  At this time, the reproduction permission determination unit 35c and the reproduction condition output determination unit 35d determine that the right protection period has expired, for example, when the right protection period of the content management table is a date before the system date. Yes (expiration of rights protection period). Further, the reproduction permission determination unit 35c and the reproduction condition output determination unit 35d determine that the right protection period has not expired, for example, when the right protection period of the content management table is a date after the system date ( Within the protection period).

  Then, when the determination result is reproduction management, the reproduction management determination unit 35 a outputs the user ID and the content ID together with the determination result to the key information acquisition unit 36 and the user secret key acquisition unit 37. Further, when the determination result indicates that the reproduction is prohibited, the reproduction prohibition determination unit 35b outputs the user ID and the content ID together with the determination result to the message transmission unit 41. Then, when the determination result is reproduction permission, the reproduction permission determination unit 35 c outputs the user ID and the content ID together with the determination result to the message transmission unit 41. Furthermore, when the determination result is the reproduction condition output, the reproduction condition output determination unit 35d outputs the user ID and the content ID together with the determination result to the message transmission unit 41.

  If the reproduction management determination unit 35a determines not to manage content reproduction, the content reproduction management device 3 may not perform any processing. In this case, the content distribution device 2 may distribute the content to the receiving device 5, and the receiving device 5 may play the content unconditionally.

When the determination result is input from the determination unit 35, the key information acquisition unit 36 searches the content management table for the number of reproductions using the user ID and content ID from the determination unit 35 as search conditions. Then, when the number of reproductions is 2 or more, the key information acquisition unit 36 retrieves key information (secret key Ks and public key Kp) from the key information table using the user ID, the content ID, and the number of reproductions as search conditions. Further, the key information acquisition unit 36 outputs the user ID and content ID and the searched key information to the key information encryption unit 38. The key information acquisition unit 36 outputs the content key Kc and the public key Kp ₁ as key information to the key information encryption unit 38 in the case of the first reproduction.

  When the determination result is input from the determination unit 35, the user secret key acquisition unit 37 searches for the user secret key Km from the user secret key table using the user ID from the determination unit 35 as a search condition. Then, the user secret key acquisition unit 37 outputs the searched user secret key Km to the key information encryption unit 38.

The key information encryption unit 38 uses the user secret key Km from the user secret key acquisition unit 37 to encrypt the key information from the key information acquisition unit 36. Then, the key information encryption unit 38 outputs the user ID and content ID from the key information acquisition unit 36 and the encrypted key information to the key information transmission unit 39. Note that the key information encryption unit 38 encrypts the content key Kc and the public key Kp ₁ as key information in the case of the first reproduction.

The key information transmission unit 39 transmits the key information encrypted by the key information encryption unit 38 to the reception device 5 via the communication unit 33. The key information transmission unit 39 outputs the user ID and content ID from the key information encryption unit 38 to the reproduction count update unit 40. The key information encryption unit 38 transmits the encrypted key information (content key Kc and public key Kp ₁ ) to the receiving device 5 in the case of the first reproduction.

  The reproduction count update means 40 searches the content management table for the reproduction count using the user ID and content ID from the key information transmission means 39 as search conditions. Then, the playback count update means 40 increments the searched playback count (adds 1). The reproduction number update means 40 corresponds to the control information management means described in the claims. The content management table in FIG. 7 corresponds to information managed by the control information management unit.

  The message transmission unit 41 transmits a message according to the determination result of the determination unit 35 to the reception device 5 via the communication unit 33. Specifically, when the determination result indicates that reproduction is prohibited, the message transmission unit 41 transmits a reproduction prohibition message indicating content reproduction prohibition to the receiving device 5. In addition, when the determination result is reproduction permission, the message transmission unit 41 transmits a reproduction permission message indicating content reproduction permission to the receiving device 5.

  Further, when the determination result is a reproduction condition output, the message transmission unit 41 transmits a reproduction condition message in which the content reproduction condition is described to the receiving device 5. For example, the playback condition is set in advance by the administrator of the content playback management apparatus 3 and includes the maximum number of times of content playback and the maximum number of times of content replication.

[Operation of Content Playback Management Device]
<Overall operation>
Hereinafter, the overall operation of the content reproduction management apparatus 3 will be described with reference to FIG. 9 (see FIG. 5 as appropriate). First, the content reproduction management device 3 receives a reproduction request signal from the reception device 5 by the reproduction request receiving means 34 (step S31).

  Subsequent to the process of step S31, the content reproduction management device 3 extracts the user ID and the content ID included in the reproduction request signal received in step S31 by the reproduction request receiving unit 34 (step S32).

  Subsequent to the processing of step S32, the content reproduction management device 3 uses the determination means 35 to determine whether (1) reproduction management, (2) reproduction prohibition, (3) reproduction permission, or (4) reproduction condition output is described. It is determined whether or not the condition is satisfied (step S33). Then, the content reproduction management device 3 performs processing according to the determination result of step S33 (steps S40 to S70).

<Reproduction management processing>
Hereinafter, the details of the reproduction management process (step S40) in FIG. 9 will be described with reference to FIG. 10 (see FIGS. 5 and 9 as appropriate). First, the content reproduction management device 3 searches the user private key Km from the user private key table by using the user private key acquisition unit 37 using the user ID as a search condition (step S41).

  Following the processing of step S41, the content reproduction management device 3 uses the key information acquisition unit 36 to retrieve the number of reproductions from the content management table using the user ID and content ID as search conditions. Then, the content reproduction management apparatus 3 searches the key information (secret key Ks and public key Kp) from the key information table using the key information acquisition unit 36 by using the user ID, the content ID, and the number of reproductions as search conditions (step S42). ).

  Following the processing of step S42, the content reproduction management device 3 encrypts the key information acquired in step S42 using the user secret key Km by the key information encryption unit 38 (step S43).

  Following the processing in step S43, the content reproduction management device 3 transmits the key information encrypted in step S43 to the receiving device 5 by the key information transmission unit 39 (step S44).

  Subsequent to the processing of step S44, the content reproduction management apparatus 3 searches the content management table for the number of reproductions corresponding to the user ID and the content ID by the reproduction number updating means 40. Then, the content reproduction management device 3 increments the reproduction number by the reproduction number updating means 40 (step S45).

<Reproduction prohibition processing>
Hereinafter, the details of the reproduction prohibiting process (step S50) of FIG. 9 will be described with reference to FIG. 11A (see FIGS. 5 and 9 as appropriate). First, the content reproduction management device 3 outputs a reproduction prohibition message to the communication unit 33 by the message transmission unit 41 (step S51). Subsequent to the processing of step S51, the content reproduction management device 3 transmits a reproduction prohibition message to the reception device 5 through the communication unit 33 (step S52).

<Playback permission processing>
Hereinafter, the details of the reproduction permission process (step S60) of FIG. 9 will be described with reference to FIG. 11B (see FIGS. 5 and 9 as appropriate). First, the content reproduction management device 3 outputs a reproduction permission message to the communication unit 33 by the message transmission unit 41 (step S61). Subsequent to the process of step S61, the content reproduction management device 3 transmits a reproduction permission message to the receiving device 5 through the communication unit 33 (step S62).

<Reproduction condition processing>
Hereinafter, the details of the reproduction condition output process (step S70) of FIG. 9 will be described with reference to FIG. 11C (see FIGS. 5 and 9 as appropriate). First, the content reproduction management device 3 outputs a reproduction condition message to the communication unit 33 by the message transmission unit 41 (step S71). Subsequent to the process of step S71, the content reproduction management device 3 transmits a reproduction condition message to the receiving device 5 through the communication unit 33 (step S72).

[Receiver configuration]
Hereinafter, the configuration of the receiving device 5 will be described with reference to FIG. As shown in FIG. 12, the reception device 5 includes a reproduction request input unit 51, a reproduction request transmission unit 52, a communication unit 53, a storage unit 54, an encrypted content reception unit 55, and a key information reception unit (control). Information receiving means) 56, key information decrypting means (control information decrypting means) 57, key information updating means (control information updating means) 58, content key decrypting means 59, reproducing means 60, and display means 61. Prepare.

The reproduction request input means 51 requests the user to reproduce the content, and outputs a reproduction request signal to the reproduction request transmission means 52 in response to this request.
The reproduction request transmission unit 52 transmits the reproduction request signal from the reproduction request transmission unit 52 to the content reproduction management device 3 via the communication unit 53.

  The communication unit 53 performs communication control between the content distribution device 2 (see FIG. 1) and the content reproduction management device 3 (see FIG. 1) via the network N and the broadcast wave H. Specifically, the communication unit 53 transmits the reproduction request signal from the reproduction request transmission unit 52 to the content reproduction management device 3. Further, the communication unit 53 receives the key information (the secret key Ks and the public key Kp) from the content reproduction management device 3 and the encrypted content from the content distribution device 2.

  The storage unit 54 stores the encrypted content, the encrypted content key SKc, the decrypted content, the content key Kc, the user secret key Km, the secret key Ks, and the public key Kp. For example, the storage means 54 may be composed of a temporary storage means 54a, an external storage means 54b, and a tamper resistant device not shown. The temporary storage unit 54a is an area that can be referred to only by the reproduction unit 60 that stores the decrypted content and the content key Kc. Further, the external storage unit 54b is an area that can be referred to from the outside for storing the encrypted content and the encrypted content key SKc, and is, for example, a hard disk or a memory. Further, the tamper resistant device stores, for example, a user secret key Km, a secret key Ks, and a public key Kp.

  The encrypted content receiving unit 55 receives the encrypted content from the content distribution device 2 via the communication unit 53. Then, the encrypted content receiving unit 55 stores the received encrypted content in the storage unit 54 (external storage unit 54b).

The key information receiving unit 56 receives key information from the content reproduction management device 3 via the communication unit 53. Then, the key information receiving unit 56 outputs the received key information to the key information decrypting unit 57. Here, the key information receiving means 56 receives the content key Kc and the public key Kp ₁ as key information from the content reproduction management device 3 in the case of the first reproduction. The key information receiving unit 56 corresponds to the control information receiving unit described in the claims.

  The key information decrypting means 57 decrypts the key information from the key information receiving means 56 using the user secret key Km stored in the storage means 54 (tamper resistant device). Then, the key information decryption unit 57 stores the decrypted key information in the storage unit 54 (tamper resistant device). Here, the key information decryption means 57 stores only the decrypted public key Kp in the storage means 54 (tamper resistant device) in the case of the first reproduction. The key information decryption means 57 corresponds to the control information decryption means described in the claims.

  The key information update unit 58 reads the secret key Ks and the encrypted content key SKc stored in the storage unit 54 (tamper resistant device) and outputs them to the content key decryption unit 59. The key information update unit 58 receives the content key Kc decrypted by the content key decryption unit 59 from the content key decryption unit 59. Then, the key information update unit 58 encrypts the content key Kc with the public key Kp stored in the storage unit 54 (tamper resistant device), and stores the encrypted content key SKc in the storage unit 54 (external storage unit 54b). Remember me. As described above, it is preferable that the key information update unit 58 encrypts the decrypted content key Kc as soon as possible by using the public key Kp from the viewpoint of security. The key information update unit 58 corresponds to the control information update unit described in the claims.

  The content key decryption unit 59 decrypts the encrypted content key SKc from the key information update unit 58 using the secret key Ks from the key information update unit 58 and outputs the content key Kc to the reproduction unit 60. Further, the content key decrypting means 59 outputs the content key Kc to the key information updating means 58. Further, the content key decrypting means 59 outputs the content key Kc to the key information updating means 58.

Using the content key Kc from the content key decryption unit 59, the reproduction unit 60 decrypts the encrypted content stored in the storage unit 54 (external storage unit 54b) and reproduces the content. Here, the reproducing means 60 stores the content key Kc in the storage means 54 (temporary storage means 54a), for example. Then, the reproducing unit 60, for example, partially copies the encrypted content to the storage unit 54 (temporary storage unit 54a), and reproduces the copy while decrypting with the content key Kc.
The display unit 61 is, for example, a display that displays content to be played back by the playback unit 60.

In the receiving device 5, when the reproduction of the content is completed, the reproduction unit 60 deletes the content and the content key Kc stored in the storage unit 54 (temporary storage unit 54a).
In addition, when receiving a playback prohibition message from the content playback management device 3, the receiving device 5 prohibits playback of the content.
In addition, when receiving a playback permission message from the content playback management device 3, the receiving device 5 stores the content decrypted by the playback unit 60 in the storage unit 54, and plays back the content without management from the next playback. May be.

  In addition, when receiving a playback condition message from the content playback management apparatus 3, the receiving device 5 limits content playback according to the playback condition included in the playback condition message. Specifically, when the maximum number of reproductions is set as the reproduction condition, the receiving device 5 cannot reproduce the content more than the maximum number of reproductions. Further, when the maximum number of times of copying is set as the reproduction condition, the receiving device 5 prevents the content from being copied more than this maximum number of times of copying.

[Receiver operation]
<Playback request transmission process>
Hereinafter, with reference to FIG. 13, the reproduction request transmission process in the reception device 5 will be described (see FIG. 12 as appropriate). First, the receiving device 5 outputs a reproduction request signal to the reproduction request transmission unit 52 in response to a request from the user by the reproduction request input unit 51 (step S101). Subsequent to the processing in step S101, the receiving apparatus 5 transmits the reproduction request signal input in step S101 to the content reproduction management apparatus 3 by the reproduction request transmitting unit 52 (step S102).

<Content playback processing>
Hereinafter, the content reproduction processing in the receiving device 5 will be described with reference to FIG. 14 (see FIG. 12 as appropriate). In FIG. 14, it is assumed that the user secret key Km, the encrypted content key SKc, and the encrypted content are stored in the storage unit 54.

  First, the receiving device 5 receives the encrypted key information (secret key Ks and public key Kp) from the content reproduction management device 3 by the key information receiving unit 56. The receiving device 5 uses the key information decrypting unit 57 to decrypt this key information using the user secret key Km (step S111).

  Following the processing in step S111, the receiving device 5 stores the decrypted key information by the key information decrypting means 57 (step S112). Following the processing of step S112, the receiving device 5 reads the key information stored in step S112 by the key information update unit 58 (step S113).

  Following the processing in step S113, the receiving device 5 uses the content key decrypting unit 59 to decrypt the encrypted content key SKc using the key information (secret key Ks) read in step S113 (step S114).

  Following the processing in step S114, the receiving device 5 encrypts the content key Kc with the public key Kp by the key information update unit 58 and stores the encrypted content key SKc (step S115).

  Subsequent to the processing of step S115, the receiving device 5 uses the playback unit 60 to decrypt the encrypted content using the content key Kc decrypted in step S114 (step S116), and plays back the content (step S117). ). Thereafter, the receiving device 5 deletes the content key Kc and the content from the storage unit 54 (temporary storage unit 54a) by the reproduction unit 60.

As described above, the content reproduction management device 3 transmits different key information to the reception device 5 in response to the reproduction request signal from the reception device 5. Further, every time the content is reproduced, the receiving device 5 encrypts the content key Kc with a different public key Kp. Therefore, when the n-th reproduced, even as the secret key Ks _n-1 from the key information transmitted from the content reproduction management apparatus 3 is stolen, the receiving apparatus 5, the encrypted content key Kc using the public key Kp _n After that, the content key Kc cannot be decrypted and acquired, and the content cannot be reproduced. Furthermore, the content reproduction management device 3 transmits various messages to the receiving device 5 according to the status of the right processing. Then, the receiving device 5 performs processing such as prohibition or permission of content reproduction according to various messages. As described above, in the first embodiment of the present invention, since the reproduction of the distributed content can be managed, the content can be distributed to the receiving device before the right processing is determined.

In the present invention, when another user uses the same content key Kc, the encrypted content may be redistributed by the user.
The public key Kp may be the same key for all users, or a unique key for each user. At this time, when a public key Kp unique to each user is used, the public key Kp may not be encrypted when transmitted to the receiving device 5.

(Second Embodiment)
[Receiver configuration]
Hereinafter, with reference to FIG. 15, a reception apparatus 5A according to the second embodiment of the present invention will be described. In the second embodiment, the content reproduction management device 3 (see FIG. 5) has the same configuration as that of the first embodiment, and thus description thereof is omitted.

  As shown in FIG. 15, the receiving device 5A includes a reproduction request input unit 51, a reproduction request transmission unit 52, a display unit 61, a user secret key storage unit 62, a content key storage unit 63, and an encrypted content storage. Means 64, reproduction number storage means 65, encryption key information reception means (control information reception means) 66, encryption key information decryption means (control information decryption means) 67, key information extraction means 68, content key Output means 69, content key encryption key output means 70, content key encryption means (control information update means) 71, encrypted content key decryption key output means 72, content key decryption means 73, encryption Content receiving means 74, content key selecting means 75, encrypted content decrypting means 76, message receiving means 77, and content reproducing means 78.

  In FIG. 15, for simplicity of explanation, a means for processing content is a content processing section, a means for processing key information is a key information processing section, and a means for performing other processing is shown as another processing section. did. In FIG. 15, the communication means is not shown.

  The reproduction request input unit 51, the reproduction request transmission unit 52, and the display unit 61 are the same as the respective units in FIG.

The user secret key storage means 62 is a tamper resistant device that stores the user secret key Km.
The content key storage unit 63 is, for example, a hard disk or a memory that stores the encrypted content key SKc.
The encrypted content storage unit 64 is, for example, a hard disk or a memory that stores the encrypted content.
The reproduction frequency storage means 65 is a tamper resistant device that stores the reproduction frequency of the content for each content.

The encryption key information receiving unit 66 receives the encrypted key information (secret key Ks and public key Kp) from the content reproduction management device 3. Then, the encryption key information receiving unit 66 outputs the received key information to the encryption key information decrypting unit 67. Note that the encryption key information receiving unit 66 receives the content key Kc and the public key Kp ₁ from the content reproduction management device 3 as key information in the case of the first reproduction. Further, the encryption key information receiving unit 66 corresponds to the control information receiving unit described in the claims.

  The encryption key information decryption unit 67 decrypts the key information from the encryption key information reception unit 66 using the user secret key Km stored in the user secret key storage unit 62. Then, the encryption key information decrypting unit 67 outputs the decrypted key information to the key information extracting unit 68. The encryption key information decryption means 67 corresponds to the control information decryption means described in the claims.

  The key information extraction unit 68 refers to the number of reproductions stored in the reproduction number storage unit 65 and determines whether or not the reproduction is the first reproduction. For example, the key information extraction unit 68 determines that the first reproduction is performed if the number of reproductions is 1, and determines that the first reproduction is not performed if the number of reproductions is 2 or more. In the case of the first reproduction, the key information extraction unit 68 extracts the content key Kc and the public key Kp from this key information. Then, the key information extraction unit 68 outputs the content key Kc to the content key output unit 69 and outputs the public key Kp to the content key encryption key output unit 70.

  Further, the key information extracting means 68 extracts the secret key Ks and the public key Kp from this key information when it is not the first reproduction. Then, the key information extraction unit 68 outputs the public key Kp to the content key encryption key output unit 70 and outputs the secret key Ks to the encrypted content key decryption key output unit 72.

The content key output unit 69 outputs the content key Kc from the key information extraction unit 68 to the content key encryption unit 71 and the content key selection unit 75.
The content key encryption key output unit 70 outputs the public key Kp from the key information extraction unit 68 to the content key encryption unit 71.

  The content key encryption unit 71 encrypts the content key Kc from the content key output unit 69 using the public key Kp from the content key encryption key output unit 70 to generate an encrypted content key SKc. Then, the content key encryption unit 71 stores the encrypted content key SKc in the content key storage unit 63. The content key encryption unit 71 corresponds to the control information update unit described in the claims.

The encrypted content key decryption key output means 72 outputs the secret key Ks from the key information extraction means 68 to the content key decryption means 73.
The content key decryption unit 73 decrypts the encrypted content key SKc stored in the content key storage unit 63 using the secret key Ks from the encrypted content key decryption key output unit 72. Then, the content key decrypting unit 73 outputs the decrypted content key Kc to the content key selecting unit 75.

  The encrypted content receiving unit 74 determines whether or not the encrypted content is stored in the encrypted content storage unit 64. When the encrypted content is not stored, the encrypted content receiving unit 74 receives the encrypted content from the content distribution device 2 (see FIG. 1). The encrypted content receiving unit 74 stores the encrypted content in the encrypted content storage unit 64.

  The content key selection unit 75 selects the input of the content key Kc according to the number of reproductions stored in the reproduction number storage unit 65. Specifically, in the case of the first playback, the content key selection unit 75 selects the content key Kc from the content key output unit 69 and outputs it to the encrypted content decryption unit 76. When the number of times of reproduction is 2 or more, the content key selection unit 75 selects the content key Kc decrypted by the content key decryption unit 73 and outputs it to the encrypted content decryption unit 76.

  The encrypted content decrypting unit 76 uses the content key Kc from the content key selecting unit 75 to decrypt the encrypted content stored in the encrypted content storage unit 64. Then, the encrypted content decrypting unit 76 outputs the decrypted content to the content reproducing unit 78.

  The message receiving unit 77 receives various messages (reproduction prohibition message, reproduction permission message, and reproduction condition message) from the content reproduction management device 3. Then, the message reception unit 77 outputs the received various messages to the content reproduction unit 78.

  The content playback unit 78 plays back the content decrypted by the encrypted content decryption unit 76. In addition, the content reproduction unit 78 updates (increments) the number of reproductions stored in the reproduction number storage unit 65 when the reproduction of the content is completed. Further, when the content reproduction ends, the content reproduction means 78 deletes the content key Kc used for reproduction and the content. The encrypted content decrypting means 76 and the content reproducing means 78 correspond to the reproducing means described in the claims.

  Further, the content reproduction means 78 may perform the following processing in accordance with various messages from the message reception means 77. In the case of a playback prohibition message, the content playback unit 78 prohibits playback of the content. In the case of a playback permission message, the content playback means 78 may store the content decrypted by the encrypted content decryption means 76 in the encrypted content storage means 64 and play this content from the next playback.

  Further, when the reproduction condition message is received, the content reproduction unit 78 may restrict the reproduction of the content according to the reproduction condition included in the reproduction condition message. Specifically, when the maximum number of reproductions is set as the reproduction condition, the content reproduction unit 78 prevents the content from being reproduced more than the maximum number of reproductions.

  When the content reproduction unit 78 has a function of copying content, the following processing may be performed. When the maximum number of times of copying is set as the above-described reproduction condition, the content reproducing unit 78 prevents the content from being copied more than this maximum number of times of copying.

[Receiver operation]
Hereinafter, the operation of the receiving device 5A of FIG. 15 will be described with reference to FIGS. First, the receiving device 5A receives the encrypted key information by the encryption key information receiving unit 66 (step S201).

  Following the processing in step S201, the receiving device 5A reads the user secret key Km stored in the user secret key storage unit 62 by the encryption key information decryption unit 67 (step S202). Then, the receiving device 5A decrypts the key information received in step S201 using the user secret key Km read in step S202 by the encryption key information decrypting means 67 (step S203).

Subsequent to the process of step S203, the receiving apparatus 5A determines whether or not the reproduction is the first reproduction by the key information extraction unit 68 (step S204). In the case of the first reproduction (Yes in Step S204), the receiving device 5A extracts the content key Kc and the public key Kp from the key information decrypted in Step S203 by the key information extraction unit 68 (Step S205).

On the other hand, if it is not the initial reproduction (No at step S204), the receiving apparatus 5A, by the key information extracting unit 68 extracts a public key Kp _n and the secret key Ks _n-1 from the key information decrypted in step S203 (step S206).

  Subsequent to the processing in step S206, the receiving device 5A reads the encrypted content key SKc from the content key storage unit 63 by the content key decrypting unit 73 (step S207). Then, the receiving device 5A decrypts the encrypted content key SKc read out in step S207 by the content key decrypting unit 73 using the secret key Ks extracted in S206 (step S208).

  Subsequent to the processing of step S205 or step S208, the receiving apparatus 5A encrypts the content key Kc by using the public key Kp extracted in step S205 or step S206 by the content key encryption unit 71 and encrypts the content key. SKc is generated (step S209). Then, the receiving device 5A stores the encrypted content key SKc generated in step S209 in the content key storage unit 63 (step S210). If it is not the first reproduction, the receiving device 5A overwrites the encrypted content key SKc in step S210.

  Subsequent to the process of step S210, the receiving apparatus 5A determines whether or not the encrypted content is stored in the encrypted content storage unit 64 by the encrypted content reception unit 74 (step S211).

  In the case of No in step S211, the receiving device 5A receives the encrypted content by the encrypted content receiving unit 74 (step S212). Then, the receiving apparatus 5A causes the encrypted content receiving unit 74 to store the encrypted content received in step S212 in the encrypted content storage unit 64 (step S213).

  Following the processing in step S213 or in the case of Yes in step S211, the reception device 5A reads the encrypted content stored in the encrypted content storage unit 64 by the encrypted content decrypting unit 76 (step S214).

  Subsequent to the processing of step S214, the receiving device 5A selects the input of the content key Kc by the content key selection means 75 according to the number of reproductions. In the case of the first reproduction, the receiving device 5A selects the content key Kc extracted in step S205 by the content key selection means 75. If it is not the first playback, the receiving device 5A selects the content key Kc decrypted in step S210 by the content key selection means 75 (step S215).

  Following the processing in step S215, the receiving apparatus 5A uses the encrypted content decrypting unit 76 to decrypt the encrypted content stored in the encrypted content storage unit 64 using the content key Kc selected in step S213 ( Step S216).

  Subsequent to the processing in step S216, the receiving device 5A reproduces the content decrypted in step S216 by the content reproduction unit 78 (step S217). Then, when the content reproduction unit 78 finishes reproducing the content, the reception device 5A updates (increments) the number of reproductions stored in the reproduction number storage unit 65 (step S218). Further, the receiving device 5A deletes the content key Kc used for reproduction and the content by the content reproduction means 78 (step S219).

  As described above, according to the second embodiment of the present invention, similarly to the first embodiment, the reproduction of the distributed content can be managed, so that the content can be distributed to the receiving device 5A before the right processing is finalized. .

(Modification 1)
In the first embodiment and the second embodiment, the key information generation unit 32 in FIG. 5 has been described as using a public key cryptosystem. However, the present invention is not limited to this. Hereinafter, with reference to FIG. 5, an example using the common key cryptosystem will be described as a first modification.

  The key information generation unit 32 generates a plurality of common keys using a common key cryptosystem. Then, the key information generation unit 32 uses the same common key key for the public key Kp corresponding to the (n-1) th reproduction request signal and the secret key Ks corresponding to the nth reproduction request signal in the key information table of FIG. Register as a key.

  As described above, according to the first modification of the present invention, it is possible to manage the reproduction of content even using a common key cryptosystem. Further, according to the first modification of the present invention, since the common key cryptosystem is used, the load on the content reproduction management device 3 can be reduced.

DESCRIPTION OF SYMBOLS 1 Content distribution system 2 Content distribution apparatus 3 Content reproduction management apparatus 31 Storage means 32 Key information generation means 33 Communication means 34 Reproduction request reception means 35 Determination means 35a Reproduction management determination means 35b Reproduction prohibition determination means 35c Reproduction permission determination means 35d Reproduction conditions Output determination means 36 Key information acquisition means (control information acquisition means)
37 User secret key acquisition means 38 Key information encryption means (control information encryption means)
39 Key information transmission means (control information transmission means)
40 Reproduction count update means (control information management means)
41 Message transmission means 5, 5A Receiving device 51 Reproduction request input means 52 Reproduction request transmission means 53 Communication means 54 Storage means 54a Temporary storage means 54b External storage means 55 Encrypted content reception means 56 Key information reception means (control information reception means)
57 Key information decryption means (control information decryption means)
58 Key information update means (control information update means)
59 Content key decryption means 60 Reproduction means 61 Display means 62 User secret key storage means 63 Content key storage means 64 Encrypted content storage means 65 Reproduction count storage means 66 Encryption key information reception means (control information reception means)
67 Encryption key information decryption means (control information decryption means)
68 Key information extraction means 69 Content key output means 70 Content key encryption key output means 71 Content key encryption means (control information update means)
72 Encrypted content key decryption key output means 73 Content key decryption means 74 Encrypted content reception means 75 Content key selection means 76 Encrypted content decryption means 77 Message reception means 78 Content playback means H Broadcast wave N Network

Claims (9)

First receiving control information for encrypting the content key and receiving the content key encrypted with the first control information in a receiving device that uses a content key for decrypting encrypted content that is encrypted content A content reproduction management device for transmitting at least the reproduction of the content that has been distributed to the receiving device,
Storage means for storing a plurality of the first control information and the second control information;
Reproduction request receiving means for receiving a reproduction request signal for requesting reproduction of the content from the receiving device;
When the rights processing flag added in advance to the content is incomplete, it is determined that the reproduction of the content is managed. When the rights processing flag is completed or unnecessary, the content that has already been distributed is reproduced. Replay management determination means for determining that management is not performed,
Control information management means for storing, in the storage means, information indicating that the first control information and the second control information are transmitted to the receiving apparatus together with information indicating the receiving apparatus;
When it is determined by the playback management determination means to manage playback of the distributed content, the first control information different from the previous transmission and the previous transmission request signal transmitted to the receiving device Control information acquisition means for acquiring the second control information corresponding to the first control information from the storage means;
Control information encryption means for encrypting the first control information and the second control information acquired by the control information acquisition means using a user secret key that is different for each receiving device;
Control information transmitting means for transmitting the first control information and the second control information encrypted by the control information encryption means to the receiving device;
A content reproduction management device comprising: The storage means stores the first control information that is a public key in a public key cryptosystem and the second control information that is a secret key in the public key cryptosystem,
The control information acquisition unit acquires from the storage unit the public key and the secret key that forms a key pair with the public key transmitted to the receiving device in response to the previous reproduction request signal. The content reproduction management apparatus according to claim 1.   The content reproduction management apparatus according to claim 1, wherein the storage unit stores the first control information and the second control information which are common keys in a common key cryptosystem. Reproduction prohibition judging means for judging that reproduction of the content is prohibited when the preset reproduction prohibition flag indicates prohibition in the content to which the right processing flag indicating incomplete is added,
2. A message transmission unit that transmits a reproduction prohibition message for prohibiting the reproduction of the content when the reproduction prohibition determination unit determines that the reproduction of the content is prohibited. Item 4. The content reproduction management device according to any one of Items 3 to 4. It is determined whether a preset right protection period for each content has expired, and it is determined that the right protection period has expired for the content to which the right processing flag indicating the incomplete is added. For those, further comprising a reproduction permission determination means for determining that the reproduction of the content is permitted,
5. The message transmission unit further transmits a reproduction permission message for permitting reproduction of the content when the reproduction permission determination unit determines that the reproduction of the content is permitted. Content reproduction management device. It is determined whether or not the right protection period has expired, and reproduction of the content of the content to which the right protection flag indicating completion has been determined that the right protection period has not expired is determined. It further comprises a reproduction condition output determination means that determines that the condition is transmitted,
The said message transmission means further transmits the information which shows the reproduction conditions of the said content, when it determines with the said reproduction condition output determination means transmitting the reproduction conditions of the said content. Content reproduction management device. The content key that decrypts the encrypted content that is the encrypted content is used, and the first control information that encrypts the content key and the content key that is encrypted with the first control information are decrypted Receiving the second control information from the content reproduction management device and managing at least the reproduction of the distributed content,
Storage means for storing the encrypted content and an encrypted content key that is the content key encrypted with the first control information;
Reproduction request transmitting means for transmitting a reproduction request signal for requesting reproduction of the content to the content reproduction management device;
Corresponds to the first control information encrypted using a different user secret key for each receiving device and the first control information received from the content reproduction management device in response to the previous reproduction request signal. Control information receiving means for receiving the second control information from the content reproduction management device;
Control information decryption means for decrypting the first control information and the second control information received by the control information reception means using the user secret key;
Content key decrypting means for decrypting the encrypted content key into the content key using the second control information decrypted by the control information decrypting means;
Using the content key decrypted by the content key decrypting means, decrypting the encrypted content and reproducing the content;
Control information updating means for encrypting the content key using the first control information decrypted by the control information decrypting means and storing it in the storage means as the encrypted content key;
A receiving apparatus comprising:   The control information receiving means receives the first control information that is a public key in a public key cryptosystem and the second control information that is a secret key in the public key cryptosystem. Item 8. The receiving device according to Item 7.   The receiving apparatus according to claim 7, wherein the control information receiving unit receives the first control information and the second control information that are common keys in a common key cryptosystem.

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