WO2024089775A1 - Data management device and data management method - Google Patents

Abstract

When a second operation is performed to update component data (D12) to component data (D13) and update component data (D21) to component data (D22) at the same time, then a control device (21) of a client server (2) creates a record (RA3) including a hash value of the component data (D13) in a first evidence chain (distributed ledger 51), and creates a record (RB2) including a hash value of the component data (D22) in a second evidence chain (distributed ledger 52). The control device (21) generates a terminal hash value that includes a record hash value of the record (RA3) and a record hash value of the record (RB2), and obtains a timestamp token for the terminal hash value.

Description

Data management device and data management method

This disclosure relates to a data management device and a data management method that manage data using distributed ledger technology.

Patent Publication No. 6694204 (Patent Document 1) discloses a data management system that configures a distributed ledger (asset) with a Directed Acyclic Graph (DAG) structure for each key (ID) used to identify managed objects, and manages information for each ID.

Patent No. 6694204

In the data management system disclosed in Patent Document 1, for example, when data of an object managed with a certain ID is updated, the data is added to the assets prepared for that certain ID. Also, when data of an object managed with another ID is updated, data is added to the assets prepared for that other ID.

Here, in order to prove the existence time of the data added to each asset, it is conceivable to obtain a timestamp token for the latest asset record each time each asset is updated. However, if a timestamp token is obtained for each asset, the cost of obtaining the timestamp token may increase, and the system load may also increase.

The present disclosure has been made to solve the above problems, and the purpose of the present disclosure is to make it possible to easily prove the time of existence of data stored in multiple distributed ledgers in a system that has multiple distributed ledgers.

(1) A data management device according to an aspect of the present disclosure is a data management device that manages data using distributed ledger technology. The data management device includes a storage device that stores a distributed ledger that chronologically stores records including information about the data, a control device that adds records to the distributed ledger, and a communication device configured to be able to communicate with a time stamp authority. The data includes first data and second data. The distributed ledger includes a first distributed ledger that chronologically stores records including first information about the first data, and a second distributed ledger that chronologically stores records including second information about the second data. The control device generates a terminal value that includes information about the end record of the first distributed ledger and information about the end record of the second distributed ledger, and obtains a time stamp token for the terminal value from the time stamp authority via the communication device.

According to the above configuration, a timestamp token is obtained for an end value that includes information on the end record of the first distributed ledger and information on the end record of the second distributed ledger. By obtaining a timestamp token for the end value, it is possible to obtain a proof of existence of the first information stored in the first distributed ledger and the second information stored in the second distributed ledger together at the time indicated by the timestamp token.

(2) In one embodiment, the control device stores a record including the timestamp token in at least one of the first distributed ledger and the second distributed ledger.

With the above configuration, the timestamp token is stored in at least one of the first distributed ledger and the second distributed ledger, thereby improving the tamper resistance of the timestamp token.

(3) In one embodiment, the communication device is further configured to be able to communicate with an external server different from the data management device. The control device stores the timestamp token in the storage device and transmits the timestamp token to the external server via the communication device.

With the above configuration, the timestamp token is managed by the data management device and also by the external server. In order to tamper with the timestamp token, both the timestamp token managed by the data management device and the timestamp token managed by the external server must be tampered with. By managing the timestamp token by the external server as well, the tamper-resistance of the timestamp token can be improved compared to when the timestamp token is managed only by the data management device.

(4) In one embodiment, the control device generates a terminal value when it stores a record including the first information in the first distributed ledger and stores a record including the second information in the second distributed ledger in response to updates to the first data and the second data.

According to the above configuration, a user of the data management device can obtain a timestamp token for the terminal value by performing a user operation to update the first data and the second data.

(5) In one embodiment, the control device generates a terminal value when a predetermined time has elapsed since the last timestamp token was obtained.

With the above configuration, a timestamp token for the terminal value can be automatically obtained every time a specified time has elapsed.

(6) In one embodiment, the information of the end record of the first distributed ledger is a hash value of the end record of the first distributed ledger, and the information of the end record of the second distributed ledger is a hash value of the end record of the second distributed ledger.

With the above configuration, the record information contained in the terminal value is the hash value of the record, so the record itself is not sent to the time stamp authority. Therefore, the record itself can be kept secret when obtaining the time stamp token.

(7) In one embodiment, the first information is a hash value of the first data, and the second information is a hash value of the second data.

According to the above configuration, the records stored in the first distributed ledger and the second distributed ledger each include a hash value of the first data and a hash value of the second data. Since the first data and the second data are not stored in the first distributed ledger and the second distributed ledger, the first data and the second data themselves can be kept secret from other data management devices that form the distributed ledger network.

(8) A data management method according to another aspect of the present disclosure is a data management method of a data management device that manages data using distributed ledger technology. The data management device includes a storage device that stores a distributed ledger that chronologically stores records including information about the data, a control device that adds records to the distributed ledger, and a communication device configured to be able to communicate with a time stamp authority. The data includes first data and second data. The distributed ledger includes a first distributed ledger that chronologically stores records including first information about the first data, and a second distributed ledger that chronologically stores records including second information about the second data. The data management method includes the steps of generating a terminal value that includes information about a record at the end of the first distributed ledger and information about a record at the end of the second distributed ledger, and obtaining a time stamp token for the terminal value from the time stamp authority via the communication device.

According to the present disclosure, in a system having multiple distributed ledgers, it is possible to easily prove the time of existence of data stored in multiple distributed ledgers.

1 is a diagram showing a schematic configuration of a data management system according to a first embodiment; FIG. 1 is a diagram showing an example of the configuration of a distributed ledger set (part 1). FIG. 13 is a diagram for explaining the existence proof process. FIG. 2 is a diagram showing an example of the configuration of a distributed ledger set (part 2). FIG. 4 is a functional block diagram of a control device for executing a process in response to a first operation. FIG. 11 is a functional block diagram of a control device for executing a process in response to a second operation. FIG. 4 is a functional block diagram of a control device for executing received transaction data. 13 is a flowchart showing a procedure for generating transaction data when a first request is received. 13 is a flowchart showing a procedure for generating transaction data when a second request is received. 11 is a flowchart showing a procedure of a process executed when transaction data is received. FIG. 11 is a diagram showing a schematic configuration of a data management system according to a second embodiment. FIG. 13 is a diagram showing an example of the configuration of a distributed ledger set relating to embodiment 2. FIG. 11 is a diagram for explaining the existence proof processing in the second embodiment. FIG. 11 is a functional block diagram of a control device for executing the existence proof process in embodiment 2. 13 is a flowchart showing a procedure for a process of acquiring a time stamp token. FIG. 11 is a diagram showing a schematic configuration of a data management system according to a third embodiment. A diagram showing an example of the configuration of a ledger set. 4A and 4B are diagrams illustrating an example of a configuration of a suspension table. FIG. 13 is a diagram illustrating an example of the configuration of a commit table. 13 is a flowchart showing a procedure of a process executed in the data management system when an update request (first request, second request) is received.

Below, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings will be given the same reference numerals and their description will not be repeated.

[First embodiment]
<Overall configuration of the data management system>
FIG. 1 is a diagram showing a schematic configuration of a data management system 1 according to the first embodiment. The data management system 1 according to the first embodiment is a system for forming a consortium network (hereinafter also simply referred to as a "network") NW among a plurality of companies and managing data using a distributed ledger technology. The data management system 1 according to the first embodiment manages data of parts constituting a vehicle (hereinafter also simply referred to as "parts data"). The parts data may be, for example, a specification of the parts. Note that the data managed by the data management system 1 is not limited to data of parts constituting a vehicle, and may be various types of data.

Referring to FIG. 1, the data management system 1 includes four client servers 2, a platform server 5, and a Time Stamp Authority (TSA) 8. Each of the four client servers 2 belongs to a different company (e.g., company A, company B, company C, and company D).

The platform server 5 manages the network NW. The platform server 5 accepts applications from each client server 2 to join the network NW. The platform server 5 permits the client server 2 to join the network NW based on an operation by the platform server 5 administrator to permit participation, or based on the results of judging predetermined conditions. In the first embodiment, four client servers 2 belonging to each of companies A, B, C, and D are permitted to join the network NW.

The four client servers 2 form a network NW, and store hash values of part data in their respective distributed ledgers. Distributed ledger platform software is installed in each of the client servers 2, and each client server 2 functions as a node as a result of the installed distributed ledger platform software functioning. In the following, the client server 2 of Company A will be described as a representative example, but the client servers of Company B, Company C, and Company D also have the same configuration and function. The client server 2 corresponds to an example of a "data management device" according to the present disclosure.

The client server 2 is configured to be able to communicate with a user terminal device 7. The user terminal device 7 is, for example, a desktop PC (Personal Computer), a notebook PC, a tablet terminal, a smartphone, or any other information processing terminal with communication capabilities, loaned to an employee of Company A.

Also, a database 4 is connected to the client server 2. The database 4 stores part data. The database 4 stores and updates the part data in accordance with control signals from the client server 2. For example, a user of the client server 2 (e.g., an employee of Company A) can request an update of the part data by operating an input device 25 (described later) of the client server 2, or by operating a user terminal device 7. The client server 2 (control device 21) generates a control signal for storing/updating the part data in response to an input to the input device 25 or a request from the user terminal device 7, and outputs the control signal to the database 4.

When the client server 2 stores/updates part data in the database 4, it generates a hash value of the part data and generates transaction data for storing the hash value in the distributed ledger. The client server 2 then transmits the generated transaction data to the other client servers 2 that form the network NW, i.e., the client servers 2 of companies B, C, and D. The distributed ledger stores the hash values of the part data in chronological order, forming an evidence chain for proving the existence of the part data. Note that, in the data management system 1 according to the first embodiment, an example in which the network NW includes four client servers will be described, but the number of client servers 2 included in the network NW is arbitrary and may be, for example, less than four or five or more.

The time-stamp authority 8 includes a server belonging to a certification authority that issues time-stamp tokens. The time-stamp authority issues a time-stamp token in response to a time-stamp issuance request from an applicant (in the first embodiment, the client server 2). More specifically, the time-stamp authority transmits to the applicant a time-stamp token that combines data received from the applicant (in the first embodiment, a terminal hash value, described below) with time information based on a time source that is traceable to international standard time.

The client server 2 includes a control device 21, a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, a communication device 24, an input device 25, a display device 26, and a storage device 27. The control device 21, the ROM 22, the RAM 23, the communication device 24, the input device 25, the display device 26, and the storage device 27 are connected to a bus 29.

The control device 21 is formed, for example, by an integrated circuit including a CPU (Central Processing Unit). The control device 21 deploys various programs stored in the ROM 22 into the RAM 23 and executes them. The various programs include an operating system, etc. The RAM 23 functions as a working memory and temporarily stores various data required for the execution of the various programs. As will be explained in detail later, the control device 21 has the function of updating part data recorded in the database 4, generating transaction data for updating the distributed ledger, and acquiring timestamp tokens.

The communication device 24 is configured to be capable of communicating with external devices. External devices include, for example, other client servers 2, user terminal devices 7, and time certification authorities 8. Communication between the communication device 24 and external devices is performed using the Internet, a wide area network (WAN), a local area network (LAN), an Ethernet (registered trademark) network, a public network, a private network, a wired network, a wireless network, or the like, or a combination of these.

The input device 25 includes an input device. The input device is, for example, a mouse, a keyboard, a touch panel, and/or other device capable of receiving user operations.

The display device 26 includes a display. The display device 26 displays various images on the display in accordance with control signals from the control device 21. The display is, for example, a liquid crystal display, an organic EL (Electro Luminescence) display, or other display device.

The storage device 27 includes a storage medium such as a hard disk or a flash memory. The storage device 27 stores a private key 271, a plurality of public keys 272, and a distributed ledger set 50.

The private key 271 is the private key of Company A. For example, when client server 2 first joins network NW, control device 21 generates a private key and a public key. Then, control device 21 sends the generated public key to a certification authority (not shown) for authentication. A certification authority is a certification body that issues electronic certificates. The certification authority issues an electronic certificate that includes information about the public key. Control device 21 stores private key 271 corresponding to the authenticated public key in storage device 27. Control device 21 also sends authenticated public keys (electronic certificates) 272 to client servers 2 of companies B, C, and D.

The multiple public keys 272 include the public key of Company B, the public key of Company C, and the public key of Company D. The control device 21 stores the public keys received from the other client servers 2 in the storage device 27. The storage device 27 may also store its own (Company A's) public key.

The distributed ledger set 50 includes multiple distributed ledgers. A distributed ledger is prepared for each part that constitutes a vehicle. FIG. 2 is a diagram showing an example of the configuration of the distributed ledger set 50. In the first embodiment, an example will be described in which two parts (first part, second part) that constitute a vehicle are managed by the data management system 1. That is, the distributed ledger set 50 includes a distributed ledger 51 that stores the update state of the part data of the first part in chronological order and serves as an evidence chain for the part data of the first part, and a distributed ledger 52 that stores the update state of the part data of the second part in chronological order and serves as an evidence chain for the part data of the second part. If the number of parts that constitute a vehicle that are managed by the data management system 1 is N (a natural number equal to or greater than 2), the distributed ledger set 50 includes N distributed ledgers. Hereinafter, the parts whose data are managed in the distributed ledger are also referred to as "target parts". That is, the target parts in the first embodiment are the first part and the second part.

The distributed ledger 51 stores records in chronological order, each record including a hash value of the part data of the first part. The records include the following information: "Key", "Age", "Obj-HV", "Nonce", "Sig", "Prev-HV", and "HV".

Key is information that indicates the ID of the target part (first part). The first part is assigned an ID of k1.

Age is information that indicates the generation of a record. In the first record of the first part stored in the distributed ledger 51, Age is 0. When the first part is updated and a record is added, Age is incremented.

Obj-HV is a hash value of the part data of the first part. For example, when the part data of the first part registered in the database 4 is updated, a hash value of the updated part data (e.g., "OH2" in FIG. 2) is generated and used as Obj-HV. A hash value is a numerical value obtained as a result of hashing part data using a hash function. Details will be described later, but Obj-HV may also store a timestamp token (e.g., "TM" in FIG. 4 described below).

Nonce is a nonce value that indicates the number of transaction data. In other words, when part data of a first part stored in the database 4 is updated, for example, the nonce value is generated by the client server 2 (control device 21) as a processing number for storing the hash value of the updated part data in the distributed ledger 51. The nonce value is a hash value that is cryptographically difficult to collide with.

Sig is an electronic signature created using the private key 271 of the client server 2 that issued the transaction data. The electronic signature is created, for example, by encrypting Obj-HV (i.e., the hash value of the part data of the first part) with the private key 271. Alternatively, the electronic signature may be created, for example, by encrypting Nonce (nonce value) with the private key 271. Furthermore, the electronic signature may be created, for example, by encrypting Obj-HV and Nonce with the private key 271.

Prev-HV is the hash value of the record (parent record) of the generation before the latest (end) record. In other words, Prev-HV is the HV of the parent record.

HV is the hash value of the latest (end) record. Specifically, HV is the hash value (hereinafter also referred to as the "record hash value") of the record information excluding HV (Key, Age, Obj-HV, Nonce, Sig, and Prev-HV).

For example, as shown in FIG. 2, looking at the latest (terminal) record (record with Age "2") in the distributed ledger 51, the Prev-HV of the terminal record is "H2", which is the HV of the parent record (Age "1"). If the part data for the first part is then updated and a record with Age "3" is added, the Prev-HV of the record with Age "3" becomes "H3", which is the HV of the record with Age "2". In this way, the terminal record has a structure that includes the record hash value of the parent record. In other words, a chain of records is realized between the Prev-HV of the terminal record and the HV of the parent record. In this way, the distributed ledger 51 has a DAG structure.

Distributed ledger 52 stores records in chronological order, each of which includes a hash value of part data for the second part. The records include the following information: "Key", "Age", "Obj-HV", "Nonce", "Sig", "Prev-HV", and "HV". Details of these are similar to those of the records in distributed ledger 51, and will not be described again.

When the client server 2 (control device 21) receives an update operation for part data via, for example, the input device 25 or the user terminal device 7, it updates the part data stored in the database 4. The client server 2 (control device 21) then generates transaction data for adding a record including the hash value of the updated part data to the distributed ledger set 50 (distributed ledger 51 or distributed ledger 52). This transaction data includes the information "Key", "Age", "Obj-HV", "Nonce", "Sig", "Prev-HV", and "HV".

The transaction data may further include time information when the transaction data is broadcast to the network NW (sent to the network NW), and sender information of the transaction data. The time information may be, for example, information indicating the time when the part data of the target part was recorded in database 4. The sender information is, for example, information indicating Company A. In addition, in more detail, the sender information of the transaction data may be information indicating the department (a division of Company A) that performed the operation to send the transaction data to the network NW, or information indicating an individual (an employee of Company A) that performed the operation to send the transaction data to the network NW.

<Proof of time stamp>
Here, there are cases where it is desired to prove the order indicating which data existed first between the part data of the first part and the part data of the second part, and the time indicating the time of existence of these data. As a method for proving the order and time, for example, each time a record is added to each of the distributed ledgers 51 and 52, a time stamp token is obtained for the record hash value of the added record (terminal record), thereby proving the time when the record was added, and proving the order and time of the two data. However, in this method, a time stamp token must be obtained each time a record is added to the distributed ledgers 51 and 52, which increases the labor and cost. In addition, the processing load on the data management system 1 also increases.

Therefore, in the data management system 1 according to the first embodiment, a terminal hash value including a record hash value of the distributed ledger 51 and a record hash value of the distributed ledger 52 is generated, and a time stamp token for the terminal hash value can be obtained. By obtaining a time stamp token for the terminal hash value, the time of the part data of the first part and the part data of the second part at the time when the time stamp token was obtained can be simultaneously proven. Furthermore, in the data management system 1 according to the first embodiment, the above time stamp token can be incorporated into at least one record of the distributed ledgers 51 and 52. By incorporating the time stamp token obtained for the terminal hash value into at least one record of the distributed ledgers 51 and 52, the tamper resistance of the time stamp token can be improved. A specific description will be given below with reference to FIG. 3. In the following, the process of generating a terminal hash value and obtaining a time stamp token for the terminal hash value is also referred to as "existence proof process".

FIG. 3 is a diagram for explaining the existence proof process. The upper part of FIG. 3 shows a schematic representation of distributed ledger 51, which is the evidence chain for the first part, and the lower part of FIG. 3 shows a schematic representation of distributed ledger 52, which is the evidence chain for the second part. Hereinafter, the evidence chain for the first part will also be referred to as the "first evidence chain," and the evidence chain for the second part will also be referred to as the "second evidence chain."

In the following description, an operation for updating only one of the part data of the first part and the part data of the second part is also referred to as a "first operation." An operation for simultaneously updating the part data of the first part and the part data of the second part is also referred to as a "second operation."

In the first evidence chain (distributed ledger 51), records including hash values of the part data of the first part are stored in chronological order. When the first operation is performed and the part data D10 of the first part is initially registered in the database 4, a record RA0 with Age "0" including the hash value of the part data D10 is stored in the distributed ledger 51. Next, when the first operation is performed and the part data of the first part is updated and the updated part data D11 is registered in the database 4, a record RA1 with Age "1" including the hash value of the updated part data D11 and the record hash value of the parent record RA0 with Age "0" is stored in the distributed ledger 51. Furthermore, when the first operation is performed and the part data of the first part is updated and the updated part data D12 is registered in the database 4, a record RA2 with Age "2" including the hash value of the updated part data D12 and the record hash value of the parent record RA1 with Age "1" is stored in the distributed ledger 51.

The second evidence chain (distributed ledger 52) stores records in chronological order, including hash values of the part data of the second part. When the first operation is performed and part data D20 of the second part is initially registered in database 4, record RB0 with Age "0" including the hash value of the part data D20 is stored in distributed ledger 52. Next, when the first operation is performed and the part data of the second part is updated and the updated part data D21 is registered in database 4, record RB1 with Age "1" including the hash value of the updated part data D21 and the record hash value of parent record RB0 with Age "0" is stored in distributed ledger 52.

As described above, it is assumed that in distributed ledger 51, record RA2 with Age "2" is the latest (end) record, and in distributed ledger 52, record RB1 with Age "1" is the latest (end) record. In this state, it is assumed that a second operation has been performed on input device 25 or user terminal device 7 to simultaneously update the part data of the first part and the part data of the second part. In embodiment 1, when the second operation has been performed, the existence proof process is executed. In other words, the second operation is a condition for executing the existence proof process.

The second operation may be, for example, an operation of inputting the IDs (keys) of two target parts on the display screen of the display device 26 or the user terminal device 7 and selecting the displayed update button. Furthermore, the display screen for performing the second operation may be provided with, for example, a "target input field" for inputting the ID (key) of the target part into which the acquired time stamp token is to be incorporated. For example, if k1 is input into the target input field, the time stamp token acquired by the existence proof process is incorporated into the record of the first evidence chain (distributed ledger 51). For example, if k2 is input into the target input field, the time stamp token acquired by the existence proof process is incorporated into the record of the second evidence chain (distributed ledger 52). For example, if k1 and k2 are input into the target input field, the time stamp token acquired by the existence proof process is incorporated into the record of the first evidence chain (distributed ledger 51) and the record of the second evidence chain (distributed ledger 52). In the example shown in FIG. 3, it is assumed that k2 is input into the target input field.

Referring to Figures 2 and 3, when a second operation is performed to simultaneously update the part data of the first part and the part data of the second part, the control device 21 first updates the part data D12 of the first part stored in the database 4 to part data D13, and updates the part data D21 of the second part to part data D22. Note that when the part data D10 of the first part is stored in the database 4 first, the control device 21 only needs to newly store the part data of the first part in the database 4. Similarly, when the part data D20 of the second part is stored in the database 4 first, the control device 21 only needs to newly store the part data of the second part in the database 4.

Next, the control device 21 creates a record RA3 of Age "3" including the hash value of the part data D13 and the record hash value of the parent record RA2, and stores it in the distributed ledger 51. The control device 21 also generates transaction data (hereinafter also referred to as "transaction data A") for adding the record RA3 to the distributed ledger 51. The control device 21 also creates a record RB2 of Age "2" including the hash value of the part data D22 and the record hash value of the parent record RB1, and stores it in the distributed ledger 52. The control device 21 also generates transaction data (hereinafter also referred to as "transaction data B") for adding the record RB2 to the distributed ledger 52. The control device 21 transmits the generated transaction data A and B to the client servers 2 of Company B, Company C, and Company D via the communication device 24. The transaction process for executing the transaction data A is performed in each of the client servers 2 of Company B, Company C, and Company D, and thereby the record RA3 is stored in the distributed ledger 51 of each client server 2. When transaction processing for executing transaction data B is performed at each of the client servers 2 of company B, company C, and company D, record RB2 is stored in the distributed ledger 52 of each of the client servers 2. Note that transaction data A and B may be generated as a single transaction data.

When the control device 21 stores records RA3 and RB2 in the distributed ledgers 51 and 52, respectively, it generates a record hash value for record RA3 and a record hash value for record RB2. The control device 21 then generates a terminal hash value that includes the record hash value for record RA3 and the record hash value for record RB2. The control device 21 transmits the terminal hash value to the time stamp authority 8 via the communication device 24, and obtains a time stamp token for the terminal hash value from the time stamp authority 8.

Then, the control device 21 creates record RB3 including the timestamp token and the record hash value of record RB2 (parent record) in the distributed ledger 52, and stores it in the distributed ledger 52. The control device 21 also generates transaction data for adding record RB3 to the distributed ledger 52. The control device 21 transmits the generated transaction data to the client servers 2 of Company B, Company C, and Company D via the communication device 24. Transaction processing for executing this transaction data is performed in each of the client servers 2 of Company B, Company C, and Company D, and record RB3 is stored in the distributed ledger 52 of each client server 2.

FIG. 4 shows an example of a specific structure of the distributed ledger 52 corresponding to FIG. 3. FIG. 4 shows an example of the configuration of the distributed ledger set 50. By the second operation of simultaneously updating part data D12 to part data D13 and updating part data D21 to part data D22, a record RA3 with Age "3" is added to the distributed ledger 51, and a record RB2 with Age "2" is added to the distributed ledger 52. Then, a record RB3 with Age "3" in which a timestamp token obtained for the terminal hash value is stored is added to the distributed ledger 52. The record RB3 with Age "3" in the distributed ledger 52 includes the timestamp token TM as Obj-HV.

As described above, when an operation (second operation) for simultaneously updating the part data of the first part and the part data of the second part is performed, specifically, an operation for simultaneously updating part data D12 to part data D13 and updating part data D21 to part data D22, the control device 21 adds record RA3 including the hash value of part data D13 to the distributed ledger 51, and adds record RB2 including the hash value of part data D22 to the distributed ledger 52. The control device 21 then generates a terminal hash value including the record hash value of record RA3 and the record hash value of record RB2. The control device 21 transmits the terminal hash value to the time stamp authority 8 and obtains a time stamp token for the terminal hash value. By obtaining a time stamp token for the terminal hash value including the record hash value of record RA3 and the record hash value of record RB2, it can be proved that the part data D10 to D13 of the first part existed and the part data D20 to D22 of the second part existed at the time proven by the time stamp token. Also, as shown in FIG. 3, part data D13 has been updated to part data D14, and part data D22 has been updated to part data D23 after the time stamp token was acquired. As described above, by acquiring a time stamp token for the terminal hash value, it is possible to prove that part data D14 and part data D23 were registered after the time stamp token was acquired. Compared to acquiring a time stamp token for each record RA3 and RB2 in distributed ledgers 51 and 52, the labor hours, costs, system load, and the like can be reduced.

Furthermore, by incorporating the timestamp token into the record of distributed ledger 52, the tamper resistance of the timestamp token can be improved. Note that the timestamp token may be incorporated into the record of distributed ledger 51, or into the record of distributed ledger 51 and the record of distributed ledger 52.

If the part data of the first part is further updated from D13 to D14, then a record RA4 with Age "4" containing the hash value of part data D14 and the record hash value of record RA3 is added to the distributed ledger 51. Similarly, if the part data of the second part is further updated from D22 to D23, then a record RB4 with Age "4" containing the hash value of part data D23 and the record hash value of record RB3 is added to the distributed ledger 52.

<Function block>
Fig. 5 is a functional block diagram of control device 21 for executing a process in response to a first operation. Referring to Fig. 5, control device 21 includes information acquisition unit 2101, hash generation unit 2102, nonce generation unit 2103, digital signature unit 2104, transaction data generation unit 2105, and transaction data transmission unit 2106. Control device 21 functions as information acquisition unit 2101, hash generation unit 2102, nonce generation unit 2103, digital signature unit 2104, transaction data generation unit 2105, and transaction data transmission unit 2106, for example, by executing a program stored in ROM 22. Note that information acquisition unit 2101, hash generation unit 2102, nonce generation unit 2103, digital signature unit 2104, transaction data generation unit 2105, and transaction data transmission unit 2106 may be realized by, for example, dedicated hardware (electronic circuit).

When a first operation for updating part data of a target part (first part or second part) is performed on the input device 25 or the user terminal device 7, the input device 25 or the user terminal device 7 outputs a first request indicating that the first operation has been performed.

The information acquisition unit 2101 acquires a first request from the input device 25 or the user terminal device 7. For example, when a user of the client server 2 operates the input device 25 to save (register/update) part data of a target part in the database 4, the first request is input to the information acquisition unit 2101. The first request includes an ID (Key) for identifying the target part. When the information acquisition unit 2101 acquires the first request, it outputs the first request to the hash generation unit 2102 and the nonce generation unit 2103.

When the hash generation unit 2102 receives the first request, it reads out part data of the target part from the database 4, for example, and generates a hash value of the read out part data. The hash generation unit 2102 outputs the generated hash value and the ID of the target part to the digital signature unit 2104 and the transaction data generation unit 2105.

When the nonce generation unit 2103 receives the first request, it generates a nonce value. The nonce value is a hash value that is cryptographically unlikely to collide. The nonce generation unit 2103 outputs the generated nonce value and the ID of the target part to the transaction data generation unit 2105. Note that when a nonce value is used to create a digital signature, the nonce generation unit 2103 may output the nonce value and the ID of the target part to the digital signature unit 2104.

The electronic signature unit 2104 reads the private key 271 from the storage device 27. The electronic signature unit 2104 creates an electronic signature by encrypting the hash value received from the hash generation unit 2102 with the private key 271. The electronic signature unit 2104 outputs the created electronic signature and the ID of the target part to the transaction data generation unit 2105. The electronic signature unit 2104 may also create an electronic signature by encrypting the nonce value received from the nonce generation unit 2103 with the private key 271. The electronic signature unit 2104 may also create an electronic signature by encrypting the hash value and the nonce value with the private key 271.

The transaction data generation unit 2105 generates transaction data to be sent to the network NW. For example, the transaction data generation unit 2105 generates transaction data including information on Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV. For example, the transaction data generation unit 2105 recognizes the Age of the parent record by querying the distributed ledger set 50 for the Key, and increments the Age of the parent record to set it as the Age of the record to be added. The transaction data generation unit 2105 sets the hash value generated by the hash generation unit 2102 as Obj-HV, the nonce value generated by the nonce generation unit 2103 as Nonce, and the electronic signature created by the electronic signature unit 2104 as Sig. The transaction data generation unit 2105 also sets the record hash value of the parent record as Prev-HV. The transaction data generation unit 2105 hashes the information of Key, Age, Obj-HV, Nonce, Sig, and Prev-HV to generate HV. The transaction data may further include time information when the transaction data is broadcast (sent to the network NW) to the network NW, and sender information of the transaction data. The transaction data generation unit 2105 outputs the generated transaction data to the transaction data transmission unit 2106.

The transaction data transmission unit 2106 outputs a control signal to the communication device 24 to transmit the transaction data to the network NW. As a result, the transaction data is transmitted to the network NW via the communication device 24.

6 is a functional block diagram of the control device 21 for executing a process responsive to the second operation. Referring to FIG. 6, the control device 21 includes an information acquisition unit 2111, a record addition unit 2112, a terminal hash generation unit 2113, a nonce generation unit 2114, a timestamp token acquisition unit 2115, a digital signature unit 2116, a transaction data generation unit 2117, and a transaction data transmission unit 2118. The control device 21 functions as the information acquisition unit 2111, the record addition unit 2112, the terminal hash generation unit 2113, the nonce generation unit 2114, the timestamp token acquisition unit 2115, the digital signature unit 2116, the transaction data generation unit 2117, and the transaction data transmission unit 2118, for example, by executing a program stored in ROM 22. The information acquisition unit 2111, the record addition unit 2112, the termination hash generation unit 2113, the nonce generation unit 2114, the timestamp token acquisition unit 2115, the digital signature unit 2116, the transaction data generation unit 2117, and the transaction data transmission unit 2118 may be realized, for example, by dedicated hardware (electronic circuitry).

When a second operation for simultaneously updating the part data of the first part and the part data of the second part is performed on the input device 25 or the user terminal device 7, the input device 25 or the user terminal device 7 outputs a second request indicating that the second operation has been performed.

The information acquisition unit 2111 acquires the second request from the input device 25 or the user terminal device 7. For example, when a user of the client server 2 operates the input device 25 to save (register/update) the part data of the first part and the second part in the database 4, the second request is input to the information acquisition unit 2111. The second request includes an ID (k1 and k2) for identifying the target part, and an ID (for example, k2) of the target part into which the timestamp token is to be incorporated, which is entered in the target input field. When the information acquisition unit 2111 acquires the second request, it outputs the second request to the record addition unit 2112.

The record adding unit 2112 has the same function as that described in FIG. 5. Specifically, the record adding unit 2112 executes the same process as that shown in FIG. 5 for the target part identified by the ID, generates transaction data A for adding a record including a hash value of the part data of the first part (e.g., record RA3 in FIG. 3) to the distributed ledger 51, and transaction data B for adding a record including a hash value of the part data of the second part (e.g., record RB2 in FIG. 3) to the distributed ledger 52, and transmits these to the network NW. When the record adding unit 2112 completes transmission of the transaction data A and B to the network NW, it outputs a second request to the termination hash generation unit 2113 and the nonce generation unit 2114.

The terminal hash generation unit 2113 generates a terminal hash value that includes the record hash value of the latest (terminal) record in the distributed ledger 51 (e.g., record RA3 in FIG. 3) and the record hash value of the latest (terminal) record in the distributed ledger 52 (e.g., record RB2 in FIG. 3). The terminal hash generation unit 2113 outputs the generated terminal hash value and the ID of the target component into which the timestamp token is to be embedded (e.g., k2) to the timestamp token acquisition unit 2115.

When the nonce generation unit 2114 receives the second request, it generates a nonce value. The nonce generation unit 2114 outputs the generated nonce value and the ID (e.g., k2) of the target component into which the timestamp token is to be embedded to the transaction data generation unit 2117. Note that when a nonce value is used to create an electronic signature, the nonce generation unit 2114 may output the nonce value and the ID (e.g., k2) of the target component into which the timestamp token is to be embedded to the electronic signature unit 2116.

The timestamp token acquisition unit 2115 acquires a timestamp token for the termination hash value received from the termination hash generation unit 2113. Specifically, the timestamp token acquisition unit 2115 outputs a control signal to the communication device 24 to transmit the termination hash value to the time-stamp authority 8. As a result, the termination hash value is transmitted to the time-stamp authority 8 via the communication device 24. The time-stamp authority 8 that has received the termination hash value returns a timestamp token to the client server 2 that transmitted the termination hash value. The timestamp token acquisition unit 2115 acquires a timestamp token from the time-stamp authority 8 via the communication device 24. The timestamp token acquisition unit 2115 outputs the timestamp token and the ID (e.g. k2) of the target component into which the timestamp token is to be embedded to the electronic signature unit 2116 and the transaction data generation unit 2117.

The electronic signature unit 2116 reads out the private key 271 from the storage device 27. The electronic signature unit 2116 creates an electronic signature by encrypting the timestamp token received from the timestamp token acquisition unit 2115 with the private key 271. The electronic signature unit 2116 outputs the created electronic signature and the ID (e.g. k2) of the target component into which the timestamp token is to be embedded to the transaction data generation unit 2117. The electronic signature unit 2116 may also create an electronic signature by encrypting the nonce value received from the nonce generation unit 2114 with the private key 271. The electronic signature unit 2116 may also create an electronic signature by encrypting the timestamp token and the nonce value with the private key 271.

The transaction data generation unit 2117 generates transaction data (hereinafter also referred to as "transaction data C") to be sent to the network NW. For example, the transaction data generation unit 2117 generates transaction data including information on Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV. The transaction data generation unit 2117 sets the ID (for example, k2) of the target component into which the timestamp token is to be embedded as the Key. The transaction data generation unit 2117 also sets the timestamp token as Obj-HV. Other functions of the transaction data generation unit 2117 are basically the same as those of the transaction data generation unit 2105 described in FIG. 5.

The transaction data transmission unit 2118 outputs a control signal to the communication device 24 to transmit the transaction data C to the network NW. As a result, the transaction data C is transmitted to the network NW via the communication device 24.

FIG. 7 is a functional block diagram of the control device 21 for executing received transaction data. Referring to FIG. 7, the control device 21 includes a transaction data acquisition unit 2121, a signature verification unit 2122, a record creation unit 2123, a ledger update unit 2124, and an output unit 2125. The control device 21 functions as the transaction data acquisition unit 2121, the signature verification unit 2122, the record creation unit 2123, the ledger update unit 2124, and the output unit 2125, for example, by executing a program stored in the ROM 22. Note that the transaction data acquisition unit 2121, the signature verification unit 2122, the record creation unit 2123, the ledger update unit 2124, and the output unit 2125 may be realized, for example, by dedicated hardware (electronic circuitry).

The transaction data acquisition unit 2121 acquires transaction data sent from other client servers 2. The transaction data acquisition unit 2121 outputs the acquired transaction data to the signature verification unit 2122.

The signature verification unit 2122 verifies the validity of the electronic signature (Sig) included in the transaction data. First, the signature verification unit 2122 identifies the client server 2 that sent the transaction data based on the sender information included in the transaction data. Then, the signature verification unit 2122 reads the public key (one of the multiple public keys 272) of the identified client server 2 from the storage device 27. The signature verification unit 2122 uses the read public key to decrypt the electronic signature included in the transaction data. As described above, the electronic signature is a hash value or timestamp token of the part data encrypted using the private key of the sending client server 2. The signature verification unit 2122 compares the decrypted value with the Obj-HV (hash value or timestamp token) included in the transaction data. By confirming that the two match, the signature verification unit 2122 recognizes the validity of the electronic signature.

If the validity of the electronic signature is confirmed, the record creation unit 2123 creates a record to be added to the distributed ledger set 50 based on the transaction data. The record creation unit 2123 reads the information of Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV from the transaction data, and creates a record including this information.

The ledger update unit 2124 adds the record created by the record creation unit 2123 to the distributed ledger set 50, and updates the distributed ledger set 50. Specifically, the ledger update unit 2124 references the key of the created record and identifies the distributed ledger to which the record is to be added. For example, the transaction data generated in response to the first operation that updates the part data of the first part has "k1" indicating the ID of the first part as the key. The record created based on this transaction data also has "k1" as the key. Therefore, the ledger update unit 2124 adds the record to the distributed ledger 51, which is the evidence chain for the part data of the first part.

Furthermore, the above-mentioned transaction data A generated in response to the second operation has "k1" indicating the ID of the first part as a key. The record created based on the transaction data A also has "k1" as a key. Therefore, the ledger update unit 2124 adds the record to the distributed ledger 51, which is the evidence chain of the part data of the first part. Furthermore, the above-mentioned transaction data B generated in response to the second operation has "k2" indicating the ID of the second part as a key. The record created based on the transaction data B also has "k2" as a key. Therefore, the ledger update unit 2124 adds the record to the distributed ledger 52, which is the evidence chain of the part data of the second part. Furthermore, the above-mentioned transaction data C generated in response to the second operation has "k2" indicating the ID of the second part as a key in the above example. The record created based on the transaction data C also has "k2" as a key. Therefore, the ledger update unit 2124 adds the record to the distributed ledger 52, which is the evidence chain for the part data of the second part. As a result, a record including the timestamp token is stored in the distributed ledger 52.

When the update of the distributed ledger set 50 is completed, the ledger update unit 2124 outputs a message to that effect to the output unit 2125.

The output unit 2125 outputs a control signal to the communication device 24 to notify the client server 2 that transmitted the transaction data that the process of executing the transaction data (transaction processing) has been completed. As a result, a report of the completion of the transaction processing is transmitted via the communication device 24 to the client server 2 that transmitted the transaction data.

<Flowchart>
Fig. 8 is a flowchart showing the procedure of a process for generating transaction data when a first request is received. The process of the flowchart shown in Fig. 8 is executed by the control device 21 when a first request is received from the input device 25 or the user terminal device 7. Note that each step (hereinafter, steps are abbreviated as "S") of the flowcharts shown in Fig. 8 and Figs. 9 and 10 described below will be described as being realized by software processing by the control device 21, but a part or all of the steps may be realized by hardware (electronic circuits) created within the control device 21.

In S1, the control device 21 generates a nonce value. This nonce value is used as a number for the transaction data.

In S2, the control device 21 reads the part data of the target part from the database 4 based on the ID for identifying the target part included in the first request, and generates a hash value of the part data.

In S3, the control device 21 reads the private key 271 from the storage device 27, and uses the private key 271 to encrypt the hash value generated in S2 to create an electronic signature. The control device 21 may also use the private key 271 to encrypt the nonce value generated in S1 to create an electronic signature. The control device 21 may also use the private key 271 to encrypt the hash value generated in S2 and the nonce value generated in S1 to create an electronic signature.

In S4, the control device 21 generates transaction data including information on Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV. Specifically, the control device 21 sets the ID of the target part included in the first request as Key. The control device 21 also sets the nonce value generated in S1 as Nonce, the hash value generated in S2 as Obj-HV, and the electronic signature created in S3 as Sig. The control device 21 also queries the distributed ledger set 50 for the Key to recognize the Age of the parent record, and sets the Age to the incremented Age of the parent record. The control device 21 also sets the record hash (HV) of the parent record as Prev-HV. The control device 21 also hashes the information on Key, Age, Obj-HV, Nonce, Sig, and Prev-HV, excluding the HV information, to HV. The control device 21 may also include in the transaction data time information for broadcasting the transaction data to the network NW and sender information of the transaction data.

In S5, the control device 21 outputs a control signal to the communication device 24 to transmit the transaction data generated in S4 to the network NW. As a result, the transaction data is transmitted to the network NW via the communication device 24.

FIG. 9 is a flowchart showing the procedure for processing to generate transaction data when a second request is received. The processing of the flowchart shown in FIG. 9 is executed by the control device 21 when a second request is received from the input device 25 or the user terminal device 7.

In S11, the control device 21 executes a process of transmitting transaction data for adding records in response to the updates to the part data of the first part and the part data of the second part to the distributed ledgers 51 and 52, respectively. Specifically, the control device 21 executes a process similar to that described in FIG. 8 to generate transaction data A for adding a record in response to the updates to the part data of the first part to the distributed ledger 51, and outputs a control signal to the communication device 24 for transmitting the transaction data A to the network NW. The control device 21 also executes a process similar to that described in FIG. 8 to generate transaction data B for adding a record in response to the updates to the part data of the second part to the distributed ledger 52, and outputs a control signal to the communication device 24 for transmitting the transaction data B to the network NW.

In S12, the control device 21 generates a nonce value. This nonce value is used as the number of the transaction data generated in S16, which will be described later.

In S13, the control device 21 creates a terminal hash value that includes the record hash value of the terminal record of the distributed ledger 51 (i.e., the record that is added to the distributed ledger 51 by executing the transaction data A sent in S11) and the record hash value of the terminal record of the distributed ledger 52 (i.e., the record that is added to the distributed ledger 52 by executing the transaction data B sent in S11).

In S14, the control device 21 outputs a control signal to the communication device 24 to transmit the termination hash value generated in S13 to the time-stamp authority 8. As a result, the termination hash value is transmitted to the time-stamp authority 8 via the communication device 24. The time-stamp authority 8 that has received the termination hash value returns a timestamp token to the client server 2 that transmitted the termination hash value. The control device 21 obtains the timestamp token from the time-stamp authority 8 via the communication device 24.

In S15, the control device 21 reads the private key 271 from the storage device 27, and uses the private key 271 to encrypt the timestamp token acquired in S14 to create an electronic signature. The control device 21 may also use the private key 271 to encrypt the nonce value generated in S12 to create an electronic signature. The control device 21 may also use the private key 271 to encrypt the timestamp token acquired in S14 and the nonce value generated in S12 to create an electronic signature.

In S16, the control device 21 generates transaction data including information on Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV. The control device 21 sets the ID entered in the "target input field" (k2 in the above example) as the Key. The control device 21 also sets the timestamp token acquired in S14 as Obj-HV. The other processes in S16 are basically the same as those in S4 of FIG. 8, so they will not be described again.

In S17, the control device 21 outputs a control signal to the communication device 24 to transmit the transaction data generated in S16 to the network NW. As a result, the transaction data is transmitted to the network NW via the communication device 24.

FIG. 10 is a flowchart showing the procedure of the process executed when transaction data is received. The process of the flowchart shown in FIG. 10 is executed by the control device 21 when transaction data is received.

In S21, the control device 21 identifies the client server 2 that sent the transaction data based on the sender information included in the received transaction data.

In S22, the control device 21 reads the public key of the client server 2 identified in S21 from the storage device 27.

In S23, the control device 21 uses the public key read in S22 to decrypt the electronic signature included in the transaction data.

In S24, the control device 21 verifies the validity of the electronic signature decrypted in S23. Specifically, the control device 21 compares the decrypted value of the electronic signature with Obj-HV (hash value or timestamp token) included in the transaction data. If the two do not match, the control device 21 does not recognize the validity of the electronic signature (NO in S24) and proceeds to S25. If the two match, the control device 21 recognizes the validity of the electronic signature (YES in S24) and proceeds to S26.

In S25, the control device 21 discards the currently received transaction data because the electronic signature is not valid, and ends the process. The control device 21 may cause the display device 26 to display a message indicating that the transaction data may have been tampered with. The control device 21 may also transmit a message indicating that the transaction data may have been tampered with to the client server 2 that sent the transaction data.

In S26, the control device 21 reads the Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV information from the received transaction data, and creates a record containing this information.

In S27, the control device 21 identifies the distributed ledger to which the record will be added based on the key of the record created in S26. The control device 21 then adds the record to the identified distributed ledger. This updates the distributed ledger set 50.

In S28, the control device 21 sends a notification (completion report) indicating that the transaction processing has been completed to the client server 2 that sent the transaction data.

As described above, in the data management system 1 according to the first embodiment, the client server 2 holds a distributed ledger set 50 including two distributed ledgers 51 and 52. The distributed ledger 51 is an evidence chain for proving the existence of the part data of the first part, and the distributed ledger 52 is an evidence chain for proving the existence of the part data of the second part. When a second operation is performed to simultaneously update the part data of the first part and the part data of the second part, the client server 2 adds a record including a hash value of the updated part data of the first part to the distributed ledger 51, and adds a record including a hash value of the updated part data of the second part to the distributed ledger 52. The client server 2 then generates a terminal hash value including the record hash value of the record added to the distributed ledger 51 and the record hash value of the record added to the distributed ledger 52. The client server 2 then obtains a timestamp token for the terminal hash value. By acquiring a time stamp token for the terminal hash value, for example, as in the example of FIG. 3, it is possible to prove that the part data D10 to D13 of the first part existed and that the part data D20 to D22 of the second part existed at the time proven by the time stamp token. It is also possible to prove that the part data D14 and the part data D23 were registered after the time stamp token was acquired. In other words, it is possible to prove that the part data D14 and the part data D23 existed after the part data D10 to D13 and the part data D20 to D22 were saved. According to the data management system 1 of the first embodiment, it is possible to reduce the labor, costs, system load, and the like, compared to the case where a time stamp token is acquired for the record hash value of each record added to each of the distributed ledgers 51 and 52.

In addition, by incorporating the timestamp token into at least one distributed ledger record included in the distributed ledger set 50, the tamper-resistance of the timestamp token can be improved.

[Modification 1]
In the first embodiment, the existence proof process, i.e., the process of generating a termination hash value and acquiring a time stamp token, is executed when a second operation is performed to simultaneously update the part data of the first part and the part data of the second part. That is, in the first embodiment, the existence proof process is executed due to a user operation. However, the existence proof process may be executed automatically. For example, the existence proof process may be executed when a predetermined time has elapsed since the previous time stamp token was acquired. That is, the existence proof process may be executed every predetermined time. Then, the acquired time stamp token may be stored in at least one of the distributed ledger records of the distributed ledger set 50. Even with the configuration of the first modification, the same effect as that of the first embodiment can be achieved.

[Embodiment 2]
In the data management system 1 according to the first embodiment, an example has been described in which a time stamp token obtained for a termination hash value is stored in the distributed ledger set 50 (at least one of the distributed ledgers 51 and 52). This improves the tamper resistance of the time stamp token. In the second embodiment, an example will be described in which the tamper resistance of the time stamp token is improved by another method.

FIG. 11 is a diagram showing a schematic configuration of a data management system 1A according to embodiment 2. In comparison with the data management system 1 according to embodiment 1, data management system 1A changes the client server 2 to a client server 2A and further includes an external server 9. The rest of the configuration of data management system 1A is similar to that of data management system 1 according to embodiment 1, and therefore the description thereof will not be repeated.

Compared to the client server 2 according to the first embodiment, client server 2A has changed control device 21 to control device 21A, communication device 24 to communication device 24A, and distributed ledger set 50 included in memory device 27 to distributed ledger set 55. The rest of the configuration of client server 2A is the same as that of client server 2 according to the first embodiment, and therefore the description thereof will not be repeated.

FIG. 12 is a diagram showing an example of the configuration of distributed ledger set 55 according to the second embodiment. Referring to FIG. 12, distributed ledger set 55 includes distributed ledger 56 that stores the update state of part data of a first part in chronological order and serves as an evidence chain for the part data of the first part, and distributed ledger 57 that stores the update state of part data of a second part in chronological order and serves as an evidence chain for the part data of the second part. Like distributed ledgers 51 and 52 according to the first embodiment, distributed ledgers 56 and 57 store records in chronological order that include information on "Key", "Age", "Obj-HV", "Nonce", "Sig", "Prev-HV", and "HV".

Referring to Figures 11 and 12, client server 2A and client server 2 have different timings for executing the existence proof process (the process of generating a termination hash value and obtaining a timestamp token). Client server 2 according to embodiment 1 executes the existence proof process in response to a second request indicating that a second operation has been performed to simultaneously update the part data of the first part and the part data of the second part. Client server 2A according to embodiment 2 executes the existence proof process in response to a third request indicating that a third operation has been performed to request obtaining a timestamp token.

In response to the first and second requests, the client server 2A (control device 21A) executes the process of FIG. 8 described in the first embodiment, and adds records to the distributed ledger 56 and/or the distributed ledger 57. More specifically, when the control device 21A updates the database 4 in response to the first operation that updates the part data of the first part, for example, the control device 21A adds a record including a hash value of the updated part data of the first part to the distributed ledger 56. Also, when the control device 21A updates the database 4 in response to the first operation that updates the part data of the second part, for example, the control device 21A adds a record including a hash value of the updated part data of the second part to the distributed ledger 57. Furthermore, when the control device 21A updates the database 4 in response to the second operation that simultaneously updates the part data of the first and second parts, for example, the control device 21A adds a record including a hash value of the updated part data of the first part to the distributed ledger 56, and adds a record including a hash value of the updated part data of the second part to the distributed ledger 57. In response to the second request, the client server 2A according to the second embodiment does not generate a termination hash value or obtain a timestamp token. The processing for the first and second requests in the second embodiment is as described in FIGS. 5 and 8 in the first embodiment, and therefore the details will not be repeated. In addition, the processing when transaction data is received from another client server 2A in the second embodiment is as described in FIGS. 7 and 10 in the first embodiment, and therefore the details will not be repeated.

FIG. 13 is a diagram for explaining the proof of existence process in embodiment 2. The upper part of FIG. 13 shows a schematic representation of distributed ledger 56, which is the evidence chain of the first part, and the lower part of FIG. 3 shows a schematic representation of distributed ledger 57, which is the evidence chain of the second part.

The first evidence chain (distributed ledger 56) stores records in chronological order including hash values of the part data of the first part. The second evidence chain (distributed ledger 57) stores records in chronological order including hash values of the part data of the second part. Here, as shown in FIG. 13, it is assumed that in the distributed ledger 56, record RA3 with Age "3" is the newest (end) record, and in the distributed ledger 52, record RB2 with Age "2" is the newest (end) record. In this state, it is assumed that a third operation has been performed on the input device 25 or the user terminal device 7 to request the acquisition of a timestamp token.

Upon receiving the third operation, the input device 25 or the user terminal device 7 outputs a third request indicating that the third operation has been performed. The third operation may be, for example, an operation of selecting a button requesting acquisition of a timestamp token displayed on the display device 26 or the display screen of the user terminal device 7. Upon receiving the third request, the control device 21A generates a terminal hash value including the record hash value of the terminal record RA3 of the distributed ledger 56 and the record hash value of the terminal record RB2 of the distributed ledger 57. The control device 21A then transmits the terminal hash value to the time stamp authority 8 via the communication device 24A. The time stamp authority 8 transmits to the client server 2A a time stamp token in which the terminal hash value is combined with time information based on a time source that is traceable to international standard time. The control device 21A stores the time stamp token as a time certificate in the storage device 27. In the second embodiment, by acquiring a time stamp token for the end hash value including the record hash value of the end record RA3 of the distributed ledger 56 and the record hash value of the end record RB2 of the distributed ledger 57, it is possible to prove that the part data D10-D13 of the first part existed and the part data D20-D22 of the second part existed at the time proven by the time stamp token. In addition, if a record is added to the distributed ledgers 56 and 57 after acquiring the time stamp token, it is possible to prove that the part data corresponding to the record was registered after the time proven by the time stamp token. Compared to the case where a time stamp token is acquired for the record hash value of the record each time a record is added to each of the distributed ledgers 56 and 57, the labor hours, costs, system load, etc. can be reduced.

Furthermore, the communication device 24A is configured to be able to communicate with the external server 9. The control device 21A transmits the time certificate to the external server 9 via the communication device 24A.

External server 9 is a server that is separated from network NW (i.e., a server that does not participate in network NW) and is managed by a management entity that is not Company A, Company B, Company C, or Company D. By storing and managing the time certificate in storage device 27 and also managing the time certificate in external server 9, it is possible to increase the resistance to tampering of the time certificate (i.e., time stamp token).

FIG. 14 is a functional block diagram of control device 21A for executing the existence proof process in embodiment 2. Referring to FIG. 14, control device 21A includes an information acquisition unit 2131, a terminal hash generation unit 2132, a timestamp token acquisition unit 2133, and an output unit 2134. Control device 21A functions as information acquisition unit 2131, terminal hash generation unit 2132, timestamp token acquisition unit 2133, and output unit 2134, for example, by executing a program stored in ROM 22. Note that information acquisition unit 2131, terminal hash generation unit 2132, timestamp token acquisition unit 2133, and output unit 2134 may be realized, for example, by dedicated hardware (electronic circuitry).

When a third operation is performed on the input device 25 or the user terminal device 7, the input device 25 or the user terminal device 7 outputs a third request indicating that the third operation has been performed.

The information acquisition unit 2131 acquires the third request from the input device 25 or the user terminal device 7. For example, when a user of the client server 2A operates the input device 25 to select a button requesting acquisition of a timestamp token on the display screen of the display device 26 (performs the third operation), the third request is input to the information acquisition unit 2131. Upon acquiring the third request, the information acquisition unit 2131 outputs the third request to the termination hash generation unit 2132.

When the terminal hash generation unit 2132 receives the third request, it generates a record hash value of the latest (terminal) record stored in the distributed ledger 56 and a record hash value of the latest (terminal) record stored in the distributed ledger 57, and generates a terminal hash value that includes these. The terminal hash generation unit 2132 outputs the generated terminal hash value to the timestamp token acquisition unit 2133.

The time stamp token acquisition unit 2133 outputs a control signal to the communication device 24A to transmit the termination hash value received from the termination hash generation unit 2132 to the time stamp authority 8. As a result, the termination hash value is transmitted to the time stamp authority 8 via the communication device 24A.

The time stamp authority 8 that receives the termination hash value returns a time stamp token to the client server 2.

The timestamp token acquisition unit 2133 receives a timestamp token from the time-stamp authority 8 via the communication device 24A. The timestamp token acquisition unit 2133 outputs the acquired timestamp token to the output unit 2134.

The output unit 2134 stores the timestamp token received from the timestamp token acquisition unit 2133 in the storage device 27. Alternatively, the output unit 2134 may store the timestamp token received from the timestamp token acquisition unit 2133 in the database 4. This makes it possible to obtain proof of the existence time of the part data of the first part and the part data of the second part.

Furthermore, the output unit 2134 transmits the time stamp token received from the time stamp token acquisition unit 2133 to the external server 9 as a time certificate. Specifically, the output unit 2134 outputs a control signal to the communication device 24A for transmitting the time certificate to the external server 9. As a result, the time certificate is transmitted to the external server 9 via the communication device 24A, and the time certificate is managed by the external server 9. For example, in order to tamper with the time stamp token, in addition to the time stamp token managed by the client server 2A, the time certificate (time stamp token) managed by the external server 9 must also be tampered with. By managing the time certificate in the external server 9 as well, the tamper-resistance of the time stamp token can be improved.

FIG. 15 is a flowchart showing the steps of the process for acquiring a timestamp token. The process of the flowchart shown in FIG. 15 is executed by the control device 21A when a third request is received from the input device 25 or the user terminal device 7.

In S31, the control device 21A generates a record hash value of the latest (terminal) record stored in the distributed ledger 56.

In S32, the control device 21A generates a record hash value of the latest (terminal) record stored in the distributed ledger 57.

In S33, the control device 21A generates a termination hash value that includes the record hash values generated in S31 and S32.

In S34, the control device 21A obtains a timestamp token for the termination hash value generated in S33. Specifically, the control device 21A outputs a control signal to the communication device 24A to transmit the termination hash value to the time-stamp authority 8. As a result, the record hash value is transmitted to the time-stamp authority 8 via the communication device 24A. The control device 21A then obtains a timestamp token for the termination hash value from the time-stamp authority 8 via the communication device 24A.

In S35, the control device 21A stores the timestamp token acquired in S34 in the storage device 27. The control device 21A may also store the timestamp token in the database 4.

In S36, the control device 21A transmits the time stamp token acquired in S34 to the external server 9 as a time certificate. Specifically, the control device 21A outputs a control signal to the communication device 24A to transmit the time certificate to the external server 9. As a result, the time certificate is transmitted to the external server 9 via the communication device 24A.

As described above, in the data management system 1A according to the second embodiment, the client server 2A, in response to the third operation, obtains a timestamp token for a terminal hash value including the record hash values of the latest (terminal) records of the two distributed ledgers 56, 57. The client server 2A then stores the timestamp token in the storage device 27 and transmits the timestamp token (time certificate) to the external server 9. By also managing the timestamp token on the external server 9, it is possible to increase the tamper-resistance of the timestamp token.

[Embodiment 3]
In the first embodiment, an example has been described in which the platform server 5 has a function of permitting participation in the network NW. The finality of the transaction data is provided by confirming the validity of an electronic signature between the client servers 2 permitted to participate in the network NW. In the third embodiment, an example will be described in which the platform server 6 has a function of granting finality to the transaction data in addition to the function of permitting participation in the network NW.

FIG. 16 is a diagram showing a schematic configuration of a data management system 1B according to the third embodiment. The data management system 1B has the same functions as the data management system 1 according to the first embodiment. The data management system 1B includes four client servers 3, a platform server 6, and a time authentication authority 8. As in the first embodiment, each of the four client servers 3 is a server belonging to a different company (for example, company A, company B, company C, and company D). In the following, the client server 3 of company A will be described as a representative example, but the client servers 3 of companies B, C, and D also have the same functions.

Similar to the platform server 5 according to the first and second embodiments, the platform server 6 manages the network NW and accepts applications from each client server 3 to participate in the network NW. The platform server 6 permits the client server 3 to participate in the network NW based on an operation by the platform server 6 administrator to permit participation, or based on the result of judging a predetermined condition. In the third embodiment as well, four client servers 3 belonging to each of companies A, B, C, and D are permitted to participate in the network NW.

The four client servers 3 and the platform server 6 form a network NW. Distributed ledger infrastructure software is installed in each of the client servers 3, and each of the client servers 3 functions as a node as a result of the installed distributed ledger infrastructure software functioning. The client servers 3 are configured to be able to communicate with a user terminal device 7, similar to the client server 2 in embodiment 1.

Furthermore, like the client server 2 in the first embodiment, the client server 3 is connected to a database 4. The client server 3 (control device 31) generates a control signal for storing/updating part data in response to an input to the input device 35 or a request from the user terminal device 7, and outputs the control signal to the database 4.

When the client server 3 stores/updates part data in the database 4, it creates a hash value for the part data and generates transaction data for storing the hash value in the ledger held by the platform server 6 and in the distributed ledger held by each client server 3. The client server 3 then transmits the generated transaction data to the platform server 6.

The platform server 6 has the function of providing finality to transaction data. The platform server 6 holds a ledger set 60, processes transaction data received from the client server 3, and updates the ledger set 60. When the platform server 6 updates the ledger set 60, it transmits records (proof records described below) that have been added to the ledger by the update to all client servers 3 participating in the network NW. The client server 3 stores a commit table 374 that stores commit records, and stores the proof records received from the platform server 6 in the commit table 374 as commit records. The commit table 374 corresponds to an example of a "distributed ledger" according to the present disclosure.

17 is a diagram showing an example of the configuration of ledger set 60. Ledger set 60 includes ledger 67 and ledger 68. Ledger 67, like distributed ledger 51 according to embodiment 1, stores the update state of the part data of the first part in chronological order, forming an evidence chain for the part data of the first part. Ledger 68, like distributed ledger 52 according to embodiment 1, stores the update state of the part data of the second part in chronological order, forming an evidence chain for the part data of the second part. Ledger set 60, ledger 67, and ledger 68 have the same configuration as distributed ledger set 50, distributed ledger 51, and distributed ledger 52 according to embodiment 1, respectively. Therefore, detailed description of these will not be repeated. Note that FIG. 17 shows the data structures of ledgers 67 and 68 corresponding to the example shown in FIG. 3. That is, in ledgers 67 and 68, a record of Age "3" is stored as the latest (terminal) record.

Referring again to FIG. 16, the client server 3 includes a control device 31, a ROM 32, a RAM 33, a communication device 34, an input device 35, a display device 36, and a storage device 37. The control device 31, the ROM 32, the RAM 33, the communication device 34, the input device 35, the display device 36, and the storage device 37 are connected to a bus 39. The ROM 32, the RAM 33, the communication device 34, the input device 35, and the display device 36 are basically configured in the same manner as the ROM 22, the RAM 23, the communication device 24, the input device 25, and the display device 26 of the client server 2 according to the first embodiment, respectively, and therefore the description thereof will not be repeated.

The storage device 37 stores a private key 371 and proof data 372. The private key 371 is the private key of company A. For example, when the client server 3 first joins the network NW, the control device 31 generates a private key and a public key. The control device 31 then sends the generated public key to a certification authority (not shown) for authentication. The certification authority issues an electronic certificate including information about the public key. The control device 31 stores the private key 371 corresponding to the authenticated public key in the storage device 37. The control device 31 also sends the authenticated public key (electronic certificate) 651 to the platform server 6.

The proof data 372 includes a suspension table 373 and a commit table 374. FIG. 18 is a diagram for explaining an example of the configuration of the suspension table 373. FIG. 19 is a diagram for explaining an example of the configuration of the commit table 374. The suspension table 373 and the commit table 374 have a record for each target part.

18, the suspension table 373 includes a predetermined type of information included in unused transaction data. Specifically, the suspension table 373 stores suspension records including, for example, key and nonce information. The control device 31 stores the key and nonce information included in the transaction data generated in response to the first or second request as a suspension record in the suspension table 373. The first and second requests received by the client server 3 from the input device 35 or the user terminal device 7 include the ID of the target part. For example, if the target of the first request is the first part, the first request includes an ID indicating "k1", and if the target of the first request is the second part, the first request includes an ID indicating "k2". The second request includes an ID indicating "k1" and an ID indicating "k2". In other words, the ID of the target part included in the first or second request becomes the key. In addition, when the first or second request is received, the control device 31 generates a nonce value. The nonce value represents the processing number of the first or second request (i.e., the transaction data number). The control device 31 creates a suspension record including the key and nonce information, and registers the suspension record in the suspension table 373. FIG. 18 shows an example in which a suspension record including the key k1 is registered in the suspension table 373. In the following, when there is no particular distinction between the first request and the second request, both are collectively referred to as "update request."

When processing responding to the update request is executed (i.e., when the transaction data is used), the control device 31 deletes from the suspension table 373 the suspension record that contains information about a key that is the same as the key contained in the transaction data used to execute the transaction processing.

Duplicate suspension records containing the same key information are not registered in the suspension table 373. When registering a suspension record in the suspension table 373, the control device 31 judges whether a suspension record containing a key matching the key contained in the suspension record to be registered has already been registered in the suspension table 373. If a suspension record containing a key matching the key contained in the suspension record to be registered has not been registered in the suspension table 373, the control device 31 registers the suspension record in the suspension table 373. If a suspension record containing a key matching the key contained in the suspension record to be registered has been registered in the suspension table 373, the control device 31 waits for the suspension record containing the matching key to be deleted from the suspension table 373. In other words, in the example shown in FIG. 18, a suspension record containing a key k2 can be registered in the suspension table 373, but a suspension record containing a key k1 cannot be registered.

The commit table 374 contains a predetermined type of information contained in used transaction data. Specifically, the commit table 374 stores a commit record containing information on Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV. In the third embodiment, the commit record contains the same information as the records in the ledger set 60. The commit table 374 contains commit data 375 that stores a commit record having a key of k1, and commit data 376 that stores a commit record having a key of k2.

When the platform server 6 executes transaction processing and updates the ledgers in the ledger set 60, it creates a proof record and transmits the proof record to all client servers 3 participating in the network NW. The proof record is a record that includes, for example, the Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV information of a record that was added to the ledger by a transaction processing executed using the transaction data.

When the control device 31 receives the proof record, it adds the proof record to the commit table 374 (commit data 375 or commit data 376) as a commit record. The control device 31 then deletes from the suspension table 373 any suspension records that contain the same key as the key contained in the added commit record.

Referring again to FIG. 16, the platform server 6 includes a control device 61, a ROM 62, a RAM 63, a communication device 64, and a storage device 65. The control device 61, the ROM 62, the RAM 63, the communication device 64, and the storage device 65 are connected to a bus 69.

The control device 61 is composed of an integrated circuit including a CPU. The control device 61 loads various programs stored in the ROM 62 into the RAM 63 and executes them. The various programs include an operating system, etc. The RAM 63 functions as a working memory, and temporarily stores various data required for the execution of the various programs. The control device 61 receives transaction data from the client server 3 and executes transaction processing.

The communication device 64 is configured to be able to communicate with the client server 3 participating in the network NW.

The storage device 65 stores multiple public keys 651 and ledger set 60. The multiple public keys 651 include the public keys of companies that manage client servers 3 participating in the network NW. Specifically, the multiple public keys 651 include the public key of company A, the public key of company B, the public key of company C, and the public key of company D.

As described above, ledger set 60 has the same configuration as distributed ledger set 50 according to embodiment 1.

Below, we will explain the process of responding to update requests (first request, second request) in embodiment 3, using a flowchart.

FIG. 20 is a flowchart showing the procedure of processing executed by the data management system 1B when an update request (first request, second request) is received. The processing of the flowchart shown in FIG. 20 is started by the control device 31 of the client server 3 when an update request (first request, second request) is received from the input device 25 or the user terminal device 7.

In S40, the control device 31 of the client server 3 generates a nonce value. This nonce value is used as the number of the transaction data that is generated in response to the update request.

In S41, the control device 31 of the client server 3 generates a suspension record. Specifically, the control device 31 of the client server 3 reads the ID of the target part included in the update request and sets it as the Key information, and generates a suspension record using the nonce value generated in S40 as the Nonce information. Note that if the update request is a second request, the control device 31 generates a suspension record with the ID (k1) of the first part as the Key information and a suspension record with the ID (k2) of the second part as the Key information.

In S42, the control device 31 of the client server 3 judges whether the suspension record generated in S41 can be registered in the suspension table 373. If a suspension record having the same key information as the suspension record generated in S41 is registered in the suspension table 373, the control device 31 of the client server 3 makes a negative judgment (NO in S42) and waits for the suspension record having the same key information to be deleted from the suspension table 373. On the other hand, if a suspension record having the same key information as the suspension record generated in S41 is not registered in the suspension table 373, the control device 31 of the client server 3 makes an affirmative judgment (YES in S42) and proceeds to S43.

In S43, the control device 31 of the client server 3 registers the suspension record in the suspension table 373.

In S44, the control device 31 of the client server 3 generates transaction data to respond to the update request. Specifically, if the update request is a first request, the control device 31 of the client server 3 executes processes similar to the processes of S2 to S4 described in FIG. 8 to generate transaction data. If the update request is a second request, the control device 31 of the client server 3 executes processes similar to the process of S11 described in FIG. 9 to generate transaction data corresponding to the updates of the first part and the second part. Furthermore, if the update request is a second request, the control device 31 of the client server 3 executes processes similar to the processes of S13 to S16 described in FIG. 9 to generate transaction data. Details of each process are as described in FIG. 8 and FIG. 9, so they will not be described repeatedly.

In S45, the control device 31 of the client server 3 outputs a control signal to the communication device 34 to transmit the transaction data generated in S44 to the platform server 6. As a result, the transaction data is transmitted to the platform server 6 via the communication device 34.

In S50, the control device 61 of the platform server 6 decrypts the electronic signature included in the received transaction data to verify its validity. Specifically, the control device 61 of the platform server 6 executes the same processes as those of S21 to S23 described in FIG. 10 to decrypt the electronic signature. Details of each process are as described in FIG. 10, so they will not be described again.

In S51, the control device 61 of the platform server 6 verifies the validity of the electronic signature decrypted in S50. Specifically, the control device 61 of the platform server 6 compares the decrypted value of the electronic signature with a hash value included in the transaction data (in transaction data generated in response to a first request, this is the hash value of the part data of the target part, and in transaction data generated in response to a second request, this is the timestamp token). If the two do not match, the control device 61 of the platform server 6 does not recognize the validity of the electronic signature (NO in S51) and proceeds to S52. If the two match, the control device 61 of the platform server 6 recognizes the validity of the electronic signature (YES in S51) and proceeds to S53.

In S52, the control device 61 of the platform server 6 determines that the transaction data received from the client server 3 may have been tampered with, discards the transaction data, and creates an abnormality report indicating the possibility of tampering. The control device 61 of the platform server 6 then advances the process to S56.

In S53, the control device 61 of the platform server 6 executes transaction processing. Specifically, the control device 61 of the platform server 6 executes processing similar to the processing of S26 and S27 described in FIG. 10, generates a ledger record identified by the key information included in the transaction data, adds the generated record to the ledger, and updates the ledger set 60.

In S54, the control device 61 of the platform server 6 generates a proof record. The proof record includes the Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV information contained in the record added to the ledger.

In S55, the control device 61 of the platform server 6 creates a success report indicating that the update of the ledger set 60 has been completed (i.e., the transaction data has been processed). The control device 61 of the platform server 6 includes a proof record in the success report.

In S56, the control device 61 of the platform server 6 outputs a control signal to the communication device 64 to transmit the abnormality report created in S52 or the normality report created in S55 to the client server 3 that is the sender of the transaction data. As a result, the abnormality report or normality report is transmitted to the client server 3 via the communication device 64.

In addition, in S56, the control device 61 of the platform server 6 outputs a control signal to the communication device 64 to transmit the proof record to other client servers 3 other than the sender of the transaction data (for example, the client servers 3 of companies B, C, and D). As a result, the proof record is transmitted to the other client servers 3 via the communication device 64.

In S46, the control device 31 of the client server 3 determines whether or not a normal report has been received from the platform server 6. If it determines that a normal report has been received (YES in S46), the control device 31 of the client server 3 advances the process to S47. On the other hand, if it determines that a normal report has not been received, i.e., that an abnormality report has been received (NO in S46), the control device 31 of the client server 3 advances the process to S49.

In S47, the control device 31 of the client server 3 adds the proof record included in the normal report as a commit record to the commit table 374. Specifically, the control device 31 of the client server 3 determines whether the target to which the commit record is to be added is commit data 375 or commit data 376, based on the key information of the proof record. Then, the control device 31 of the client server 3 adds the commit record to the target commit data.

In S48, the control device 31 of the client server 3 deletes the suspension record that has the same key information as the added commit record from the suspension table 373.

In S49, the control device 31 of the client server 3 displays the results of the processing for the update request on the display device 36 or transmits them to the user terminal device 7, for example.

In addition, the other client servers 3 (client servers 3 of companies B, C, and D) that received the proof record sent in S56 also add the proof record to their commit tables 374 in a similar manner, thereby updating the commit tables 374.

As described above, in the data management system 1B according to the third embodiment, the platform server 6 provides finality to transaction data. The platform server 6 holds a ledger set 60 including two ledgers 67 and 68. The ledger 67 stores the update state of the part data of the first part in chronological order, and the ledger 68 stores the update state of the part data of the second part in chronological order. When the ledger set 60 is updated, a proof record having information of the record added to the ledger set 60 is sent from the platform server 6 to each client server 3. Each client server 3 adds the proof record to the commit table 374 as a commit record. The commit table 374 corresponds to the distributed ledger set 50 according to the first embodiment. In the configuration of the data management system 1B according to the third embodiment, in response to the second request, record hash values of the latest (terminal) records of the two commit data 375 and 376 are generated, and a terminal hash value including these is generated. Then, a timestamp token is obtained for the terminal hash value. By obtaining a timestamp token for the terminal hash value, it is possible to prove, for example, as in the example of FIG. 3 in embodiment 1, that component data for the first component (e.g., D10 to D13 in the example of FIG. 3) existed at the time proven by the timestamp token, and that component data for the second component (e.g., D20 to D22 in the example of FIG. 3) existed.

In addition, by incorporating the timestamp token into the record of at least one ledger included in the ledger set 60, the timestamp token is incorporated into at least one commit data included in the commit table 374. This makes it possible to increase the tamper-resistance of the timestamp token.

[Modification 2]
In the third embodiment, an example has been described in which the commit table 374 has information similar to that contained in the ledger set 60. Specifically, each of the commit data 375, 376 in the commit table 374 has information on Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV. The commit table 374 may have a part of the information contained in the ledger set 60. For example, each of the commit data 375, 376 in the commit table 374 may be configured to include information on Key, Age, Obj-HV, HV, and Nonce from the information on Key, Age, Obj-HV, Nonce, Sig, Prev-HV, and HV contained in each of the ledgers 67, 68 in the ledger set 60. In this case, the proof record is also generated to include information on Key, Age, Obj-HV, HV, and Nonce. That is, the commit data 375, 376 are summaries of the ledgers 67, 68. By making the commit data 375, 376 a summary of the ledgers 67, 68, the amount of data stored in the storage device 37 of the client server 3 can be reduced compared to a case in which the commit data 375, 376 and the ledgers 67, 68 have similar information.

[Modification 3]
It is also possible to combine the configuration of the second embodiment with the third embodiment. That is, in the third embodiment, the existence proof process may be executed in response to the third request. Even in such a configuration, it is possible to achieve the same effect as the second embodiment.

The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The technical scope of the present disclosure is indicated by the claims, not by the description of the embodiments above, and is intended to include all modifications within the meaning and scope of the claims.

1, 1A, 1B Data management system, 2, 2A, 3 Client server, 4 Database, 5, 6 Platform server, 7 User terminal device, 8 Time authentication authority, 9 External server, 21, 21A Control device, 22 ROM, 23 RAM, 24, 24A Communication device, 25 Input device, 26 Display device, 27 Storage device, 29 Bus, 31 Control device, 32 ROM, 33 RAM, 34 Communication device, 35 Input power device, 36 display device, 37 storage device, 39 bus, 50 distributed ledger set, 51, 52 distributed ledger, 55 distributed ledger set, 56, 57 distributed ledger, 60 ledger set, 61 control device, 62 ROM, 63 RAM, 64 communication device, 65 storage device, 67, 68 ledger, 69 bus, 271 private key, 272 multiple public keys, 371 private key, 372 proof data, 373 suspension table , 374 commit table, 375, 376 commit data, 651 multiple public keys, 2101 information acquisition unit, 2102 hash generation unit, 2103 nonce generation unit, 2104 digital signature unit, 2105 transaction data generation unit, 2106 transaction data transmission unit, 2111 information acquisition unit, 2112 record addition unit, 2113 termination hash generation unit, 2114 nonce generation unit, 2115 time stamp token acquisition unit, 2116 electronic signature unit, 2117 transaction data generation unit, 2118 transaction data transmission unit, 2121 transaction data acquisition unit, 2122 signature verification unit, 2123 record creation unit, 2124 ledger update unit, 2125 output unit, 2131 information acquisition unit, 2132 termination hash generation unit, 2133 timestamp token acquisition unit, 2134 output unit, NW network.

Claims (8)

1. A data management device that manages data using distributed ledger technology,
   A storage device that stores a distributed ledger that chronologically stores records including information about the data;
   a control device for adding the record to the distributed ledger;
   A communication device configured to be able to communicate with a time stamp authority,
   the data includes first data and second data;
   The distributed ledger includes a first distributed ledger that chronologically stores records including first information about the first data, and a second distributed ledger that chronologically stores records including second information about the second data,
   The control device includes:
   Generate an end value that includes information of an end record of the first distributed ledger and information of an end record of the second distributed ledger;
   A data management device that obtains a time stamp token for the terminal value from the time stamp authority via the communication device.
2. The data management device of claim 1, wherein the control device stores a record including the timestamp token in at least one of the first distributed ledger and the second distributed ledger.
3. The communication device is further configured to be able to communicate with an external server different from the data management device,
   The data management device according to claim 1 , wherein the control device stores the time stamp token in the storage device and transmits the time stamp token to the external server via the communication device.
4. The data management device according to any one of claims 1 to 3, wherein the control device stores a record including the first information in the first distributed ledger in response to updates to the first data and the second data, and generates the terminal value when it stores a record including the second information in the second distributed ledger.
5. The data management device according to any one of claims 1 to 3, wherein the control device generates the terminal value when a predetermined time has elapsed since the previous timestamp token was acquired.
6. The information of the end record of the first distributed ledger is a hash value of the end record of the first distributed ledger,
   The data management device according to claim 1 , wherein the information of the record at the end of the second distributed ledger is a hash value of the record at the end of the second distributed ledger.
7. the first information is a hash value of the first data,
   The data management device according to claim 1 , wherein the second information is a hash value of the second data.
8. A data management method for a data management device that manages data using distributed ledger technology, comprising:
   The data management device includes:
   A storage device that stores a distributed ledger that chronologically stores records including information about the data;
   a control device for adding the record to the distributed ledger;
   A communication device configured to be able to communicate with a time stamp authority,
   the data includes first data and second data;
   The distributed ledger includes a first distributed ledger that chronologically stores records including first information about the first data, and a second distributed ledger that chronologically stores records including second information about the second data,
   The data management method includes:
   generating an end value including information of an end record of the first distributed ledger and information of an end record of the second distributed ledger;
   and obtaining a time stamp token for the terminal value from the time stamp authority via the communication device.

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