Information processing method, information processing device, and program

Abstract

This information processing method is executed by one node among a plurality of nodes constituting a distributed ledger system. The information processing method: acquires transaction data including a first electronic signature generated by a first signature method (S20); acquires performance information indicating performance of a computer for decrypting the electronic signature (S50); determines whether or not transaction data including the first electronic signature is to be included in a block of a blockchain, on the basis of a mining reward obtained by mining the transaction data including the first electronic signature, the mining reward having been changed from a predetermined mining reward in accordance with the performance information (S60); and generates a block including the transaction data when it is determined that the transaction data is to be included (S70, S90).

Description

Information processing method, information processing device, and program

[0001] The present disclosure relates to an information processing method, an information processing device, and a program.

[0002] Transaction data recorded using a distributed ledger system such as a blockchain includes, in addition to the transaction itself, a digital signature (also simply referred to as a signature) assigned by the generator of the transaction data (see, for example, Patent Document 1).

[0003] Patent No. 7550941

[0004] The security of signature methods (also called signature algorithms) for generating signatures is subject to deterioration due to improvements in computer computing power, etc., so in the future it is desirable to transition to more secure signature methods, such as by changing the key length or by transitioning to next-generation algorithms.

[0005] Therefore, the present disclosure provides an information processing method, an information processing device, and a program that can support the transition to a highly secure signature method.

[0006] An information processing method according to one aspect of the present disclosure is an information processing method executed by one of multiple nodes constituting a distributed ledger system, which acquires transaction data including a first electronic signature generated using a first signature method, acquires performance information indicating the performance of a computer for decrypting the electronic signature, and determines whether to include the transaction data including the first electronic signature in a block of a blockchain based on a mining reward obtained by mining the transaction data including the first electronic signature, the mining reward being changed from a predetermined mining reward in accordance with the performance information, and generates the block including the transaction data if it is determined to be included.

[0007] An information processing device according to one aspect of the present disclosure is an information processing device that is one of multiple nodes constituting a distributed ledger system, and includes: an acquisition unit that acquires transaction data including a first electronic signature generated using a first signature method and performance information indicating the performance of a computer for decrypting the electronic signature; an execution unit that determines whether to include the transaction data including the first electronic signature in a block of a blockchain based on a mining reward obtained by mining the transaction data including the first electronic signature, the mining reward being changed from a predetermined mining reward in accordance with the performance information; and a ledger management unit that generates the block including the transaction data when it is determined to include the transaction data.

[0008] A program according to one aspect of the present disclosure is a program for causing a computer to execute the above-described information processing method.

[0009] According to one aspect of the present disclosure, it is possible to realize an information processing method or the like that can support a transition to a highly secure signature method.

[0010] FIG. 1 is a diagram showing the configuration of an information processing system according to an embodiment. FIG. 2 is a block diagram showing the functional configuration of a ledger server according to an embodiment. FIG. 3 is a sequence diagram showing the operation of an information processing system according to an embodiment. FIG. 4 is a table showing mining reward rates according to an embodiment. FIG. 5 is an explanatory diagram showing the data structure of a blockchain, which is an example of a distributed ledger. FIG. 6 is an explanatory diagram showing the data structure of transaction data. FIG. 7 is an explanatory diagram showing transaction data related to the execution of a smart contract. FIG. 8 is a flowchart showing processing related to the execution of a smart contract. FIG. 9 is an explanatory diagram showing the structures of NFTs and metadata.

[0011] (Background to the Invention of the Present Disclosure) Before describing the present disclosure, the background to the invention of the present disclosure will be described.

[0012] As described in the above "Problem to be Solved by the Invention," the security of signature schemes is compromised by improvements in computer computing power, and therefore, it is desirable to take measures to improve the security of signature schemes in the future, such as changing the key length or migrating to a next-generation algorithm. Improvements in computer computing power are achieved through advances in computers. Examples of advances in computers include improvements in the performance of conventional computers (e.g., so-called classical computers) and the development of next-generation computers such as quantum computers. Examples of next-generation algorithms include, but are not limited to, PQC (Post-Quantum Cryptography). The key length of a signature algorithm and the signature algorithm are examples of a signature scheme. Changing the key length of a signature algorithm (e.g., making it longer) and migrating the signature algorithm to a next-generation algorithm are examples of migrating a signature scheme. Transitioning the signature algorithm to a next-generation algorithm may be, for example, transitioning from a signature algorithm that is not compliant with quantum-computer-resistant cryptography to a signature algorithm that is compliant with quantum-computer-resistant cryptography.

[0013] On the other hand, changing the key length or migrating to a next-generation algorithm requires more resources for, for example, signature generation and verification, so it is desirable to migrate at an appropriate time. In other words, to prepare for a possible compromise that could raise doubts about the security of the signature method used in blockchain, etc., it is desirable to appropriately determine the timing of the signature method migration (e.g., the start of the migration). However, determining the right time to migrate is difficult even for experts.

[0014] Therefore, the inventors of the present application have conducted extensive research into information processing methods and the like that can assist in the transition to a more secure signature method at a more appropriate time, and have devised the information processing methods and the like shown below.

[0015] Furthermore, because the migration cost of migrating signature methods is high, it is conceivable to migrate signature methods only for important transaction data (Tx) in the early stages of the migration, but there are also issues regarding how to select important transaction data.

[0016] Therefore, the inventors of the present application are also conducting extensive research into information processing methods and the like that can assist in selecting transaction data to be migrated.

[0017] An information processing method according to a first aspect of the present disclosure is an information processing method executed by one of multiple nodes constituting a distributed ledger system, which acquires transaction data including a first electronic signature generated using a first signature method, acquires performance information indicating the performance of a computer for decrypting the electronic signature, and determines whether to include the transaction data including the first electronic signature in a block of a blockchain based on a mining reward obtained by mining the transaction data including the first electronic signature, the mining reward being changed from a predetermined mining reward in accordance with the performance information, and generates the block including the transaction data if it is determined to be included.

[0018] This makes it possible to suppress the storage of transaction data including the first digital signature in a block according to the performance information of the computer, thereby encouraging migration from the current signature scheme, which has low security, to a signature scheme with high security.

[0019] Also, for example, the information processing method according to the second aspect may be the information processing method according to the first aspect, wherein the performance information includes first performance information indicating the computer's ability to decrypt the electronic signature and second performance information indicating the performance of a quantum computer, and the mining reward may be changed based on the first performance information and the second performance information.

[0020] This makes it possible to identify the mining reward according to the first performance information and the second performance information.

[0021] Furthermore, for example, the information processing method according to the third aspect may be the information processing method according to the second aspect, in which a table is obtained in which the decryption capability of an electronic signature and the performance of a quantum computer are associated with information indicating mining rewards, and the mining reward for the transaction data including the first electronic signature is determined based on the performance information at the time of acquisition of the transaction data and the table.

[0022] This makes it easy to identify mining rewards using the table.

[0023] Furthermore, for example, an information processing method according to a fourth aspect may be the information processing method according to the third aspect, wherein the digital signature decryption capability included in the table includes two or more degrees of difficulty indicating the difficulty of decrypting the signature by the computer, the quantum computer performance included in the table includes two or more degrees of scale indicating the scale of the problem to be solved by the quantum computer, and the table may have multiple degrees of reduction in the mining reward set according to combinations of the two or more degrees of difficulty and the two or more degrees of scale.

[0024] This makes it possible to identify the optimal mining reward based on the first performance information and the second performance information at the time of transaction data acquisition.

[0025] Furthermore, for example, the information processing method according to the fifth aspect may be the information processing method according to the fourth aspect, wherein the table includes setting the mining reward to zero depending on the combination of the two or more difficulty levels and the two or more scale levels.

[0026] This effectively reduces the number of transactions containing the first digital signature that miners include in blocks, as the mining reward becomes zero, thereby effectively supporting the transition to a more secure signature scheme.

[0027] Furthermore, for example, an information processing method according to a sixth aspect may be an information processing method according to any one of the first to fifth aspects, in which the table is obtained from a distributed ledger and the performance information is obtained off-chain.

[0028] This makes it possible to effectively obtain correct tables that have not been tampered with, as well as performance information that is not held by the ledger system.

[0029] Furthermore, for example, an information processing method according to a seventh aspect may be an information processing method according to any one of the first to sixth aspects, in which, if the security of the first signature scheme is low, the transaction data is not stored in the block, and the creator of the transaction data is notified that it has not been stored in the block.

[0030] This will encourage the creator of the transaction data to switch signature methods.

[0031] Furthermore, for example, an information processing method according to an eighth aspect may be an information processing method according to any one of the first to sixth aspects, and if the security of the first signature scheme is low, the transaction data may not be stored in the block, and a notification may be sent to change the first signature scheme to a more secure signature scheme.

[0032] This effectively encourages the creator of the transaction data to switch signature methods.

[0033] Furthermore, for example, an information processing method according to a ninth aspect may be the information processing method according to either the seventh or eighth aspect, in which changing to the highly secure signature scheme includes at least one of increasing the key length of a signature algorithm that generates a signature, and changing from a signature algorithm that is not quantum-resistant to a signature algorithm that is quantum-resistant.

[0034] This effectively encourages a transition to a more secure signature method by at least one of increasing the key length of the signature algorithm and transitioning to a signature algorithm compatible with quantum-computer-resistant cryptography.

[0035] Furthermore, for example, an information processing device according to a tenth aspect is an information processing device that is one of multiple nodes constituting a distributed ledger system, and includes: an acquisition unit that acquires transaction data including a first electronic signature generated using a first signature method and performance information indicating the performance of a computer for decrypting the electronic signature; an execution unit that determines whether or not to include the transaction data including the first electronic signature in a block of a blockchain based on a mining reward obtained by mining the transaction data including the first electronic signature, the mining reward being changed from a predetermined mining reward in accordance with the performance information; and a ledger management unit that generates the block including the transaction data when it is determined to include the transaction data.

[0036] This provides the same effect as the above-described information processing method.

[0037] A program according to an eleventh aspect is a program for causing a computer to execute the information processing method according to any one of the first to ninth aspects.

[0038] This provides the same effect as the above-described information processing method.

[0039] These general or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or as any combination of the system, method, integrated circuit, computer program, or recording medium. The program may be pre-stored in the recording medium, or may be supplied to the recording medium via a wide area communication network including the Internet.

[0040] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0041] The embodiments described below are all comprehensive or specific examples. The numerical values, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not described in independent claims are described as optional components.

[0042] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of the figures do not necessarily match. Furthermore, in each figure, substantially the same components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0043] Furthermore, in this specification, numerical values ​​and numerical ranges are not expressions that express only the strict meaning, but are expressions that mean that they also include a substantially equivalent range, for example, a difference of about several percent (or about 10%).

[0044] Furthermore, in this specification, when a comparison is made, for example, with "above a threshold" or "below a threshold," it means that the distinction is made at the threshold, and may mean "greater than the threshold" or "below the threshold," respectively.

[0045] (Embodiment) Hereinafter, an information processing method and the like according to the present embodiment will be described with reference to FIGS.

[0046] [1. Configuration of Information Processing System] First, the configuration of an information processing system according to this embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a diagram showing the configuration of an information processing system 10 according to this embodiment. Note that Fig. 1 shows an exemplary functional configuration of the information processing system 10, and the functional configuration of the information processing system 10 is not limited to that shown in Fig. 1.

[0047] As shown in Fig. 1, the information processing system 10 includes ledger servers 100a, 100b, and 100c and an information processing device 200. These are communicatively connected via a communication network 300. The ledger servers 100a, 100b, and 100c constitute a ledger system (distributed ledger system). In other words, each of the ledger servers 100a, 100b, and 100c is one of multiple participating nodes (nodes) that constitute the ledger system.

[0048] A ledger system is a system that stores information using a distributed ledger. A variety of data can be stored in the distributed ledger of the ledger system. The data stored in the distributed ledger of the ledger system may be, for example, the generation history of NFTs (Non-Fungible Tokens) associated with objects in real space, and the history of changes to the NFTs. The information included in the NFTs is not particularly limited, and may include information regarding transactions of goods, etc.

[0049] The ledger system can execute processes using smart contracts (SCs) using a distributed ledger, and can generate NFTs and perform processes related to updating NFTs using smart contract processes.

[0050] The ledger server 100a is a computer server that holds and manages a distributed ledger. The ledger server 100a holds the distributed ledger and updates it while synchronizing with other ledger servers (specifically, ledger servers 100b and 100c).

[0051] The ledger servers 100b and 100c are similar to the ledger server 100a, but operate independently of the ledger server 100a.

[0052] Hereinafter, the ledger servers 100a, 100b, and 100c will also be referred to as ledger servers 100a, etc. (ledger servers 100a to 100c). Furthermore, the storage devices 101a, 101b, and 101c will also be referred to as storage devices 101a, etc. (storage devices 101a to 101c).

[0053] The ledger server 100a etc. is connected to the storage device 101a etc. The ledger server 100a etc. may be connected to the storage device 101a etc. via the communication network 300, or may include the storage device 101a etc. internally. The storage device 101a etc. has a distributed ledger in which transaction data and blocks of the blockchain are electronically recorded.

[0054] The ledger system manages a distributed ledger using a blockchain. The number of ledger servers that make up the ledger system is not limited to three, and may be three or more.

[0055] In this embodiment, the ledger server 100a is a server (also called a miner terminal) managed by a miner who executes the mining process of the blockchain, and the ledger server 100b is a server (user terminal) managed by a user who transmits transaction data to the miner terminal. Note that the user terminal may be a server that does not hold a distributed ledger, and the server may be connected to the ledger server 100b that holds a distributed ledger via a communication network.

[0056] The information processing device 200 is a device not included in the ledger system and therefore performs processing off-chain. The information processing device 200 acquires and manages the decryption status of conventional signatures (also referred to as the decryption capability of conventional signatures) and the development status of quantum computers (also referred to as the performance of quantum computers), which will be described later. Then, in response to a request from the ledger server 100a, the information processing device 200 transmits the decryption status of conventional signatures and the development status of quantum computers to the ledger server 100a. The decryption status of conventional signatures and the development status of quantum computers are also referred to as performance information. A conventional signature is an example of a first electronic signature.

[0057] The information processing system 10 executes a process to support timely implementation of measures to improve the security of the signature algorithm of the signature included in the transaction data. Specifically, the information processing system 10 evaluates the security of the signature algorithm by using the decryption status of conventional signatures, which are signatures generated using conventional signature methods, and the development status of quantum computers, and sets (changes) the reward ratio of the mining reward for miner terminals obtained by mining transaction data that uses a smart contract, depending on the decryption status of the conventional signature and the development status of the quantum computer. Note that "use" refers to the execution of a smart contract by storing transaction data in a distributed ledger.

[0058] More specifically, when the signature included in the transaction data is a conventional signature, the information processing system 10 changes the mining reward from a predetermined value depending on the status of conventional signature decryption and the development status of quantum computers, thereby changing the priority of the miner terminal for storing transaction data including conventional signatures in blocks. Changing the mining reward from a predetermined value may refer to a reduction from the predetermined value, and the miner terminal lowers the priority for storing transaction data in blocks (i.e., lowers the priority for storing in the distributed ledger). Because the miner terminal preferentially stores transaction data with high mining rewards in blocks, transaction data with reduced mining rewards is less likely to be stored in blocks. An example of a mining reward being reduced from a predetermined value will be described in detail below. The information processing system 10 determines the timing of the signature scheme transition based on the status of conventional signature decryption and the development status of quantum computers.

[0059] Note that smart contracts stored in the distributed ledger are executed when transaction data containing command information for executing the smart contract is stored in the distributed ledger. On the other hand, if transaction data containing a conventional signature is not stored in the distributed ledger, the command information for executing the smart contract included in the transaction is also not stored in the distributed ledger, and the smart contract is not executed.

[0060] A conventional signature refers to a signature generated using a conventional key length (currently used key length) or a conventional signature algorithm (currently used signature algorithm). In other words, a conventional signature is a signature generated using a signature method before the signature method was changed. Key lengths include, but are not limited to, 128 bits, 256 bits, 512 bits, 1024 bits, 2048 bits, 3072 bits, and 4096 bits. Furthermore, conventional signature algorithms include, but are not limited to, RSA and DSA (Digital Signature Algorithm).

[0061] This makes it less likely that transaction data containing conventional signatures will be included in blocks, encouraging transaction data generators to switch to signature methods with improved security.

[0062] The components of the ledger server 100a and the like will be described below with reference to Fig. 2. Fig. 2 is a block diagram showing the functional configuration of the ledger server 100a according to this embodiment. Since the configurations of the ledger servers 100b and 100c are similar to that of the ledger server 100a, the ledger server 100a will be used as an example for the description. Note that Fig. 2 shows an exemplary functional configuration of the ledger server 100a, and the functional configuration of the ledger server 100a is not limited to that shown in Fig. 2.

[0063] 2, the ledger server 100a includes a communication unit 111, a ledger management unit 112, an execution unit 113, a storage unit 114, and a transaction data generation unit 115. At least some of the functional units included in the ledger server 100a are realized by a processor (e.g., a CPU) included in the ledger server 100a executing a program using a memory.

[0064] The communication unit 111 is a communication interface communicatively connected to the communication network 300. The communication unit 111 may be a communication interface of a wired communication standard (e.g., Ethernet (registered trademark) or the like), or may be a communication interface of a wireless communication standard (e.g., Wi-Fi (registered trademark) or the like, or a mobile communication system (3G, 4G, 5G, or the like)). The communication unit 111 is used when a functional unit included in the ledger server 100a communicates with another device. For example, the communication unit 111 is used when a functional unit included in the ledger server 100a communicates with the information processing device 200 or any of the ledger servers 100b and 100c. The communication unit 111 may be configured to include, for example, a communication circuit (or a communication module).

[0065] The ledger management unit 112 processes the distributed ledger 114a and transaction data. Specifically, when the ledger management unit 112 receives transaction data, it verifies the digital signature included in the received transaction data and controls storage of successfully verified transaction data in the distributed ledger 114a held by the storage unit 114. When storing transaction data in the distributed ledger 114a, the ledger management unit 112 generates a block including the transaction data to be stored, and can control storage of the generated block in the distributed ledger 114a when consensus is reached with the ledger management units of the other ledger servers, ledger servers 100b and 100c.

[0066] The ledger management unit 112 also acquires transaction data containing instruction information for executing a smart contract and a digital signature. When mining the acquired transaction data, it checks the mining reward for the transaction data based on the signature scheme used to generate the digital signature and a table (e.g., the table shown in FIG. 4 , described later) recorded on the distributed ledger 114a. As will be described in detail later, the table associates the decryption status of the digital signature with the development status of the quantum computer and the mining reward reduction rate. The decryption status of the digital signature is not limited to the decryption status of a conventional signature, but may also be the decryption status of a next-generation signature. The table shown in FIG. 4 may associate the decryption status of the next-generation signature with the development status of the quantum computer and the mining reward reduction rate. The decryption status of the digital signature may indicate the degree of improvement in the computer's processing performance, and the development status of the quantum computer may indicate the degree of improvement in the quantum computer's processing performance. The ledger management unit 112 determines whether to store the transaction data in a block based on the mining reward determined based on the table. If the decryption status of conventional signatures or the development status of quantum computers advances, that is, if there is a possibility that the signature method used to generate the electronic signature included in the transaction data is insecure, the mining reward will be reduced, and the priority of the miner terminal to process the transaction data into a block will be lowered. A reduction in the mining reward is an example of a change from the specified mining reward. The more the decryption status of conventional signatures or the development status of quantum computers advances, that is, the lower the security of conventional signatures, the more the mining reward may be reduced.

[0067] Processing related to mining rewards may be performed using smart contracts or without using smart contracts.

[0068] The execution unit 113 executes information processing. The execution unit 113 can execute information processing, for example, by executing a smart contract stored in the distributed ledger 114a. As an example of information processing, the execution unit 113 executes information processing related to NFTs, such as processing to generate NFTs, and processing related to the payment of mining rewards. Note that when a smart contract is not used, the execution unit 113 executes information processing according to normal program code.

[0069] The storage unit 114 is a storage device that stores information. The storage unit 114 stores the distributed ledger 114a. The storage unit 114 is realized by a non-volatile storage device (SSD or HDD) or the like.

[0070] The distributed ledger 114a stores data having a structure in which one or more blocks, each containing one or more transaction data, are linked in a chain. The one or more transaction data stored in the distributed ledger 114a include transaction data containing the contract code of a smart contract, transaction data containing command information for executing the smart contract, or transaction data containing other information. The other information may include information related to a table shown in FIG. 4 (described below) (e.g., a URL indicating the table). In this embodiment, the distributed ledger 114a is a blockchain.

[0071] A smart contract can be deployed by storing transaction data containing the contract code of the smart contract in a distributed ledger, and a smart contract stored in a distributed ledger can be executed by storing transaction data containing instruction information for executing the smart contract in a distributed ledger.

[0072] The transaction data generation unit 115 generates transaction data to be stored in the blockchain. For example, the transaction data generation unit 115 generates transaction data including a blockchain address held by a user, data to be managed in the blockchain, and a signature. The transaction data generation unit 115 may also generate transaction data including the contract code of a smart contract and transaction data including command information for executing the smart contract. Storing transaction data including the contract code of a smart contract in the distributed ledger allows the smart contract to be deployed. Storing transaction data including command information for executing the smart contract in the distributed ledger allows the smart contract stored in the distributed ledger to be executed.

[0073] [2. Operation of Information Processing System] Next, the operation of the information processing system 10 configured as described above will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a sequence diagram showing the operation (information processing method) of the information processing system 10 according to this embodiment. Fig. 3 shows processing for usage transaction data (hereinafter referred to as "usage Tx") indicating transaction data including information on a usage fee to be paid to a smart contract for executing the smart contract.

[0074] As shown in Figure 3, the ledger server 100b generates a usage Tx and sends the generated usage Tx to the storage device 101a (S10). Assume that the usage Tx includes a signature using a conventional signature method. The storage device 101a stores (adds) the usage Tx. The usage Tx can also be said to be stored in a Tx pool, which stores transaction data before it is stored in a block. The Tx pool is a temporary list that stores transaction data and is maintained by each node in the ledger system. The Tx pool can also be said to exist so that miners can select Txs to mine.

[0075] In addition, the usage Tx is not limited to being transmitted from a node that constitutes the ledger system, but may also be transmitted from an information processing device that is communicatively connected to a node of the ledger system.

[0076] Next, the communication unit 111 of the ledger server 100a acquires one or more transaction data from the storage device 101a (S20). Assume that the acquired one or more transaction data includes a usage Tx. The communication unit 111 functions as an acquisition unit.

[0077] Next, the ledger management unit 112 of the ledger server 100a determines whether the signature included in each acquired transaction data is a conventional signature (S30). The execution unit 113 determines, for example, whether the signature included in the usage Tx is a conventional signature. For example, if information indicating whether the signature is a conventional signature or a next-generation signature is included in the transaction data, the ledger management unit 112 may make the determination in step S30 based on that information, or may verify the signature using a public key for verifying the conventional signature and make the determination in step S30 based on whether the verification is successful.

[0078] Next, if the execution unit 113 determines that the signature is a conventional signature (Yes in S30), the communication unit 111 acquires the table stored in the distributed ledger 114a (S40). On the other hand, if the execution unit 113 determines that the signature is not a conventional signature (No in S30), the communication unit 111 proceeds to step S60. In other words, if the acquired transaction data does not include transaction data that includes a usage Tx or a conventional signature, the execution unit 113 does not need to acquire the table.

[0079] Here, the table acquired by the execution unit 113 will be described with reference to FIG. 4. FIG. 4 is a table referenced to determine the mining reward according to this embodiment. The table shown in FIG. 4 is a rule indicating how much to reduce the mining reward for the used Tx based on the decryption status of the electronic signature and the development status of the quantum computer. The vertical axis of FIG. 4 indicates the key length (number of bits) of the signature decrypted by the computer, and the horizontal axis indicates the size (number of bits) of the problem solved by the quantum computer.

[0080] As shown in FIG. 4, the table is used to change the miner reward paid to miners based on two factors: the status of conventional signature decryption and the development status of quantum computers. The table shows the mining reward ratio for each status of conventional signature decryption and quantum computer development. The table associates the status of conventional signature decryption and the development status of quantum computers with the mining reward ratio. Here, a table may be generated for each type of signature algorithm and stored in the distributed ledger 114a. For example, if a first algorithm and a second algorithm exist as signature algorithms, a table is generated for each algorithm. In this case, the "conventional signature" shown in FIG. 4 refers to the first algorithm or the second algorithm. The ledger management unit 112 identifies a table corresponding to the electronic signature included in the acquired transaction data from among multiple tables stored in the distributed ledger 114a.

[0081] The decryption status of a conventional signature includes at least one or more signature key lengths, for example, two or more key lengths. The signature key length is an example of a difficulty level indicating the difficulty of decrypting the signature by a computer. Note that the computer may be a device that does not constitute a distributed ledger system, and includes quantum computers and general computers other than quantum computers. Furthermore, the development status of quantum computers includes at least one or more scale levels indicating the scale of problems to be solved by quantum computers, for example, two or more scale levels.

[0082] The mining reward ratio indicates the ratio (0 to 1) to the originally set mining reward, and the reward obtained by multiplying the original mining reward by the mining reward ratio becomes the mining reward for transaction data that includes a conventional signature. The smaller the mining reward ratio, the more the reward is deducted from the originally set mining reward. A mining reward ratio of "1" indicates that the mining reward will not be deducted.

[0083] In the table, the security of using conventional signatures decreases as conventional signatures become easier to decrypt (as the number of bits on the vertical axis shown in FIG. 4 increases) and as quantum computer development progresses (as the number of bits on the horizontal axis shown in FIG. 4 increases). Therefore, the mining reward ratio is set to reduce the mining reward for transaction data using conventional signatures. As an example, if the conventional signature decryption status is 48 bits and the quantum computer development status is 24 bits, the mining reward ratio is 0.8. If the preset mining reward value is 5 bitcoins, the reward after the reduction is 5 bitcoins multiplied by 0.8, resulting in 4 bitcoins. In this way, the mining reward ratio is set so that the mining reward obtained when mining transaction data containing conventional signatures is gradually reduced as conventional signatures become easier to decrypt and as quantum computer development progresses.

[0084] 4, multiple mining reward ratios are set, which are the degree to which the mining reward is reduced, depending on the combination of two or more difficulty levels and two or more scale levels. The table also includes a setting of zero mining reward depending on the combination of two or more difficulty levels and two or more scale levels.

[0085] Note that the status of decryption of conventional signatures and the development status of quantum computers refer to the performance of computers outside the ledger system, not the performance of the computers used by miners.

[0086] 3 again, the communication unit 111 then acquires performance information at the time of acquiring the transaction data from the information processing device 200, which is an external device of the ledger system (S50). The communication unit 111 acquires performance information including first performance information indicating the status of decryption of conventional signatures in the computer at the time of acquiring the transaction data, and second performance information indicating the development status of the quantum computer.

[0087] The decryption status of a conventional signature indicates information indicating the difficulty of decrypting the signature when decrypting it by a computer (e.g., the key length of the private key used to generate the signature). Multiple problems that serve as the basis for the security of conventional signatures are created for each level of difficulty (e.g., 24-bit security equivalent, 48-bit security equivalent, etc.) and recorded in an external device (i.e., off-chain) of the distributed ledger system. The information processing device 200, which is the solver, obtains a problem and, if the problem is successfully decrypted, records information indicating the successful decryption. This makes it possible to generate a decryption status for the conventional signature. There is a relationship between the decryption of a problem and the degree of decryption of the conventional signature. This makes it possible to know to what extent a computer can decrypt a conventional signature at the time of acquiring transaction data. Examples of problems include, but are not limited to, the elliptic curve discrete logarithm problem and the prime factorization problem. Problem creation and other operations may be performed by the information processing device 200. More specifically, for example, if the problem is a discrete logarithm problem on an elliptic curve, an integer s that satisfies Q=sP is calculated from two points P and Q on the elliptic curve. A specific algorithm may be, but is not limited to, the ρ method or exponential calculation method. In the relationship between the problem and elliptic curve cryptography, point P corresponds to the public parameter, point Q corresponds to the public key, and integer s corresponds to the signature key. Therefore, solving the problem is equivalent to being able to calculate the private key from the public parameters and the public key, and therefore it becomes possible to decrypt the signature from the public key information.

[0088] An example of a method for calculating the decryption status of an electronic signature shown in a table will now be described in detail. As an example, if the information processing device 200 is a device of a government organization, the device calculates the decryption status for each type of electronic signature, and current status information with the government organization's signature attached to the decryption status is recorded in the distributed ledger 114a. Note that the current status information may be recorded in an off-chain device, or current status information output by each of two or more government organizations may be recorded in the distributed ledger. The ledger management unit 112 calculates the decryption status of an electronic signature using one or more pieces of current status information recorded in the distributed ledger 114a and stores the calculated decryption status as a decryption status shown in a table. If there is two or more pieces of current status information, the average value of the decryption status corresponding to each piece of current status information may be calculated and stored as the decryption status of the electronic signature shown in the table.

[0089] As another example, a calculation method for calculating the decryption status of an electronic signature shown in a table based on a prize-bearing calculation problem stored in advance in the distributed ledger 114a will be described in detail. The calculation problem includes information on the bit length of the elliptic curve cryptography that the calculation problem corresponds to. The information processing device 200 obtains the calculation problem from the distributed ledger 114a, and if the calculation problem is successfully decrypted, records information indicating successful decryption in the distributed ledger 114a. The ledger management unit 112 calculates the decryption status of the electronic signature using one or more pieces of information indicating successful decryption recorded in the distributed ledger 114a, and stores the calculated decryption status as the decryption status shown in the table.

[0090] The development status of quantum computers indicates information based on the scale of problems to be solved by quantum computers (e.g., difficulty of solving). Problems that cannot be solved in a realistic time by conventional computers but can be efficiently solved by a quantum computer of a certain scale are created for each level of difficulty (equivalent to 24-bit security, 48-bit security, etc.) and published off-chain. The information processing device 200, which solves them, issues the answer as a transaction. This makes it possible to know the scale of problems that the quantum computer can solve at the time of acquiring the transaction data. Examples of problems include, but are not limited to, quantum simulation, prime factorization, hash collision search, and random number generation. Problem creation may be performed by the information processing device 200.

[0091] An example of a method for calculating the development status of a quantum computer shown in a table will be described in detail. As an example, if the information processing device 200 is a device of a government organization, the device calculates the development status of the quantum computer, and current status information with the government organization's signature attached to the development status is recorded in the distributed ledger 114a. The current status information may be recorded in an off-chain device. Current status information output by each of two or more government organizations may be recorded in the distributed ledger. The ledger management unit 112 calculates the development status of the quantum computer using one or more pieces of current status information recorded in the distributed ledger 114a, and stores the calculated development status as a development status shown in a table. If there is two or more pieces of current status information, the average value of the development status corresponding to each piece of current status information may be calculated and stored as the development status shown in the table.

[0092] As another example, a method for calculating the decryption status of an electronic signature shown in a table based on a bounty calculation problem stored in advance in the distributed ledger 114a will be described in detail. The calculation problem includes information on the bit length of the elliptic curve cryptography that the problem corresponds to. The information processing device 200 obtains the calculation problem from the distributed ledger 114a, and when the problem is successfully decrypted using a quantum computer, records information indicating the successful decryption in the distributed ledger 114a. The ledger management unit 112 calculates the development status of the quantum computer using one or more pieces of information indicating successful decryption recorded in the distributed ledger 114a, and stores the calculated development status as the development status shown in a table.

[0093] Next, the ledger management unit 112 determines whether to include the use Tx containing the conventional signature in a block based on the acquired table and the performance information at the time of acquiring the transaction data (S60). The ledger management unit 112 identifies first performance information, which is the decryption status of the electronic signature included in the transaction data at the time of acquiring the transaction data, and second performance information, which is the development status of the quantum computer. Next, by referring to the table, the ledger management unit 112 identifies the mining reward ratio corresponding to the identified first performance information and second performance information. Next, the ledger management unit 112 multiplies the predetermined mining reward by the identified mining reward ratio to calculate the mining reward after multiplication. The ledger management unit 112 then determines whether the mining reward for the use Tx is equal to or greater than a threshold, and determines whether to include the use Tx in a block based on the determination result. For example, if the mining reward for the use Tx is less than the threshold, the execution unit 113 determines not to include the use Tx in a block (No in S60). Note that the threshold is set in advance and stored in the storage unit 114.

[0094] In this case, the ledger management unit 112 of the ledger server 100a creates a block that does not include a usage Tx (S70). In this way, since the mining reward is zero or less than the threshold, the transaction data (here, usage Tx) is not mined, and therefore such transaction data is not stored in the block.

[0095] Next, the execution unit 113 notifies the ledger server 100b (i.e., the user) of information that the used Tx has not been stored in the block (S80). The notification content may include information that the used Tx has been determined not to be included in the block, information indicating that the signature method needs to be changed, or information indicating a signature method that is recommended to be used.

[0096] This effectively encourages users to sign their transaction data with longer private keys or with next-generation algorithms in order to store it in the distributed ledger.

[0097] Furthermore, for example, if the mining reward for the used Tx is equal to or greater than a threshold, the execution unit 113 determines to include the used Tx in the block (Yes in S60). Also, for example, if the determination is No in step S30, that is, if the used Tx includes a next-generation signature using a next-generation algorithm, the determination is Yes in step S60.

[0098] In this case, the ledger management unit 112 creates a block including the used Tx (S90).

[0099] Steps S70 and S90 are an example of generating a block according to the determination result.

[0100] Next, the ledger management unit 112 sends the created block to the distributed ledger 114a (S100), thereby storing the block in the distributed ledger 114a.

[0101] As described above, when transaction data (here, "Used Tx") includes a conventional signature, whether or not to include the transaction data including the conventional signature in a block is determined based on the mining reward for the transaction data including the conventional signature, which is reduced according to the performance information. Determining whether or not to include the Used Tx in a block can help change the signature method at a timing that depends on the degree of compromise of the conventional signature and the performance of the quantum computer. For example, if a transaction includes a conventional signature, the mining reward is reduced, and therefore miners will no longer include transaction data including the conventional signature in a block. On the other hand, users who want to store transaction data in a distributed ledger will use private keys with longer key lengths or next-generation signature algorithms.

[0102] Note that if a signature using a next-generation signature algorithm is included, the mining reward will not be reduced. Also, as conventional signatures become easier to decrypt (as the number of bits on the vertical axis in FIG. 4 increases) and as the development of quantum computers progresses (as the number of bits on the horizontal axis in FIG. 4 increases), the security of using conventional signatures decreases, so the mining fee paid by users who use private keys with longer key lengths or next-generation signature algorithms may be reduced.

[0103] Here, the data structure of a distributed ledger, the execution of smart contracts, and the data structure of NFTs will be described with reference to Figures 5 to 9.

[0104] FIG. 5 is an explanatory diagram showing the data structure of a blockchain, which is an example of a distributed ledger.

[0105] A blockchain is a chain of blocks, which are units of record. Each block contains multiple transaction data and the hash value of the previous block.

[0106] FIG. 5 shows blocks B1, B2, and B3 included in the blockchain.

[0107] For example, block B2 contains the hash value of the previous block B1, which is calculated by performing a hash algorithm on the contents of block B1.

[0108] Furthermore, block B3 includes, as the hash value of block B2, a hash value calculated from multiple transaction data included in block B2 and the hash value of block B1.

[0109] In this way, a blockchain is structured so that blocks containing the contents of the previous block as a hash value are connected in a chain, which effectively prevents tampering with the recorded transaction data.

[0110] If past transaction data is changed (in other words, tampered with), the hash value of the block containing that transaction data will be different from the value before the change. In that case, to make the block containing the changed transaction data appear correct, all blocks after that block in the distributed ledger stored on multiple servers would have to be recreated, which is extremely difficult in reality. This feature makes it virtually impossible to tamper with transaction data contained in the blockchain.

[0111] When a node stores transaction data in a blockchain, it generates a block containing the transaction data to be stored and attempts to reach consensus on the generated block by executing processing based on a consensus algorithm with other nodes. Then, when consensus is reached, the node controls the storage of the block in the blockchain. This allows multiple nodes operating in an autonomous and decentralized manner to connect legitimate blocks to the blockchain. As a consensus algorithm, PBFT (Practical Byzantine Fault Tolerance), PoW (Proof of Work), PoS (Proof of Stake), or the like may be used. When Hyperledger Fabric is used as an example of a distributed ledger technology, a consensus algorithm does not need to be executed.

[0112] FIG. 6 is an explanatory diagram showing the data structure of the transaction data.

[0113] 6 includes a transaction body BP1 and a digital signature BP2 (also simply referred to as a signature). The transaction body BP1 is the data body included in the transaction data. The digital signature BP2 is generated by encrypting the hash value of the transaction body BP1 with the signature key (in other words, the private key) of the creator of the transaction data.

[0114] A node that receives transaction data can verify that the transaction body BP1 is legitimate (in other words, that it has not been tampered with) using the digital signature BP2 included in the transaction data. This makes it virtually impossible to tamper with the data included in the transaction body BP1. Furthermore, by storing successfully verified transaction data in the blockchain, the legitimacy of the transaction data stored in the blockchain can be maintained.

[0115] As described above, transaction data included in the blockchain is stored in a chain using the hash values ​​of the transaction data and the hash values ​​of the blocks. This allows the transaction data included in the blockchain to be stored and maintained substantially without being tampered with. This is an advantage over a database or a distributed database that simply stores a collection of data.

[0116] Fig. 7 is an explanatory diagram showing transaction data related to the execution of a smart contract. Fig. 8 is a flow diagram showing processing (information processing information) related to the execution of a smart contract.

[0117] A series of processes related to the execution of a smart contract using a distributed ledger will be described with reference to Figures 7 and 8.

[0118] In step SB1, the node stores transaction data B11, including contract code B12 that describes the processing of the smart contract, in the distributed ledger B10. For example, the node acquires transaction data B11 by receiving the transaction data B11 from an information processing device via communication or by the node itself generating the transaction data B11, and stores the acquired transaction data B11 in the distributed ledger B10. Step SB1 is performed before executing the smart contract.

[0119] In step SB2, the node stores transaction data B15, including instructions B16 for executing the smart contract, in the distributed ledger B10. For example, the node receives transaction data B15 from an information processing device via communication and stores the received transaction data B15 in the distributed ledger B10.

[0120] In step SB3, in response to the transaction data B15 including the instruction B16 being stored in the distributed ledger B10 in step SB2, the node reads the contract code B12 from the distributed ledger B10 and executes processing based on the contract code B12. The results of the processing may be included in the transaction data and stored in the distributed ledger B10.

[0121] Through the above series of processes, when the ledger system receives transaction data B15 including instructions B16 for executing a smart contract, it automatically (i.e., without manual intervention) executes the processing in accordance with the instructions B16, enabling highly efficient (i.e., high speed or short processing time). Achieving highly efficient processing has the effect of reducing power consumption. Furthermore, since no manual intervention is required, it is possible to prevent human tampering with information, fraud, or human error. Furthermore, since the results of the processing thus executed are stored in the blockchain, it is virtually impossible to tamper with the results of the processing.

[0122] FIG. 9 is an explanatory diagram showing the structure of an NFT and metadata. An NFT is a token stored in a distributed ledger and is a unique token (in other words, a non-fungible token). NFTs are standardized, for example, as ERC (Ethereum Request for Comments) 721, but are not limited to this. NFTs may conform to a different standard or may be non-standard (for example, proprietary to an organization). While ERC 721 is a standard for unique tokens, the NFTs described herein do not necessarily have to be unique tokens.

[0123] 9 shows transaction data B21 stored in the distributed ledger. The transaction data B21 stores an NFT. The NFT includes a token ID (i.e., identification information that can uniquely identify the NFT) and a metadata Uniform Resource Identifier (URI).

[0124] The NFT has metadata. The metadata may be located in a location accessible via a network (e.g., storage device B22). A metadata URI indicating the location of the metadata may be calculated using the NFT's token ID and a predetermined base URI.

[0125] The information managed as an NFT may be included in the transaction data B21 or in the metadata. Including the information managed as an NFT in the metadata has the advantage of reducing the amount of information included in the transaction data B21 (in other words, the information included in the blockchain). In this case, it can be said that the metadata contains the actual information managed as an NFT. When an image is managed as an NFT, a URL indicating the image data of the image may be managed as an NFT.

[0126] (Other Embodiments) While the information processing method according to one or more aspects has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as it does not deviate from the spirit of the present disclosure, various modifications conceivable by a person skilled in the art to the present embodiments and embodiments constructed by combining components of different embodiments may also be included in the present disclosure.

[0127] For example, although the above embodiment uses a blockchain, it is not necessary to use a blockchain. Also, instead of a blockchain, a distributed ledger technology such as a hash graph may be used.

[0128] Furthermore, the table shown in Figure 4 in the above embodiment is not limited to being stored in the distributed ledger 114a, but may be stored off-chain (for example, stored in the information processing device 200).

[0129] Furthermore, the mining reward for transaction data including a conventional signature according to the above embodiment may be determined based on at least one of the status of decryption of the conventional signature and the development status of quantum computers. In other words, the table shown in FIG. 4 may be a table showing the relationship between the mining reward ratio and at least one of the status of decryption of the conventional signature and the development status of quantum computers.

[0130] Furthermore, the questions that indicate the development status of quantum computers in the above embodiments may have a prize. For example, transaction data containing the answer to the question may be issued, and if the transaction data is approved, coins may be transferred to the creator of the transaction data. In other words, there may be an incentive for the creator (e.g., a quantum computer developer) to disclose the development status of quantum computers. This allows for more accurate acquisition of the development status of quantum computers.

[0131] Furthermore, each device in the above embodiments is specifically a computer system comprising a microprocessor, ROM, RAM, hard disk unit, display unit, keyboard, mouse, etc. A computer program is recorded in the RAM or hard disk unit. Each device achieves its function when the microprocessor operates in accordance with the computer program. Here, a computer program is composed of a combination of multiple instruction codes that indicate instructions to a computer to achieve a predetermined function.

[0132] In addition, some or all of the constituent elements of each device in the above embodiments may be configured from a single LSI (Large Scale Integration). A system LSI is an ultra-multifunctional LSI manufactured by integrating multiple components on a single chip, and specifically, is a computer system configured to include a microprocessor, ROM, RAM, etc. A computer program is stored in the RAM. The system LSI achieves its functions when the microprocessor operates in accordance with the computer program. Furthermore, each component of each device may be individually integrated into a single chip, or some or all of the components may be integrated into a single chip. Here, the term system LSI is used, but it may also be called an IC, LSI, super LSI, or ultra LSI depending on the degree of integration.

[0133] The present disclosure may also be embodied as the methods described above. Furthermore, the present disclosure may also be embodied as a computer program that implements these methods on a computer, or as a digital signal comprising the computer program. For example, one aspect of the present disclosure may be a computer program that causes a computer to execute each of the characteristic steps included in the information processing method shown in FIG. 3 or FIG. 8.

[0134] The present disclosure may also be a computer program or a digital signal recorded on a computer-readable recording medium, such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray (registered trademark) Disc), semiconductor memory, or the like. It may also be a digital signal recorded on such a recording medium. The present disclosure may also be a computer program or a digital signal transmitted via a telecommunications line, a wireless or wired communication line, a network such as the Internet, data broadcasting, or the like.

[0135] The present disclosure may also be a computer system having a microprocessor and a memory, the memory storing the computer program, and the microprocessor operating in accordance with the computer program.

[0136] Furthermore, the program or digital signal may be recorded on a recording medium and transferred, or the program or digital signal may be transferred via a network or the like, so that the program or digital signal may be implemented by another independent computer system.

[0137] In the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0138] The order in which the steps in the flowchart are executed is merely an example for specifically explaining the present disclosure, and other orders may be used. Some of the steps may be executed simultaneously (in parallel) with other steps, or some of the steps may not be executed.

[0139] The division of functional blocks in the block diagram is an example, and multiple functional blocks may be realized as a single functional block, one functional block may be divided into multiple blocks, or some functions may be moved to another functional block.Furthermore, the functions of multiple functional blocks having similar functions may be processed in parallel or in time-sharing by a single piece of hardware or software.

[0140] Furthermore, each of the ledger servers according to the above embodiments may be realized as a single device or may be realized by multiple devices. When the ledger server is realized by multiple devices, the components of the ledger server may be distributed in any manner among the multiple devices. When the ledger server is realized by multiple devices, the communication method between the multiple devices is not particularly limited and may be wireless communication or wired communication. Furthermore, wireless communication and wired communication may be combined between the devices.

[0141] The present disclosure is useful for information processing devices and the like that manage distributed ledgers.

[0142] DESCRIPTION OF SYMBOLS 10 Information processing system 100a, 100b, 100c Ledger server 101a, 101b, 101c Storage device 111 Communication unit (acquisition unit) 112 Ledger management unit 113 Execution unit 114 Storage unit 114a, B10 Distributed ledger 115 Transaction data generation unit 200 Information processing device 300 Communication network B1, B2, B3 Block B11, B15, B21 Transaction data B12 Contract code B16 Instruction B22 Storage device BP1 Transaction body BP2 Digital signature

Claims

1. An information processing method executed by one of multiple nodes constituting a distributed ledger system, comprising: acquiring transaction data including a first electronic signature generated using a first signature method; acquiring performance information indicating the performance of a computer for decrypting the electronic signature; determining whether to include the transaction data including the first electronic signature in a block of a blockchain based on a mining reward obtained by mining the transaction data including the first electronic signature, the mining reward being changed from a predetermined mining reward in accordance with the performance information; and generating the block including the transaction data if it is determined that the transaction data should be included.

2. The information processing method of claim 1, wherein the performance information includes first performance information indicating the computer's ability to decrypt the electronic signature and second performance information indicating the performance of the quantum computer, and the mining reward is changed based on the first performance information and the second performance information.

3. The information processing method of claim 2, further comprising: acquiring a table in which the ability to decrypt electronic signatures and the performance of a quantum computer are associated with information indicating mining rewards; and determining the mining reward for the transaction data including the first electronic signature based on the performance information at the time of acquiring the transaction data and the table.

4. The information processing method of claim 3, wherein the ability to decrypt an electronic signature included in the table includes two or more degrees of difficulty indicating the difficulty of decrypting the signature using the computer, the performance of the quantum computer included in the table includes two or more degrees of scale indicating the scale of the problem to be solved by the quantum computer, and the table has multiple settings for reducing the mining reward according to combinations of the two or more degrees of difficulty and the two or more degrees of scale.

5. The information processing method according to claim 4, wherein the table includes setting the mining reward to zero depending on the combination of the two or more difficulty levels and the two or more scale levels.

6. The information processing method according to any one of claims 3 to 5, wherein the table is obtained from a distributed ledger, and the performance information is obtained off-chain.

7. An information processing method according to any one of claims 1 to 5, wherein if the security of the first signature scheme is low, the transaction data is not stored in the block, and the creator of the transaction data is notified that the transaction data has not been stored in the block.

8. An information processing method according to any one of claims 1 to 5, wherein if the security of the first signature scheme is low, the transaction data is not stored in the block, and a notification is sent to change the first signature scheme to a signature scheme with high security.

9. The information processing method according to claim 7, wherein changing to a more secure signature scheme includes at least one of increasing the key length of a signature algorithm used to generate a signature, and changing from a quantum-resistant signature algorithm to a quantum-resistant signature algorithm.

10. An information processing device that is one of multiple nodes constituting a distributed ledger system, comprising: an acquisition unit that acquires transaction data including a first electronic signature generated using a first signature method and performance information indicating the performance of a computer for decrypting the electronic signature; an execution unit that determines whether or not to include the transaction data including the first electronic signature in a block of a blockchain based on a mining reward obtained by mining the transaction data including the first electronic signature, the mining reward being changed from a predetermined mining reward in accordance with the performance information; and a ledger management unit that generates the block including the transaction data if it is determined that the transaction data should be included.

11. A program for causing a computer to execute the information processing method according to any one of claims 1 to 5.

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