JP4740574B2 - License information generation device and program thereof, distribution content generation device and program thereof, content decryption device and program thereof, and content decryption method - Google Patents

Description

  The present invention relates to a content distribution system, and more particularly to a license information generation apparatus and program thereof, a distribution content generation apparatus and program thereof, a content decryption apparatus and program thereof, and a content decryption method.

  In recent years, various contents such as video and audio have been distributed on the Internet (network). Conventionally, in a content distribution system, in order to protect copyright and prevent unauthorized use of content by a malicious user, the digital copyright management in which content cannot be used unless the user obtains a license (license information) of the content (DRM: Digital Rights Management) is used. This DRM is a technique for allowing a user to use (reproduce or copy) content properly using an encryption technique or the like (see, for example, Patent Document 1).

  A content distribution system using this DRM includes a content server (a content distributor and a provider), a license holder (a license creator and an administrator), and a user, a content server, a license server, and a user, respectively. It is operated by using a terminal. As the content provider, the content holder encrypts the content and distributes it to the user, and the license holder issues a license to the user. On the other hand, the user using the content can decrypt the content using the license and view the content.

  At this time, when using a certain content, the user requests the license holder to issue a license. On the other hand, the license holder issues a license after performing a user authentication process or the like. When a user uses paid content, the user is charged, but this charging process is performed by the license holder who has signed a contract with the content holder together with the authentication process. A usage fee is collected from the user by paying a predetermined fee.

  In this case, the content holder transmits the usage conditions including the content usage fee set by the content holder in advance to the license holder before distributing the content. The license holder stores the usage conditions in a dedicated database, and when a license request is received from the user, the license holder issues a license describing the stored usage conditions with reference to the database. To do.

Here, the usage conditions are “content can be used up to a specified period or due date, the usage fee for that period is A”, “the usage count for the content is set, and the usage fee for the set count is B”, etc. It is decided so. For example, there may be a case where a plurality of usage conditions are set for one content, and the usage conditions desired by the user can be selected.
JP 2004-226849 A (paragraphs 0079 to 0098, FIG. 1)

  However, in the billing process of the conventional content distribution system, it is necessary to share the usage conditions for each content before the content distribution between the content holder and the license holder, and an office procedure for that is indispensable.

  In addition, the content holder must notify the license holder every time the number or content of the usage conditions of the content is changed. Further, the license holder must update the database that associates the content with the use condition when the use condition is changed by the content holder. In particular, when there are a large number of content holders or when there are a large number of license holders, both the content holders and the license holders require enormous office work.

  In particular, various contents such as movies and music distributed on the network are popular, and even if the content holder does not actively change the usage conditions, its value will change over time. Therefore, it is necessary to review the usage fee relatively early. For this reason, the administrative procedure of changing usage conditions is chronic.

  The present invention has been made in view of the above problems, and a license information generation apparatus capable of reducing office work procedures between a content holder and a license holder when distributing content, and its It is an object of the present invention to provide a program, a distribution content generation device and program thereof, a content decryption device and program thereof, and a content decryption method.

The present invention was created to achieve the above object, and first, the license information generating apparatus according to claim 1 includes an encrypted content encrypted with a content key for encrypting the content , A content restriction information indicating a use condition, which is information determined by the content distributor, and an encryption obtained by encrypting the content key with encryption information disclosed by a license distributor to encrypt the content key. A distribution content generating apparatus that distributes the combined distribution content including the encrypted content key, and a content decryption apparatus that decrypts the encrypted content using license information for decrypting and using the encrypted content; , license information for generating the license information in response to a request from the content decoder Wherein a license information generation apparatus and the generator is in a content distribution system that are communicatively connected to each other via a network, and the license server public information generation unit, a public information transmission means, and license requisition acquiring unit, license The configuration includes a request document separation unit, a use condition verification unit, an encryption unit, a license information generation unit, and a license information transmission unit .

According to such a configuration, the license information generating apparatus generates the license distributor public information as encrypted information for encrypting the content key by the license server public information generating unit . Here, the encryption information is a public key generated at the same time as the secret key, or public information generated at a different time from the secret key. Then, the license information generating device transmits the public information to the distribution content generating device by using public information transmitting means. Then, the license information generation device receives, from the content decryption device that has received the distribution content by the license request acquisition unit, data indicating a use condition desired by a user of the content , the content restriction information , A license request document including an encrypted content key or content identification information and the user public key of the user is acquired. The usage condition (content restriction information) includes, for example, a content usage period and billing information. Then, the license information generating device uses the license request separating unit to convert the license request into the content restriction information, the use condition desired by the user, the encrypted content key or the content identification information, Separated from user public key.

Then, the license information generation apparatus, the use condition verification means, by matching the operating conditions desired of the user included in the license request instructions and with said content restriction information, the use conditions desired of the user by determining whether within the scope of the content restriction information, the use conditions desired of the user to verify whether it is valid. Thereby, damage due to falsification of the use conditions can be prevented. Then, the license information generation device uses the encryption unit to decrypt the separated encrypted content key with the previously generated secret key of the license information generation device , or the separated content Either one of the secret key of the license information generating device generated based on the identification information and the secret information corresponding to the transmitted encrypted information is encrypted with the separated user public key and encrypted. Generate a key . Thereby, the secret key or the content key can be safely delivered to the sender of the license request document. When the license information generating unit verifies that the use condition desired by the user is valid by the license information generating unit, the license information generating unit uses the use condition and the encryption unit. The license information is generated by synthesizing the encrypted encryption key .

The license information generated in this way is supplied to the sender side of the license request document having the encrypted content. That is, the license information generating apparatus transmits the license information to the content decrypting apparatus by a license information transmitting unit. The sender of the license request form decrypts the content key with the secret key in the license information and decrypts the encrypted content with the decrypted content key, or encrypts with the content key in the license information Content can be decrypted.

The license information generation program according to claim 2 is an encrypted content encrypted with a content key for encrypting the content, and a content indicating a use condition that is information defined by a distributor of the content Distributing content for distributing distribution content including restriction information and an encrypted content key obtained by encrypting the content key with encryption information published by a license distributor to encrypt the content key A generating device; a content decrypting device that decrypts the encrypted content using license information for decrypting and using the encrypted content; and a license that generates the license information in response to a request from the content decrypting device Communication with each other via an information generation device The computer constituting the license information generation apparatus in connection content distribution system, the license server public information generating means, the public information transmitting means, the license requisition acquiring unit, license requisition separating means, use condition verification means, encryption means The license information generating unit and the license information transmitting unit function.

According to such a configuration, the license information generation program generates the license distributor public information as the encryption information for encrypting the content key by the license server public information generation unit . Here, the encryption information is a public key generated at the same time as the secret key, or public information generated at a different time from the secret key. Then, the license information generation program transmits the public information to the distribution content generation device by public information transmission means. Then, the license information generation program receives data indicating usage conditions desired by the user of the content , the content restriction information , the encryption code from the content decryption device that has received the distribution content by the license request document acquisition unit. A license request document including an encrypted content key or content identification information and the user public key of the user is acquired. Then, the license information generation program uses the license request document separating unit to convert the license request document into the content restriction information, the use condition desired by the user, the encrypted content key or the content identification information, Separated from user public key.

Then, the license information generation program, the use condition verification means, by matching the operating conditions desired of the user included in the license request instructions and with said content restriction information, the use conditions desired of the user by determining whether within the scope of the content restriction information, the use conditions desired of the user to verify whether it is valid. Then, the license information generation program decrypts the separated encrypted content key with the secret key of the license information generation device generated in advance by the encryption unit , or the separated content Either one of the secret key of the license information generating device generated based on the identification information and the secret information corresponding to the transmitted encrypted information is encrypted with the separated user public key and encrypted. Generate a key . Then, the license information generation program, the license information generating means, when the use conditions desired of the user is verified to be of validity by use condition verification means, and the use conditions, in encrypting means The license information is generated by synthesizing the encrypted encryption key . Then, the license information generation program transmits the license information to the content decryption device by a license information transmission unit.
As a result, the sender of the license request form decrypts the content key with the secret key in the license information and decrypts the encrypted content with the decrypted content key or encrypts with the content key in the license information. Content can be decrypted.

The distribution content creating apparatus according to claim 3, the content showing the encrypted contents encrypted by the content key for encrypting the content, the use condition is information defined by the distributor the content restriction information and, distribution content the content key distributing content for delivery synthesized and a encrypted contents key obtained by encrypting the content key by the encryption information published by the license distributor to encrypt A generating device; a content decrypting device that decrypts the encrypted content using license information for decrypting and using the encrypted content; and a license that generates the license information in response to a request from the content decrypting device Connected to the information generator via a network so that they can communicate with each other. A the distribution content generating device in a content distribution system, the encrypted information acquiring unit, a content distribution acceptance unit, a content key generating unit, a content encryption unit, a content key encryption means, and combining means And a distribution means .

According to such a configuration, the distribution content generation apparatus, the encryption information acquisition means, acquires the public information as the encryption information license information generating device generates. Then, the distribution content generation device receives a distribution request including content identification information transmitted from the content decryption device by the content distribution reception unit. Then, the distribution content generation device generates a content key for encrypting the content by the content key generation unit, and encrypts the requested content with the content key generated by the content key generation unit by the content encryption unit. To generate encrypted content.

Then, the distribution content generation apparatus encrypts the content key obtained by encrypting the content with the encryption information acquired by the encryption information acquisition unit by the content key encryption unit, and generates an encrypted content key. Further, the distribution content generation device distributes the synthesized content by synthesizing the encrypted content generated by the content encryption unit, the encrypted content key generated by the content key encryption unit, and the content restriction information. Generate content. As a result, the distribution content is formed as a file or stream in which the encrypted content, the encrypted content key, and the content restriction information are integrated. The distribution content generation device distributes the distribution content to the content decryption device by distribution means.

Furthermore, the distribution content generation program according to claim 4, content indicating the encrypted contents encrypted by the content key for encrypting the content and a is used condition information determined by the distributor of the content Distribution content generation that distributes distribution content synthesized including restriction information and an encrypted content key obtained by encrypting the content key with encryption information disclosed by a license distributor to encrypt the content key A device, a content decrypting device for decrypting the encrypted content using license information for decrypting and using the encrypted content, and license information for generating the license information in response to a request from the content decrypting device Communicate with each other over a network The computer constituting the distribution content generating device in connection content distribution system, encrypted information acquiring unit, a content distribution acceptance unit, a content key generating unit, the content encryption unit, content key encryption unit, combining means, delivery It was decided to function as a means .

According to such a configuration, distribution content generation program, the encryption information acquisition means, acquires the public information as the encryption information license information generating device generates. Then, the distribution content generation program receives the distribution request including the content identification information transmitted from the content decryption device by the content distribution reception unit. Then, the distribution content generation program generates a content key for encrypting the content by the content key generation unit, and encrypts the requested content with the content key generated by the content key generation unit by the content encryption unit. To generate encrypted content.

Then, the distribution content generation program generates the encrypted content key by encrypting the content key obtained by encrypting the content with the encryption information acquired by the encrypted information acquisition unit by the content key encryption unit. Further, the distribution content generation program distributes the composition by synthesizing the encrypted content generated by the content encryption unit, the encrypted content key generated by the content key encryption unit, and the content restriction information. Generate content. As a result, the distribution content is formed as a file or stream in which the encrypted content, the encrypted content key, and the content restriction information are integrated. Then, the distribution content generation program distributes the distribution content to the content decryption device by distribution means.

The content decryption device according to claim 5 is a content restriction that indicates an encrypted content encrypted with a content key for encrypting the content and a use condition that is information defined by a distributor of the content. Distribution content generation for distributing a distribution content including information and an encrypted content key obtained by encrypting the content key with encryption information published by a license distributor to encrypt the content key A device, a content decrypting device for decrypting the encrypted content using license information for decrypting and using the encrypted content, and license information for generating the license information in response to a request from the content decrypting device The generators are connected to each other via a network. A the content decoder in content distribution system, configuration including an acquiring unit, a license request form generating means, and license requisition transmission means, and license information receiving means, and an encryption key decrypting unit, a content decryption unit It was.

According to such a configuration, the content decrypting device uses the obtaining unit to encrypt content that has been encrypted with the content key from the content generating device for distribution and content that indicates usage conditions that are information determined by the content distributor. The restriction information and the encrypted content key that has been encrypted are acquired. Then, the content decryption device uses the license request document generation means to provide content restriction information, data indicating usage conditions desired by the content user, the encrypted content key or content identification information, and the user's public disclosure. Generate a license request containing the key . The use conditions used here are a part of the content restriction information. Then, the content decryption device transmits the license request document to the license information generation device by a license request document transmission unit, and receives the license information from the license information generation device by a license information reception unit. Then, the content decryption device decrypts the encryption key included in the license information with the user secret key of the user by an encryption key decryption unit, and the content key or the secret of the license information generation device One of the keys is generated. And the content decrypting device is the content key decrypted by the content decrypting means by the user secret key, or the content key decrypted by the secret key of the license information generating device decrypted by the user secret key, The encrypted content is decrypted based on one of the above. If the key included in the license information is a secret key for decrypting the content key, the content decryption device decrypts the content key with the secret key and decrypts the encrypted content with the decrypted content key. If the key included in the license information is a content key, the encrypted content can be decrypted with the content key.

The content decryption program according to claim 6 is an encrypted content encrypted with a content key for encrypting the content, and a content restriction indicating a use condition that is information defined by a distributor of the content Distribution content generation for distributing a distribution content including information and an encrypted content key obtained by encrypting the content key with encryption information published by a license distributor to encrypt the content key A device, a content decrypting device for decrypting the encrypted content using license information for decrypting and using the encrypted content, and license information for generating the license information in response to a request from the content decrypting device Connected to the generator so that they can communicate with each other via a network The computer constituting the content decoder of the content distribution system, acquiring means, license request form generating means, the license requisition transmitting unit, license information receiving means, the encryption key decrypting unit, and made to function as a content decryption means did.

According to such a configuration, the content decryption program uses the acquisition unit to transmit the encrypted content encrypted with the content key from the distribution content generation device, and the content indicating the use condition that is information determined by the content distributor The restriction information and the encrypted content key that has been encrypted are acquired. Then, the content decryption program uses the license request document generation means to provide content restriction information, data indicating usage conditions desired by the content user, the encrypted content key or content identification information, and the user's public disclosure. Generate a license request containing the key . Then, the content decryption program transmits the license request document to the license information generation device by a license request document transmission unit, and receives the license information from the license information generation device by a license information reception unit. Then, the content decryption program decrypts the encryption key included in the license information with the user private key of the user by an encryption key decryption unit, and the content key or the secret of the license information generation device One of the keys is generated. The content decryption program includes the content key decrypted with the user secret key by the content decryption unit , or the content key decrypted with the secret key of the license information generation device decrypted with the user secret key, The encrypted content is decrypted based on one of the above. If the key included in the license information is a secret key for decrypting the content key, the content decryption program decrypts the content key with the secret key, and decrypts the encrypted content with the decrypted content key. If the key included in the license information is a content key, the encrypted content can be decrypted with the content key.

The content decrypting method according to claim 7 is a content decrypting method in a content distribution system in which a content server, a content decrypting device, and a license server are connected to each other via a network. A content decryption method for decrypting encrypted content encrypted with a key based on license information including a key used for decrypting the content , the content request transmitting step, and the content request receiving step A distribution content transmission step, a distribution content reception step, a license request document transmission step, a license request document reception step, a separation step, a verification step, an encryption key generation step, a license information transmission step, and license information. Receive state And flop, characterized in that it includes an encryption key decoding step, and a content decoding step.

According to this procedure, the content decryption method is content that is electronic information in which a content requester (content decryption apparatus) requesting content specifies electronic content desired by a user who views the content in the content request transmission step. The request is transmitted to the content distribution source (content server). In the content decryption method, the content distribution server receives the content request in the content request reception step, and encrypts the content specified in the content request in the distribution content transmission step with the content key. Then, the distribution content including the encrypted content key obtained by encrypting the content key with the encrypted information and the content restriction information indicating the use condition, which is information determined by the content distributor , is transmitted to the content request source.

Subsequently, in the content decryption method, the content decryption device receives the distribution content in the distribution content reception step, and in the license request transmission step, the content restriction information, the data indicating the usage condition desired by the user, the encryption The license request form, which is electronic information including the encrypted content key or content identification information and the user public key of the user , is transmitted to the license distribution source (license server). In the content decryption method, the license server receives the license request in the license request receiving step and encrypts the license request in the license server by using the separation step, the content restriction information, the usage conditions desired by the user, and the encryption. Separated into a content key or content identification information and a user public key. The verification step compares the usage conditions desired by the user with the content restriction information and determines whether the usage conditions desired by the user are within the range of the content restriction information. Verify that the desired usage conditions are valid. If the usage condition desired by the user is valid , the content key obtained by decrypting the encrypted content key separated by the secret key generated in advance by the license server in the encryption key generation step , or the separation and content identification information, the secret key of the license server the license server generated based on the secret information corresponding to the encrypted information, one of the encrypted encryption key in the user public key The license information including the encryption key is transmitted to the content decrypting apparatus by the license information transmitting step. Further, in the content decryption method, the license information is received in the content decryption device in the license information reception step. Then, in the encryption key decryption step, the encryption key included in the license information is decrypted with the user private key of the user to generate either the content key or the license server private key, and in the content decryption step, content key is decrypted by the user's private key or a content key decrypted by the private key of the license server decoded by the user's private key, based on one of, it decrypts the encrypted content.

  According to the first or second aspect of the invention, in the content decrypting device, the license information generated by the license information generating device or the program thereof is acquired, so that the secret key or the content key included in the license information is obtained. Based on this, it becomes possible to decrypt the encrypted content and use the content. In this case, the license request generated by the license information generating apparatus or the program thereof includes content restriction information indicating the use conditions defined by the content distributor including the use conditions desired by the content user. ing. As a result, the license information generation apparatus or the license holder that operates the program does not need to acquire the content restriction information before the content distribution or acquire the change notification of the content restriction information, and stores and manages the content restriction information. You don't need a database to do. As a result, the license holder can reduce various office procedures performed with the content holder regarding the content restriction information.

  According to the invention described in claim 3 or claim 4, in the content decrypting device, by acquiring the distribution content generated by the distribution content generation device or the program thereof, the encrypted content and the encryption included in the distribution content are obtained. It is possible to acquire the encrypted content key and the content restriction information indicating the use conditions determined by the content distributor. Since the encrypted content key is encrypted with the encryption information corresponding to the secret key generated by the license information generation device or the program thereof, the user of the content decryption device operates the license information generation device or the program thereof. Data must be exchanged with the license holder to obtain a secret key or content key. Through the exchange of data, the distribution content generation apparatus or the content holder that operates the program can indirectly transmit the content restriction information to the license holder.

  According to the invention described in claim 5 or claim 6, in the content decryption device or the program thereof, the encryption included in the distribution content by acquiring the distribution content generated by the distribution content generation device or the program thereof It is possible to acquire the content, the encrypted content key, and the content restriction information indicating the use conditions determined by the content distributor. Further, in the content decryption apparatus or the program thereof, a license request is made by sending a license request form including content restriction information including the usage conditions of the user to the license holder. As a result, the distribution content generation apparatus or the content holder that operates the program can indirectly transmit the content restriction information to the license holder.

  According to the seventh aspect of the present invention, in the process of decrypting the content, the distribution content including the encrypted content, the encrypted content key, and the content restriction information is transmitted from the content distribution source to the content request source, and the content restriction is performed. A license request including information, usage conditions, and encrypted content key or content identification information is transmitted from the content request source to the license distribution source. As a result, the content restriction information is transferred from the content distribution source to the license distribution source. As a result, the license holder does not need to acquire content restriction information or content change information change notification before content distribution, and does not need a database for storing and managing the content restriction information.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
[Content distribution system configuration]
First, the configuration of the content distribution system according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a content distribution system. The content distribution system 1 includes a content server 10, a license server 30, and a user terminal 50, and distributes content from the content server 10 to the user terminal 50 via the Internet 3.

  The content server (distribution content generation device) 10 encrypts the content with the content key, encrypts the content key with the public key (encrypted information) of the license server 30 (encrypted content key), and synthesizes it with the content restriction information Thus, content (distributed content) to be distributed to the user terminal 50 is generated. The content server 10 holds a plurality of distribution contents and transmits the distribution contents requested from the user terminal 50 to the user terminal 50.

The license server (license information generating device) 30 receives a license request form including an encrypted content key and content restriction information from the user terminal 50, and becomes a license that is information for decrypting the distribution content generated by the content server 10. Information is generated. The license information generated here includes a content key for decrypting the content encrypted by the content server 10.
The license server 30 generates a public key and a secret key, and acquires the content key by decrypting the encrypted content key acquired from the content server 10 with the secret key. Further, the license server 30 encrypts the acquired content key and transmits it to the user terminal 50.

The user terminal (content decryption device) 50 requests the content server 10 for content (distributed content) desired by the user (content user) and also obtains a license (license information) for viewing the content. 30, and the distribution content acquired from the content server 10 is decrypted with the license acquired from the license server 30.
Hereinafter, each configuration of the content server 10, the license server 30, and the user terminal 50 will be described in order.

(Content server configuration)
Next, the configuration of the content server will be described with reference to FIG. 2 (refer to FIG. 1 as appropriate). FIG. 2 is a block diagram showing the configuration of the content server. Here, the content server 10 includes a license server public key acquisition unit 11, a license server public key storage unit 12, a content distribution reception unit 13, a content storage unit 14, a content restriction information storage unit 15, and a content key generation. Means 16, content encryption means 17, content key encryption means 18, restriction information electronic signature means 19, composition means 20, distribution content electronic signature means 21, and distribution means 22 are provided.

The license server public key acquisition unit (encrypted information acquisition unit) 11 receives the public key K _P (encrypted information) from the license server 30 via the Internet 3 and stores the received public key K _P in the license server public key storage. It supplies to the means 12.
The license server public key storage unit 12 stores the public key K _P acquired by the license server public key acquisition unit 11 in association with the content.

  The content distribution accepting unit 13 receives a distribution request Req (content request document) including content identification information (identification information id) transmitted from the user terminal 50 via the Internet 3. The content distribution receiving unit 13 supplies the identification information id included in the distribution request Req to the content encryption unit 17, the content key encryption unit 18, and the restriction information electronic signature unit 19. Further, the content distribution accepting unit 13 supplies the distribution unit 22 with the terminal identification information of the user terminal 50 that has transmitted the distribution request Req.

The content storage unit 14 stores content c to be distributed to the user terminal 50, and is a general storage device such as a hard disk. The content c stored in the content storage unit 14 is read from the content encryption unit 17.
The content restriction information storage unit 15 stores content restriction information (hereinafter referred to as restriction information) s indicating usage conditions (usage period, billing information, etc.) corresponding to the content c stored in the content storage unit 14 for each content. It is a general storage device such as a hard disk. The restriction information s stored in the content restriction information storage unit 15 is determined by the content distributor, and is read by the restriction information electronic signature unit 19.

The content key generation unit 16, and generates the content key K _A is a key for encrypting the content c. The content key K _A generated here is transmitted to the content encryption unit 17 and the content key encryption unit 18. Incidentally, the content key K _A is a content key used in content encryption unit 17, the pseudo random number generation means, not shown, are randomized with a hash (Hash) function or the like, aligned with key length Is.

The content encryption unit 17 reads the content c corresponding to the identification information id supplied from the content distribution reception unit 13 from the content storage unit 14, and reads the read content c from the content key K _A generated by the content key generation unit 16. To generate encrypted content m. The encrypted content m generated here is output to the synthesizing means 20. The content encryption unit 17, using the content key K _A, encrypts the content c by a common key encryption scheme. Note that the content to be encrypted is assumed to be information with a large amount of data such as video, so here, the common key encryption method, which is faster than the public key encryption method, is used. I will do it. For example, a common common key encryption method such as AES (Advanced Encryption Standard) may be used.

The content key encryption unit 18 reads out the public key K _P for encrypting the content c corresponding to the identification information id supplied from the content distribution reception unit 13 from the license server public key storage unit 12, and reads the read public key in K _P, the content c encrypts the encrypted content key K _a, and generates an encrypted content key K _B. The encrypted content key K _B generated here is output to the synthesizing means 20.

The restriction information electronic signature means 19 reads the restriction information s corresponding to the content c corresponding to the identification information id supplied from the content distribution accepting means 13 from the content restriction information storage means 15, and puts the electronic signature on the read restriction information s. It is attached.
Combining means 20, and the encrypted content m generated by the content encryption unit 17, and the encrypted content key K _B generated by the content key encryption unit 18, read from the content restriction information storage unit 15 limits The distribution content H is generated by combining the information s. The distribution content H generated here is given unique identification information (for example, a file name). The distribution content H is supplied to the distribution content electronic signature means 21.

The distribution content electronic signature means 21 attaches an electronic signature to the distribution content H synthesized by the synthesis means 20.
The distribution unit 22 distributes the distribution content H output from the distribution content electronic signature unit 21 to the requested user terminal 50.

By thus configuring the content server 10, content server 10 encrypts the content c in the content key K _A, and the encrypted contents encrypted m, and the encrypted content key K _B, restriction information s And the distribution content H can be generated.
The content server 10 can also realize a general computer as a distribution content generation program that causes each of the above-described units to function. This distribution content generation program can be distributed via a communication line, or can be distributed by writing on a recording medium such as a CD-ROM.

(License server configuration)
Next, the configuration of the license server will be described with reference to FIG. 3 (refer to FIG. 1 as appropriate). FIG. 3 is a block diagram showing the configuration of the license server. Here, the license server 30 includes the public key pair generation unit 31, the public key transmission unit 32, the license request reception unit 33, the user electronic signature verification unit 34, the license request document separation unit 35, and the restriction information electronic. Signature verification means 36, use condition verification means 37, content key decryption means 38, content key encryption means 39, license information synthesis means 40, electronic signature means 41, and license information transmission means 42 are provided. Configured.

The public key pair generation unit 31 (secret key generation unit) generates a pair of the public key K _P of the license server 30 and the secret key K _Q corresponding to the public key K _P. The public key K _P generated here is supplied to the public key transmission means 32. The secret key K _Q generated here is supplied to the content key decrypting means 38.
The public key transmission unit 32 transmits the public key K _P generated by the public key pair generation unit 31 to the content server 10 via the Internet 3.

The license request document receiving unit (license request document obtaining unit) 33 receives a license request document Lreq for requesting transmission of a license from the user terminal 50 via the Internet 3 and supplies the license request document Lreq to the user electronic signature verification unit 34. Is. The license request document receiving unit 33 supplies the terminal identification information of the user terminal 50 to the license information transmitting unit 42.
Note that the license requisition Lreq includes a restriction information s, and usage conditions U (user desires usage conditions), the encrypted content key K _B, and a user public key K _U are combined, the electronic signature of the user is attached Is configured.

The user electronic signature verification unit 34 verifies the user's electronic signature attached to the license request document Lreq, and supplies the verified license request document Lreq to the license request document separation unit 35.
License requisition separating means 35, the license request document Lreq, and restriction information s, and use conditions U, and the encrypted content key K _B, is to separate the user public key K _U. The restriction information s separated here is supplied to the restriction information electronic signature verification means 36. Also, the use condition U is used condition verification unit 37, the encrypted content key K _B is the content key decrypting unit 38, the user public key K _U is supplied to the content key encryption unit 39. Note that the license request document separating means 35 can separate all the synthesized ones at a time, and can separate the synthesized ones step by step as necessary.

The restriction information electronic signature verification means 36 verifies the electronic signature of the content server 10 attached to the restriction information s separated by the license request document separation means 35, and the restriction information s is sent from the content server 10. The restriction information s verified to be is supplied to the use condition verification means 37.
The use condition verification unit 37 compares the use condition U separated by the license request document separation unit 35 with the restriction information s supplied from the restriction information electronic signature verification unit 36, and the use condition U is within the range of the restriction information s. It is verified whether or not the use condition U is valid by determining whether or not it is a product. The use condition U verified as valid here is supplied to the license information synthesis means 40.

Content key decryption means 38, which the license request document separating means 35 by the separated encrypted content key K _B, and decrypted by the secret key K _Q public key pair generation unit 31 generates, it generates a content key K _A It is. The content key K _A generated here is supplied to the content key encryption means 39.
The content key encrypting unit 39, the supplied content key K _A, encrypted by the user public key K _U separated by the license requisition separating means 35, to generate an encrypted content key K _C (encryption key) Is. The encrypted content key K _C generated here is supplied to the license information synthesis means 40.

License information combining means (license information generating means) 40 generates the license information L by combining the use conditions U validated, the user public key K _U and encrypted encrypted content key K _C, The generated license information L is supplied to the electronic signature means 41.
The electronic signature unit 41 attaches the electronic signature of the license server 30 to the license information L synthesized by the license information synthesis unit 40.
The license information transmitting unit 42 transmits the license information L attached with the electronic signature to the user terminal 50 that has transmitted the license request document Lreq.

  The license server 30 can also realize a general computer as a license information generation program that causes each of the above-described units to function. This license information generation program can be distributed via a communication line, or can be distributed by writing on a recording medium such as a CD-ROM.

(User terminal configuration)
Next, the configuration of the user terminal will be described with reference to FIG. 4 (see FIG. 1 as appropriate). FIG. 4 is a block diagram showing the configuration of the user terminal. Here, the user terminal (content decryption terminal) 50 includes a content request unit 51, a content reception unit 52, a content separation unit 53, a use condition acquisition unit 54, a use condition electronic signature unit 55, and a user public key pair. Generating means 56, license request document synthesizing means 57, license request electronic signature means 58, license request document transmitting means 59, license information receiving means 60, license information storage means 61, license information separating means 62, , A use condition determining unit 63, a content key decrypting unit 64, a content decrypting unit 65, and a content presenting unit 66.

The content request unit 51 transmits a content distribution request Req (including content identification information id) desired by the user to the content server 10 via the Internet 3. For example, the content requesting unit 51 receives an identification information id (for example, a file name) for specifying the content desired by the user by an input unit (not shown), and thereby sends a distribution request Req including this identification information. Generate and send to the content server 10.
The content reception means (acquisition means) 52 receives content (distributed content H) requested by the user from the content server 10 via the Internet 3. The distribution content H received here is output to the content separation means 53.

Content separating means 53, a distribution content H content receiving unit 52 receives the restriction information s, and the encrypted content key K _B, is to separate the encrypted contents m. The restriction information s separated here is supplied to the use condition acquisition means 54 and the license request document composition means 57. Further, the encrypted content key K _B is supplied to the license request document combining unit 57, the encrypted content m is supplied to the content decrypting unit 65. Note that the content separation means 53 can separate all the synthesized ones at a time, and can separate the synthesized ones step by step as necessary.

The usage condition acquisition unit 54 presents the restriction information s separated by the content separation unit 53 to the user, and the usage condition U selected by the user from the presented restriction information s (use condition desired by the user). Is something to get. The use condition acquisition unit 54 includes a display for allowing the user to visually recognize the restriction information s and an input device such as a keyboard and a mouse for inputting the use condition U.
The use condition electronic signature unit 55 attaches an electronic signature to the use condition U acquired by the use condition acquisition unit 54 and supplies it to the license request document combining unit 57.

The user public key pair generating means 56 is for generating a pair of a user public key K _U of the user terminal 50, a user private key K _V corresponding to the user public key K _U. User public key K _U generated here is supplied to the license request document combining unit 57, and the user secret key K _V is fed to the content key decryption unit 64.
License requisition combining means (license request form generating means) 57, a restriction information s and the encrypted content key K _B separated by the content separation means 53, and use conditions U the electronic signature is attached, the user public key pair and it generates a license request document Lreq a user public key K _U generated by the generation means 56 synthesizes.

The license request electronic signature unit 58 attaches an electronic signature to the license request document synthesized by the license request document synthesis unit 57.
Based on the identification information id of the content c, the license request document transmission means 59 transmits a license request document Lreq attached with an electronic signature to the license server 30 via the Internet 3.
The license information receiving unit 60 receives license information L corresponding to the license request document Lreq from the license server 30 via the Internet 3.

The license information storage unit 61 stores the license information L received by the license information receiving unit 60 for each content c. The license information storage unit 61 outputs the stored license information to the license information separation unit 62 in accordance with an operation signal from an operation unit (not shown) operated by the user.
The license information separation unit 62 separates the license information L output from the license information storage unit 61 into an encrypted content key K _C and a use condition U. The separated encrypted content key K _C is supplied to the content key decrypting unit 64, and the use condition U is supplied to the use condition determining unit 63.

  The use condition determination unit 63 includes a not-shown presentation unit that presents the use condition U to the user and an input unit that receives an input from the user. The use condition determination unit 63 sets the use condition U presented by the user based on the input from the user. This is to determine whether or not you agree. In addition, when the user agrees to the use condition U, the use condition determining unit 63 supplies an agreement signal indicating that to the content key decrypting unit 64 and the content decrypting unit 65. The presenting means is composed of a display for allowing the user to visually recognize the use condition U, and the input means is composed of an input device such as a keyboard and a mouse for inputting information indicating consent to the use condition U.

When the consent signal from the use condition determining unit 63 is supplied, the content key decrypting unit 64 generates the encrypted content key K _C separated by the license information separating unit 62 by the user public key pair generating unit 56. decrypted by the user's private key K _V, and generates the content key K _a.
The content decrypting unit 65 uses the content key K _A generated by the content key decrypting unit 64 to convert the encrypted content m separated by the content separating unit 53 when the consent signal from the use condition determining unit 63 is supplied. The content c is decrypted and generated.
The content presenting means 66 presents the content c generated by the content decrypting means 65 to the user, and is composed of, for example, a display or a speaker.

  Note that the user terminal 50 can also realize a general computer as a content decryption program that causes each of the above-described units to function. This content decryption program can be distributed via a communication line, or can be distributed by writing on a recording medium such as a CD-ROM.

[Operation of content distribution system]
Next, the operation of the content distribution system according to the first embodiment will be described with reference to FIGS.

(Distributed content generation operation)
First, with reference to FIG. 5 (refer to FIGS. 1 and 2 as appropriate), an operation for generating distribution content in the content distribution system 1 will be described. FIG. 5 is a flowchart showing an operation of generating distribution content in the content distribution system.

The content server 10 acquires the public key K _P of the license server 30 from the license server 30 via the Internet 3 by the license server public key acquisition unit 11 in advance and stores it in the license server public key storage unit 12. Shall.
First, the content server 10 acquires the distribution request Req (including the identification information id of the content c) from the user terminal 50 via the Internet 3 by the content distribution receiving unit 13 (Step S10: Content Request Form). Receiving step). Then, the content server 10 generates the content key K _A by the content key generation means 16. Then, the content server 10, the content encryption unit 17 reads the content c based on the identification information id from the content storage unit 14, encrypts the read content c in the content key K _A, to generate an encrypted content m (Step S11).

The content server 10 encrypts the content key K _A with the license server public key K _P by the content key encryption means 18 to generate an encrypted content key K _B (step S12). Then, the content server 10 reads the restriction information s based on the identification information id from the content restriction information storage unit 15 by the restriction information electronic signature unit 19, and attaches the electronic signature to the read restriction information s (step S13). Subsequently, the content server 10, the synthesizing means 20, and the encrypted content m, an encrypted content key K _B, by synthesizing the control information s to generate a distribution content H, by distribution contents electronic signature unit 21, An electronic signature is attached to the distribution content H (step S14). Then, the content server 10 distributes the distribution content H attached with the electronic signature to the user terminal 50 via the Internet 3 by the distribution means 22 (step S15: distribution content transmission step).

(License information generation operation)
Next, referring to FIG. 6 (refer to FIGS. 1 and 3 as appropriate), the operation of generating license information in the content distribution system 1 will be described. FIG. 6 is a flowchart showing an operation of generating license information in the content distribution system.

License server 30 in advance, the public key pair generating means 31 generates a public key K _P and the secret key K _Q of the license server 30, the public key transmitting unit 32, the public key K _P via the Internet 3 content It is assumed that it is transmitted to the server 10.
The license server 30 receives the license request Lreq from the user terminal 50 via the Internet 3 by the license request receiving unit 33 (step S31: license request receiving step). Then, the license server 30 determines whether or not the license request document Lreq is sent from a valid user by the user electronic signature verification unit 34 (step S32). In step S32, if the license request is not sent from a legitimate user, the license server 30 ends the process. On the other hand, in the case of a license request document sent from a legitimate user, the license server 30 uses the license request document separation unit 35 to convert the license request document Lreq into the restriction information s, the use condition U, and the encrypted content key K. _B, and it separates the user's public key K _U (step S33).

Then, the license server 30 verifies that the restriction information s is sent from the content server 10 by the restriction information electronic signature verification means 36. Thus, when the restriction information s has been tampered with by a malicious user, the content key K _A can be prevented from inadvertently passing for this user. Subsequently, the license server 30 compares the use condition U with the restriction information s by the use condition verifying unit 37 and determines whether the use condition U is within the range of the restriction information s, thereby determining the use condition U. Is verified as valid (step S34). In step S34, if the use condition U is not valid, the license server 30 ends the process. On the other hand, if the use condition U is valid, the license server 30 supplies the use condition U to the license information combining means 40 by the use condition verification means 37.

Then, the license server 30 uses the content key decrypting means 38 to decrypt the encrypted content key K _B encrypted by the content server 10 with the public key K _P of the license server using the secret key K _Q of the license server, and the content c the generating the encrypted content key K _a (step S35). Subsequently, the license server 30, the content key encryption unit 39 encrypts the content key K _A in the user public key K _U, to generate an encrypted content key K _C (step S36: the encryption key generating step).

Then, the license server 30 generates the license information L by combining the encrypted content key K _C and the use condition U by the license information combining unit 40 (step S37). Then, the license server 30 attaches an electronic signature to the license information L by the electronic signature means 41, and sends the license request Lreq to the user terminal 50 that has sent the license request Lreq by the license information transmission means 42 via the Internet 3. Is returned (step S38: license information transmission step).

(Distributed content decoding operation)
Next, referring to FIG. 7 (refer to FIG. 1 and FIG. 4 as appropriate), the operation of decrypting the distribution content in the content distribution system 1 will be described. FIG. 7 is a flowchart showing an operation of decrypting distribution content in the content distribution system.

The user terminal 50 transmits the distribution request Req (including the content identification information id) of the content c to the content server 10 by inputting the identification information id of the content c from an input unit (not shown) (step S50). : Content request sending step), and receiving the distribution content H including the encrypted content m obtained by encrypting the content c from the content server 10 (step S51: distribution content receiving step). Then, the user terminal 50 separates the distribution content H into the encrypted content m, the encrypted content key K _B , and the restriction information s by the content separation unit 53 (step S52).

  Then, the user terminal 50 presents the restriction information s to the user by the use condition obtaining unit 54 and obtains the use condition U selected by the user. Here, specific examples of the restriction information s and the usage conditions U will be described. The restriction information s is information indicating the relationship between the usage period of the content c and the billing, and is composed of, for example, three pieces of information: “1000 yen per month”, “300 yen per week”, and “50 yen per day”. The The use condition U at this time is selected by the user from the three pieces of restriction information s, and is, for example, information “50 yen per day”. The selected use condition U is attached with an electronic signature by the use condition electronic signature means 55 to prove that the user has selected the use condition U.

Then, the user terminal 50, the user public key pair generating means 56 generates the user's public key K _U and the user's private key K _V of the user terminal 50. The user public key K _U and the user's private key K _V is for sending from the license server 30 encrypts the content key that is attached to the license (license information) to the user terminal 50. Subsequently, the user terminal 50, the license request specification synthesizing means 57, use conditions U, restriction information s, encrypted content key K _B, to synthesize the user's public key K _U, generates a license request document Lreq (step S53 ). Then, the user terminal 50 attaches an electronic signature to the license request document Lreq by the license request document electronic signature unit 58, and transmits the license request document Lreq to the license server 30 via the Internet 3 by the license request document transmission unit 59. (Step S54: License request transmission step). Then, the user terminal 50 receives the license information L corresponding to the license request document Lreq from the license server 30 via the Internet 3 by the license information receiving means 60 (step S55: license information receiving step), and stores the license information. Store in the means 61.

Then, the user terminal 50 separates the license information L into the encrypted content key K _C and the use condition U by the license information separating means 62 (step S56). Then, the user terminal 50 presents the use condition U separated from the license information L to the user by the use condition determining means 63, and determines whether or not the user has agreed to the use condition U (step S57). That is, it is determined whether or not consent information is input by the user. In step S57, when the user agrees to the use condition U (when the consent information is input by the user), the user terminal 50 uses the content key decrypting means 64 to convert the encrypted content key K _C using the user secret key K _V. It decrypts the content c to generate encrypted content key K _a (step S58: encryption key decoding step).

Furthermore, the user terminal 50, when the user agrees to the conditions of use U, the content decrypting unit 65 decrypts the encrypted content m using the content key K _A, generates content c (Step S59: Content decoding step ). Then, the user terminal 50 presents the decrypted content c to the user by the content presentation unit 66 (step S60). Thereby, the user can obtain viewing data and view content c.

  According to the present embodiment, the restriction information s included in the distribution content H acquired by the user terminal 50 from the content server 10 and the usage conditions U desired by the user are combined into the license request document Lreq and stored in the license server 30. Sent. Therefore, when the restriction information s is changed in the content server 10, the license server 30 recognizes the new restriction information s ′ without notifying the license server 30 of the new restriction information s ′. Can do.

Specifically, the content holder (content distributor) that distributes the content c when the content c of the usage condition “100 yen per day” for viewing is reduced to “50 yen per day” A procedure for notifying the (license distributor) that the use condition (restriction information) of the content c has been changed is not required. This is because the restriction information s attached to the distribution content H distributed by the content holder by the content server 10 is delivered to the license server 30 via the user terminal 50.
As a result, it is possible to reduce administrative procedures (such as renewal of a contract related to billing) conventionally required between the content holder and the license holder, and to manage a large number of licenses (or contents). ) Management work can be streamlined.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment. For example, in this embodiment, the license server 30 generates a public key K _P and private key K _Q pair, and the content server 10 and the license server 30 use this pair via the user terminal 50 and the content server. 10 is delivered to the encrypted content key K _a content c to be distributed, is further passed the content key K _a to the user terminal 50 from the license server 30, and shall be content at the user terminal is decoded. However, according to the present invention, it is not always necessary to simultaneously generate a public key and a secret key for encrypting a content key. For example, the content key may be encrypted by an ID-Based encryption method. An embodiment in this case will be described as a second embodiment.

(Second Embodiment)
[Content distribution system configuration]
The configuration of the content distribution system according to the second embodiment is the same as the configuration of the content distribution system 1 shown in FIG. 1, and the content server 10a shown in FIG. 8, the license server 30a shown in FIG. A user terminal 50a. Note that the same components as those in FIG.

  The content server 10a encrypts the content with the content key, ID-Based encryption (encrypted content key) with the public information (encrypted information) of the license server 30a, and synthesizes the content key with the content restriction information. Content to be distributed to the user terminal 50a (distributed content) is generated.

The license server 30a receives a license request form including identification information (content identification information) and content restriction information from the user terminal 50a, and generates license information that is information for decrypting the distribution content generated by the content server 10a. To do. The license information generated here includes a secret key K _S generated using the public information R ₁ of the license server 30a and the requested content identification information id.

The license server 30a generates public information R ₁ based on the randomly generated license server secret information R ₀ . Then, the license server 30a generates a secret key K _S using the secret information R ₀ and the identification information (content identification information) id acquired from the content server 10a. Further, the license server 30a encrypts the generated secret key K _S and transmits it to the user terminal 50a.

The user terminal (content decryption apparatus) 50a acquires the content desired by the user and the encrypted content key K _B ′ encrypted after encrypting the content from the content server 10a, and the secret acquired from the license server 30a. The encrypted content key K _B ′ is decrypted with the key K _S and the encrypted content m is decrypted with the decrypted content key K _A.
Hereinafter, the components of the content server 10a, the license server 30a, and the user terminal 50a will be sequentially described.

(Content server configuration)
Next, the configuration of the content server will be described with reference to FIG. 8 (refer to FIG. 1 as appropriate). FIG. 8 is a block diagram showing the configuration of the content server of the second embodiment.
Since the content server 10a has basically the same configuration as the content server 10 of the first embodiment, the same reference numerals are given to the same configuration as the content server 10 of the first embodiment, Description is omitted.

The content server 10a receives the public information R ₁ (encrypted information) from the license server 30a via the Internet 3 by the license server public information acquisition unit 11a, and uses the received public information R ₁ as the license server public information storage unit 12a. To remember.
The content key encrypting unit 18a reads the public information R ₁ to encrypt the content c in accordance with the identification information id supplied from the content distribution acceptance unit 13 from the license server public information memory means 12a, read public information The content key K _A obtained by encrypting the content c is Rd-encrypted by R ₁ to generate an encrypted content key K _B ′.
The synthesizing unit 20a includes the encrypted content m generated by the content encrypting unit 17, the encrypted content key K _B ′ generated by the content key encrypting unit 18a, the identification information id for identifying the content c, the content The distribution information H ′ is generated by combining the restriction information s read from the restriction information storage unit 15.

(License server configuration)
Next, the configuration of the license server will be described with reference to FIG. 9 (refer to FIG. 1 as appropriate). FIG. 9 is a block diagram illustrating the configuration of the license server according to the second embodiment.
Since the license server 30a has basically the same configuration as the license server 30 of the first embodiment, the same reference numerals are given to the same configurations as the license server 30 of the first embodiment, Description is omitted.

The license server public information generation means 44 generates public information R ₁ of the license server 30a, and generates secret information R _{0 in the} process of generating the public information R ₁ . The public information R ₁ and secret information R ₀ generated here are stored in the public information storage means 45.

This license server public information generation means 44 has two prime numbers p and q, where p mod 3 = 2 and p = 6q−1, and an elliptic curve E: y on the finite field GF (p). ² = x ³ +1 is prepared, and secret information R ₀ is randomly selected from the set {1, 2,..., Q−1}. Further, the license server public information generating unit 44 selects the element P having the order q and selects the one-way function F (•). Then, the license server public information generating unit 44 generates public information R ₁ shown in the following equation (1).

R ₁ = {p, q, E, P, F (•), R ₀ × P} (1)

Public information transmitting unit 46 reads out public information R ₁ stored in the public information memory unit 45, and transmits the read public information R ₁ to the content server 10a via the Internet 3.
License requisition Lreq license requisition receiving unit 33 receives' includes a restriction information s, and use conditions U, the identification information id, is synthesized and the user public key K _U, electronic signature of the user is attached configuration It is what has been. Thus, the license requisition separating means 35, the license request document Lreq ', the restriction information s, and use conditions U, the identification information id, is separated into a user public key K _U. Identification information id separated here is fed to the secret key generation unit 47, and the user public key K _U is fed to the secret key encryption means 48.

The secret key generation unit 47 generates a secret key K _S for the content identification information id based on the identification information id separated by the license request document separation unit 35 and the secret information R ₀ stored in the public information storage unit 45. Is. The secret key K _S generated here is supplied to the secret key encryption means 48. The secret key generation means 47 generates a secret key K _S by the following equation (2). Here, F (•) is a one-way function, and id is identification information.

K _S = R ₀ × F (id) (2)

The secret key encryption means 48, the supplied secret key K _S, encrypted with the user public key K _U separated by the license requisition separating means 35, to generate an encrypted secret key K _T (encryption key) Is. The generated encrypted private key K _T is supplied to the license information combining means 40a.
License information combining unit 40a includes the use condition U validated, is to generate the license information L 'by combining the encrypted encryption private key K _T in the user public key K _U. Here, the generated license information L ′ is attached with an electronic signature by the electronic signature means 41, and is transmitted by the license information transmission means 42 to the user terminal 50 a that has transmitted the license request document Lreq ′.

(User terminal configuration)
Next, the configuration of the user terminal will be described with reference to FIG. 10 (refer to FIG. 1 as appropriate). FIG. 10 is a block diagram illustrating a configuration of a user terminal according to the second embodiment.
Since the user terminal 50a has basically the same configuration as the user terminal 50 of the first embodiment, the same reference numerals are given to the same configuration as the user terminal 50 of the first embodiment, Description is omitted.

The content separating unit 53 separates the distribution content H ′ received by the content receiving unit 52 into restriction information s, encrypted content key K _B ′, identification information id, and encrypted content m. Identification information id separated here is fed to the license request document combining means 57, also, the encrypted content key K _B is stored in the encrypted content key storage unit 67.

The user secret key K _V generated by the user public key pair generation unit 56 is supplied to the license server secret key decryption unit 68.
The license request document synthesizing unit 57a includes the restriction information s and the identification information id separated by the content separating unit 53, the use condition U attached with the electronic signature, and the user public key generated by the user public key pair generating unit 56. by synthesizing the K _U and generates a license request document Lreq '.

The license information separation means 62a reads the license information L ′ stored in the license information storage means 61 and separates it into the encrypted secret key K _T and the use condition U. The encrypted private key K _T separated here is supplied to the license server private key decrypting means 68, and the use condition U is supplied to the use condition determining means 63. When the user agrees to the use condition U, the use condition determination unit 63 supplies an agreement signal indicating that to the license server private key decryption unit 68 and the content decryption unit 65.

License server private key decryption unit 68, when the agreement signal from the use condition determining means 63 is supplied, the encrypted private key K _T separated by the license information separating means 62a, the user public key pair generating means 56 The secret key K _S is generated by decrypting with the generated user secret key K _V.
The content key decrypting unit 69, from the encrypted content key storage unit 67, 'reads the encrypted content key K _B that read' public information R ₁ encrypted content key is Id-Based Encryption with K _B license The content key K _A is generated by decrypting with the secret key K _S generated by the server secret key decryption means 68.

  Note that the content server 10a, the license server 30a, and the user terminal 50a can also realize a general computer as a program that causes each of the above-described units to function, as in the first embodiment.

[Operation of content distribution system]
Next, the operation of the content distribution system according to the second embodiment will be described with reference to FIGS.

(Distributed content generation operation)
The operation of the content server 10a of the second embodiment is the same as the operation of the content server 10 of the first embodiment, except for step S12 in the flowchart shown in FIG. Instead of the step S12, the content server 10a is the content key encryption unit 18a, and ID-based encrypts the content key K _A in the license server public information R ₁ and identification information id, the encrypted content key K _B ' Is generated.

(License information generation operation)
Next, with reference to FIG. 11 (see FIG. 9 as appropriate), an operation of generating license information in the content distribution system of the second embodiment will be described. FIG. 11 is a flowchart showing an operation of generating license information in the content distribution system.

The license server 30a uses the license server public information generation unit 44 in advance to obtain two prime numbers p and q, where p mod 3 = 2 and p = 6q−1, and a finite field GF (p). Elliptic curve E: y ² = x ³ +1 is prepared, and secret information R ₀ is randomly selected from the set {1, 2,..., Q−1}. Then, the license server 30a selects the element P having the order q by the license server public information generation unit 44, and selects the one-way function F (•). Further, the license server 30 a generates the public information R ₁ (refer to the formula (1)) by the license server public information generation unit 44 and stores it in the public information storage unit 45. The license server 30 a transmits the public information R ₁ of the license server 30 a stored in the public information storage unit 45 to the content server 10 a via the Internet 3 by the public information transmission unit 46.

First, the license server 30a receives the license request document Lreq ′ from the user terminal 50a via the Internet 3 by the license request document receiving means 33 (step S71: license request document reception step). Then, the license server 30a determines whether or not the license request document Lreq ′ is sent from a valid user by the user electronic signature verification unit 34 (step S72). If it is not sent from a valid user, the license server 30a ends the process. On the other hand, if the license server 30a is sent from a legitimate user, the license request document separating means 35 sends the license request document Lreq ′ to the restriction information s, the use condition U, the identification information id, and the user. separating the public key K _U (step S73).

  Subsequently, the license server 30a verifies that the restriction information s is sent from the content server 10a by the restriction information electronic signature verification means 36. Then, the license server 30a compares the use condition U with the restriction information s by the use condition verifying unit 37, and determines whether the use condition U is within the range of the restriction information s. It is verified that it is valid (step S74). If the use condition U is not valid, the license server 30a terminates the process, and if the use condition U is valid, the use condition verification means 37 converts the use condition U into license information combining means. 40a.

Based on the identification information id separated from the license request document Lreq ′ by the secret key generation unit 47 and the secret information R ₀ stored in the public information storage unit 45, the license server 30a A secret key K _S (see equation (2) above) is generated (step S75). Subsequently, the license server 30a uses the secret key encryption unit 48 to encrypt the secret key K _S with the user public key K _U and generates an encrypted secret key K _T (step S76: encryption key generation step).

Further, the license server 30a generates the license information L ′ by combining the encrypted secret key K _T and the use condition U by the license information combining means 40a (step S77). Then, the license server 30a attaches an electronic signature to the license information L 'by the electronic signature means 41, and sends a license via the Internet 3 to the user terminal 50a that sent the license request document Lreq' by the license information transmission means 42. Information L ′ is returned (step S78: license information transmission step).

(Distributed content decoding operation)
Next, with reference to FIG. 12 (refer to FIG. 10 as appropriate), an operation for decoding the distribution content in the content distribution system of the second embodiment will be described. FIG. 12 is a flowchart showing an operation of decrypting distribution content in the content distribution system.

The user terminal 50a transmits the distribution request Req (including the identification information id of the content c) of the content c to the content server 10a by inputting the identification information id of the content c from an input unit (not shown) (step S80: Content request sending step), and the distribution content H ′ including the encrypted content m obtained by encrypting the content c is received from the content server 10a (step S81: distribution content receiving step). Then, the user terminal 50a uses the content separation means 53 to separate the distribution content H ′ into the encrypted content m, the encrypted content key K _B ′, the identification information id, and the restriction information s (step S82).

Further, the user terminal 50a presents the restriction information s to the user by the use condition obtaining unit 54, and obtains the use condition U selected by the user. An electronic signature is attached to the selected use condition U by the use condition electronic signature means 55. On the other hand, the user terminal 50a is the user public key pair generating means 56 generates the user's public key K _U and the user's private key K _V of the user terminal 50a. The user public key K _U and the user's private key K _V is for sending from the license server 30a to the user terminal 50a by encrypting the private key is attached to the license (license information).

Subsequently, the user terminal 50a is the license requisition combining means 57a, using conditions U, restriction information s, identification information id, to synthesize the user's public key K _U, it generates a license request document Lreq '(step S83). Then, the user terminal 50a attaches an electronic signature to the license request document Lreq ′ by the license request document electronic signature unit 58, and sends the license request document Lreq ′ to the license server 30a via the Internet 3 by the license request document transmission unit 59. (Step S84: License request document transmission step). On the other hand, the user terminal 50a receives the license information L ′ corresponding to the license request document Lreq ′ from the license server 30a via the Internet 3 by the license information receiving means 60 (step S85: license information receiving step). ) And stored in the license information storage means 61. Then, the user terminal 50a separates the license information L ′ into the encrypted secret key K _T and the use condition U by the license information separating means 62a (step S86).

Subsequently, the user terminal 50a presents the user with the use condition U separated from the license information L ′ by the use condition determining unit 63, and determines whether or not the user has agreed to the use condition U (step S87). That is, it is determined whether or not consent information is input by the user. When the user agrees with the use condition U (when consent information is input by the user), the user terminal 50a decrypts the encrypted secret key K _T with the user secret key K _V by the license server secret key decryption means 68. Then, a secret key K _S corresponding to the public information R ₁ obtained by encrypting the content key K _A is generated (step S88: encryption key decryption step).

Then, the user terminal 50a uses the content key decrypting unit 69 to decrypt the encrypted content key K _B ′ stored in the encrypted content key storage unit 67 with the secret key K _S to generate the content key K _A (step) S89). Furthermore, the user terminal 50a, if the user agrees to the conditions of use U, the content decrypting unit 65 decrypts the encrypted content m using the content key K _A, generates content c (Step S90: Content decoding step ). Then, the user terminal 50a presents the decrypted content c to the user by the content presentation unit 66 (step S91).

  According to the present embodiment, as in the first embodiment, the restriction information s included in the distribution content H ′ acquired by the user terminal 50a from the content server 10a and the usage conditions U desired by the user are the license request. Since it is combined with the document Lreq ′ and transmitted to the license server 30a, it is possible to reduce the administrative procedure (such as renewal of the contract related to billing) required between the content holder and the license holder, and a large number of licenses (or It is possible to rationalize the management of license holders (or content holders) that manage content.

It is a block diagram which shows the structure of the content delivery system which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the content server which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the license server which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the user terminal (content decoding apparatus) which concerns on the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the content server which concerns on the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the license server which concerns on the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the user terminal (content decoding apparatus) which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the content server which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the license server which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the user terminal (content decoding apparatus) which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the license server which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the user terminal (content decoding apparatus) which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

1 Content Distribution System 10 Content Server (Distribution Content Generation Device)
11 License server public key acquisition means (encrypted information acquisition means)
12 License Server Public Key Storage Unit 13 Content Distribution Accepting Unit 14 Content Storage Unit 15 Content Restriction Information Storage Unit 16 Content Key Generation Unit 17 Content Encryption Unit 18 Content Key Encryption Unit 19 Restriction Information Digital Signature Unit 20 Composition Unit 21 Distribution Content Electronic signature means 22 Distribution means 30 License server (license information generating device)
31 Public key pair generation means (secret key generation means)
32 public key transmission means 33 license request reception means (license request acquisition means)
34 User electronic signature verification means 35 License request document separation means 36 Restriction information electronic signature verification means 37 Usage condition verification means 38 Content key decryption means 39 Content key encryption means (encryption means)
40 License information synthesizing means (license information generating means)
41 Electronic signature means 42 License information transmission means 44 License server public information generation means (secret key generation means)
48 Secret key encryption means (encryption means)
50 User terminal (content decryption device)
51 Content requesting means 52 Content receiving means (acquisition means)
53 Content Separation Unit 54 Usage Condition Acquisition Unit 55 Usage Condition Electronic Signature Unit 56 User Public Key Pair Generation Unit 57 License Request Form Synthesis Unit (License Request Form Generation Unit)
58 license request electronic signature means 59 license request transmission means 60 license information reception means 61 license information storage means 62 license information separation means 63 usage condition determination means 64 content key decryption means 65 content decryption means 66 content presentation means

Claims (7)

Encrypted content encrypted with a content key for encrypting content, content restriction information indicating use conditions as information determined by a distributor of the content, and a license for encrypting the content key A distribution content generation apparatus that distributes a distribution content that is synthesized by including an encrypted content key obtained by encrypting the content key using encryption information disclosed by a distributor, and decrypts and uses the encrypted content A content decrypting device that decrypts the encrypted content using license information for use and a license information generating device that generates the license information in response to a request from the content decrypting device are connected to each other via a network The license in the distributed content distribution system A multi-address generating device,
License server public information generating means for generating public information of the license distributor as encrypted information for encrypting the content key ;
Public information transmitting means for transmitting the public information to the distribution content generation device;
Data indicating usage conditions desired by the user of the content , the content restriction information , the encrypted content key or content identification information, and the user of the user from the content decryption device that has received the content for distribution A license request acquisition means for acquiring a license request including a public key ;
License request separation means for separating the license request into the content restriction information, the usage conditions desired by the user, the encrypted content key or content identification information, and the user public key;
Wherein by matching using conditions and the content restriction information desired by the user included in the license request document, whether the use conditions desired of the user is within the scope of the content restriction information by determining, with use condition verification means for the use conditions desired of the user to verify whether legitimate,
The content key obtained by decrypting the separated encrypted content key with the previously generated secret key of the license information generation device , or the secret corresponding to the separated content identification information and the transmitted encrypted information Encryption means for generating an encryption key by encrypting any one of the secret key of the license information generation device generated based on the information with the separated user public key ;
When the use conditions desired of the user is verified to be of legitimate by the use condition verification means, the use conditions desired of the user, encrypted encryption by said encryption means License information generating means for generating the license information by synthesizing a key ;
License information transmitting means for transmitting the license information to the content decryption device;
A license information generating apparatus comprising: Encrypted content encrypted with a content key for encrypting content, content restriction information indicating use conditions as information determined by a distributor of the content, and a license for encrypting the content key A distribution content generation apparatus that distributes a distribution content that is synthesized by including an encrypted content key obtained by encrypting the content key using encryption information disclosed by a distributor, and decrypts and uses the encrypted content A content decrypting device that decrypts the encrypted content using license information for use and a license information generating device that generates the license information in response to a request from the content decrypting device are connected to each other via a network The license in the distributed content distribution system The computer constituting the broadcast generator,
License server public information generating means for generating public information of the license distributor as encrypted information for encrypting the content key ;
Public information transmission means for transmitting the public information to the distribution content generation device;
Data indicating usage conditions desired by the user of the content , the content restriction information , the encrypted content key or content identification information, and the user's public disclosure from the content decrypting device that has received the distribution content A license request acquisition means for acquiring a license request including a key ;
A license request separating means for separating the license request into the content restriction information, the use condition desired by the user, the encrypted content key or content identification information, and the user public key;
Wherein by matching using conditions and the content restriction information desired by the user included in the license request document, whether the use conditions desired of the user is within the scope of the content restriction information by determining, using condition verification means for the use conditions desired of the user to verify whether legitimate,
Corresponding to the content key obtained by decrypting the separated encrypted content key with the secret key of the license information generating device generated in advance , or the separated content identification information and the transmitted encrypted information Encryption means for generating an encryption key by encrypting any one of the secret key of the license information generating device generated based on the secret information with the separated user public key ,
When the use conditions desired of the user is verified to be of legitimate by the use condition verification means, the use conditions desired of the user, encrypted encryption by said encryption means License information generating means for generating the license information by synthesizing a key ;
License information transmission means for transmitting the license information to the content decryption device;
License information generation program to function as Licenses to encrypt and contents encrypted by the content key, and a content limitation information indicating a usage condition which is information determined by the distributor of the content, the content key for encrypting the content A distribution content generation apparatus that distributes a distribution content that is synthesized by including an encrypted content key obtained by encrypting the content key using encryption information disclosed by a distributor, and decrypts and uses the encrypted content A content decrypting device that decrypts the encrypted content using license information for use and a license information generating device that generates the license information in response to a request from the content decrypting device are connected to each other via a network the distribution configuration in content distribution system A Ntsu generation device,
And encrypted information acquiring unit for acquiring the public information as said encrypted information by the license information generating device generates according to claim 1,
Content distribution accepting means for receiving a distribution request including content identification information transmitted from the content decrypting device;
Content key generating means for generating a content key for encrypting the content;
Content encryption means for generating encrypted content by encrypting the requested content with the content key generated by the content key generation means;
A content key encryption unit that encrypts the content key obtained by encrypting the content with the encryption information acquired by the encryption information acquisition unit, and generates an encrypted content key;
A synthesizing unit that generates the distribution content by synthesizing the encrypted content generated by the content encryption unit, the encrypted content key generated by the content key encryption unit, and the content restriction information; ,
Delivery means for delivering the delivery content to the content decryption device;
A content generating apparatus for distribution, comprising: Licenses to encrypt and contents encrypted by the content key, and a content limitation information indicating a usage condition which is information determined by the distributor of the content, the content key for encrypting the content A distribution content generation apparatus that distributes a distribution content that is synthesized by including an encrypted content key obtained by encrypting the content key using encryption information disclosed by a distributor, and decrypts and uses the encrypted content A content decrypting device that decrypts the encrypted content using license information for use and a license information generating device that generates the license information in response to a request from the content decrypting device are connected to each other via a network In the distributed content distribution system The computer constituting the Ntsu generator,
Encrypted information acquiring unit for acquiring the public information as the encryption information in which the license information generating device generates according to claim 1,
Content distribution acceptance means for receiving a distribution request including content identification information transmitted from the content decryption device;
Content key generating means for generating a content key for encrypting the content;
Content encryption means for generating encrypted content by encrypting the requested content with the content key generated by the content key generation means;
A content key encryption unit that encrypts the content key obtained by encrypting the content with the encryption information acquired by the encryption information acquisition unit, and generates an encrypted content key;
Combining means for generating the distribution content by combining the encrypted content generated by the content encryption means, the encrypted content key generated by the content key encryption means, and the content restriction information;
Distribution means for distributing the distribution content to the content decryption device;
Distribution content generation program for functioning as a. Encrypted content encrypted with a content key for encrypting content, content restriction information indicating use conditions as information determined by a distributor of the content, and a license for encrypting the content key A distribution content generation apparatus that distributes a distribution content that is synthesized by including an encrypted content key obtained by encrypting the content key using encryption information disclosed by a distributor, and decrypts and uses the encrypted content A content decrypting device that decrypts the encrypted content using license information for use and a license information generating device that generates the license information in response to a request from the content decrypting device are connected to each other via a network the content in the content delivery system A No. apparatus,
Wherein the distribution content creating apparatus according to claim 3, and the encrypted contents encrypted by the content key, and a content limitation information indicating a usage condition which is information determined by the distributor of the content, encryption Obtaining means for obtaining the encrypted content key,
License request for generating a license request including the content restriction information, data indicating usage conditions desired by the content user, the encrypted content key or content identification information, and the user public key of the user Document generation means;
A license request transmission means for transmitting the license request to the license information generating device according to claim 1;
License information receiving means for receiving the license information from the license information generating device;
By decrypting the encrypted key included in the license information by the user private key of the user, the content key or the secret key of the license information generating apparatus, the encryption key decrypting means for generating one of, When,
The encrypted content based on either the content key decrypted with the user private key or the content key decrypted with the private key of the license information generating device decrypted with the user private key Content decrypting means for decrypting
A content decrypting apparatus comprising: Encrypted content encrypted with a content key for encrypting content, content restriction information indicating use conditions as information determined by a distributor of the content, and a license for encrypting the content key A distribution content generation apparatus that distributes a distribution content that is synthesized by including an encrypted content key obtained by encrypting the content key using encryption information disclosed by a distributor, and decrypts and uses the encrypted content A content decrypting device that decrypts the encrypted content using license information for use and a license information generating device that generates the license information in response to a request from the content decrypting device are connected to each other via a network Content in a distributed content distribution system The computer on which you want to configure the issue apparatus,
A content encrypted by the content key, content restriction information indicating a use condition that is information determined by a distributor of the content, and the encrypted content from the content generating apparatus for distribution according to claim 3 An obtaining means for obtaining an encrypted content key;
License request for generating a license request including the content restriction information, data indicating usage conditions desired by the content user, the encrypted content key or content identification information, and the user public key of the user Document generation means,
License request transmission means for transmitting the license request to the license information generating device according to claim 1,
License information receiving means for receiving the license information from the license information generating device;
Wherein the encryption key included in the license information decoded by the user's private key of the user, the content key or the encryption key decoding means for generating one of the private key of the license information generation unit,
The encrypted content based on either the content key decrypted with the user private key or the content key decrypted with the private key of the license information generating device decrypted with the user private key Content decrypting means for decrypting
Content decryption program to function as In a content distribution system in which a content server, a content decryption device, and a license server are connected to be communicable with each other via a network , the encrypted content encrypted with a content key for encrypting the content is A content decryption method for decrypting based on license information including a key used for decrypting
In the content decryption device requesting the content, a content request manual transmission step of transmitting the content request document to the content server is an electronic information specified by the user content to be desired to view the content,
A content request receiving step for receiving the content request in the content server ;
An encrypted content obtained by encrypting the content specified by the content requisition by the content key, and the encrypted content key encrypted by the encrypted information of the content key is the information determined by the distributor of the content A distribution content transmission step of transmitting distribution content including content restriction information indicating a use condition to the content decoding device ;
A delivery content receiving step of receiving the delivery content in the content decryption device ;
Wherein said content restriction information, and data indicating the use conditions desired of the user, and the encrypted content key or the content identification information, a license requisition is an electronic information and a user public key of the user license Sending a license request to the server ;
A license request receiving step for receiving the license request in the license server ;
Separating the license request into the content restriction information, the usage conditions desired by the user, the encrypted content key or content identification information, and the user public key;
By comparing the use condition desired by the user with the content restriction information, and determining whether the use condition desired by the user is within the range of the content restriction information. Verifying that said desired use conditions are valid;
A content key obtained by decrypting the separated encrypted content key with a secret key generated in advance by the license server , or the separated content identification, when the use condition desired by the user is valid generating information, the secret key of the license server generated based on the secret information corresponding to the encrypted information of the license server, one of the encryption key encrypted with the user public key An encryption key generation step;
A license information transmission step of transmitting license information including the encryption key to the content decryption device ;
In the content decrypting apparatus , a license information receiving step for receiving the license information;
An encryption key decryption step of decrypting an encryption key included in the license information with the user secret key of the user to generate either the content key or the secret key of the license server ;
Wherein the content key is decrypted by the user's private key, or the content key decrypted by the private key of the license server decoded by the user private key, based on one of, decrypting the encrypted content Content decrypting step to perform,
A content decryption method comprising:

Images