Information processing device, computer program, information processing system, and information processing method

Abstract

The present invention provides an information processing device, a computer program, an information processing system, and an information processing method that allow secure use of secret sharing fragments while verifying the physical location of a terminal device. [Solution] The information processing device includes a control unit, which acquires location information of multiple terminal devices, determines whether the locations of the multiple terminal devices are within a predetermined geographical range based on the acquired location information, and determines whether or not to allow the use of the secret sharing fragments held by each of the multiple terminal devices according to the determination result.

Description

Technical Field

[0001] The present invention relates to an information processing apparatus, a computer program, an information processing system, and an information processing method.

Background Art

[0002] In recent years, with the spread of cloud services and mobile terminals, cryptographic techniques such as public-key cryptography, secret-key cryptography, or a hybrid cryptography method combining these are used for the secure storage and use of digital assets.

[0003] In a single key management method, there is a possibility of causing a security incident when a key is leaked or there is unauthorized access. Therefore, a technique that combines multi-party computation (MPC) in which a secret key is divided into a plurality of secret share pieces (also referred to as "shares") and held by a plurality of terminal devices (which may include a server), and further, cryptographic operations are executed using each distributed secret share piece has attracted attention.

[0004] Multi-party computation is a cryptographic technique that can securely execute a desired computation without revealing the secret share pieces held by a plurality of parties. Patent Document 1 discloses a technique in which a plurality of parties can classify confidential data without sharing the confidential data with other parties by multi-party computation using a secret sharing key.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] While multi-party computing techniques can eliminate the single point of failure associated with managing a single secret key, the possibility of key theft or misuse still exists. Therefore, it is necessary to ensure security when multiple terminal devices cooperate to use secret sharing fragments.

[0007] This invention has been made in view of the above circumstances, and aims to provide an information processing device, a computer program, an information processing system, and an information processing method that can securely use secret sharing fragments while verifying the physical location of a terminal device. [Means for solving the problem]

[0008] The present invention includes several means for solving the above problem, but to give one example, the information processing device includes a control unit, which acquires location information of a plurality of terminal devices, determines whether the locations of the plurality of terminal devices are within a predetermined geographical range based on the acquired location information, and determines whether or not to use the secret sharing fragments held by each of the plurality of terminal devices according to the determination result. [Effects of the Invention]

[0009] According to the present invention, the secret sharing fragment can be used securely while verifying the physical location of the terminal device. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an example of the configuration of the information processing system according to the first embodiment. [Figure 2] This figure shows a first example of a method for determining the position of a terminal device in the first embodiment. [Figure 3] This figure shows a second example of a method for determining the position of a terminal device in the first embodiment. [Figure 4] This figure shows an example of a method for determining time information when acquiring location information of a terminal device in the first embodiment. [Figure 5] This figure shows an example of a method for calculating the reliability of the terminal device's position in the first embodiment. [Figure 6] This figure shows an example of threshold BLS signature processing by the information processing device of the first embodiment. [Figure 7] This figure shows an example of the processing procedure for generating, encrypting, and storing secret sharing fragments on each terminal device. [Figure 8] This figure shows an example of processing using a secret sharing fragment by the information processing device of the first embodiment. [Figure 9] This figure shows an example of the configuration of the information processing system according to the second embodiment. [Figure 10] This figure shows an example of processing using a secret sharing fragment by the information processing device of the second embodiment. [Modes for carrying out the invention]

[0011] (First Embodiment) Embodiments of the present invention will be described below. Figure 1 is a diagram showing an example of the configuration of an information processing system of the first embodiment. The information processing system of the first embodiment is also a secret sharing computation system that performs cryptographic operations using secret sharing pieces (shares). The secret sharing computation system includes a threshold multiparty computation means that performs cryptographic operations only when k (threshold: k≦n) or more of a plurality of secret sharing pieces (for example, n pieces) participate. A secret sharing piece is also called a "share". The information processing system includes an information processing device 50 and a plurality of (in the example of Figure 1, n) terminal devices 101~10 n It is equipped with multiple terminal devices 101-10 via the communication network 1. n The information processing device 50 is connected to a blockchain 100 that records calculation results and location proof data in a way that is difficult to tamper with. For convenience, multiple terminal devices 101-10 n This is also referred to as terminal device 10.

[0012] The information processing system of the first embodiment is a common key management method based on multi-party computation (MPC) with added geographical location authentication. In the common key management method, a secret key is divided into n secret shards, and a plurality of terminal devices 10 each hold their respective secret shards. Only when each of the secret shards with a predetermined threshold k (1 < k ≤ n) gathers within a geographically permitted range, cryptographic operations (such as signature generation, decryption, etc.) can be executed by the MPC protocol. The common key management in the common key management method can be applied to ensuring security in the B2B area, such as an enterprise internal system for managing digital assets in multiple departments and multiple locations or a cryptocurrency exchange.

[0013] Each of the plurality of terminal devices 10 can be composed of, for example, a smartphone, a tablet terminal, or a notebook computer, etc. Each of the plurality of terminal devices 10 includes a communication module for communicating with the information processing device 50, a position measurement unit for measuring the position information of the terminal device itself, a secure memory for holding the secret shards and terminal attribute information, a CPU (not shown in any figure) for controlling the entire terminal device, etc. In the example of FIG. 1, each individual terminal device 10 holds the secret shards S1, S2, S3,..., Sn respectively. The position measurement unit includes, for example, a satellite positioning system (GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), Galileo, BeiDou, etc.), a position estimation system via a base station, WiFi, a beacon, etc. The plurality of terminal devices 10 can be carried by their respective users. The terminal attribute information includes information unique to the terminal device, and includes, for example, information obtained by calculating with a required algorithm based on information such as the serial number of the terminal device and the unique information for each CPU held by the CPU.

[0014] The information processing device 50 includes a control unit 51 for controlling the entire device, a communication unit 52, a memory 53, an authentication unit 54, a determination unit 55, an availability determination unit 56, a reliability calculation unit 57, a processing unit 58, and a storage unit 59.

[0015] The control unit 51 may be configured by incorporating a required number of CPUs (Central Processing Units), MPUs (Micro-Processing Units), GPUs (Graphics Processing Units), etc. Further, the control unit 51 may be configured by combining DSPs (Digital Signal Processors), FPGAs (Field-Programmable Gate Arrays), etc.

[0016] The communication unit 52 includes a communication module and has a function of communicating with each of the plurality of terminal devices 10 via the communication network 1. The communication unit 52 can acquire the position information of each of the plurality of terminal devices 10 and the encrypted partial signature generated by the terminal device 10 from each of the plurality of terminal devices 10.

[0017] The authentication unit 54 performs terminal device authentication for each of the plurality of terminal devices 10 and user authentication for each user using the plurality of terminal devices 10.

[0018] Specifically, the authentication unit 54 acquires the terminal attribute information held by the terminal device 10 via the communication unit 52 and authenticates the terminal device based on the acquired terminal attribute information. Further, the authentication unit 54 acquires user authentication information (including biometric information such as fingerprints, faces, veins, etc., as well as PINs or one-time passwords, etc.) from the terminal device 10 via the communication unit 52 and authenticates the user based on the acquired user authentication information.

[0019] The determination unit 55 acquires location information (e.g., latitude, longitude, and reference point) for each of the multiple terminal devices 10 via the communication unit 52, and determines whether the location of each of the multiple terminal devices 10 is within a predetermined geographical range (e.g., a circular area with a radius of 100m from the central coordinates (x0,y0)) based on the acquired location information. The determination unit 55 also acquires time information when the location information of the multiple terminal devices 10 was acquired via the communication unit 52, and determines whether the acquired time information is within a predetermined temporal range. Alternatively, the determination result and the result of the reliability calculation unit 57 may be combined, and only terminal devices 10 that exceed the threshold may be determined to be "valid".

[0020] The usability determination unit 56 determines whether or not to allow the use of the secret sharing fragments held by each of the multiple terminal devices 10, according to the determination result by the determination unit 55. For example, if the usability determination unit 56 determines that the locations of each of the multiple terminal devices 10 are within a predetermined geographical range, it determines that the use of the secret sharing fragments held by each of the multiple terminal devices 10 is permitted. If the usability determination unit 56 determines that one of the locations of the multiple terminal devices 10 is not within the predetermined geographical range, it determines that the use of the secret sharing fragments held by each of the multiple terminal devices 10 is not permitted. Furthermore, if the usability determination unit 56 determines that the time information when the location information of the multiple terminal devices 10 was acquired is within a predetermined temporal range, it determines that the use of the secret sharing fragments held by each of the multiple terminal devices 10 is permitted. If the usability determination unit 56 determines that one of the time information when the location information of the multiple terminal devices 10 was acquired is not within the predetermined temporal range, it determines that the use of the secret sharing fragments held by each of the multiple terminal devices 10 is not permitted.

[0021] The reliability calculation unit 57 acquires location information for each of the multiple terminal devices 10 multiple times via the communication unit 52, and calculates the reliability of the location of the terminal device 10 based on the acquired location information. The reliability can be divided into, for example, high reliability and low reliability. If an unnatural speed or distance of movement is detected in the trajectory (or history) of the terminal device's location information, the reliability can be set to low, and if a natural speed or distance of movement is detected, the reliability can be set to high.

[0022] The processing unit 58 can perform processing using multiple secret sharing fragments. For example, the processing unit 58 can perform signature processing using multiple secret sharing fragments, but is not limited to signature processing; it may also perform cryptographic operations or other processing. The processing of the processing unit 58 can be executed, for example, on a secure hardware environment (e.g., TEE: Trusted Execution Environment) or a secure computing environment (including Secure Enclave or homomorphic encryption). This prevents the leakage of information such as terminal device IDs, user IDs, passwords, and payment information.

[0023] The storage unit 59 can be made up of semiconductor memory or a hard disk, and stores a computer program (program product) 60 and other necessary information.

[0024] The computer program 60 can be read by a recording medium (e.g., an optically readable disc storage medium such as a CD-ROM) M using a recording medium reading unit (not shown) and stored in the storage unit 59. The computer program 60 may also be read by a recording medium such as a storage device (semiconductor memory such as an SSD (Solid State Drive)) connected by a standard for connecting to a computer (e.g., USB (Universal Serial Bus) or other standards) and stored in the storage unit 59. Alternatively, the computer program 60 may be downloaded from an external device via a communication unit 52 and stored in the storage unit 59.

[0025] The memory 53 can be composed of semiconductor memories such as SRAM (Static Random Access Memory), DRAM (Dynamic Random Access Memory), and flash memory. A computer program 60 can be deployed in the memory 53, and the control unit 51 can execute the computer program 60. The control unit 51 can execute the processes defined by the computer program 60. That is, the processes by the control unit 51 are also the processes by the computer program 60.

[0026] All or part of the authentication unit 54, determination unit 55, usage permission determination unit 56, reliability calculation unit 57, and processing unit 58 may be realized by the processes of the computer program 60 (the processes of the control unit 51). In this specification, the processes of the authentication unit 54, determination unit 55, usage permission determination unit 56, reliability calculation unit 57, and processing unit 58 are also described as the processes of the control unit 51 alternatively. For example, the process of the authentication unit 54 can be treated as the process by the control unit 51.

[0027] FIG. 2 is a diagram showing a first example of a method for determining the positions of the terminal devices 10 in the first embodiment. In FIG. 2, a predetermined threshold value k (1 < k ≦ n) is set to 3, and only three terminal devices 10 are illustrated. That is, actually, there are n terminal devices 10, and the positions of k terminal devices 10 among the n terminal devices are to be determined. Also, a predetermined geographical range is represented by A1, A2, and A3, and the geographical range is defined by a polygonal geopfence or a circular area with a center coordinate (xi, yi) and a radius ri. Inside the geographical range, for example, it can be within a specific area that has been previously permitted to the user, such as a store, inside a company office, inside a factory, inside a warehouse, inside a data center, a public facility, or inside the user's home.

[0028] As shown in Figure 2, assume that terminal device (D1) 10 is located within a predetermined geographical range A1, terminal device (D2) 10 is located within a predetermined geographical range A2, and terminal device (D3) 10 is located within a predetermined geographical range A3. In this case, all target terminal devices 10 are located within the predetermined geographical range.

[0029] The control unit 51 acquires location information of multiple terminal devices (D1, D2, D3) 10 via the communication unit 52, and determines whether each of the locations of the multiple terminal devices (D1, D2, D3) 10 is within a predetermined geographical range (A1, A2, A3) based on the acquired location information. Based on the determination result, it can decide whether or not to use the secret sharing fragments (e.g., S1, S2, S3) held by each of the multiple terminal devices (D1, D2, D3) 10. Note that the geographical ranges A1, A2, and A3 may be different from each other, or they may be all or partly the same.

[0030] With the above configuration, the use of secret sharing fragments is permitted if the terminal device 10 is located within a specific geographical range that has been pre-approved. If even one device is not located within the geographical range, the secret sharing fragments of the corresponding terminal are invalidated, and if the predetermined threshold k is not reached, the MPC calculation is terminated. This makes unauthorized access or location spoofing difficult and ensures security when using secret sharing fragments.

[0031] In other words, if the control unit 51 determines that the terminal device 10 is located within a predetermined geographical range, it may decide that the secret sharing fragment held by the terminal device 10 is available for use.

[0032] Furthermore, the control unit 51 may stop using the secret sharing fragment held by the terminal device 10 if the terminal device 10 moves outside a specific geographical range. Stopping the use of the secret sharing fragment may include invalidating its use. This ensures that if signs of unauthorized use or leakage of the secret sharing fragment are detected, the secret sharing fragment cannot be used, thus preventing unauthorized use of the secret sharing fragment at an early stage.

[0033] Furthermore, if the control unit 51 detects that the terminal device 10 is located outside the geographical range and that the terminal device 10 is attempting to read or transmit a secret sharing fragment, it may temporarily or permanently restrict the terminal device 10 from using the secret sharing fragment. In this case, since it is highly likely that the secret sharing fragment held by the terminal device 10 has been illegally obtained, for example, the terminal device 10 or the user account can be blacklisted to restrict future use. This improves the security of using secret sharing fragments.

[0034] Figure 3 shows a second example of a method for determining the location of terminal devices 10 in the first embodiment. In the second example of Figure 3, unlike the first example shown in Figure 2, it is assumed that the location of terminal device (D1) 10 is outside a predetermined geographical range A1, the location of terminal device (D2) 10 is within a predetermined geographical range A2, and the location of terminal device (D3) 10 is within a predetermined geographical range A3. In this case, none of the target terminal devices 10 are located within the predetermined geographical range. The control unit 51 acquires location information of the multiple terminal devices (D1, D2, D3) 10 via the communication unit 52, and based on the acquired location information, if at least one of the locations of the multiple terminal devices (D1, D2, D3) 10 is outside a predetermined geographical range (A1, A2, A3), it can determine that the use of the secret sharing fragments (e.g., S1, S2, S3) held by each of the multiple terminal devices (D1, D2, D3) 10 is prohibited.

[0035] As described above, since the secret sharing fragments cannot be combined unless a predetermined threshold number of terminal devices 10 are located within a predetermined geographical range, cryptographic operations cannot be performed even if an imposter user is present, thus improving security.

[0036] FIG. 4 is a diagram showing an example of a method for determining time information when acquiring the position information of the terminal device 10 in the first embodiment. In FIG. 4, a predetermined threshold value k (1 < k ≦ n) is set to 3, and only three terminal devices (D1, D2, D3) 10 are illustrated. That is, actually, there are n terminal devices 10, and the position information of k terminal devices 10 among the n terminal devices is acquired. Each of the terminal devices (D1, D2, D3) 10 is assumed to be within geographical ranges A1, A2, and A3. In the example shown in FIG. 4, in addition to the position information of the terminal device 10, it is determined whether the time information when the position information is acquired is within a predetermined time range. As shown in FIG. 4, the time range (for example, time zone) may be from 9:00 to 13:00 on April 10, or may be within 60 minutes from the current time (for example, the time when the position information is acquired). Note that the time range is not limited to the example of FIG. 4.

[0037] As described above, the control unit 51 may acquire the time information when acquiring the position information of each of the plurality of terminal devices 10 via the communication unit 52, determine whether the acquired time information is within a predetermined time range, and determine whether the secret dispersion piece can be used according to the determination result.

[0038] Thereby, by considering the time information when the position information is acquired in addition to the position of the terminal device, the conditions for determining whether the secret dispersion piece can be used can be further tightened, and the security when using the secret dispersion piece can be improved.

[0039] FIG. 5 is a diagram showing an example of a method for calculating the reliability of the position of the terminal device 10 in the first embodiment. The reliability of the position of the terminal device 10 can be calculated based on the transition of the position information of the terminal device 10 (for example, the trajectory of the position, the history of the position, etc.). As shown in FIG. 5A, it is assumed that the position of the terminal device moves as time t1, t2, t3, t4 (for example, the present) elapses. In the case of FIG. 5A, at times t1 to t4, if the position of the terminal device 10 is within the geographical range and the moving speed or moving distance of the terminal device 10 is natural (reasonable), the reliability can be considered high.

[0040] Furthermore, as shown in Figure 5B, suppose the position of the terminal device moves as time t1, t2, t3, and t4 (for example, the present) progress. Suppose that at times t1, t2, and t3, the position of terminal device 10 is within the geographical range, and at time t4, the position of terminal device 10 is outside the geographical range. If the speed or distance of movement from time t3 to time t4 is unnatural (not reasonable), the reliability can be considered low.

[0041] As described above, the control unit 51 may acquire location information of the terminal device 10 multiple times, calculate the confidence level of the terminal device 10's location based on the multiple location information, authenticate the terminal device based on the calculated confidence level, and decide whether or not to allow the use of the secret sharing fragment according to the authentication result. Specifically, if the calculated confidence level is above a predetermined threshold, the location of the terminal device 10 is within a predetermined geographical range, and the time information is within a predetermined temporal range, the control unit 51 may include the secret sharing fragment in the threshold calculation.

[0042] Assuming that the location information of the terminal device 10 changes continuously, location information falsification can be detected by simulating and determining unusual movement patterns, thereby improving security when using secret sharing fragments.

[0043] The reliability can be calculated using two categories, such as high reliability and low reliability, as shown in the example in Figure 5, but the reliability is not limited to the example in Figure 5. For example, the reliability can be reduced as the travel speed or travel distance increases, and the reliability can be expressed numerically on a scale of 0 to 100, or in stages such as reliability 1, 2, 3, 4, 5. Furthermore, the reliability can be reduced as the number of times the terminal device 10 was outside the geographical range within a predetermined time period increases.

[0044] FIG. 6 is a diagram showing an example of threshold BLS signature processing by the information processing apparatus 50 of the first embodiment. In the example of FIG. 6, the secret shards S1, S2, …, Sn held by each of the plurality of terminal devices (D1, D2, …, Dn) 10 have been determined to be available, and the terminal devices 10 with a predetermined threshold k (1 < k ≦ n) or more among the n secret shards participate in the signature operation. Hereinafter, it will be described with k = n.

[0045] The control unit 51 generates a message to be transmitted to other devices, calculates a hash value Hd by hashing the message generated using the hash function H. The control unit 51 transmits the generated hash value Hd to each terminal device 10. Each terminal device 10 generates partial signatures Hd1, Hd2, …, Hdn using the secret shards S1, S2, …, Sn it holds. The control unit 51 receives a number of partial signatures equal to the predetermined threshold k (in the example of FIG. 6, n) from each terminal device 10, and synthesizes a master signature Hm by a known method such as Lagrange interpolation. The synthesized master signature Hm can be verified with the publicly available master verification key Pm. The control unit 51 transmits the message and the master signature to other devices. The other device can verify the master signature Hm with the publicly available master verification key Pm.

[0046] As described above, when the control unit 51 determines that the positions of each of the plurality of terminal devices 10 are within a predetermined geographical range, the control unit 51 can acquire partial signatures from each of the plurality of terminal devices 10. The control unit 51 can execute signature processing using the acquired partial signatures.

[0047] According to this embodiment, since only partial signatures are generated on the terminal device 10 side and the secret split pieces S1, S2, …, Sn are not transmitted externally, the risk of leakage of the secret split pieces can be reduced. Also, by setting the threshold k (1 < k ≤ n), signature generation can continue even if some of the terminal devices 10 malfunction or communication is interrupted, ensuring availability. Furthermore, by combining pre-filtering based on location, time information, and reliability with operations within the TEE (Trusted Execution Environment), high resistance against remote unauthorized access, location information spoofing, or malware intrusion can be achieved. Thus, even if the master secret key is permanently discarded or erased, signature processing can be performed securely, and the security level in distributed key management can be significantly improved.

[0048] FIG. 7 is a diagram showing an example of a processing procedure for generating and encrypting secret split pieces and storing them in each terminal device 10. In this embodiment, the information processing device 50 will be described as performing the processing, but equivalent processing may be performed by another device different from the information processing device 50.

[0049] The control unit 51 generates a master verification key Pm from the master secret key held in advance (S11). The control unit 51 generates n secret split pieces S1, S2, …, Sn from the master secret key (S12). Note that distributed verification keys P1, P2, …, Pn corresponding to the generated secret split pieces S1, S2, …, Sn can be generated respectively.

[0050] The control unit 51 generates a key pair including a public key (corresponding to an encryption key) and a private key (corresponding to a decryption key) in an encryption method (for example, a public key encryption method) to be applied to the n secret split pieces (S13). Note that when the symmetric key encryption method is adopted, the encryption key and the decryption key are the same. The control unit 51 encrypts the secret split pieces S1, S2, …, Sn with the generated public key (encryption key) to generate encrypted secret split pieces S1′, S2′, …, Sn′ (S14).

[0051] The control unit 51 stores the secret key (decryption key) and publishes the master verification key Pm (S15). The secret key (decryption key) is information to be concealed and is the key for decrypting the encrypted secret dispersion pieces S1′, S2′, …, Sn′. The decryption key may be stored in a key server (not shown). The publication of the master verification key Pm may be achieved by storing the master verification key Pm in a key server (not shown), or by using key publication techniques or the like used in the blockchain 100. As a condition for being able to obtain the decryption key or the master verification key Pm from the key server, it may be set that the required authentication process is successful. The control unit 51 stores the encrypted secret dispersion pieces S1′, S2′, …, Sn′ in the plurality of terminal devices (D1, D2, …, Dn) 10 respectively (S16), discards the master secret key (S17), and ends the process.

[0052] In the above example, the process of encrypting the secret dispersion pieces S1, S2, …, Sn is included. However, if the encryption process is not performed, the process of step S14 may be omitted.

[0053] FIG. 8 is a diagram showing an example of processing using secret dispersion pieces by the information processing apparatus 50 according to the first embodiment. In the example of FIG. 8, it is assumed that each of the plurality of terminal devices (D1, D2, …, Dn) 10 holds the secret dispersion pieces S1, S2, …, Sn, and the position information of the terminal devices 10 of a predetermined threshold k (1 < k ≦ n) or more among the n terminal devices is determined. Hereinafter, the description will be made with k = n. The control unit 51 acquires the position information of each of the plurality of terminal devices (D1, D2, …, Dn) 10 (S21), and determines whether the position of each of the plurality of terminal devices (D1, D2, …, Dn) 10 exists within a predetermined geographical range (A1, A2, …, An) (S22).

[0054] When the position of each of the plurality of terminal devices (D1, D2, …, Dn) 10 exists within the predetermined geographical range (A1, A2, …, An) (YES in S22), the control unit 51 determines whether the time information at the time of acquiring the position information is within a predetermined time range (S23).

[0055] If the time information obtained when the location information is acquired falls within a predetermined time range (YES in S23), the control unit 51 decides that the secret sharing fragments S1, S2, ..., Sn held by each of the multiple terminal devices (D1, D2, ..., Dn) 10 are usable (S24). The control unit 51 sends the hash value Hd obtained by hashing the message to each of the multiple terminal devices (D1, D2, ..., Dn) 10 and receives the partial signatures Hd1, Hd2, ..., Hdn generated by the multiple terminal devices (D1, D2, ..., Dn) 10 (S25).

[0056] The control unit 51 generates a master signature Hm from the received partial signatures Hd1, Hd2, ..., Hdn (S26) and outputs the master signature Hm along with the message (S27).

[0057] The control unit 51 records the results of determining whether the location of each of the multiple terminal devices (D1, D2, ..., Dn) 10 is within a predetermined geographical range (A1, A2, ..., An), the results of determining whether the time information when the location information was acquired is within a predetermined time range, and the results of determining whether the secret sharing fragments S1, S2, ..., Sn can be used in the blockchain 100 (S28), and then terminates the process.

[0058] If the location of each of the multiple terminal devices (D1, D2, ..., Dn) 10 is not within a predetermined geographical range (A1, A2, ..., An), that is, if the location of at least one of the multiple terminal devices (D1, D2, ..., Dn) 10 is outside the predetermined geographical range (A1, A2, ..., An) (NO in S22), or if the time information of each of the location information acquired is not within a predetermined temporal range, that is, if the time information of at least one of the multiple terminal devices (D1, D2, ..., Dn) 10 is outside the predetermined temporal range (NO in S23), the control unit 51 decides that the secret sharing fragment is unusable (S29) and records it in the blockchain 100 in the same way as in step S28. If the secret sharing fragment is determined to be unusable, the control unit 51 does not receive the partial signatures Hd1, Hd2, ..., Hdn.

[0059] As described above, the control unit 51 can record in the blockchain 100 the determination result of whether the location of the terminal device 10 is within a geographical range, the determination result of whether the time information when the location information was acquired is within a predetermined time range, and the determination result of whether the terminal device 10 can use the secret sharing fragment.

[0060] According to this embodiment, a threshold signature is generated only when at least k terminal devices 10 that satisfy geographical and temporal constraints cooperate, and the audit log is also stored in an immutable format. Therefore, the security and traceability when using secret sharing fragments can be greatly improved while verifying the physical location of the terminal devices 10.

[0061] (Second Embodiment) Figure 9 shows an example of the configuration of the information processing system in the second embodiment. In the first embodiment, the case of a shared key management type (for B2B) was described, but in the second embodiment, the case of a composite authentication type (toC wallet) based on single-location authentication will be described. A composite authentication type is a method in which a master private key is divided into multiple secret sharing fragments, each of the divided secret sharing fragments is associated with different predetermined authentication elements such as location, biometrics, and service-side verification, and cryptographic operations are permitted only when all predetermined authentication elements or a threshold of k authentication elements are satisfied. In this embodiment, the threshold k is set to k=2 (where n=3), and cryptographic operations are permitted if the secret sharing fragment S3 on the server side and either of the secret sharing fragments (S1 or S2) on the terminal device side satisfy the conditions. The composite authentication type uses a personal wallet used by a single end user (e.g., a consumer), and key management is performed by combining multiple authentication elements such as the user themselves, the user's location information, the user's biometric information (e.g., the user's fingerprint, facial information, etc.), and the service provider (information processing device 50). As shown in Figure 9, the difference from the first embodiment is that it includes one terminal device 10, which holds a secret sharing fragment S1 associated with the location of the terminal device 10 and a secret sharing fragment S2 associated with the user's biometric information. The information processing device 50 also holds a secret sharing fragment S3 in a secret sharing fragment storage unit 61. The secret sharing fragment storage unit 61 can be configured as a secure memory. The other configurations (communication unit 52, memory 53, authentication unit 54, determination unit 55, usability determination unit 56, reliability calculation unit 57, and processing unit 58) are the same as in the first embodiment.

[0062] Figure 10 shows an example of processing using a secret sharing fragment by the information processing device 50 of the second embodiment. The control unit 51 acquires location information of the terminal device 10 (S41) and determines whether the location of the terminal device 10 is within a predetermined geographical range (S42).

[0063] If the terminal device 10 is located within a predetermined geographical range (YES in S42), the control unit 51 determines whether the time information at the time the location information was acquired is within a predetermined time range (S43).

[0064] If the time information obtained when the location information is acquired falls within a predetermined time range (YES in S43), the control unit 51 acquires the user's biometric information (S44). The terminal device 10 can acquire the biometric information by displaying a screen prompting the user to input their biometric information.

[0065] The control unit 51 determines whether user authentication was successful based on the acquired biometric information (S45). If user authentication is successful (YES in S45), it decides that the secret sharing fragments S1 and S2 held by the terminal device 10, and the secret sharing fragment S3 held by itself, are available for use (S46). The control unit 51 sends the hash value Hd obtained by hashing the message to the terminal device 10, and the terminal device 10 receives the partial signatures Hd1 and Hd2 generated using the shared secret fragments S1 and S2 (S47).

[0066] The control unit 51 generates (combines) a master signature Hm using the received partial signatures Hd1 and Hd2, and the partial signature Hd3 generated using the secret sharing fragment S3 held by itself (S48), and outputs the master signature Hm along with the message (S49).

[0067] The control unit 51 records the result of determining whether the terminal device 10 is located within a predetermined geographical range, the result of determining whether the time information when the location information was acquired is within a predetermined time range, and the result of determining whether the secret sharing fragments S1, S2, and S3 can be used in the blockchain 100 (S50), and then terminates the process.

[0068] If the terminal device 10 is not located within a predetermined geographical range (NO in S42), if the time information at the time of acquisition of the location information is not within a predetermined time range (NO in S43), or if user authentication is unsuccessful (NO in S45), the control unit 51 determines that the secret sharing fragments S1, S2, and S3 are unusable (S51) and performs the processing in step S50. If the secret sharing fragments are determined to be unusable, the control unit 51 does not receive the partial signatures Hd1 and Hd2 from the terminal device 10. If the secret sharing fragments are determined to be unusable, the terminal device 10 does not generate the partial signatures Hd1 and Hd2.

[0069] As described above, the control unit 51 acquires location information of the terminal device 10, determines whether the location of the terminal device 10 is within a predetermined geographical range based on the acquired location information, and determines whether or not to use the secret sharing fragments held by the terminal device 10 and the information processing device 50, respectively, according to the determination result.

[0070] With the above configuration, the use of the secret sharing fragments held by the terminal device 10 and the information processing device 50 is determined based on whether or not the terminal device 10 is located within a pre-approved specific area. This makes unauthorized access or location spoofing difficult and ensures security when using the secret sharing fragments.

[0071] Furthermore, if the control unit 51 determines that the terminal device 10 is located within a predetermined geographical range, it may decide that the terminal device 10 and the information processing device 50 can use the secret sharing fragment.

[0072] Furthermore, the control unit 51 may stop using the secret sharing fragment if the location of the terminal device 10 moves outside the geographical range. Stopping the use of the secret sharing fragment may include disabling its use. This ensures that if signs of unauthorized use or leakage of the secret sharing fragment are detected, the secret sharing fragment cannot be used, thus preventing unauthorized use of the secret sharing fragment at an early stage.

[0073] Furthermore, if the control unit 51 detects that the terminal device 10 is located outside the geographical range and that the terminal device 10 is attempting to read or transmit a secret sharing fragment, it may temporarily or permanently restrict the use of the secret sharing fragment by the terminal device 10 and the information processing device 50. In this case, since it is highly likely that the secret sharing fragment held by the terminal device 10 has been illegally obtained, for example, the terminal device 10 or the user account can be blacklisted to restrict future use. This improves the security of using secret sharing fragments.

[0074] Furthermore, the control unit 51 may acquire terminal attribute information held by the terminal device 10, authenticate the terminal device 10 based on the acquired terminal attribute information, and decide whether or not to allow the use of the secret sharing fragment according to the authentication result.

[0075] Furthermore, the control unit 51 may acquire user authentication information (primarily biometric information such as fingerprints, facial features, and vein patterns, but also including PINs or one-time passwords, etc.) from the terminal device 10, authenticate the user based on the acquired authentication information, and, depending on the authentication result, decide whether or not to allow the use of the secret sharing fragment held in the terminal device 10 and associated with the biometric information.

[0076] In multi-factor authentication, signing a transaction requires multiple elements (geographical range, device authentication, and user authentication), allowing for multi-stage verification and dramatically improving security strength. Note that the multiple elements may also include a temporal range.

[0077] In the first embodiment described above, each of the multiple terminal devices 10 held a secret sharing fragment, and the information processing device 50 did not hold a secret sharing fragment. However, in the first embodiment, as in the second embodiment, the information processing device 50 may also hold a secret sharing fragment.

[0078] (Note 1) The information processing device includes a control unit, which acquires location information of a plurality of terminal devices, determines whether the locations of the plurality of terminal devices are within a predetermined geographical range based on the acquired location information, and determines whether or not the secret sharing fragments held by each of the plurality of terminal devices can be used according to the determination result.

[0079] (Note 2) The information processing device is an information processing device comprising a control unit, the control unit acquires location information of a terminal device, determines whether the location of the terminal device is within a predetermined geographical range based on the acquired location information, and determines whether or not to use the secret sharing fragments held by the terminal device and the information processing device, respectively, according to the determination result.

[0080] (Note 3) In the information processing device, according to Note 1 or Note 2, the control unit determines that the location of the terminal device is within the predetermined geographical range, and decides that the secret sharing fragment can be used.

[0081] (Note 4) In any one of Notes 1 to 3, the information processing device determines that the secret sharing fragment can be used if the number of terminal devices determined to be located within the predetermined geographical range is a predetermined number.

[0082] (Note 5) In any one of Notes 1 to 4, the information processing device, when the control unit determines that the location of the terminal device is within the predetermined geographical range, performs at least one of cryptographic and signature operations using each secret sharing fragment.

[0083] (Note 6) In any one of Notes 1 to 5, the information processing device, if the control unit determines that the number of terminal devices located within the predetermined geographical area is a predetermined number, performs at least one cryptographic operation and a signature operation using each secret sharing fragment.

[0084] (Note 7) In any one of Notes 1 to 6, the information processing device, the control unit, determines whether the time information at the time the location information was acquired falls within a predetermined time range, and determines whether or not to use the secret sharing fragment according to the determination result.

[0085] (Note 8) In any one of Notes 1 to 7, the information processing device, the control unit, acquires terminal attribute information held by the terminal device, authenticates the terminal device based on the acquired terminal attribute information, and determines whether or not to use the secret sharing fragment according to the authentication result.

[0086] (Note 9) In any one of Notes 1 to 8, the information processing device, the control unit, acquires the user's biometric information from the terminal device, authenticates the user based on the acquired biometric information, and determines whether or not to use the secret sharing fragment held in the terminal device and associated with the biometric information, according to the authentication result.

[0087] (Note 10) In any one of Notes 1 to 9, the information processing device, the control unit, acquires the location information multiple times, calculates the reliability of the terminal device's location based on the multiple location information, authenticates the terminal device based on the calculated reliability, and determines whether or not to use the secret sharing fragment according to the authentication result.

[0088] (Note 11) In any one of Notes 1 to 10, the information processing device shall, if the location of the terminal device is outside the geographical range, cease using the secret sharing fragment.

[0089] (Note 12) In any one of Notes 1 to 11, the information processing device, if the control unit detects that the terminal device is located outside the geographical range and that the terminal device is using a secret sharing fragment, will temporarily or permanently restrict the terminal device's use of the secret sharing fragment.

[0090] (Note 13) In Note 2, the control unit of the information processing device shall temporarily or permanently restrict the use of secret sharing fragments by the information processing device if the terminal device is located outside the geographical range and the terminal device has used secret sharing fragments.

[0091] (Note 14) In any one of Notes 1 to 13, the control unit of the information processing device records in the blockchain the determination result of whether or not the location of the terminal device is within the geographical range, and the determination result of whether or not the terminal device can use the secret sharing fragment.

[0092] (Note 15) The computer program causes the computer to perform the following processing: acquire location information of multiple terminal devices, determine whether the locations of the multiple terminal devices are within a predetermined geographical range based on the acquired location information, and, according to the determination result, decide whether or not to use the secret sharing fragments held by each of the multiple terminal devices.

[0093] (Note 16) The computer program causes the computer to perform the following steps: acquire location information of the terminal device, determine whether the location of the terminal device is within a predetermined geographical range based on the acquired location information, and, according to the determination result, decide whether or not to use the secret sharing fragments held by the terminal device and the computer, respectively.

[0094] (Note 17) The information processing system comprises a plurality of terminal devices and an information processing device, each of the plurality of terminal devices holds a secret sharing fragment and acquires location information, the information processing device acquires the location information of the plurality of terminal devices and determines whether the locations of the plurality of terminal devices are within a predetermined geographical range based on the acquired location information, and determines whether or not to use the secret sharing fragment held by each of the plurality of terminal devices according to the determination result.

[0095] (Note 18) The information processing system comprises a terminal device and an information processing device. The terminal device holds a secret sharing fragment and acquires location information. The information processing device holds a secret sharing fragment and acquires location information of the terminal device. Based on the acquired location information, it determines whether the terminal device is located within a predetermined geographical range, and determines whether the secret sharing fragments held by the terminal device and the information processing device can be used, respectively, according to the determination result.

[0096] (Note 19) The information processing method is as follows: Each of the multiple terminal devices holds a secret sharing fragment and acquires location information; the information processing device acquires the location information of the multiple terminal devices, determines whether the locations of the multiple terminal devices are within a predetermined geographical range based on the acquired location information, and determines whether or not to use the secret sharing fragment held by each of the multiple terminal devices according to the determination result.

[0097] (Note 20) The information processing method is as follows: The terminal device holds a secret sharing fragment and acquires location information; the information processing device holds a secret sharing fragment and acquires location information of the terminal device; based on the acquired location information, it determines whether the location of the terminal device is within a predetermined geographical range; and, according to the determination result, it determines whether the secret sharing fragments held by the terminal device and the information processing device, respectively, can be used.

[0098] The matters described in each embodiment can be combined with each other. Furthermore, the independent and dependent claims described in the claims can be combined with each other in any combination, regardless of the form of reference. In addition, the claims use a form in which claims referencing two or more other claims (multi-claim form), but are not limited to this. A form in which multi-claims referencing at least one multi-claim (multi-multi-claim) may also be used. [Explanation of Symbols]

[0099] 1. Communication Network 10 Terminal devices 50 Information Processing Devices 51 Control Unit 52 Communications Department 53 memory 54 Certification Department 55 Judgment section 56 Usability determination section 57. Confidence Calculation Unit 58 Processing Unit 59 Memory section 60 Computer Programs 61 Secret Dispersion Fragment Storage Unit 100 Blockchains

Claims

1. Equipped with a control unit, The control unit, Acquire location information from multiple terminal devices, Based on the acquired location information, it is determined whether the locations of the multiple terminal devices are within a predetermined geographical range. If the number of terminal devices determined to be located within the predetermined geographical area is a predetermined number, it is decided that the use of the secret sharing fragments held by each of the multiple terminal devices is permitted. Information processing device.

2. An information processing device comprising a control unit, The control unit, The location information of the terminal device is obtained, Based on the acquired location information, it is determined whether the location of the terminal device is within a predetermined geographical range. Depending on the determination result, the terminal device and the information processing device will determine whether or not to allow the use of the secret sharing fragments held by the terminal device and the information processing device, respectively. Information processing device.

3. The control unit, If it is determined that the location of the terminal device is within the predetermined geographical range, it is decided that the secret sharing fragment can be used. The information processing apparatus according to claim 1 or claim 2.

4. The control unit, If the number of terminal devices determined to be located within the predetermined geographical area is a predetermined number, the secret sharing fragment is deemed usable. The information processing apparatus according to claim 2.

5. The control unit, If it is determined that the terminal device is located within the predetermined geographical range, at least one of cryptographic and signature operations is performed using each secret sharing fragment. The information processing apparatus according to claim 1 or claim 2.

6. The control unit, If the number of terminal devices determined to be located within the predetermined geographical area is a predetermined number, then at least one of cryptographic and signature operations is performed using each secret sharing fragment. The information processing apparatus according to claim 1 or claim 2.

7. The control unit, Determine whether the time information obtained when the location information was acquired falls within a predetermined time range. The decision on whether or not to use the secret sharing fragment is made based on the result of the determination. The information processing apparatus according to claim 1 or claim 2.

8. The control unit, The terminal device acquires the terminal attribute information it holds, The terminal device is authenticated based on the acquired terminal attribute information. The decision on whether or not to use the secret sharing fragment is made based on the authentication result. The information processing apparatus according to claim 1 or claim 2.

9. The control unit, The user's biometric information is obtained from the aforementioned terminal device. The user is authenticated based on the acquired biometric information. Depending on the authentication result, the terminal device determines whether or not to use the secret sharing fragment that is held in the terminal device and associated with the biometric information. The information processing apparatus according to claim 1 or claim 2.

10. The control unit, The aforementioned location information is acquired multiple times, The reliability of the terminal device's location is calculated based on multiple location information, The terminal device is authenticated based on the calculated confidence level. The decision on whether or not to use the secret sharing fragment is made based on the authentication result. The information processing apparatus according to claim 1 or claim 2.

11. The control unit, If the location of the terminal device moves outside the geographical range, the use of the secret sharing fragment is stopped. The information processing apparatus according to claim 1 or claim 2.

12. The control unit, If the location of the terminal device is outside the geographical range and the use of a secret sharing fragment by the terminal device is detected, the use of the secret sharing fragment by the terminal device is temporarily or permanently restricted. The information processing apparatus according to claim 1 or claim 2.

13. The control unit, If the location of the terminal device is outside the geographical range and the use of a secret sharing fragment by the terminal device is detected, the use of the secret sharing fragment by the information processing device is temporarily or permanently restricted. The information processing apparatus according to claim 2.

14. The control unit, The determination result of whether the location of the terminal device is within the geographical range, and the determination result of whether or not the terminal device can use the secret sharing fragment are recorded on the blockchain. The information processing apparatus according to claim 1 or claim 2.

15. Acquire location information from multiple terminal devices, Based on the acquired location information, it is determined whether the locations of the multiple terminal devices are within a predetermined geographical range. If the number of terminal devices determined to be located within the predetermined geographical area is a predetermined number, it is decided that the use of the secret sharing fragments held by each of the multiple terminal devices is permitted. A computer program that instructs a computer to perform a process.

16. The location information of the terminal device is obtained, Based on the acquired location information, it is determined whether the location of the terminal device is within a predetermined geographical range. Depending on the determination result, the terminal device and the computer will determine whether or not the secret sharing fragments held by the terminal device and the computer can be used by the terminal device and the computer, respectively. A computer program that instructs a computer to perform a process.

17. Equipped with multiple terminal devices and information processing devices, Each of the aforementioned multiple terminal devices is: Hold the secret distribution fragment, Obtain location information, The aforementioned information processing device is The location information of the aforementioned multiple terminal devices is acquired, Based on the acquired location information, it is determined whether the locations of the multiple terminal devices are within a predetermined geographical range. If the number of terminal devices determined to be located within the predetermined geographical area is a predetermined number, it is decided that the use of the secret sharing fragments held by each of the multiple terminal devices by the terminal devices is permitted. Information processing system.

18. It comprises a terminal device and an information processing device, The aforementioned terminal device is Hold the secret distribution fragment, Obtain location information, The aforementioned information processing device is Hold the secret distribution fragment, The location information of the terminal device is acquired, Based on the acquired location information, it is determined whether the location of the terminal device is within a predetermined geographical range. Depending on the determination result, the terminal device and the information processing device will determine whether or not to allow the use of the secret sharing fragments held by the terminal device and the information processing device, respectively. Information processing system.

19. Each of the multiple terminal devices is, Hold the secret distribution fragment, Obtain location information, Information processing equipment, The location information of the aforementioned multiple terminal devices is acquired, Based on the acquired location information, it is determined whether the locations of the multiple terminal devices are within a predetermined geographical range. If the number of terminal devices determined to be located within the predetermined geographical area is a predetermined number, it is decided that the use of the secret sharing fragments held by each of the multiple terminal devices is permitted. Information processing methods.

20. The terminal device is Hold the secret distribution fragment, Obtain location information, Information processing equipment, Hold the secret distribution fragment, The location information of the terminal device is acquired, Based on the acquired location information, it is determined whether the location of the terminal device is within a predetermined geographical range. Depending on the determination result, the terminal device and the information processing device will determine whether or not to allow the use of the secret sharing fragments held by the terminal device and the information processing device, respectively. Information processing methods.

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