Patent ID: 12223072

MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described with reference to the drawings. In illustrations below of the drawings, the same or similar parts are denoted with the same or similar reference numerals.

(Content Usage System)

A content usage system10that includes and uses a right-holder terminal1and a user terminal2according to an embodiment of the present invention will be described. The content usage system10includes a blockchain system5and a file management system8.

In the blockchain system5, blockchain data (a distributed ledger) is shared among terminals that belong to the system. The blockchain data is data in which blocks including transactions issued by terminals that belong to the blockchain system5are linked. The blockchain system5includes the right-holder terminal1and the user terminal2. The blockchain system5may further include a plurality of blockchain control terminals3. Each terminal that belongs to the blockchain system5makes P2P (Peer to Peer) connection through a blockchain network4. As illustrated inFIGS.2and3, each terminal that belongs to the blockchain system5includes blockchain data B and a blockchain control unit for synchronizing the blockchain data B.

The file management system8registers content data distributed in the content usage system10. The file management system8includes the right-holder terminal1and the user terminal2. The file management system8may further include a plurality of file management control terminals6. The file management system8may be a centralized system in which a server (not illustrated) manages files, or alternatively may be a decentralized system without a server, in which terminals that belong to the file management system8are individually distributed and manage the files. If the file management system8is the centralized system, each terminal that belongs to the file management system8is connected to the server through a file management network7. Alternatively, if the file management system8is the decentralized system, each terminal that belongs to the file management system8makes P2P connection through the file management network7.

The right-holder terminal1is used by a right holder of the content and transmits permission data for the content to a user of the content. Alternatively, the user terminal2is used by the user of the content and transmits permission request data for the content to the right holder of the content. The blockchain control terminal3is used by users of the blockchain system5except for the right holder and the user of the content. The file management control terminal6is used by users of the file management system8except for the right holder and the user of the content.

In an example illustrated inFIG.1, the number of blockchain control terminal3and the number of file management control terminal6are not limited. The blockchain control terminal3and the file management control terminal6may be different from each other. Alternatively, a single terminal may have functions of the blockchain control terminal3and the file management control terminal6.

In an embodiment of the present invention, a case where an example of a distributed ledger is a blockchain, and information on the right holder and the user of content is transmitted and received via the blockchain is described, but the present invention is not limited to the case. For example, other distributed ledgers may be used instead of the blockchain to transmit and receive information on the right holder and the user of the content.

(Right-Holder Terminal)

The right-holder terminal1according to an embodiment of the present invention will be described with reference toFIG.2. The right-holder terminal1is a general computer that includes a storage device110, a processing device120, and a communication control device130. By the general computer executing a right-holder program, functions illustrated inFIG.2are realized.

The storage device110is a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk or the like, and stores various pieces of data such as input data, output data, and intermediate data that are required for the processing device120to perform processes. The processing device120is a CPU (Central Processing Unit) which reads and writes data stored in the storage device110, and receives data from the communication control device130or outputs data to the communication control device130to perform processes in the right-holder terminal1. The communication control device130is an interface through which the right-holder terminal1is communicably connected to terminals that belong to the blockchain network4or the file management network7.

The storage device110stores the right-holder program, and also stores the blockchain data B.

The blockchain data B is data of the blockchain that is synchronized with each terminal of the blockchain system5illustrated inFIG.1. The blockchain data B is updated by the blockchain control unit121.

Although not illustrated inFIG.2, the storage device110stores pieces of data necessary for the connection to the blockchain system5and the file management system8. Specifically, the storage device110stores a secret key and a public key for an electronic signature of the right holder. In the blockchain system5and the file management system8, different secret keys and public keys may be used, or alternatively, a common secret key and a common public key may be used.

The processing device120includes a blockchain control unit121, a permission request receiving unit122, a verification unit123, and a permission issuing unit124.

The blockchain control unit121causes the blockchain data B to be gently synchronized with blockchain data of another terminal and controls the blockchain data B so that the blockchain data B becomes data in the latest state nearly in real time. The blockchain is formed by connecting a plurality of blocks in a chain shape. If a plurality of transactions are generated, the blockchain is updated after verifying whether it is possible to add, to a current blockchain, a block in which the plurality of transactions are collected.

The permission request receiving unit122receives, from the file management system8, the permission request data for the content including an identifier of a user. The permission request data also includes an identifier or the like of the content that the user desires for use.

The identifier of the user in the file management system8is registered in advance in the blockchain data B by the user, and a verification unit123verifies that the identifier of the user registered in the blockchain data B corresponds to the identifier of the user included in the permission request data. The verification unit123refers to the identifier of the user registered as a valid user of the content data in the blockchain data B, and verifies that the user who transmits the permission request data is the valid user.

After the verification unit123verifies that the identifier of the user registered in the blockchain data B corresponds to the identifier of the user included in the permission request data, the permission issuing unit124transmits, to the file management system8, the permission data for permitting the use of the content by the user.

(User Terminal)

With reference toFIG.3, the user terminal2according to an embodiment of the present invention will be described. The user terminal2is a general computer that includes a storage device210, a processing device220, and a communication control device230. By the general computer executing the right-holder program, functions illustrated inFIG.3are realized.

The storage device210is a ROM (Read-Only Memory), a RAM (Random-Access Memory), a hard disk or the like, and stores various pieces of data such as input data, output data, and intermediate data that are required for the processing device220to perform processes. The processing device220is a CPU (Central Processing Unit) which reads and writes data stored in the storage device210and receives data from the communication control device230or outputs data to the communication control device230to perform processes in the right-holder terminal1. The communication control device230is an interface through which the user terminal2is communicably connected to terminals that belong to the blockchain network4or the file management network7.

The storage device210stores a user program and also stores blockchain data B.

The blockchain data B is similar to the blockchain data B described with reference toFIG.2.

Although not illustrated inFIG.3, the storage device210stores pieces of data necessary for the connection to the blockchain system5and the file management system8. Specifically, the storage device210stores a secret key and a public key for an electronic signature of the user. In the blockchain system5and the file management system8, different secret keys and public keys may be used, or alternatively, a common secret key and a common public key may be used.

The processing device220includes a blockchain control unit221, a registration unit222, a permission request transmitting unit223, and a content usage unit224.

The blockchain control unit221functions in the similar manner as the blockchain control unit121described with reference toFIG.2.

The registration unit222registers the identifier of the user in the file management system8in the blockchain data B. The registration unit222associates the identifier of the content to be used with the identifier of the user in the file management system8as information on the valid user of the content, and registers the associated identifier in the blockchain data B. The registration unit222issues a transaction for registering, in blockchain data B, the identifier of the user in the file management system8, and broadcasts the issued transaction to the blockchain network4. The broadcasted transactions are verified by terminals that belong to the blockchain network4such as the blockchain control terminal3, are collected into a new block, and are included in the blockchain data B.

The permission request transmitting unit223transmits the permission request data for the content including the identifier of the user via the file management system8. The permission request data also includes an identifier or the like of the content that the user desires to use.

The content usage unit224receives, from the file management system8, the permission data for permitting the use of the content by the user, and then, uses the content. After it is verified in the right-holder terminal1that the identifier of the user registered in the blockchain data B corresponds to the identifier of the user included in the permission request data, the right-holder terminal1transmits the permission data to the file management system8. The file management system8provides content to the user terminal2in accordance with the permission data transmitted from the right-holder terminal1.

(Content Usage Method)

A content usage method according to an embodiment of the present invention will be described with reference toFIG.4. In an example illustrated inFIG.4, a case is described in which the file management system8is a distributed file management system and the right-holder terminal1stores the content data. Further, in the example illustrated inFIG.4, it is assumed that, to the blockchain data B, the identifier of the right holder of the right-holder terminal1is registered in advance as a valid right holder who has right to distribute the content data.

The processes of the blockchain data B illustrated inFIG.4are processes to be performed by terminals that belong to the blockchain system5. Similarly, if the file management system8includes a server, the processes of the file management system8are processes to be performed by the server, and alternatively, if the file management system8does not include a server, the processes of the file management system8are processes to be performed by terminals that belong to the file management system8.

First, in step S1, the user terminal2transmits, to the blockchain network4, a transaction for registering, in the blockchain data B, the identifier of the user in the file management system8. The transaction is verified by terminals that belong to the blockchain system5and is included in the blockchain data B. At this time, in step S2, the identifier of the user included in the transaction is included in the blockchain data B. The blockchain data B including the identifier of the user is synchronized among terminals that belong to the blockchain system5.

In step S3, the user terminal2requests a file table to the file management system8, and acquires the file table in step S4. The file table includes information on the right holder of the content data that is managed in the file management system8. In step S5, the user terminal2specifies, from the file table acquired in step S4, the identifier in the file management system8, the identifier being an identifier of the right holder of currently available content. At this time, the user terminal2also confirms that the right-holder terminal1is in an online state capable of distributing the content.

In step S6, the user terminal2refers to the blockchain data B, inquires about right that the right holder specified in step S5holds for the content data, and confirms that the right holder has the right to distribute the content data in step S7. This enables the user to confirm that the right holder is a valid right holder concerning the distribution of the content.

In step S8, the user terminal2transmits the permission request data intended for the right-holder terminal1to the file management system8. The permission request data includes the identifier of the user in the file management system8. In step S9, the file management system8transmits the permission request data received from the user terminal2to the right-holder terminal1.

After receiving the permission request data, in step310, the right-holder terminal1inquires about information on the user who has transmitted the permission request data to the blockchain data B. In step S11, the right-holder terminal1acquires, from the blockchain data B, the identifier of the user as the information on the user.

In step S12, the right-holder terminal1confirms that the permission request data received in step S9is transmitted from a valid user, and the permission request data is a request from the valid user. Specifically, the right-holder terminal1confirms that the user identifier in the file management system8, which identifier is included in the permission request data, matches the user identifier in the file management system8, which identifier is registered in the blockchain data B in the file management system8. The right-holder terminal1may further refer to the blockchain data B to confirm that a predetermined amount of payment is made for the use of the content.

After confirming in step S12that the permission request data is the request from the valid user, in step313, the right-holder terminal1transmits the content data to the file management system8. In step S14, the file management system8transmits the content data to the user terminal2.

If the file management system8is a centralized system with a server that manages content, in step S13, the right-holder terminal1notifies a server to distribute the contents data to the user terminal2. The server distributes the content data to the user terminal2in accordance with an instruction received from the right-holder terminal1.

In an embodiment of the present invention, the user terminal2registers, in the blockchain data B, the identifier of the user in the file management system8, and transmits, to the right-holder terminal1, the identifier of the user terminal2in the file management system8at the time of requesting permission for the content data. If the identifier of the user terminal2in the file management system8received when permission for the content data is requested by the user terminal2matches the identifier of the user terminal2in the file management system8acquired from the blockchain data B, the right-holder terminal1determines that the request is made from the valid user and, makes an instruction to distribute the content data to the user terminal2.

Further, by registering, in the blockchain data B, a fact that the user has valid right when the user acquires the right to use the content data or the like, the right-holder terminal1may confirm that the user acquires the valid right to use the content data.

In the content usage system10according to an embodiment of the present invention, when digital content held by the file management system8is distributed, pieces of information on the right holder and the user are held in the blockchain data B. This enables the right holder and the user to verify validities each other via the blockchain data B. Further, by registering distribution, use, viewing/listening histories and the like of the content in the blockchain, the blockchain becomes possible to manage the respective histories of the content from a transaction history to distribution, use, and viewing/listening histories.

In the content usage system10according to an embodiment of the present invention, the file management system8operates according to instructions by the right-holder terminal1and the user terminal2based on information registered in the blockchain system5. This limits the distribution of files by the file management system8and enables the proper distribution of the content. Further, the blockchain system5holds information on file right and does not need to hold the content data itself, and thus, the blockchain data B can be prevented from being bloated.

Next, first to fourth modified examples will be described with reference toFIGS.5to9B.

First Modified Example

In the first modified example, a case is described in which the right-holder terminal1and the user terminal2do not directly authenticate each other, but authenticate each other after receiving authentications from the file management system8. In the first modified example, communication among terminals such as the right-holder terminal1and the user terminal2may be encrypted.

As illustrated inFIG.5, the processing device120of the right-holder terminal1according to the first modified example includes an authentication request unit125. The authentication request unit125transmits a connection request to the file management system8, and if the terminal is authenticated by the file management system8, is connected to the file management system8. The right-holder terminal1performs the processes illustrated inFIG.4after being connected to the file management system8.

Similarly, as illustrated inFIG.6, the processing device220of the user terminal2according to the first modified example includes an authentication request unit225. The authentication request unit225transmits a connection request to the file management system8, and if the terminal is authenticated by the file management system8, is connected to the file management system8. The user terminal2performs the processes illustrated inFIG.4after being connected to the file management system8.

Second Modified Example

In the second modified example, the user terminal2registers, in the blockchain data B, the identifier of the user in the file management system8, and transmits, to the right-holder terminal1, an electronic signature acquired by electronically signing based on an electronic signature method in which a user public key can be restored.

The public key used in the second modified example is a user public key in the file management system8. While it is possible to generate an identifier of the user from a user public key, it is not possible to generate the user public key from the identifier of the user. For example, a predetermined bit value of the user public key becomes the identifier of the user.

In the second modified example, functional blocks of the right-holder terminal1and the user terminal2are the same as those illustrated inFIGS.2and3, but differ in the following points.

In the second modified example, the permission request receiving unit122of the right-holder terminal1receives, from the file management system8, the permission request data for the content having the electronic signature of the user acquired by electronically signing based on the electronic signature method in which the user public key in the file management system8can be restored.

The verification unit123verifies that the identifier of the user corresponding to the user public key restored from the electronic signature corresponds to the identifier of the user registered in the blockchain data B. Further, the verification unit123confirms that the electronic signature is acquired by electronically signing a known message for the right-holder terminal1by using a secret key corresponding to the restored user public key.

In the second modified example, the registration unit222of the user terminal2registers, in the blockchain data B, the identifier of the user in the file management system8. The registration unit222associates the identifier of the content to be used with the identifier of the user in the file management system8as the information on the valid user of the content, and registers the associated identifiers in blockchain data B.

The permission request transmitting unit223transmits the permission request data for the content having the electronic signature of the user acquired by electronically signing based on the electronic signature method in which the public key can be restored via the file management system8. After the user electronically signs the known message for the right-holder terminal1by using the user secret key in the file management system8, the permission request transmitting unit223transmits the known message.

If the right-holder terminal1verifies that the identifier of the user corresponding to the user public key restored from the electronic signature corresponds to (matches) the identifier of the user registered in the blockchain data B, the right-holder terminal1transmits permission data for permitting the use of the content by the user. Thereafter, by the permission data being transferred by the file management system8, the content usage unit224receives, from the file management system8, the permission data for permitting the use of the content by the user, and then, uses the content.

Examples of the electronic signature method in which the user public key can be restored include, for example, ECDSA (Elliptic Curve Digital Signature Algorithm). The electronic signature of the user is data acquired by the user terminal2electronically signing the known message for the right-holder terminal1based on the electronic signature method in which the user public key can be restored by using the user secret key.

With reference toFIG.7, a content usage method according to a second modified example will be described. Hereinafter, descriptions will be given by focusing on the difference from the content usage method according to an embodiment of the present invention illustrated inFIG.4.

Processes of steps S101to S107are the same as the processes of steps S1to S7inFIG.4.

In step S108, the user terminal2transmits, to the file management system8, the permission request data intended for the right-holder terminal1. The permission request data includes the electronic signature of the user acquired by electronically signing based on the electronic signature method in which the user public key can be restored by using the user secret key in the file management system8. In step S109, the file management system8transmits, to the right-holder terminal1, the permission request data received from the user terminal2.

Processes of steps S110and S111are the same as the processes of steps S10and S11inFIG.4. In step S112, the right-holder terminal1confirms that the user is a valid right holder. Specifically, the right-holder terminal1confirms that the identifier of the user corresponding to the user public key restored from the electronic signature received in step S109corresponds to (matches) the identifier of the user acquired from the blockchain data B in step S111.

If it is confirmed in step S112that the permission request data is a request from a valid user, in step S113, the right-holder terminal1transmits the content data to the file management system8. In step S114, the file management system8transmits the content data to the user terminal2.

In the second modified example, the user terminal2registers, in the blockchain data B, the identifier of the user in the file management system8, and transmits the electronic signature of the user acquired by electronically signing based on the electronic signature method in which the user public key in the file management system8can be restored at the time of requesting permission for the content. If the identifier of the user corresponding to the user public key restored from the electronic signature matches the identifier of the user registered in advance in the blockchain data B by the user, the right-holder terminal1determines that a request is from a valid user and makes an instruction to distribute the content data to the user terminal2.

In the second modified example, if the identifier of the user in the file management system8is included in the permission request data transmitted from the user terminal2, the right-holder terminal1may also verify that the user public key restored from the electronic signature corresponds to the identifier of the user included in the permission request data.

Third Modified Example

In a third modified example, the user terminal2registers, in the blockchain data B, the user public key in the file management system8, and transmits, to the right-holder terminal1, the electronic signature acquired by using the secret key corresponding to the user public key.

While it is possible to generate the identifier of the user from the user public key, it is not possible to generate the user public key from the identifier of the user. For example, a predetermined bit value of the user public key becomes the identifier of the user.

In the third modified example, functional blocks of the right-holder terminal1and the user terminal2are the same as those illustrated inFIGS.2and3except for the following points.

In the third modified example, the permission request receiving unit122of the right-holder terminal1receives, from the file management system8, the permission request data for the content having the electronic signature of the user.

The verification unit123verifies that the user public key registered in the blockchain data B corresponds to the electronic signature. Specifically, the verification unit123confirms that the electronic signature is acquired by electronically signing the known message for the right-holder terminal1by using the secret key corresponding to the user public key.

In the third modified example, the registration unit222of the user terminal2registers, in the blockchain data B, the user public key in the file management system8. The registration unit222associates the identifier of the content to be used with the user public key in the file management system8as the information on the valid user of the content, and registers the associated identifier and user public key in the blockchain data B.

The permission request transmitting unit223generates the electronic signature by using the user secret key in the file management system8, and transmits the permission request data for the content having the electronic signature of the user via the file management system8. The user secret key used for the generation of the electronic signature corresponds to the user public key registered in the blockchain data B.

If the right-holder terminal1verifies that the user public key registered in the blockchain data B corresponds to the electronic signature, the right-holder terminal1transmits the permission data for permitting the use of the content by the user. Thereafter, by the permission data being transferred by the file management system8, the content usage unit224receives, from the file management system8, the permission data for permitting the use of the content by the user, and then, uses the content.

A content usage method according to a third modified example will be described with reference toFIG.8. Hereinafter, descriptions will be given by focusing on a difference from the content usage method according to an embodiment of the present invention illustrated inFIG.4.

In step S201, the user terminal2transmits a transaction for registering, in the blockchain data B, the user public key in the file management system8. The transaction is verified by the terminals that belong to the blockchain system5and is included in the blockchain data B. In step202, the user public key included in the transaction is included in the blockchain data B. The blockchain data B including the user public key is synchronized among the terminals that belong to the blockchain system5.

Processes of steps S203to S207are the same as the processes of steps S3to S7inFIG.4.

In step S208, the user terminal2transmits, to the file management system8, the permission request data intended for the right-holder terminal1. The permission request data includes the electronic signature of the user acquired by electronically signing using the secret key corresponding to the user public key registered in the blockchain data B in the file management system8. In step S209, the file management system8transmits, to the right-holder terminal1, the permission request data received from the user terminal2.

After receiving the permission request data, in step S210, the right-holder terminal1inquires about information on the user who has transmitted the permission request data to the blockchain data B. In step S211, the right-holder terminal1acquires the user public key from the blockchain data B as information on the user.

In step S212, the right-holder terminal1confirms that the user who has transmitted the permission request data received in step S209is a valid user, and the permission request data is a request from the valid user. Specifically, the right-holder terminal1verifies that the user public key registered in the blockchain data B corresponds to the electronic signature. If the identifier of the user is included in the permission request data, the right-holder terminal1may confirm that the identifier of the user corresponds to the user public key registered in the blockchain data B. The right-holder terminal1may further refer to the blockchain data B to confirm that a predetermined amount of payment is made for the use of the content.

After confirming in step S212that the permission request data is the request from the valid user, in step S213, the right-holder terminal1transmits content data to the file management system8. In step S214, the file management system8transmits the content data to the user terminal2.

In the third modified example, the user terminal2registers, in the blockchain data B, the user public key in the file management system8, and transmits the electronic signature of the user acquired by electronically signing using the secret key corresponding to the user public key in the file management system8at the time of requesting permission for the content. If the user public key registered in the blockchain data B corresponds to the electronic signature, the right-holder terminal1determines that the request is from the valid user, and makes an instruction to distribute the content data to the user terminal2.

In the third modified example, if the identifier of the user in the file management system8is included in the permission request data transmitted from the user terminal2, the right-holder terminal1may also verify that the user public key registered in the blockchain data B corresponds to the identifier of the user included in the permission request data.

Fourth Modified Example

In a fourth modified example, the user terminal2registers, in the blockchain data B, the identifier of the user in the file management system8, associates the user public key in the file management system8with the identifier of the user, and registers the associated user public key and identifier in the file management system8. The user terminal2transmits, to the right-holder terminal1, the electronic signature acquired by using the secret key corresponding to the user public key registered in the file management system8.

While it is possible to generate the identifier of the user from the user public key, it is not possible to generate the user public key from the identifier of the user. For example, a predetermined bit value of the user public key becomes the identifier of the user.

In the fourth modified example, functional blocks of the right-holder terminal1and the user terminal2are the same as those illustrated inFIGS.2and3except for the following points.

In the fourth modified example, the permission request receiving unit122of the right-holder terminal1receives, from the file management system8, the permission request data for the content including the identifier of the user and the electronic signature of the user.

The verification unit123acquires, from the file management system8, the public key corresponding to the identifier of the user included in the permission request data, and verifies that the acquired public key corresponds to the electronic signature, and that the identifier of the user included in the permission request data corresponds to the identifier of the user registered in the blockchain data B. The verification unit123confirms that the electronic signature is data acquired by electronically signing the known message for the right-holder terminal1using the secret key corresponding to the user public key. The verification unit123further verifies that the public key acquired from the file management system8corresponds to the identifier of the user registered in the blockchain data B, specifically verifies that a predetermined bit value of the public key becomes the identifier of the user.

In the fourth modified example, the registration unit222of the user terminal2registers, in the blockchain data B, the identifier of the user in the file management system8, associates the identifier of the user in the file management system8with the public key, and registers, in the file management system8, the associated identifier and public key. The registration unit222associates the identifier of content to be used with the identifier of the user in the file management system8as information on the valid user of the content and registers the associated identifiers in blockchain data B.

The permission request transmitting unit223generates the electronic signature by using the secret key corresponding to the user public key registered in the file management system8, and transmits the permission request data for the content including the identifier of the user and the electronic signature of the user via the file management system8.

The right-holder terminal1acquires, from the file management system8, the public key corresponding to the identifier of the user included in the permission request data. In the right-holder terminal1, if it is verified that the acquired public key corresponds to the electronic signature, and that the identifier of the user included in the permission request data corresponds to the identifier of the user registered in the blockchain data B, the permission data for permitting the use of the content by the user is transmitted. Thereafter, by the permission data being transferred by the file management system8, the content usage unit224receives, from the file management system8, the permission data for permitting the use of the content by the user, and uses the content.

With reference toFIGS.9A and9B, a content usage method according to the fourth modified example will be described. Descriptions will be given by focusing on a difference from the content usage method according to an embodiment of the present invention illustrated inFIG.4.

First, in step S301, the user terminal2transmits a transaction for registering, in the blockchain data B, the identifier of the user in the file management system8. The transaction is verified by the terminals that belong to the blockchain system5and is included in the blockchain data B. In step S303, the identifier of the user included in the transaction is included in the blockchain data B. The blockchain data B including the identifier of the user is synchronized among the terminals that belong to the blockchain system5.

In step S302, the user terminal2associates the user public key in the file management system8with the identifier of the user, and registers the associated user public key and identifier in the file management system8.

In step S304, the user public key is registered in the file management system8.

Processes of steps S305to S309are the same as the processes of steps S3to S7inFIG.4.

In step S310, the user terminal2transmits, to the file management system8, the permission request data intended for the right-holder terminal1. The permission request data includes the identifier of the user in the file management system8and the electronic signature of the user acquired by electronically signing using the user secret key in the file management system8. In step S311, the file management system8transmits, to the right-holder terminal1, the permission request data received from the user terminal2.

Processes of steps S312and S313are the same as the processes of steps S10and S11inFIG.4.

In step S314, the right-holder terminal1inquires about the public key corresponding to the identifier of the user acquired in step S311to the file management system8, and acquires the user public key in step S315.

In step S316, the right-holder terminal1confirms that the user is a valid right holder. Specifically, the right-holder terminal1confirms that the user public key acquired from the file management system8corresponds to the electronic signature acquired in step S311, and further confirms that the identifier of the user included in the permission request data matches the identifier of the user registered in the blockchain data B.

After confirming in step S316that the permission request data is a request from the valid user, in step S317, the right-holder terminal1transmits content data to the file management system8. In step S318, the file management system8transmits the content data to the user terminal2.

In the fourth modified example, the user terminal2registers, in the blockchain data B, the identifier of the user in the file management system8, and registers, in the file management system8, the user public key in the file management system8. The user terminal2transmits the electronic signature of the user acquired by electronically signing using the secret key corresponding to the user public key registered in the file management system8at the time of requesting permission for the contents. If the public key acquired from the file management system8corresponds to the electronic signature and also if the identifier of the user included in the permission request data corresponds to (matches) the identifier of the user registered in the blockchain data B, the right-holder terminal1determines that the request is from the valid user, and makes an instruction to distribute the content data to the user terminal2.

Another Embodiment

As described above, the present invention has been described by using an embodiment and the first to fourth modified examples of the present invention, but the discussion and drawings forming part of the disclosure should not be construed as limiting the present invention. Various alternative embodiments, example, and operational techniques will be apparent to those skilled in the art from this disclosure.

For example, the right-holder terminal described in an embodiment of the present invention may be constituted on a single piece of hardware as illustrated inFIG.2, or alternatively may be constituted on a plurality of pieces of hardware depending on functions and the number of processes.

The order of the processes described with reference to sequence diagrams is merely an example, and the present invention is not limited to the described order.

It is needless to say that the present invention encompasses various embodiments and the like which are not described herein. Therefore, the technical scope of the present invention is determined only by the matters specifying the invention according to the claims which are reasonable from the above description.

EXPLANATION OF THE REFERENCE NUMERALS

1Right-holder terminal2User terminal3Blockchain control terminal4Blockchain network5Blockchain system6File management control terminal7File management network8File management system10Content usage system110,210Storage device120,220Processing device121,221Blockchain control unit122Permission request receiving unit123Verification unit124Permission issuing unit130,230Communication control device222Registration unit223Permission request transmitting unit224Content usage unitB Blockchain data