Information processing system and information processing method

Abstract

To provide an information processing system and an information processing method that can decrypt encrypted data without the need for holders of distributed private keys to gather together.SOLUTION: An information processing system 100 includes a reception processing unit that, when an instruction to decrypt encrypted data encrypted with a public key is input in any of a plurality of information processing devices 10, receives an input operation of any of a plurality of distributed private keys corresponding to the public key in each of the information processing devices 10, and a decryption processing unit that decrypts the encrypted data when the number of distributed private keys input by the input operation reaches a threshold value at which the encrypted data can be decrypted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an information processing system and an information processing method. [Background technology]

[0002] An information processing system that uses multiple distributed private keys of threshold cryptography to decrypt encrypted data that has been encrypted with public keys corresponding to the multiple distributed private keys is known as related technology (see Patent Document 1). Specifically, the information processing system according to this related technology includes a processing device to which multiple IC card readers are connected, and decrypts the encrypted data using the multiple distributed private keys read from multiple IC cards by the multiple IC card readers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-48121 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the information processing system according to the related art described above, in order to decrypt the encrypted data, the holders of the distributed private keys (holders of the IC cards) need to gather at the location where the processing device is installed.

[0005] An object of the present invention is to provide an information processing system and an information processing method that enable encrypted data to be decrypted without the holders of distributed private keys gathering together. [Means for solving the problem]

[0006] According to one aspect of the present invention, an information processing system includes a plurality of information processing devices each connected to a network, and further includes a reception processing unit and a decryption processing unit. When a command to decrypt encrypted data encrypted with a public key is input to any of the plurality of information processing devices, the reception processing unit accepts an input operation of one of a plurality of distributed private keys corresponding to the public key in each of the information processing devices. When the number of the distributed private keys input by the input operation reaches a threshold value for decrypting the encrypted data, the decryption processing unit decrypts the encrypted data.

[0007] An information processing method according to another aspect of the present invention is executed in an information processing system including a plurality of information processing devices, each connected to a network, and includes a receiving step and a decryption step. In the receiving step, when an instruction to decrypt encrypted data encrypted with a public key is input to one of the plurality of information processing devices, an input operation of one of a plurality of distributed private keys corresponding to the public key is received by each of the information processing devices. In the decryption step, when the number of the distributed private keys input by the input operation reaches a threshold value at which the encrypted data can be decrypted, the encrypted data is decrypted. [Effects of the Invention]

[0008] According to the present invention, encrypted data can be decrypted without the holders of the shared private keys gathering together. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of an information processing system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of an information processing device of the information processing system according to the embodiment of the present invention. [Figure 3] FIG. 3 is a block diagram showing the configuration of a server in an information processing system according to an embodiment of the present invention. [Figure 4]FIG. 4 is a flowchart showing an example of a data decryption process executed in the information processing system according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0011] [Information processing system 100] As shown in FIG. 1, an information processing system 100 includes a plurality of information processing devices 10 and a server 20. In the information processing system 100, the server 20 and each of the information processing devices 10 are connected to a communication network 30 (an example of a network of the present invention). For example, the communication network 30 is the Internet or a LAN (local area network). Each of the information processing devices 10 can communicate with the server 20 via the communication network 30. The number of information processing devices 10 included in the information processing system 100 may be any number equal to or greater than two.

[0012] [Information processing device 10] The information processing device 10 is, for example, a personal computer, a smartphone, a notebook computer, or a tablet terminal.

[0013] As shown in FIG. 2, the information processing device 10 includes a control unit 11, an operation display unit 12, a communication unit 13, a storage unit 14, and an IC card reader 15.

[0014] The control unit 11 performs overall control of the information processing device 10. As shown in FIG. 2, the control unit 11 includes a CPU 11A, a ROM 11B, and a RAM 11C. The CPU 11A is a processor that executes various types of arithmetic processing. The ROM 11B is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 11A to execute various types of processing. The RAM 11C is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 11A. The CPU 11A executes the various control programs stored in advance in the ROM 11B. This performs overall control of the information processing device 10.

[0015] The operation display unit 12 is a user interface of the information processing device 10. The operation display unit 12 includes a first display unit and a first operation unit. The first display unit displays various information in response to control instructions from the control unit 11. For example, the first display unit is a flat panel display such as a liquid crystal display. The first operation unit inputs various information to the control unit 11 in response to user operations. For example, the first operation unit includes a keyboard, a mouse, and a touch panel.

[0016] The communication unit 13 is a communication interface that executes wired or wireless data communication with an external communication device such as the server 20 via the communication network 30.

[0017] The storage unit 14 is a nonvolatile storage device, such as a nonvolatile memory such as a flash memory, a solid state drive (SSD), or a hard disk drive (HDD).

[0018] The storage unit 14 pre-stores client software for causing the information processing device 10 to function as a user interface for the information processing system 100. By executing the client software, the CPU 11A of the control unit 11 can input information to the information processing system 100 in response to user operations on the operation display unit 12, and display information output from the information processing system 100 on the operation display unit 12.

[0019] The IC card reader 15 reads data stored in the IC card 15A (see FIG. 2) from the IC card 15A.

[0020] [Server 20] As shown in FIG. 3, the server 20 includes a control unit 21, an operation display unit 22, a communication unit 23, and a storage unit 24.

[0021] The control unit 21 performs overall control of the server 20. As shown in Fig. 3, the control unit 21 includes a CPU 21A, a ROM 21B, and a RAM 21C. The CPU 21A, the ROM 21B, and the RAM 21C have the same functions as the CPU 11A, the ROM 11B, and the RAM 11C of the information processing device 10.

[0022] The operation display unit 22 is a user interface of the server 20. The operation display unit 22 includes a second display unit and a second operation unit. The second display unit displays various information in response to control instructions from the control unit 21. For example, the second display unit is a flat panel display such as a liquid crystal display. The second operation unit inputs various information to the control unit 21 in response to user operations. For example, the second operation unit includes a keyboard, a mouse, and a touch panel.

[0023] The communication unit 23 is a communication interface capable of performing wired or wireless data communication via the communication network 30 with an external communication device such as the information processing device 10.

[0024] The storage unit 24 is a non-volatile storage device similar to the storage unit 14 of the information processing device 10 .

[0025] The storage unit 24 stores identification information of the information processing device 10 in which the client software is installed.

[0026] Furthermore, one or more encrypted data 24A are stored in the storage unit 24. The encrypted data 24A is data encrypted using a public key of the threshold encryption.

[0027] For example, the server 20 has a function of generating the public key of the threshold cryptography and multiple distributed private keys 15B (see FIG. 2). The multiple distributed private keys 15B are obtained by distributing a private key corresponding to the public key using a secret sharing scheme. In the information processing system 100, the public key generated by the server 20 is transmitted to other information processing devices not included in the information processing system 100. Also, in the information processing system 100, each of the distributed private keys 15B generated by the server 20 is stored in an IC card 15A. The encrypted data is data encrypted by the other information processing devices using the public key and transmitted from the other information processing devices to the server 20. To decrypt the encrypted data, a number of distributed private keys 15B equal to or greater than a predetermined threshold is required. The threshold is a value equal to or greater than two and equal to or less than the total number of distributed private keys 15B.

[0028] The server 20 may generate the public key of the threshold cryptography and the multiple shared private keys 15B (see FIG. 2) using a known method. The public key of the threshold cryptography and the multiple shared private keys 15B (see FIG. 2) may be generated by the other information processing device.

[0029] The storage unit 24 also stores an owner list 24B that lists the owners of the IC cards 15A, i.e., the owners of the distributed private keys 15B. The owner list 24B includes information such as the name, job title, telephone number, and email address of each owner of the distributed private key 15B. The owner list 24B is edited in response to operations by a user who is authorized to edit the owner list 24B and can log in to the server 20.

[0030] Incidentally, a related technology is known as an information processing system that includes a processing device to which multiple IC card readers 15 are connected, and that decrypts encrypted data 24A using multiple distributed private keys 15B read from multiple IC cards 15A by the multiple IC card readers 15.

[0031] However, in the information processing system according to the related art described above, in order to decrypt the encrypted data 24A, the holders of the distributed private keys 15B (holders of the IC cards 15A) need to gather at the location where the processing device is installed.

[0032] In contrast to this, in the information processing system 100 according to the embodiment of the present invention, as will be described below, the encrypted data 24A can be decrypted without the holders of the distributed private keys 15B gathering together.

[0033] Specifically, the storage unit 24 has stored therein in advance a data decoding program for causing the control unit 21 to function as a first reception processing unit 41, a second reception processing unit 42, a decoding processing unit 43, and a display processing unit 44 shown in Fig. 3. The CPU 21A of the control unit 21 executes the data decoding program to function as each processing unit shown in Fig. 3.

[0034] Note that some or all of the processing units included in the control unit 21 may be configured with electronic circuits. Also, the data decoding program may be a program for causing a plurality of processors to function as the processing units shown in FIG.

[0035] The first reception processor 41 receives an input operation of an instruction to decrypt the encrypted data 24A in the information processing device 10.

[0036] For example, when a predetermined user operation is accepted in any of the information processing devices 10, the first acceptance processing unit 41 causes a first acceptance screen to be displayed on the operation display unit 12 of the information processing device 10. One or more pieces of encrypted data 24A stored in the storage unit 24 of the server 20 are displayed in a selectable manner on the first acceptance screen. Furthermore, with one or more pieces of encrypted data 24A selected, the first acceptance screen accepts an input operation for an instruction to decrypt each of the selected encrypted data 24A.

[0037] When an instruction to decrypt encrypted data 24A encrypted with the public key is input in any of the multiple information processing devices 10, the second reception processing unit 42 accepts an input operation of any of the multiple distributed private keys 15B corresponding to the public key in each of the information processing devices 10. The second reception processing unit 42 is an example of the reception processing unit of the present invention.

[0038] Specifically, when the first reception processing unit 41 receives an input operation of an instruction to decrypt the encrypted data 24A, the second reception processing unit 42 displays a second reception screen on the operation display unit 12 of each information processing device 10. On the second reception screen, a read operation of the distributed private key 15B stored in the IC card 15A using the IC card reader 15 is received as an input operation of the distributed private key 15B. For example, the second reception screen includes a message urging the user to read the distributed private key 15B stored in the IC card 15A using the IC card reader 15.

[0039] For example, when the number of distributed private keys 15B input in one or more second information processing devices among the multiple information processing devices 10 that are different from the first information processing device to which the decryption instruction for the encrypted data 24A was input reaches a number that is one less than the threshold value, the second reception processing device 42 terminates the acceptance of the input operation of the distributed private key 15B in each of the second information processing devices.

[0040] Furthermore, the second reception processing unit 42 receives the input operation of the distributed private key 15B in each of the information processing devices 10 until a predetermined reception deadline arrives.

[0041] For example, the acceptance time limit is set to 10 minutes after the instruction to decrypt the encrypted data 24A is input to the first information processing device. Note that the acceptance time limit may be set arbitrarily.

[0042] The decryption processing unit 43 decrypts the encrypted data 24A when the number of shared private keys 15B input by the input operation of the shared private keys 15B reaches the threshold value at which the encrypted data 24A can be decrypted.

[0043] Specifically, the decryption processing unit 43 acquires the distributed private key 15B input in each of the second information processing devices and transmits the acquired distributed private key 15B to the first information processing device. Note that the decryption processing unit 43 may instruct each of the second information processing devices to transmit the input distributed private key 15B to the first information processing device.

[0044] Moreover, the decryption processing unit 43 transmits the encrypted data 24A to be decrypted to the first information processing device.

[0045] Then, the decryption processing unit 43 decrypts the encrypted data 24A to be decrypted in the first information processing device. Specifically, the decryption processing unit 43 instructs the control unit 11 of the first information processing device to decrypt the encrypted data 24A to be decrypted, using the distributed private key 15B transmitted to the first information processing device and the distributed private key 15B input in the first information processing device.

[0046] In response to a predetermined display operation on any of the information processing devices 10, the display processing unit 44 displays the holder list 24B on the operation display unit 12 of that information processing device 10. This allows the holder of the distributed private key 15B to know the names and contact information of the holders of the other distributed private keys 15B. Therefore, when the holder of the distributed private key 15B wishes to decrypt the encrypted data 24A, he or she can contact the holders of the other distributed private keys 15B to ask for their cooperation.

[0047] The owner list 24B may be stored in a file server that is provided separately from the server 20. In this case, each information processing device 10 may acquire the owner list 24B from the file server.

[0048] [Data decryption process] 4, the information processing method of the present invention will be described below together with an example of the procedure of the data decryption process executed by the control unit 21 of the server 20 in the information processing system 100. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 21. The data decryption process is executed when an instruction to display the first reception screen is input in any of the information processing devices 10.

[0049] <Step S11> First, in step S11, the control unit 21 displays the first reception screen on the operation display unit 12 of the information processing device 10 to which the instruction to display the first reception screen has been input. The processing of step S11 is executed by the first reception processing unit 41 of the control unit 21.

[0050] <Step S12> In step S12, the control unit 21 determines whether or not an input operation for an instruction to decrypt the encrypted data 24A has been accepted on the first acceptance screen.

[0051] Here, if the control unit 21 determines that the input operation of the instruction to decrypt the encrypted data 24A has been accepted (Yes in S12), the control unit 21 shifts the process to step S13. On the other hand, if the input operation of the instruction to decrypt the encrypted data 24A has not been accepted (No in S12), the control unit 21 waits for the acceptance of the input operation of the instruction to decrypt the encrypted data 24A in step S12.

[0052] <Step S13> In step S13, the control unit 21 displays the second reception screen on the operation display unit 12 of each information processing device 10. The processing of step S13 is an example of a reception step of the present invention, and is executed by the second reception processing unit 42 of the control unit 21.

[0053] <Step S14> In step S14, the control unit 21 determines whether the acceptance deadline has arrived.

[0054] Here, if the control unit 21 determines that the acceptance deadline has arrived (Yes in S14), it shifts the process to step S19. On the other hand, if the acceptance deadline has not arrived (No in S14), the control unit 21 shifts the process to step S15.

[0055] <Step S15> In step S15, the control unit 21 determines whether or not the number of distributed private keys 15B input in one or more of the second information processing devices has reached the number that is one less than the threshold value.

[0056] Here, when the control unit 21 determines that the number of distributed private keys 15B input in one or more of the second information processing devices has reached a number that is one less than the threshold value (Yes in S15), it shifts the process to step S16. On the other hand, when the number of distributed private keys 15B input in one or more of the second information processing devices has not reached a number that is one less than the threshold value (No in S15), the control unit 21 shifts the process to step S17.

[0057] <Step S16> In step S16, the control unit 21 stops accepting the input operation of the distributed private key 15B in each of the second information processing devices. This makes it possible to prevent a number of distributed private keys 15B equal to or greater than the threshold from circulating on the communication network 30. Therefore, even if data transmitted and received on the server 20 is intercepted, for example, it is possible to prevent an interceptor from obtaining a number of distributed private keys 15B equal to or greater than the threshold.

[0058] <Step S17> In step S17, the control unit 21 determines whether the number of distributed private keys 15B input in the plurality of information processing devices 10 has reached the threshold value.

[0059] Here, if the control unit 21 determines that the number of distributed private keys 15B input from the multiple information processing devices 10 has reached the threshold value (Yes in S17), it shifts the process to step S18. On the other hand, if the number of distributed private keys 15B input from the multiple information processing devices 10 has not reached the threshold value (No in S17), the control unit 21 shifts the process to step S14.

[0060] <Step S18> In step S18, the control unit 21 decrypts the encrypted data 24A to be decrypted. The process of step S18 is an example of a decryption step of the present invention, and is executed by the decryption processing unit 43 of the control unit 21.

[0061] Specifically, the control unit 21 acquires the distributed private key 15B input in each of the second information processing devices and transmits the acquired distributed private key 15B to the first information processing device. The control unit 21 also transmits encrypted data 24A to be decrypted to the first information processing device. The control unit 21 then decrypts the encrypted data 24A to be decrypted in the first information processing device. More specifically, the decryption processing unit 43 instructs the control unit 11 of the first information processing device to decrypt the encrypted data 24A to be decrypted using the distributed private key 15B transmitted to the first information processing device and the distributed private key 15B input in the first information processing device. This makes it possible to prevent eavesdropping of the decrypted data when it is transmitted to the first information processing device via the communication network 30, compared to a configuration in which the encrypted data 24A is decrypted in the server 20.

[0062] <Step S19> In step S19, the control unit 21 notifies the user that the encrypted data 24A cannot be decrypted.

[0063] For example, the control unit 21 causes the operation display unit 12 of the first information processing device to display a message indicating that the encrypted data 24A cannot be decrypted because the number of inputs of the distributed private key 15B did not reach the threshold by the deadline.

[0064] In this way, in the information processing system 100, an input operation of the distributed private key 15B is accepted in each of the information processing devices 10 connected to the communication network 30. Then, when the number of distributed private keys 15B input in the multiple information processing devices 10 reaches the threshold value, the encrypted data 24A is decrypted. This makes it possible to decrypt the encrypted data 24A without the holders of the distributed private keys 15B gathering together.

[0065] In the information processing system 100, the distributed private key 15B may be stored in a portable storage device such as a USB memory. In this case, each information processing device 10 may be provided with a connection terminal to which the storage device is connected, such as a USB connection terminal, instead of the IC card reader 15. The distributed private key 15B may also be stored in the storage unit 14 of the information processing device 10.

[0066] Furthermore, in the information processing system 100, any one of the information processing devices 10 may have the functions of the server 20. Specifically, any one of the information processing devices 10 may have the encrypted data 24A, the owner list 24B, the first reception processing unit 41, the second reception processing unit 42, the decryption processing unit 43, and the display processing unit 44. In this case, the information processing system 100 does not need to have the server 20.

[0067] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0068] <Appendix 1> An information processing system having a plurality of information processing devices each connected to a network, the information processing system comprising: a reception processing unit that, when an instruction to decrypt encrypted data encrypted with a public key is input in one of the plurality of information processing devices, accepts an input operation of one of a plurality of distributed private keys corresponding to the public key in each of the information processing devices; and a decryption processing unit that decrypts the encrypted data when the number of distributed private keys input by the input operation reaches a threshold value at which the encrypted data can be decrypted.

[0069] <Appendix 2> The information processing system described in Appendix 1, wherein the distributed private key input by the input operation is transmitted to a first information processing device among the plurality of information processing devices to which the decryption instruction was input, and the decryption processing unit decrypts the encrypted data in the first information processing device.

[0070] <Appendix 3> The information processing system described in Appendix 2, wherein the reception processing unit terminates the acceptance of the input operation in each of the second information processing devices when the number of the distributed private keys input in one or more second information processing devices different from the first information processing device among the multiple information processing devices reaches a number one less than the threshold.

[0071] <Appendix 4> 4. The information processing system according to any one of appendices 1 to 3, wherein the reception processing unit receives the input operation until a predetermined reception deadline arrives.

[0072] <Appendix 5> An information processing method executed in an information processing system having a plurality of information processing devices each connected to a network, the information processing method including: a receiving step, when an instruction to decrypt encrypted data encrypted with a public key is input in one of the plurality of information processing devices, receiving an input operation of one of a plurality of distributed private keys corresponding to the public key in each of the information processing devices; and a decryption step, when the number of distributed private keys input by the input operation reaches a threshold value for decrypting the encrypted data. [Explanation of symbols]

[0073] 10. Information processing equipment 11 Control section 12 Operation display section 13 Communications Department 14 Storage section 15 IC card reader 15A IC card 15B Distributed private key 20 servers 21 Control section 22 Operation display section 23 Communications Department 24 Memory section 24A Encrypted Data 24B Holder List 30 Communication Network 41 First reception processing section 42 Second Reception Processing Section 43 Decryption processing unit 44 Display processing section 100 Information Processing Systems

Claims

1. An information processing system comprising a plurality of information processing devices each connected to a network, a reception processing unit that, when an instruction to decrypt encrypted data encrypted with a public key is input in any one of the plurality of information processing devices, receives an input operation of any one of a plurality of distributed private keys corresponding to the public key in each of the plurality of information processing devices; a decryption processing unit that decrypts the encrypted data when the number of the shared private keys input by the input operation reaches a threshold value at which the encrypted data can be decrypted; An information processing system comprising:

2. the shared private key input by the input operation is transmitted to a first information processing device, of the plurality of information processing devices, to which the decryption instruction has been input; the decryption processing unit decrypts the encrypted data in the first information processing device; The information processing system according to claim 1 .

3. the reception processing unit terminates the reception of the input operation in each of the second information processing devices when the number of the distributed private keys input in one or more second information processing devices different from the first information processing device among the plurality of information processing devices reaches a number that is one less than the threshold value. The information processing system according to claim 2 .

4. the reception processing unit continues to receive the input operation until a predetermined reception time limit has arrived.

4. The information processing system according to claim 1.

5. An information processing method executed in an information processing system including a plurality of information processing devices each connected to a network, comprising: a receiving step of, when an instruction to decrypt encrypted data encrypted with a public key is input in any one of the plurality of information processing devices, receiving an input operation of any one of a plurality of distributed private keys corresponding to the public key in each of the plurality of information processing devices; a decryption step of decrypting the encrypted data when the number of the shared private keys input by the input operation reaches a threshold value at which the encrypted data can be decrypted; An information processing method including:

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