JP7745896B2 - File management method, file management program, and file management system - Google Patents

Description

The present invention relates to a file management method, a file management program, and a file management system.

Conventionally, when using a network service, a system known as a client-server system has become widespread, in which a computer using the service (client) and a computer providing the service or data (server) communicate over a network. However, such systems have security issues, such as the entire system becoming unavailable if the server stops working, and because data is concentrated on the server, unauthorized access to the server can easily lead to information leakage. To solve these problems, a system known as a distributed file system is used, in which multiple geographically dispersed computers are connected via a P2P (Peer to Peer) network and data is stored. An example of such a system is proposed in, for example, Non-Patent Document 1.

For example, Non-Patent Document 1 discloses that when a file is stored in a distributed file system, it is split into smaller chunks, cryptographically hashed, and given a unique fingerprint called a Content Identifier (CID), which acts as a persistent record of the file as it exists at that time; when other nodes search for the file, they ask the node that stores the content referenced by the file's CID, and when the file is viewed or downloaded, a copy is cached.

"IPFS powers the Distributed Web," [Retrieved June 29, 2023], Internet <https://ipfs.tech/>

However, the technology proposed in Non-Patent Document 1 encrypts the divided data and stores it in a distributed manner, but has the problem that it is not possible to securely manage the information used to decrypt the encrypted files.

In light of the above issues, the present invention aims to solve the problem of providing a new technology that can store large amounts of data and manage files more securely.

To solve the above problems, the present invention provides a file management method for distributed management of information among multiple nodes via P2P communication, in which a first node that uploads a target file to be distributedly managed performs the following steps: a division step in which the target file is divided and multiple split files associated with the target file are created; an encryption step in which the split files are encrypted to generate encrypted split files; and a transmission step in which the encrypted split files and decryption information for decryption are transmitted to other nodes.

With this configuration, files to be managed in a distributed manner can be divided and the divided files can be encrypted, enabling more secure distributed management of files. Furthermore, by sending the compound information required to decrypt the encrypted file to other nodes, the security of the compound information can also be ensured, ensuring high security even if the number of participating nodes increases and the amount of data that can be stored increases.

In a preferred embodiment of the present invention, the second node that downloads the target file receives the designation of the target file and executes an acquisition step of acquiring encrypted split files associated with the target file and decryption information for the encrypted split files, and a decryption step of decrypting the encrypted split files based on the acquired decryption information.

With this configuration, encrypted split files that are managed in a distributed manner and decryption information can be obtained from other nodes, and split files can be obtained from the encrypted split files. This allows any node participating in P2P communication to obtain and decrypt the encrypted split files.

In a preferred embodiment of the present invention, the splitting step generates split files with attached linkage statuses, the acquisition step accepts the designation of the target file to be restored and acquires the encrypted split files linked to the designated target file and the decryption information, and the second node further executes a restoration step in which the designated target file is restored based on the split files obtained as a result of the decryption step and the linkage status.

With this configuration, you can specify the target file you want to restore, obtain the encrypted split files associated with that target file, decrypt the split files from the encrypted split files, and restore the specified target file. Furthermore, by generating split files with a combined status, you can prevent the wrong file from being restored.

In a preferred embodiment of the present invention, in the transmission step, the encrypted split files linked to the sharing groups are transmitted to the other nodes, and the second node that downloads the target files further executes a display processing step that displays, for each sharing group, target file information corresponding to the transmitted encrypted split files.

By configuring in this way, the encrypted split files can be linked to the sharing groups that share the target files, and the target files can be managed for each sharing group between nodes that perform P2P communication.

In a preferred embodiment of the present invention, the first node and the other node are nodes within one WAN, and in the sending step, if the first node within a first LAN and the other node within a second LAN are connected via VPN, the encrypted split files are sent to the other node located on an internal network, and if the first node and the other node are not connected via VPN, the encrypted split files are sent to the other node located on an external network.

This configuration allows the node destination to which encrypted split files are sent to to be changed depending on whether a VPN is connected or not.

In a preferred embodiment of the present invention, the first node further executes a calculation step of calculating file importance based on file operation information regarding operations performed on the target file, and a connection step of determining whether to establish a VPN connection with the other node based on the file importance.

With this configuration, the importance of the file can be calculated based on information about operations performed on the target file, and a decision can be made as to whether or not to connect to the VPN depending on the importance. This eliminates the need to always connect to the VPN depending on the importance of the target file, reducing the frequency of data communication and power consumption.

In a preferred embodiment of the present invention, the encryption step stores the multiple pieces of decryption information for each of the split files.

This configuration allows multiple pieces of decryption information to be generated to decrypt the encrypted split files, making it possible to share the target files more securely.

In a preferred embodiment of the present invention, the first node further performs an authentication step to authenticate the user based on digital authentication that verifies the user's authenticity, physical key authentication that verifies whether a physical key for file transfer is connected, and VPN authentication that verifies whether profile information for the VPN connection is set.

This configuration allows for more secure sharing of target files by requiring digital authentication, physical key authentication, and VPN authentication to accept user access.

The present invention has the effect of providing a new technology that can store large amounts of data and manage files more securely.

1 is a system configuration diagram according to an embodiment of the present invention. FIG. 1 is a diagram illustrating a hardware configuration according to an embodiment of the present invention. FIG. 1 is a functional block diagram according to an embodiment of the present invention. 10 is an example of a file sharing screen according to an embodiment of the present invention. 10 is an example of a flowchart of a process for sharing a target file according to an embodiment of the present invention. FIG. 10 is a system configuration diagram according to another embodiment of the present invention. 10 is a flowchart illustrating an example of an upload process according to another embodiment of the present invention. 10 is an example of a flowchart of a download process according to another embodiment of the present invention.

(Embodiment 1)
The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments are shown, but which may be embodied in many different forms and are not limited to the embodiments set forth herein.

For example, while this embodiment describes the configuration, operation, etc. of a file management system, similarly configured methods, computer programs, etc. can also achieve similar effects. The program may also be stored on a recording medium. Using this recording medium, the program can be installed on a computer, for example, thereby configuring a file management system. Here, the recording medium on which the program is stored may be a non-transitory recording medium, such as a CD-ROM.

In this embodiment, "unit" can include, for example, hardware resources implemented by a circuit in the broad sense, as well as software information processing that can be specifically realized by these hardware resources. In this embodiment, "information" can be represented, for example, by the physical value of a signal representing voltage or current, the high or low value of a signal as a binary bit collection consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculations can be performed on a circuit in the broad sense. A circuit in the broad sense is a circuit realized by appropriately combining a circuit, circuitry, processor, memory, etc. In other words, it includes a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), etc.

This invention relates to a system (known as a distributed file system) that uses P2P communication to distribute and manage information among multiple nodes. Here, a distributed file system is a system in which, when a node uploads information on a network made up of multiple nodes, cache files of that information are stored in succession in nodes adjacent to the node, and the cache files are distributed and managed among multiple nodes.

In this invention, information to be managed in a distributed manner (hereinafter referred to as "target files") is divided and encrypted, and the resulting encrypted split files are uploaded to a distributed file system, thereby achieving distributed management of the target files. This embodiment (embodiment 1) describes a case in which information is managed in a distributed manner using P2P communication between multiple nodes located on the same LAN (Local Area Network).

1. System Configuration of First Embodiment
1 is a block diagram showing the configuration of a system according to an embodiment of the present invention. As shown in Fig. 1, a file management system 0 includes a plurality of nodes 1, which are configured to be capable of P2P communication via a LAN.

Node 1 can be a general-purpose server computer, personal computer, smartphone, tablet terminal, wearable device, etc. In this embodiment, node 1, which aggregates the file information (described below) that serves as an index for searching files, is called the parent node, and node 1, which searches for encrypted split files based on that file information, is called the child node.

The LAN in this embodiment may be wired or wireless, but there are no restrictions on the wired cable or wireless LAN standards, and there are also no restrictions on the LAN connection format, access control method, or scale.

<1.1. Hardware configuration>
2 is a hardware configuration diagram, the node 1 includes a processing unit 11, a storage unit 12, a communication unit 13, an input unit 14, and an output unit 15.

The processing unit 11 has a processor such as a CPU that can execute an instruction set, and controls the overall operation and processing of the file management device (node) by executing the file management program according to the present invention, the OS, and other applications.
The storage unit 12 includes a volatile memory such as a RAM capable of storing an instruction set, and a non-volatile recording medium such as an HDD or SSD capable of recording an OS, a file management program, and the like.
The communication unit 13 has a communication interface device for connecting to a network, and controls communication with the LAN to input and output information.
The input unit 94 has an input device capable of input processing, such as a keyboard or a touch panel.
The output unit 95 has a display device capable of display processing, such as a display.

<1.2. Functional configuration of node 1>
3 is a functional block diagram of the node 1 in the embodiment 1. As shown in Fig. 3, the node 1 includes a division unit 101, an encryption unit 102, a transmission unit 103, an acquisition unit 104, a decryption unit 105, a restoration unit 106, an authentication unit 107, a display processing unit 108, and a database 2. This is a specific implementation of information processing by software (stored in a storage unit 12) by hardware (a processing unit 11).

<1.3. Database 2>
The database 2 stores user information, sharing group information, and file information.

<1.3.1. User Information>
User information is information about a user who uses the distributed file system. The user information includes a user ID that uniquely identifies the user, a user name, an email address, a password, the ID of the organization to which the user belongs (organization ID), and the like, and is stored in association with shared group information.

<1.3.2. Shared Group Information>
The shared group information is information that indicates a group of target files that are shared by users. In this embodiment, the shared group is information created for each project that an organization is working on, and includes a shared group ID and a shared group name that uniquely identify the shared group, and is stored in association with the organization ID.

<1.3.3. File information>
The file information is information relating to files to be managed in a distributed manner, and includes target file information relating to meta information of the target file, and split file information relating to meta information of the split files.
The target file information includes the hash value of the target file, the target file name, the target file size, the ID of the folder in which the target file is placed, the ID of the user who uploaded the target file, and the upload date and time.
The split file information includes hash values of the split files, split file names, merge status of the split files, ID of the folder in which the target file is placed, hash values of the encrypted split files, and decryption information. In this embodiment, the decryption information is one or more private keys, but it may also be a public key, a password, etc.

In this embodiment, the parent node has at least Database 2. Database 2 of the parent node stores at least the target file information and split file information sent from the child node. The parent node may also have a splitting unit 101, encryption unit 102, transmission unit 103, acquisition unit 104, decryption unit 105, restoration unit 106, authentication unit 107, and display processing unit 108. Database 2 of the child node stores encrypted split files. The encrypted split files may also be distributed and stored in Database 2 of the parent node. Node 1 does not need to include a parent node; in that case, file information is distributed and stored in Node 1 (child node).

In addition to file information, in this embodiment, user information and shared group information are stored in the parent node's database 2. Alternatively, they may be stored in an external authentication server on the Internet or in the child node's database.

<1.4. Dividing section 101>
The dividing unit 101 divides a target file and creates a plurality of split files associated with the target file. The dividing unit 101 divides the target file and creates split files to which a combined status is assigned. Here, the combined status is information necessary for restoring the target file from the split files.

<1.5. Encryption unit 102>
The encryption unit 102 performs encryption processing on the split files to generate encrypted split files. The encryption unit 102 generates one or more pieces of key information for each split file and performs encryption processing on the split files one or more times to generate encrypted split files. The encryption unit 102 then stores one or more pieces of decryption information corresponding to the key information for each encrypted split file. Note that in this embodiment, different key information is used for each split file, but the same key information may be used for all split files. Here, key information is information for encrypting the split files and includes a common key, a private key, and a public key.

<1.6. Transmitting unit 103>
The transmitting unit 103 transmits the encrypted split files and decryption information to other nodes 1. The transmitting unit 103 transmits the encrypted split files to child nodes and the decryption information to parent nodes. The transmitting unit 103 also transmits the encrypted split files linked to the sharing group to the child nodes.

<1.7. Acquisition unit 104>
The acquisition unit 104 acquires the encrypted split files and key information. The acquisition unit 104 accepts the designation of a target file and acquires the encrypted split files associated with the target file and the key information for the encrypted split files.

<1.8. Decoding unit 105>
The decryption unit 105 decrypts the encrypted split files based on the decryption information. The decryption unit 105 decrypts the encrypted split files based on the decryption information for each encrypted split file, and obtains the split files.

<1.9. Restoration Unit 106>
The restoration unit 106 restores the target file based on the split files. The restoration unit 106 restores the target file based on the split files obtained by the decryption unit 105 and the connection statuses assigned to the split files.

<1.10. Authentication unit 107>
The authentication unit 107 performs user authentication. In this embodiment, the authentication unit 107 performs user authentication based on digital authentication that proves the legitimacy of the user, physical key authentication that identifies node 1 of the distributed file system, and VPN authentication that proves whether profile information for a VPN connection is set. In this embodiment, a physical key for exchanging files is connected to node 1, and the authentication unit 107 receives, as digital authentication, a wallet ID that uniquely identifies a wallet for accessing data in the distributed file system from the physical key. As physical key authentication, the authentication unit 107 receives, from the physical key, a local IP address and a node ID (so-called Peer ID) that uniquely identifies node 1, which is generated for each node 1. As VPN authentication, the authentication unit 107 receives, from the physical key, profile information for the VPN connection, and an email address and password from the user.
<1.11. Display processing unit 108>
The display processing unit 108 displays target file information related to the target files on a file sharing screen (described later). The display processing unit 108 displays information on the target files corresponding to the encrypted split files for each sharing group, and transmits the display processing results to the second node.

In this embodiment, the display process refers to the process in which the display processing unit 108 executes processing to generate the necessary information, transmits the generated information to the output unit 95, and the output unit 95 displays the generated information.

<2. Example of file sharing screen>
4 shows an example of a file sharing screen for sharing a target file, which is displayed on node 1 when access authentication is successful. The file sharing screen W1 includes an organization display section ORD, a sharing group display section SGD, and a target file display section EFD.

The organization display unit ORD displays a changeable organization associated with the user corresponding to the email address and password entered during access authentication. The shared group display unit SGD displays a specifiable shared group associated with the organization displayed in the organization display unit ORD. Note that in this embodiment, each shared group is associated with a user who can access it, but all users belonging to the organization may also be able to access it.

The target file display area EFD displays information about the target file associated with the sharing group specified in the sharing group display area SGD, including the target file name, the user name who uploaded the target file, the upload date and time, and the hash value of the target file. In this embodiment, specifying a sharing group displays a shared folder (not shown) associated with the specified sharing group, and specifying a shared folder displays the target file information. Alternatively, specifying a sharing group may display the target file information associated with that sharing group.

Then, when the user selects and inputs the "Upload" button on the file sharing screen W1, the target file is uploaded, and when the user specifies the target file information displayed in the target file display area EFD and inputs the download-related information, the download is executed.

<3. Flowchart>
The file management method of this embodiment will be described below with reference to Fig. 5. Fig. 5 is a flowchart showing the process of sharing a target file within a LAN. Note that the following description will focus on the flowchart after successful access authentication.

<3.1. Upload process flowchart>
FIG. 5A shows a processing flowchart up to when the first node uploads the target file.

<3.1.1. Receiving shared group and shared folder designations>
First, in step S101 (hereinafter, "step SXXX" will be simply referred to as "SXXX"), the display processing unit 108 displays a shared group for each organization to which a user corresponding to the email address and password accepted at the time of access authentication belongs. Then, in S102, the display processing unit 108 accepts the designation of a shared group and displays the shared folders linked to the shared group.

<3.1.2. Creating split files>
Next, in S103, the dividing unit 101 receives a designation of a target file to be uploaded, divides the target file, and creates split files. In this embodiment, the dividing unit 101 receives a designation of a target file stored in each node 1, divides the target file, and creates split files associated with the target file.

<3.1.3. Encryption of split files>
Next, in S104, the encryption unit 102 performs encryption processing on the split files created in S103 to generate encrypted split files. In this embodiment, the encryption unit 102 performs encryption processing on each split file to generate multiple encrypted split files. The encryption unit 102 then generates multiple private keys for each encrypted split file as decryption information.

<3.1.4. Uploading encrypted split files>
In S105, the transmitting unit 103 accepts the specification of a destination to which the notification is to be sent. In this embodiment, when the specification of the target file to be uploaded is accepted, nodes 1 that can communicate via the LAN are displayed, and the transmitting unit 103 accepts the specification of the node 1 and accepts the specification of a destination to which the notification is to be sent. Then, in S106, the transmitting unit 103 accepts input of a message to be sent to the destination specified in S105.

Next, in S107, the transmitting unit 103 transmits the encrypted split files, target file information, and split file information to other nodes. In this embodiment, the transmitting unit 103 of the first node transmits multiple encrypted split files linked to the sharing group specified in S101 to other child nodes. Then, the transmitting unit 103 of the child node that received the encrypted split files from the first node transmits hash values for each encrypted split file obtained from the encrypted split files to the first node. Then, the transmitting unit 103 of the first node that received the hash values for each encrypted split file transmits, to the parent node, target file information generated based on the target file specified in S101 and split file information generated based on the split files associated with the target files and including the hash values of the received encrypted split files. The parent node then stores the received target file information and split file information for each split file.

Note that when the transmitting unit 103 of the first node transmits the encrypted split files, target file information, and split file information to other nodes, if it is unable to transmit to all other child nodes (for example, if all child nodes are powered off), the encrypted split files, target file information, and split file information are temporarily stored in the first node, and the temporarily stored information is transmitted to the other child nodes when they are powered on.

<3.1.5. Display process of target file information>
Then, in S108, the display processing unit 108 displays the target file information. In this embodiment, the display processing unit 108 displays information about the target files corresponding to the encrypted split files transmitted in S107, and displays the information for each sharing group display section SGD on the file sharing screen W1.

By performing steps S101 to S108 above, the target file is stored in the distributed file system, allowing the target file to be managed securely. Furthermore, node 1, which is connected so that it can communicate via the LAN, can download the target file by performing steps S201 to S205 below.

<3.2. Download process flowchart>
FIG. 5B shows a processing flowchart up to when the second node downloads the target file.

<3.2.1. Acceptance of designation of target file to download>
First, in S201, the display processing unit 108 displays a list of target file information associated with the organization to which the user belongs, and the acquisition unit 104 accepts a designation of a target file to be restored. Then, in S202, the acquisition unit 104 acquires encrypted split files and decryption information associated with the designated target file. In this embodiment, the acquisition unit 104 accepts a designation of information about the target file displayed in the target file display unit EFD, and acquires from the parent node all data of the target file information corresponding to the designated target file, including the target file ID, target file name, hash value of the target file, uploader ID, and upload date and time, as well as split file information corresponding to the designated target file. Then, the acquisition unit 104 acquires the encrypted split files from the child nodes based on the hash values of the encrypted split files included in the split file information.

<3.2.2. Decryption of Encrypted Split Files>
Next, in S203, the decryption unit 105 decrypts the encrypted split files based on the decryption information acquired in S202. In this embodiment, the decryption unit 105 decrypts the encrypted split files by generating public keys from the private keys using the multiple private keys in the decryption information acquired in S202.

<3.2.3. Restoring and downloading target files>
In S204, the restoration unit 106 restores the target file by combining the split files obtained as a result of the decryption in S203. In this embodiment, the restoration unit 106 restores the target file specified in S201 based on the combination status assigned to the split files. Then, in S205, a registration unit (not shown) registers the restored target file in database 2 of the second node if the hash value of the target file restored in S204 matches the hash value of the target file in the target file information acquired in S202.

As described above, the file management system of embodiment 1 enables secure information sharing by distributing and managing divided and encrypted target files among nodes located within the same LAN.

(Embodiment 2)
Next, in a second embodiment, a case will be described in which information is managed in a distributed manner by P2P communication among a plurality of nodes arranged in a WAN (Wide Area Network) in which a plurality of LANs are connected via an open network.

In the first embodiment, target files were uploaded and downloaded by communicating via the same LAN. In contrast, in this embodiment, when uploading and downloading files between nodes 1 located on different LANs, communication is performed via an open network or VPN. In the following explanation, the system according to this embodiment operates each functional configuration, and parts common to the first embodiment will be omitted.

4. System Configuration of Second Embodiment
Fig. 6 is a block diagram showing the configuration of a file management system according to this embodiment. As shown in Fig. 6, the file management system is configured with a plurality of LANs on which a plurality of nodes 1 that perform P2P communication are arranged, and each LAN is configured to be able to communicate via an open network.

In this embodiment, a node 1 located on a first LAN is configured to be able to communicate with a node 1 (internal node) located on the first LAN via the LAN, and with a node (external node) of an external distributed file system via an open network. Furthermore, a node 1 located on the first LAN is configured to be able to communicate with a node 1 (private external node) located on another LAN (second LAN) of the external distributed file system via a VPN connection, and with a node 1 (public external node) located on a public network via an open network. Note that in this embodiment, a VPN connection is established via a VPN device to enable communication between LANs, but communication may also be performed via an open network without a VPN connection.

In addition, the WAN in this embodiment is realized by a VPN connection, but there are no restrictions on the type of WAN; it can be a digital leased line, wide area Ethernet, etc., and there are no restrictions on the size of the WAN.

<4.1. Functional configuration of node 1>
In addition to the division unit 101, encryption unit 102, transmission unit 103, acquisition unit 104, decryption unit 105, restoration unit 106, authentication unit 107, display processing unit 108, and database 2, node 1 in embodiment 2 further includes a calculation unit 109 and a connection unit 110.

<4.2. Transmitting unit 103 in embodiment 2>
The transmitter 103 transmits at least the encrypted split files from the first node in the first LAN to the private external node via the VPN or the open network. In this embodiment, if the first node in the first LAN and the external node are connected via VPN, the transmitter 103 transmits the encrypted split files to the private internal node, and if the first node and the external node are not connected via VPN, the transmitter 103 transmits the encrypted split files and decryption information to the public external node.

4.3. Calculation unit 109
The calculation unit 109 calculates the file importance, which is an index for determining whether or not nodes 1 located on different LANs will establish a VPN connection. The calculation unit 109 calculates the file importance based on file operation information related to operations performed on a target file.

<4.4. Connection portion 110>
The connection unit 110 determines whether to establish a VPN connection with an external node and establishes the VPN connection based on the importance calculated by the calculation unit 109. The connection unit 110 establishes the VPN connection when the file importance is equal to or greater than a predetermined threshold.

<5. Flowchart>
The file management method of this embodiment will be described below with reference to FIGS.

<5.1. Upload process flowchart>
7 is a flowchart showing the process of uploading a target file from a first node located in a first LAN to a private external node. Note that the processes from S301 to S307 are the same as the processes (S101 to S107) for uploading encrypted split files in the first embodiment, and therefore will not be described here.

5.1.1. Calculation of file importance
In S308, the calculation unit 109 calculates the file importance based on the file operation information. In this embodiment, the calculation unit 109 sets a predetermined weight for each operation indicator that indicates whether a file is important in terms of operations performed on the file, and calculates the file importance by adding up the predetermined weights depending on whether an operation corresponding to the operation indicator has been performed.

Specifically, for example, operation indicators include "whether a message was entered when uploading," "the degree of association between the message and the file name or tags attached to the file," "the contents of tags registered in association with the file," and "whether the file was obtained from an external system." The calculation unit 109 then sets a predetermined weight for each of these operation indicators, multiplies the weight by "1" if the corresponding operation has been performed, or by "0" if the corresponding operation has not been performed, and adds up the weights to calculate the total as the file importance.

In a more preferred embodiment, the calculation unit 109 divides the numerical value obtained by adding up the weights by the number of operation indicators, and calculates the numerical value obtained by adding the quotient obtained as a result of the division and a predetermined correction term as the file importance. Also, if the file importances are the same numerical value, the calculation unit 109 obtains the latency of the packets sent to the other party, and calculates the numerical value obtained by dividing the latency tolerance set in advance by the user by the obtained latency as the communication priority.

<5.1.2. VPN connection processing>
In S309, the connection unit 110 determines whether to establish a VPN connection based on the file importance calculated in S308. If the file importance exceeds a threshold previously set by the user (YES in S309), the connection unit 110 determines to establish a VPN connection between the first node of the first LAN and the external node. In S310, the transmission unit 103 transmits the encrypted split files and decryption information to the private external node via the VPN. Note that if communications with the same file importance are performed simultaneously, the connection unit 110 determines whether to establish a VPN connection based on the communication priority calculated by the calculation unit 109.

On the other hand, if the file importance does not exceed the threshold previously set by the user (NO in S309), the connection unit 110 determines not to connect the VPN between the first node of the first LAN and the external node. Then, in S311, the transmission unit 103 transmits the encrypted split file and decryption information to the public external node via the open network.

Then, in S312, information about the target files associated with the encrypted split files is displayed for each shared group display area SGD on the file sharing screen W1 of node 1 located within the network to which the encrypted split files and decryption information were transmitted.

By performing steps S301 through S312, the target file can be stored in a distributed file system within the same WAN or open network, enabling distributed management of the target file. Furthermore, node 1, which is communicatively connected via the WAN, can download the target file by executing steps S401 through S405 below.

<5.2. Download process flowchart>
FIG. 7 is a flowchart showing the process up to when the second node located in the first LAN downloads the target file stored in the private external node.

<5.2.1. Acceptance of designation of target file to download>
First, in S401, the acquisition unit 104 receives a designation of a target file to be restored.

5.2.2. Calculation of file importance
In step S402, the calculation unit 109 calculates the file importance based on the file operation information. In the case of a download process, specific examples of operation indicators include the "number of times the file has been opened" and the "period since the file was uploaded." When a corresponding operation is performed, the "number of times the file has been opened" and the "number of days since the file was uploaded" are multiplied by weights and added up to calculate the total as the file importance. In this embodiment, the number of times the file has been opened is stored in the parent node, but if the parent node is unavailable, it is temporarily stored in a child node.

<5.2.3. VPN connection processing>
In S403, the connection unit 110 determines whether to establish a VPN connection based on the file importance calculated in S402. If the file importance exceeds a threshold value preset by the user (YES in S403), the connection unit 110 determines to establish a VPN connection between the first node of the first LAN and the external node. In S404, the acquisition unit 104 acquires the encrypted split files and decryption information associated with the target file specified in S401, which are stored in the private internal node via the VPN.

On the other hand, if the file importance does not exceed the threshold previously set by the user (NO in S403), the connection unit 110 determines not to connect the VPN between the first node of the first LAN and the external node. Then, in S405, the acquisition unit 104 acquires the encrypted split files and decryption information associated with the target file specified in S401, which are stored in the public external node via the open network.

<5.2.4. Restoring and downloading target files>
Then, in S406 to S408, the process up to downloading the target file is executed, but since this is the same as the process up to downloading the target file in the first embodiment (S203 to S205), a description thereof will be omitted.

Note that file importance may change between uploading and downloading due to updates to file operation information (such as updates to "number of times opened"). Below, we will explain the case where a file stored in a public external node had a file importance below the threshold when uploaded, but the file operation information has been updated so that the file importance exceeds the threshold, causing the file to be downloaded.

First, the connection unit 110 determines that the file importance exceeds the threshold and establishes a VPN connection. The acquisition unit 104 then transmits a query to the parent node of the private external node via the VPN connection to acquire the encrypted split files and decryption information associated with the target file specified in S401. Meanwhile, since the file is stored in the public external node, the acquisition unit 104 accepts a request from the parent node of the private external node to inquire of the parent node of the public external node, and sends a query to the parent node of the public external node via the open network to acquire the encrypted split files and decryption information. The acquisition unit 104 then acquires the encrypted split files and decryption information. Note that when a target file is uploaded, a flag indicating which external node it is stored in is associated with each target file, and the acquisition unit 104 may acquire the encrypted split files and decryption information based on the flag.

As described above, the file management system of embodiment 2 enables secure information sharing by distributing and managing divided and encrypted target files in a distributed file system within the same WAN or open network. Furthermore, by determining whether or not to establish a VPN connection based on the importance of the file, there is no need to maintain a VPN connection at all times, thereby reducing power consumption.

Note that the above describes the case where node 1 located on the first LAN downloads the target file from a private external node. However, if node 1 located on the first LAN downloads the target file from a public external node, steps S403 and S404 are not performed, and the encrypted split files associated with the target file and decryption information are obtained directly via the open network.

In addition, in this embodiment, the target file stored in node 1 is specified and uploaded to the distributed file system for distributed management of the target file, but the target file may also be specified and distributed management of the target file stored in another node 1 (for example, a data center). In this case, the above upload process (S101-108 or S308-S312) is executed, and all of the encrypted split files generated based on the target file stored in the data center are stored in the distributed file system.

Note that only a portion of the encrypted split files generated based on the target file stored in the data center may be stored in the distributed file system. In this case, the target file is restored by retrieving the encrypted split files stored in the distributed file system based on the split file information stored in the parent node, and then retrieving the remaining encrypted split files from the data center based on the encrypted split files and the target file information stored in the parent node.

0: File management system 1: Node 2: Database 11: Processing unit 12: Storage unit 13: Communication unit 14: Input unit 15: Output unit 101: Dividing unit 102: Encryption unit 103: Transmission unit 104: Acquisition unit
105: Decryption unit
106: Restoration unit 107: Authentication unit 108: Display processing unit 109: Calculation unit 110: Connection unit W1: File sharing screen ORD: Organization display unit SGD: Shared group display unit EFD: Target file display unit

Claims (9)

A file management method for managing a target file in a distributed manner among a plurality of nodes through P2P communication, comprising:
an upload node that uploads the target file to a P2P communication network,
A process of dividing the target file and creating a plurality of divided files associated with the target file;
a process of generating encrypted split files obtained by encrypting the split files and decryption information for decrypting the encrypted split files;
a process of storing the generated encrypted split files in a plurality of nodes within a P2P communication network;
causing the node that stores the encrypted split files to generate identification information for the encrypted split files, receiving the identification information for the generated encrypted split files from the node, receiving identification information for as many encrypted split files as necessary to restore the target file, and storing the identification information for the target file, the identification information for the received encrypted split files, and the decryption information generated together with the encrypted split files in association with each other in one node within the P2P communication network;
a download node that downloads the target file,
a process of receiving a designation of the target file and acquiring, from one node in the P2P communication network, identification information of the encrypted split files linked to the designated target file and the decryption information;
acquiring the encrypted split files from the plurality of nodes based on identification information of the plurality of encrypted split files;
and a process of decrypting the split files to restore the target file based on the decryption information and the obtained encrypted split files. the upload node generates the split files with a combined status assigned thereto;
The download node
2. The file management method according to claim 1, further comprising the step of restoring the specified target file based on the encrypted split file, the split file obtained based on the decryption information, and the combined status. the upload node transmits the encrypted split files linked to the sharing group to a node in the P2P communication network;
2. The file management method according to claim 1, wherein the download node that downloads the target files further executes a process of displaying target file information corresponding to the transmitted encrypted split files for each of the sharing groups. the P2P communication network includes the upload node in a first LAN and a private external node in a second LAN, the first LAN and the second LAN forming a same WAN;
When the upload node in the first LAN and the private external node in the second LAN are connected via VPN, the encrypted split files are transmitted to the private external node located in an internal network;
2. The file management method according to claim 1, wherein when the upload node and the private external node are not connected via a VPN, the encrypted split files are transmitted to another node located on an external network. The upload node further calculates file importance based on file operation information relating to operations performed on the target file;
The file management method according to claim 4 , further comprising: determining whether or not to establish a VPN connection with the private external node based on the file importance. The file management method described in claim 1, wherein the upload node stores multiple pieces of decryption information for each of the split files. The file management method described in claim 1, wherein the upload node further performs an authentication step to authenticate the user based on digital authentication that verifies the user's legitimacy, physical key authentication that verifies whether a physical key for file transfer is connected, and VPN authentication that verifies whether profile information for a VPN connection is set. A file management program for managing a target file among a plurality of nodes through P2P communication,
causing a computer to function as an upload node that uploads the target file to a P2P communication network;
The upload node:
A process of dividing the target file and creating a plurality of divided files associated with the target file;
a process of generating encrypted split files obtained by encrypting the split files and decryption information for decrypting the encrypted split files;
a process of storing the generated encrypted split files in a plurality of nodes within a P2P communication network;
causing the node that stores the encrypted split files to generate identification information for the encrypted split files, receiving the identification information for the generated encrypted split files from the node, receiving identification information for as many encrypted split files as necessary to restore the target file, and storing the identification information for the target file, the identification information for the received encrypted split files, and the decryption information generated together with the encrypted split files in association with each other in one node within the P2P communication network;
a download node that downloads the target file,
A process of accepting the designation of the target file and acquiring, from one node in the P2P communication network, identification information of the encrypted split files linked to the designated target file and the decryption information;
acquiring the encrypted split files from the plurality of nodes based on identification information of the plurality of encrypted split files;
and a file management program that executes a process of decrypting the split files to restore the target file based on the decryption information and the obtained encrypted split files. A file management system that manages target files in a distributed manner among a plurality of nodes through P2P communication,
the file management system includes an upload node that uploads the target file to a P2P communication network;
The upload node:
a division unit that divides the target file and creates a plurality of split files associated with the target file;
an encryption unit that generates encrypted split files obtained by encrypting the split files and decryption information for decrypting the encrypted split files;
a transmission unit that stores the generated encrypted split files in a plurality of nodes within a P2P communication network,
the transmitting unit causes the node that stores the encrypted split files to generate identification information for the encrypted split files, receives from the node the identification information for the generated encrypted split files, receives identification information for as many encrypted split files as necessary to restore the target file, and associates the identification information for the target file, the identification information for the received encrypted split files, and the decryption information generated together with the encrypted split files, and stores them in one node within the P2P communication network;
a download node that downloads the target file,
receiving a designation of the target file, and acquiring, from one node in the P2P communication network, identification information of the encrypted split files linked to the designated target file and the decryption information;
acquiring the encrypted split files from the plurality of nodes based on identification information of the plurality of encrypted split files;
The file management system decrypts the split files to restore the target file based on the decryption information and the obtained encrypted split files.