File management method, file management program, and file management system

Abstract

To provide novel technology that enables a large amount / capacity of data to be stored and enables information to be managed in a more secure manner.SOLUTION: In a file management method for distributed management of information among multiple nodes via P2P communication, a first node that uploads a target file subjected to distributed management executes: a splitting step of splitting the target file to create multiple split files associated with the target file; an encrypting step of encrypting the split files to generate encrypted split files; and a transmitting step of transmitting the encrypted split files and decryption information for decryption to another node.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a file management method, a file management program, and a file management system. [Background technology]

[0002] Conventionally, when using a network service, a system in which a computer (client) using the service and a computer (server) providing the service or data operate while communicating via a network, that is, a client-server system, has been widespread. However, in such a system, if the server stops, the entire system becomes unavailable, and since data is concentrated on the server, security issues exist in that information can easily be leaked if the server is illegally accessed. In order to solve such problems, a system in which multiple geographically distributed computers are connected via a P2P (Peer to Peer) network and data is stored, that is, a distributed file system, is used. An example of such a system is proposed in, for example, Non-Patent Document 1.

[0003] For example, non-patent document 1 discloses that when a file is stored in a distributed file system, the file is split into smaller chunks, cryptographically hashed, and given a unique fingerprint called a Content Identifier (CID), and this CID serves 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. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] "IPFS powers the Distributed Web", [Retrieved June 29, 2023], Internet<https: / / ipfs.tech / > Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology proposed in Non-Patent Document 1, although the divided data is encrypted and stored in a distributed manner, there is a problem in that the information for decrypting the encrypted file cannot be securely managed.

[0006] In view of the above problems, an object of the present invention is to provide a novel technique that is capable of storing large amounts of data and managing files more securely. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a file management method for distributing and managing information among multiple nodes via P2P communication, in which a first node that uploads a target file to be managed in a distributed manner executes the following steps: a division step of dividing the target file and creating multiple split files associated with the target file; an encryption step of generating encrypted split files by encrypting the split files; and a transmission step of transmitting the encrypted split files and decryption information for decryption to other nodes.

[0008] With this configuration, the files to be managed in a distributed manner can be divided and the divided files can be encrypted, allowing for more secure distributed management of the files. In addition, by transmitting composite information for decrypting the encrypted files to other nodes, the security of the composite information can be guaranteed, and high security can be ensured even if the number of participating nodes increases and the amount of data that can be stored increases.

[0009] In a preferred form of the present invention, a second node that downloads the target file accepts designation of the target file and executes an acquisition step of acquiring an encrypted split file associated with the target file and decryption information for the encrypted split file, and a decryption step of decrypting the encrypted split file based on the acquired decryption information.

[0010] With this configuration, it is possible to obtain the encrypted split files and decryption information that are managed in a distributed manner from other nodes, and obtain the split files from the encrypted split files. This allows any node that is involved in P2P communication to obtain and decrypt the encrypted split files.

[0011] In a preferred form of the present invention, in the splitting step, the split files each having a combined status assigned thereto are generated, and in the acquisition step, a specification of the target file to be restored is accepted and the encrypted split file linked to the specified target file and the decryption information are acquired, and the second node further executes a restoration step in which the specified target file is restored based on the split file obtained as a result of the decryption step and the combined status.

[0012] With this configuration, it is possible to specify a target file to be restored, obtain encrypted split files associated with the target file, decrypt the split files from the encrypted split files, and restore the specified target file. Also, by generating split files with a combined status, it is possible to prevent an incorrect file from being restored.

[0013] In a preferred embodiment of the present invention, in the transmission step, the encrypted split file linked to the sharing group is transmitted to the other node, and the second node which downloads the target file further executes a display processing step of displaying target file information corresponding to the transmitted encrypted split file for each sharing group.

[0014] With this configuration, the encrypted split files can be linked to sharing groups that share the target file, and the target files can be managed for each sharing group between nodes that perform P2P communication.

[0015] In a preferred form of the present invention, the first node and the other node are nodes within a single WAN, and in the transmitting step, if the first node in a first LAN and the other node in a second LAN are connected via VPN, the encrypted split file is transmitted to the other node located in an internal network, and if the first node and the other node are not connected via VPN, the encrypted split file is transmitted to the other node located in an external network.

[0016] With this configuration, the node destination to which the encrypted split files are transmitted can be changed depending on whether or not a VPN is connected.

[0017] In a preferred embodiment of the present invention, the first node further executes a calculation step of calculating a file importance based on file operation information regarding operations performed on the target file, and a connection step of determining whether or not to establish a VPN connection with the other node based on the file importance.

[0018] With this configuration, the importance of the file can be calculated based on information about operations performed on the file, and whether or not to connect to the VPN can be determined based on the importance. This eliminates the need to always connect to the VPN depending on the importance of the file, making it possible to reduce the frequency of data communication and power consumption.

[0019] In a preferred embodiment of the present invention, in the encryption step, the plurality of pieces of decryption information are stored for each of the divided files.

[0020] With this configuration, multiple pieces of decryption information for decrypting the encrypted split files can be generated, making it possible to share the target files more securely.

[0021] In a preferred embodiment of the present invention, the first node further executes an authentication step of authenticating the user based on digital authentication that certifies the legitimacy of the user, physical key authentication that certifies whether a physical key for file exchange is connected, and VPN authentication that certifies whether profile information for a VPN connection is set.

[0022] With this configuration, more secure sharing of target files can be achieved by requiring digital authentication, physical key authentication, and VPN authentication to accept user access. Effect of the Invention

[0023] The present invention has the effect of providing a novel technique that allows for the storage of large volumes of data and for more secure file management. [Brief description of the drawings]

[0024] [Figure 1] 1 is a system configuration diagram according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram illustrating a hardware configuration according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a functional block diagram according to an embodiment of the present invention. [Figure 4] 13 is a diagram illustrating an example of a file sharing screen according to an embodiment of the present invention. [Diagram 5] 13 is an example of a flowchart of a process for sharing a target file according to an embodiment of the present invention. [Figure 6] FIG. 11 is a system configuration diagram according to another embodiment of the present invention. [Figure 7] 13 is an example of a flowchart of an upload process according to another embodiment of the present invention. [Figure 8] 13 is an example of a flowchart of a download process according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] (Embodiment 1) The present invention will now be described more fully with reference to the accompanying drawings, in which there is shown a preferred embodiment, but which may be embodied in many different forms and is not limited to the embodiments set forth herein.

[0026] For example, the configuration, operation, etc. of the file management system will be described in this embodiment, but a method, computer program, etc. with a similar configuration can also achieve the same effects. The program may be stored in a recording medium. By using this recording medium, for example, the program can be installed in a computer, thereby configuring a file management system. Here, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

[0027] In this embodiment, the term "unit" may include, for example, a combination of hardware resources implemented by a circuit in the broad sense and software information processing that can be specifically realized by these hardware resources. In this embodiment, "information" is represented by, for example, a physical value of a signal value representing a voltage or current, a high or low signal value as a binary bit set consisting of 0 or 1, or a quantum superposition (so-called quantum bit), and communication and calculation can be performed on the circuit in the broad sense. The circuit in the broad sense is a circuit realized by appropriately combining a circuit, circuits, a processor, a memory, and the like. 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), and the like.

[0028] The present invention relates to a system (so-called distributed file system) that distributes and manages information among multiple nodes by P2P communication. Here, the distributed file system is a system in which, when a node uploads information on a network formed by multiple nodes, the cache file of the information is stored in the nodes adjacent to the node in turn, and the cache file is distributed and managed among the multiple nodes.

[0029] In the present invention, information to be managed in a distributed manner (hereinafter, referred to as a target file) is divided and encrypted, and the encrypted divided files are uploaded to a distributed file system, thereby managing the target file in a distributed manner. In this embodiment (embodiment 1), a case where information is managed in a distributed manner by P2P communication between multiple nodes arranged in the same LAN (Local Area Network) will be described.

[0030] <1. System configuration of embodiment 1> 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.

[0031] A general-purpose server computer, a personal computer, a smartphone, a tablet terminal, a wearable device, etc. can be used as the node 1. In this embodiment, the node 1 that aggregates file information (described later) that serves as an index for searching for a file is called a parent node, and the node 1 that searches for encrypted split files based on the file information is called a child node.

[0032] The LAN in this embodiment may be wired or wireless, but there is no restriction on the standard of the wired cable or wireless LAN, and there is no restriction on the connection type, access control method, or scale of the LAN.

[0033] <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.

[0034] The processing unit 11 has a processor such as a CPU capable of executing 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 executes communication control with a 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.

[0035] <1.2. Functional configuration of node 1> Fig. 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 information processing by software (stored in a storage unit 12) specifically realized by hardware (processing unit 11).

[0036] <1.3.Database 2> The database 2 stores user information, sharing group information, and file information.

[0037] <1.3.1. User information> User information is information about users who use the distributed file system. 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), etc., and is stored in association with shared group information.

[0038] <1.3.2. Shared group information> The shared group information is information indicating a group of target files shared by users. In this embodiment, the shared group is information created for each project that an organization works on, 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.

[0039] <1.3.3. File information> The file information is information about a file to be managed in a distributed manner, and includes target file information about meta-information of the target file, and split file information about meta-information of the split files. The target file information includes a 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 a hash value of the split file, a split file name, a merge status of the split file, an ID of a folder in which the target file is placed, a hash value of the encrypted split file, and decryption information. In this embodiment, the decryption information is one or more private keys, but may also be a public key, a password, or the like.

[0040] In this embodiment, the parent node includes at least database 2. Database 2 of the parent node stores at least the target file information and split file information transmitted from the child node. The parent node may include a splitting 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, and a 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 which case file information is distributed and stored in node 1 (child node).

[0041] In this embodiment, in addition to the file information, user information and sharing group information are stored in the parent node database 2. Alternatively, they may be stored in an external authentication server on the Internet or in a child node database.

[0042] <1.4. Division part 101> The division unit 101 divides a target file and creates a plurality of split files associated with the target file. The division unit 101 divides a target file and creates split files to which a combined status is assigned. Here, the combined status is information required to restore the target file from the split files.

[0043] <1.5. Encryption section 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. 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, the key information is information for encrypting the split files, and includes a common key, a private key, and a public key.

[0044] <1.6. Transmitter 103> The transmitting unit 103 transmits the encrypted split file and the decryption information to the other nodes 1. The transmitting unit 103 transmits the encrypted split file to the child node and the decryption information to the parent node. The transmitting unit 103 also transmits the encrypted split file linked to the sharing group to the child node.

[0045] <1.7. Acquisition part 104> The obtaining unit 104 obtains the encrypted split file and the key information. The obtaining unit 104 accepts the designation of a target file, and obtains the encrypted split file associated with the target file, and the key information of the encrypted split file.

[0046] <1.8. Decryption 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.

[0047] <1.9.Restore Section 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 combination statuses assigned to the split files.

[0048] <1.10. Authentication section 107> The authentication unit 107 executes user authentication. In this embodiment, the authentication unit 107 executes user authentication based on digital authentication that proves the legitimacy of the user, physical key authentication that identifies the node 1 of the distributed file system, and VPN authentication that proves whether profile information of the VPN connection is set. Here, in this embodiment, a physical key for transferring files is connected to the node 1, and the authentication unit 107 receives, as digital authentication, a wallet ID that uniquely identifies a wallet for accessing data on the distributed file system from the physical key, receives, as physical key authentication, a local IP address and a node ID (so-called Peer ID) that uniquely identifies the node 1 generated for each node 1 from the physical key, and receives, as VPN authentication, profile information of the VPN connection from the physical key, and receives an email address and a 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.

[0049] In this embodiment, the display process refers to a process in which the display processing unit 108 executes a process of generating the necessary information, and transmits the generated information to the output unit 95, whereby the output unit 95 displays the generated information.

[0050] <2. Example of file sharing screen> 4 is a display 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.

[0051] The organization display unit ORD displays a changeable organization associated with a user corresponding to the email address and password entered during access authentication. The shared group display unit SGD displays a share group associated with an organization displayed in the organization display unit ORD in a specifiable manner. In this embodiment, each shared group is associated with a user who can access it, but all users belonging to the organization may be able to access it.

[0052] The target file display unit EFD displays 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, among the information of the target file linked to the shared group specified in the shared group display unit SGD. In this embodiment, by specifying a shared group, a shared folder (not shown) linked to the specified shared group is displayed, and by specifying the shared folder, the target file information is displayed. On the other hand, by specifying a shared group, the target file information linked to the shared group may be displayed.

[0053] Then, when the user selects and inputs the "Upload" button on the file sharing screen W1, the upload of the target file is performed, and the download is performed by specifying the target file information displayed in the target file display area EFD and inputting information related to the download.

[0054] <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 describes the flowchart after access authentication has been successful.

[0055] <3.1. Upload process flowchart> FIG. 5(a) shows a process flowchart up to when the first node uploads the target file.

[0056] <3.1.1. Shared group / shared folder designation reception> First, in step S101 (hereinafter, "step SXXX" will be simply referred to as "SXXX"), the display processing unit 108 performs display processing of 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 performs display processing of a shared folder linked to the shared group.

[0057] <3.1.2. Creating split files> Next, in S103, the division unit 101 accepts a designation of a target file to be uploaded, divides the target file, and creates split files. In this embodiment, the division unit 101 accepts a designation of a target file stored in each node 1, divides the target file, and creates split files associated with the target file.

[0058] <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 for each split file to generate multiple encrypted split files. Then, the encryption unit 102 generates multiple private keys for each encrypted split file as decryption information.

[0059] <3.1.4. Uploading encrypted split files> In S105, the transmitting unit 103 accepts the designation of a destination to which the notification is to be sent. In this embodiment, when the designation of the target file to be uploaded is accepted, the node 1 that can communicate via the LAN is displayed, and the transmitting unit 103 accepts the designation of the node 1 and accepts the designation of a destination to which the notification is to be sent. Then, in S106, the transmitting unit 103 accepts the input of a message to be sent to the destination designated in S105.

[0060] Next, in S107, the transmitting unit 103 transmits the encrypted split files, the target file information, and the split file information to the other nodes. In this embodiment, the transmitting unit 103 of the first node transmits a plurality of encrypted split files linked to the shared group specified in S101 to the other child nodes. Then, the transmitting unit 103 of the child node that received the encrypted split files from the first node transmits a hash value for each encrypted split file obtained from the encrypted split file to the first node. Then, the transmitting unit 103 of the first node that received the hash value 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 file associated with the target file and including the hash value of the received encrypted split file. Then, the parent node stores the received target file information and the split file information for each split file.

[0061] In addition, when the transmitting unit 103 of the first node is in a state where it is unable to transmit the encrypted split file, target file information and split file information to other nodes (for example, when all child nodes are turned off), the encrypted split file, target file information and split file information are temporarily stored in the first node, and the temporarily stored information is transmitted when the other child nodes are turned on.

[0062] <3.1.5. Display process of target file information> Then, in S108, the display processing unit 108 performs display processing of the target file information. In this embodiment, the display processing unit 108 performs display processing of the information of the target files corresponding to the encrypted split files transmitted in S107, and displays the information for each sharing group display unit SGD on the file sharing screen W1.

[0063] As described above, by steps S101 to S108, the target file is stored in the distributed file system, and the target file can be managed securely. Also, the node 1 that is communicatively connected via the LAN can download the target file by executing the following steps S201 to S205.

[0064] <3.2. Download process flow chart> FIG. 5(b) shows a processing flowchart up to when the second node downloads the target file.

[0065] <3.2.1. Acceptance of the specification of the target file to be downloaded> First, in S201, the display processing unit 108 performs display processing of a list of target file information associated with the organization to which the user belongs, and the acquisition unit 104 accepts the designation of the target file to be restored. Then, in S202, the acquisition unit 104 acquires the encrypted split files and decryption information associated with the designated target file. In this embodiment, the acquisition unit 104 accepts the designation of the information of 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, the target file name, the hash value of the target file, the uploading user ID, and the upload date and time, and the split file information corresponding to the designated target file. Then, the acquisition unit 104 acquires the encrypted split files from the child node based on the hash value of the encrypted split file included in the split file information.

[0066] <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 uses the multiple private keys of the decryption information acquired in S202 to generate public keys from the private keys, thereby decrypting the encrypted split files.

[0067] <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 given to the split files. Then, in S205, a registration unit (not shown) registers the restored target file in the database 2 of the second node when 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.

[0068] As described above, according to the file management system of embodiment 1, divided and encrypted target files are managed in a distributed manner among nodes arranged in the same LAN, thereby enabling information to be shared securely.

[0069] (Embodiment 2) Next, in a second embodiment, a case will be described in which information is distributed and managed 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.

[0070] In the first embodiment, the target files were uploaded and downloaded by communicating via the same LAN. On the other hand, in this embodiment, when uploading and downloading files between nodes 1 arranged in different LANs, communication is performed via an open network or VPN. In the following description, the system according to this embodiment operates each functional configuration, and parts common to the first embodiment are omitted.

[0071] <4. System configuration of embodiment 2> Fig. 6 is a block diagram showing the configuration of a file management system in this embodiment. As shown in Fig. 6, the file management system is configured with multiple LANs in which multiple nodes 1 performing P2P communication are arranged, and each LAN is configured to be able to communicate with each other via an open network.

[0072] In this embodiment, the node 1 arranged in the first LAN is configured to be able to communicate with the node 1 (internal node) arranged in the first LAN via the LAN, and with a node (external node) of an external distributed file system via an open network. The node 1 arranged in the first LAN is also configured to be able to communicate with the node 1 (private external node) arranged in another LAN (second LAN) of the external distributed file system via a VPN connection, and with the node 1 (public external node) arranged in a public network via an open network. Note that in this embodiment, a VPN connection is made via a VPN device to communicate between LANs, but communication between LANs may be performed via an open network without a VPN connection.

[0073] Furthermore, although the WAN in this embodiment is realized by a VPN connection, there is no limit to the type of WAN, and it may be a digital leased line, wide area Ethernet, or the like, and furthermore, there is no limit to the scale of the WAN.

[0074] <4.1. Functional configuration of node 1> The node 1 in the second embodiment further includes a calculation unit 109 and a connection unit 110 in addition to 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.

[0075] <4.2. Transmitter 103 in the second embodiment> The transmitting unit 103 transmits at least the encrypted split file from the first node in the first LAN to the private external node via the VPN or the open network. In this embodiment, when the first node in the first LAN and the external node are connected via VPN, the transmitting unit 103 transmits the encrypted split file to the private internal node, and when the first node and the external node are not connected via VPN, the transmitting unit 103 transmits the encrypted split file and decryption information to the public external node.

[0076] Calculation unit 109 The calculation unit 109 calculates the file importance, which is an index of whether or not nodes 1 arranged 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.

[0077] <4.4. Connection part 110> The connection unit 110 determines whether or not to establish a VPN connection with an external node based on the importance calculated by the calculation unit 109, and establishes the VPN connection. The connection unit 110 establishes the VPN connection when the file importance is equal to or greater than a predetermined threshold.

[0078] <5. Flowchart> The file management method of this embodiment will be described below with reference to FIGS.

[0079] <5.1. Upload process flowchart> 7 is a flowchart showing the process until the first node arranged in the first LAN uploads a target file to a private external node. Note that the process from S301 to S307 is the same as the process (S101 to S107) until the encrypted split file is uploaded in the first embodiment, and therefore will not be described.

[0080] <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 indicating whether or not a file is important with respect to an operation performed on the file, and calculates the file importance by adding up the predetermined weight depending on whether or not an operation corresponding to the operation indicator has been performed.

[0081] Specifically, for example, the operation indicators include "whether or not a message was entered at the time of uploading," "the relevance of the message to the file name or the tag attached to the file," "the contents of the tag registered in association with the file," and "whether or not the file was obtained from an external system," etc. The calculation unit 109 sets a predetermined weight for each of these operation indicators, and 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 sum as the file importance.

[0082] 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, when the file importances become the same numerical value, the calculation unit 109 obtains the latency of the packet sent to the other party, and calculates the numerical value obtained by dividing the latency tolerance previously set by the user by the obtained latency as the communication priority.

[0083] <5.1.2.VPN connection process> In S309, the connection unit 110 determines whether or not to make a VPN connection based on the file importance calculated in S308. Then, when the file importance exceeds a threshold value previously set by the user (YES in S309), the connection unit 110 determines to connect a VPN between the first node of the first LAN and the external node. Then, in S310, the transmission unit 103 transmits the encrypted split file and decryption information to the private external node via the VPN. Note that, when communications with the same file importance are performed simultaneously, the connection unit 110 determines whether or not to make a VPN connection based on the communication priority calculated by the calculation unit 109.

[0084] On the other hand, if the file importance does not exceed the threshold value 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.

[0085] Then, in S312, on the file sharing screen W1 of node 1 located in the network to which the encrypted split files and decryption information were transmitted, information on the target files associated with the encrypted split files is displayed for each sharing group display section SGD.

[0086] As described above, by storing the target file in a distributed file system within the same WAN or open network through S301 to S312, the target file can be managed in a distributed manner. Also, the node 1 that is communicatively connected via the WAN can download the target file by executing the following S401 to S405.

[0087] <5.2. Download process flow chart> FIG. 7 is a flowchart showing a process in which a second node located in a first LAN downloads a target file stored in a private external node.

[0088] <5.2.1. Acceptance of the specification of the target file to be downloaded> First, in S401, the acquisition unit 104 accepts the designation of a target file to be restored.

[0089] <5.2.2. Calculation of file importance> Then, in S402, the calculation unit 109 calculates the file importance based on the file operation information. In the case of a download process, the calculation method of the file importance includes specific examples of operation indicators such as "the number of times the file was opened" and "the period since the file was uploaded", and when the corresponding operation is performed, the "number of times the file was opened" and "the number of days since the file was uploaded" are multiplied by weights and added up to calculate the sum as the file importance. In this embodiment, the number of times the file was opened is stored in the parent node, but if the parent node is unavailable, it is temporarily stored in the child node.

[0090] <5.2.3.VPN connection process> In S403, the connection unit 110 determines whether or not to make a VPN connection based on the file importance calculated in S402. If the file importance exceeds a threshold value previously set by the user (YES in S403), the connection unit 110 determines to connect a VPN 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.

[0091] On the other hand, if the file importance does not exceed the threshold value 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.

[0092] <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 it is similar to the process up to downloading the target file in the first embodiment (S203 to S205), a description thereof will be omitted.

[0093] In addition, the file importance may change between the time of uploading and the time of downloading due to updates to the file operation information (updating the "number of times opened" etc.). Below, we will explain the case where a file whose file importance was lower than the threshold and stored in a public external node at the time of uploading, but whose file operation information has been updated so that the file importance exceeds the threshold, is downloaded.

[0094] First, the connection unit 110 determines that the file importance exceeds a threshold and establishes a VPN connection. Then, the acquisition unit 104 transmits an inquiry to acquire the encrypted split file and decryption information associated with the target file designated in S401 to the parent node of the private external node via the VPN connection. 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 make an inquiry to the parent node of the public external node, and makes an inquiry to the parent node of the public external node via the open network to acquire the encrypted split file and decryption information. Then, the acquisition unit 104 acquires the encrypted split file and decryption information. Note that when the target file is uploaded, a flag indicating which external node the file is stored in is associated with each target file, and the acquisition unit 104 may acquire the encrypted split file and decryption information based on the flag.

[0095] As described above, according to the file management system of the second embodiment, the divided and encrypted target files are managed in a distributed file system in the same WAN or open network, so that information can be shared securely. In addition, by determining whether or not to make a VPN connection based on the importance of the file, it is no longer necessary to always have a VPN connection, and power consumption can be reduced.

[0096] Note that in the above, a case has been described in which node 1 placed in the first LAN downloads a target file from a private external node, but when node 1 placed in the first LAN downloads a target file from a public external node, steps S403 to S404 are not performed, and the encrypted split files associated with the target file and decryption information are directly obtained via the open network.

[0097] In addition, in this embodiment, the target file stored in node 1 is designated and uploaded to the distributed file system for distributed management of the target file, but the target file may be managed in a distributed manner by designating a target file stored in another node 1 (for example, a data center). In this case, the above upload process (S101 to 108 or S308 to 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.

[0098] Note that only a portion of the encrypted split file generated based on the target file stored in the data center may be stored in the distributed file system. In this case, the encrypted split file stored in the distributed file system is obtained based on the split file information stored in the parent node, and the remaining file of the encrypted split file is obtained from the data center based on the encrypted split file and the target file information stored in the parent node, thereby restoring the target file. [Explanation of symbols]

[0099] 0: File Management System 1 : Node 2: Database 11: Processing section 12: Storage section 13: Communications Department 14: Input section 15: Output section 101:Divided part 102: Encryption section 103: Transmission unit 104: Acquisition Department 105: Decoding section 106: Restoration section 107: Authentication section 108: Display processing unit 109: Calculation section 110: Connection part W1: File sharing screen ORD:Organization display section SGD: Shared Groups Display EFD: Target file display area

Claims

1. A file management method for distributing and managing information among a plurality of nodes through P2P communication, comprising the steps of: A first node that uploads a target file to be managed in a distributed manner a division step of dividing the target file to create a plurality of split files associated with the target file; an encryption step of generating encrypted split files by encrypting the split files; a transmitting step of transmitting the encrypted split files and decryption information for decryption to another node.

2. A second node that downloads the target file, an acquisition step of accepting a designation of the target file and acquiring encrypted split files associated with the target file and decryption information for the encrypted split files; 2. The file management method according to claim 1, further comprising the step of: decrypting the encrypted split file based on the acquired decryption information.

3. In the splitting step, the split files are generated to which a combined status is assigned; In the obtaining step, a designation of the target file to be restored is accepted, and the encrypted split files and the decryption information associated with the designated target file are obtained; 3. The file management method according to claim 2, wherein the second node further executes a restoration step of restoring the specified target file based on the split files obtained as a result of the decryption step and the linkage status.

4. In the transmitting step, the encrypted split file linked to the sharing group is transmitted to the other node; 2. The file management method according to claim 1, wherein the second node that downloads the target file further executes a display processing step of displaying target file information corresponding to the transmitted encrypted split file for each sharing group.

5. The first node and the other node are nodes within one WAN, and in the transmitting step, When the first node in a first LAN and the other node in a second LAN are connected via a VPN, the encrypted split file is transmitted to the other node located in an internal network; 2. The file management method according to claim 1, wherein when the first node and the other node are not connected via a VPN, the encrypted split file is transmitted to the other node located on an external network.

6. the first node further calculates a file importance based on file operation information related to an operation performed on the target file; 6. The file management method according to claim 5, further comprising a connection step of determining whether or not to establish a VPN connection with said other node based on said file importance.

7. 2. The file management method according to claim 1, wherein in said encryption step, a plurality of pieces of decryption information are stored for each of said divided files.

8. The file management method according to claim 1, wherein the first node further executes an authentication step of authenticating the user based on digital authentication that proves the legitimacy of the user, physical key authentication that proves whether a physical key for file exchange is connected, and VPN authentication that proves whether profile information for a VPN connection is set.

9. A file management program for distributing and managing information among a plurality of nodes through P2P communication, The first node that uploads the target file to be managed in a distributed manner is 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 by encrypting the split files; a file management program that functions as a transmission unit that transmits the encrypted split files and decryption information for decryption to another node.

10. A file management system that distributes and manages information among a plurality of nodes through P2P communication, The file management system includes a first node that uploads a target file to be managed in a distributed manner; The first node is 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 by encrypting the split files; a transmission unit that transmits the encrypted split files and decryption information for decryption to another node.

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