Digital asset management system and control method thereof

Abstract

To provide a technology for enabling a business operator who desires to issue and distribute digital assets to easily manage the digital assets SOLUTION: The digital asset management system includes a common area blockchain network that operates a coin associated with a cash currency, and a first additional area blockchain network that operates a first token associated with the coin, detects an instruction to transfer a second token associated with a digital asset, executes transfer of the first token after detecting the instruction to transfer the second token, and executes transfer of the second token after detecting the instruction to transfer the second token. A coin associated with the first token is transferred within the common realm blockchain network.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a digital asset management system and a control method thereof. [Background technology]

[0002] To date, multiple businesses have operated electronic payment systems for multiple electronic currencies, virtual currencies, etc. For example, Patent Document 1 discloses a system for validating virtual currency transfers (transactions). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 6521421 The issue here is that businesses wishing to issue and distribute digital assets, such as non-fungible tokens (NFTs) and virtual currencies, have a low level of convenience when managing their digital assets. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technology that allows businesses wishing to issue and distribute digital assets to easily manage their digital assets. [Means for solving the problem]

[0005] The present invention provides, for example, a digital asset management system, A common area blockchain network that operates coins associated with fiat currencies; a first additional domain blockchain network that operates a first token associated with the coin; A detection means for detecting an instruction to transfer a second token associated with the digital asset; a first execution means for executing the transfer of the first token after the detection means detects an instruction to transfer the second token; second execution means for executing the transfer of the second token after the detection means detects an instruction to transfer the second token; a transfer means for transferring the coin associated with the first token within the common area blockchain network in response to the transfer of the first token in the first additional area blockchain network; The present invention is characterized by comprising: [Effects of the Invention]

[0006] According to the present invention, a technology can be provided that allows businesses wishing to issue and distribute digital assets to easily manage the digital assets. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a digital asset management system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the hardware configuration of the issuer device, operator device, user device, relay device, and transaction management device in FIG. [Figure 3] FIG. 10 is a diagram showing an asset token issuing process. [Figure 4] FIG. 10 is a diagram showing the asset token transfer process. [Figure 5] FIG. 10 is a diagram showing a modified example of the digital asset management system. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numerals are used to designate identical or similar components, and redundant descriptions will be omitted.

[0009] The digital asset management system according to this embodiment will be described below. The digital asset management system 1 according to this embodiment includes an issuer domain 2, an issuer device 5, a common domain network 10, a relay device 15, and an additional domain network 20. In this embodiment, a first user device 3 and a second user device 4 (hereinafter, they may be referred to as user devices without distinction) are assumed to explain the management of digital assets, but the digital asset management system 1 can manage any number of users. Each user device is associated with a specific user account and has accounts in the issuer domain 2, the common domain network 10, and the additional domain network 20.

[0010] It should be noted that predetermined nodes in the external network 50 can be connected to the additional area network 20, and in this embodiment, a transaction management device 55 in the external network 50 connects to the additional area network 20 and performs operations on digital assets, which will be described later. In addition, the user devices 3 and 4 also have accounts on the external network 50, and can execute transactions related to digital assets with other communication devices in the external network 50.

[0011] The issuer domain 2 is an area managed by an issuer device 5 used by a company that has a license to issue electronic currency, such as a bank. Each user has an account (for example, a bank account) in the issuer domain 2.

[0012] The common area network 10 is a distributed ledger network (common area blockchain network) such as a blockchain, and is composed of nodes (communication devices) that operate a distributed ledger system including the issuer device 5. The common area network 10 is used to perform operations such as transferring electronic currencies (coins) 101 to 104 that are linked to the currency operated by the issuer device 5. Here, coins 101 and 103 are coins (white coins) that are not associated with an additional area, and coins 102 and 104 are coins (colored coins) that are associated with the additional area network 20.

[0013] The additional domain network 20 is a distributed ledger network (additional domain blockchain network) such as a blockchain, and is composed of nodes that operate a distributed ledger system including an operator device 25 and a user device. The additional domain network 20 is used to provide operations such as the transfer of coin tokens 121 and 122 operated by the operator device 25 and asset tokens 131 and 132 for which payments are made using coin tokens. Note that while only one additional domain network 20 is shown in FIG. 1, two or more additional domain networks 20 may be connected to one common domain network 10. In this case, a relay device 15 and an operator device 25 are arranged for each additional domain network 20. The additional domain network 20 is created for each individual use case according to the business needs of a company or the like.

[0014] The additional area network 20 according to this embodiment manages a first token (coin token) 201 associated with a coin and a second token (asset token) 211 associated with a digital asset.

[0015] A coin token is a token that is associated one-to-one with a coin managed by the common area network 10. When a coin token is issued or transferred in the additional area network 20, the common area network 10 also corresponds to the issuance or transfer of a coin to an additional area, and a colored coin is transferred.

[0016] An asset token is a digital asset such as a non-fungible token that is traded using a coin token. An asset token can be, for example, an environmental value token that proves that the user of a user device is a renewable energy user. Alternatively, an asset token can be digital art that can be circulated as an NFT. An asset token can also be a digital asset that serves as commercial information that triggers payments, such as digital certificates, specifically gift certificates, coupons, points, sightseeing passes, securities, bonds, and other claims, contract information, etc.

[0017] In this embodiment, both asset tokens and coin tokens are described as being issued and circulated by the additional domain network 20, but as will be described later, they may also be operated on separate blockchain networks.

[0018] While the authority to issue coin tokens lies with the operator account, the authority to issue asset tokens may be held by one or more user accounts different from the operator account. Also, the operator account may not have the authority to issue asset tokens. This allows multiple types of asset tokens operated by different operators to be operated in one additional area network 20.

[0019] In response to the operation of the coin in the common area network 10, the relay device 15 transmits instructions regarding the operation of the coin to the operator device 25 in the additional area network 20, and causes the operator device 25 to perform the operation of the coin token corresponding to the operated coin, thereby synchronizing the transfer of the coin token and the colored coin.

[0020] Furthermore, the additional area network 20 accepts an operation instruction for the asset token from any node in the external network 50. In this embodiment, the node that accepts the transfer instruction for the asset token is described as the operator device 25 of the additional area network 20, but this is not limited thereto, and any node in the additional area network 20 can be set to accept the operation instruction.

[0021] The operator device 25 transmits instructions regarding the operation of the coin token or asset token to the additional area network 20. In this embodiment, the instructions regarding the operation of the coin token or asset token are described as being transmitted to the additional area network 20 by broadcast or anycast transmission, but the instructions regarding the operation may be transmitted by specifying a destination such as a transfer source node or a transfer destination node.

[0022] The external network 50 manages digital asset transactions. Here, managing digital asset transactions includes storing information including at least information about the owner of the digital asset as information about the transaction when a transaction including the issuance, transfer, redemption, or exchange of a digital asset is concluded, and instructing the additional area to operate the asset token.

[0023] In this embodiment, operations on coins, coin tokens, or asset tokens include issuance, transfer, retirement, exchange, asset division, asset consolidation, and inquiry, as well as a function for setting whether division or transfer is possible, and an approval function for a token owner to grant permission to other users to operate their tokens. For example, asset token operations may include approving the issuance, retirement, exchange, division, or consolidation of an asset token via the external network 50 or the operator device 25 at the request of the asset token owner, or approving the transfer of an asset token and the associated transfer of a coin token. The approval function for granting permission to operate an asset token may also include approving an operation to confirm information such as the type and amount of asset tokens owned by a specific user via the external network 50 or the operator device 25.

[0024] The user device is a device of a user who receives a service in the additional area network 20. In this embodiment, the service in the additional area network 20 is described as the execution of a coin token operation in response to the asset token operation, and the execution of a coin operation in the common area network 10 associated with the execution of the coin token operation. In one example, the service in the additional area network 20 includes payment of a fee by an external service of the digital asset management system 1 in response to the coin token operation.

[0025] Next, the configurations of the user devices 3 and 4, the issuer device 5, the relay device 15, the operator device 25, and the transaction management device 55 (hereinafter, sometimes referred to as the communication device without distinction) will be described with reference to Figure 2. The communication device includes a processor 201, a memory 202, a storage 203, a network interface (I / F) 204, and an input / output I / F 205.

[0026] The processor 201 is a control unit that controls the operation of the entire communication device. The processor 201 includes at least one of a central processing unit (CPU), a graphics processing unit (GPU), and a microcontroller that executes a program or an operating system (OS) stored in the storage 203. The memory 202 is configured with a dynamic random access memory (DRAM), a static random access memory (SRAM), etc. that are used as a working memory for the processor 201.

[0027] The storage 203 includes a storage medium such as an HDD (Hard Disk Drive) or SSD (Solid State Drive) that stores the programs executed by the processor 201, the OS, and at least one of data tables and setting values ​​used by the programs. The input / output I / F 205 is a user interface that includes input devices including at least one of a keyboard, a touch panel, and a microphone for accepting user operations, and output devices including at least one of a display, a speaker, and an LED. Note that in this specification, the user devices 3 and 4, the issuer device 5, the relay device 15, the operator device 25, and the transaction management device 55 will be described as having the same hardware configuration. In one example, at least one of the user devices 3 and 4, the issuer device 5, the relay device 15, the operator device 25, and the transaction management device 55 may not have an input / output I / F 205, and in this case, at least one of the user devices 3 and 4, the issuer device 5, the relay device 15, the operator device 25, and the transaction management device 55 that do not have an input / output I / F 205 may accept operation instructions or output operation results via the network I / F 204. At least some of the functions of the communication devices may be realized by cloud computing connected via a communication network.

[0028] (Coin token issuance process) In the following example, a process will be described in which the user device 4 instructs the issuance of a coin token. It is assumed that the user device 4 has an account in which currency is deposited in the issuer area 2.

[0029] The user device 4 requests the issuer device 5 to issue coins. Upon receiving the request, the issuer device 5 issues white coins 103 using currency as collateral, or the issuer device 5 transfers white coins 103 to the user device 4. The user device 4 requests the issuer device 5 to issue colored coins associated with the additional area network 20, specifying a quantity up to the white coins 103 it owns. The issuer device 5 issues a transaction to the common area network 10 to convert the specified quantity of white coins 103 into colored coins 104 associated with the additional area network 20. At this timing, the specified quantity of white coins owned by the account of the user device 4 can only be used in the additional area network 20 (for example, the additional area of ​​energy trading).

[0030] When the relay device 15 detects a transaction to grant colored coins 104 to the user device 4, it communicates the transaction to the additional area network 20 to issue coin tokens to the user device 4 corresponding to the quantity of colored coins 104.

[0031] In this way, by allocating (locking) coins associated with a currency to each additional area network 20, the value of the issued coin token can be guaranteed. Also, the moment the designation is made, a coin token that gives the impression that a currency has been issued is issued to the additional area network 20. This is not the actual entity of the electronic currency, but is like a proof of instruction that gives instructions to move it, and from the viewpoint of the operating company, it looks as if the electronic currency has been issued in the additional area network.

[0032] When a transaction is made in the additional realm network 20, value is circulated by moving coin tokens issued in the additional realm network 20, which are essentially "shadows of electronic currency," in the additional realm network 20. The contents of the coins circulating in the additional realm network 20 are synchronized by the relay device 15, which allows the operations of coins and coin tokens to be synchronized and linked in the additional realm network 20 and the common realm network 10. In other words, value is transferred in the form of actual electronic currency (coins) in the common realm network 10 in synchronization with the circulation of coin tokens in the additional realm network 20.

[0033] Coins (electronic currency) issued in the common area are legally treated as deposits themselves, and represent deposit claims themselves, rather than assets that require regular deposits. Banks transfer actual electronic currency as part of their foreign exchange operations.

[0034] In addition, in this system, a bank first issues a white coin that does not specify which additional area it will be used in, and then specifies that it will be used in the additional area network 20. This system has a function to return a colored coin to a white coin, and performs an operation to cancel the designation of the additional area network 20. By using this function, it is possible to designate that a white coin returned from a colored coin will be used in a different additional area network, for example, by designating that electronic currency designated for electricity trading will be used as retail electronic currency, and thus transfer the currency without having to go to the trouble of returning it to a bank deposit.

[0035] (Asset token issuance process) In this processing example, the user device 3 is associated with the account of an electricity supplier such as a power plant, and the user device 4 is associated with the account of an electricity consumer. In this processing example, the electricity supplier operates an asset token in the additional area network 20, which includes digital certificate data that certifies that the electricity is generated from wind power, solar power, or other sources with environmental value that does not increase carbon dioxide.

[0036] 3 illustrates the issuance of an asset token. As described above, an electricity supplier generates electricity having environmental value. In this case, the user device 3 reports data indicating the identifier of the user device 3 and the amount of electricity generated to the transaction management device 55 in the external network 50 (S301). In S301, the transaction management device 55 identifies the user account associated with the user device 3 in the additional area network 20.

[0037] The transaction management device 55 instructs the additional area network 20 to issue a digital asset according to the amount of power generation based on the data indicating the amount of power generation (S302). Here, the instruction transmitted in S302 indicates that the owner of the asset token is the user account associated with the user device 3. The instruction transmitted in S302 also indicates that the value or quantity of the asset token corresponds to the amount of power generation. As a result, a digital asset according to the amount of power generation is issued in the additional area network 20 to the account associated with the user device 3.

[0038] (Asset token transfer process) Next, we will explain the case where power is supplied from user device 3 to user device 4 and an asset token including digital certificate data is transferred as proof that power having environmental value has been supplied to user device 4.

[0039] FIG. 4 is a diagram illustrating the transfer of asset tokens. In S401, power is supplied from user device 3 to user device 4, and transaction management device 55 detects that power has been supplied. For example, transaction management device 55 detects that power has been supplied when user device 3 notifies it that it has supplied a predetermined amount of power, or when user device 4 notifies it that it has supplied a predetermined amount of power. Based on the notification, transaction management device 55 identifies the identifier in additional area network 20 of user device 3, which is the power supplier, and the identifier in additional area network 20 of user device 4, which is the power recipient. When transaction management device 55 detects that power has been supplied from user device 3 to user device 4, it records the power supply as a transaction record in storage.

[0040] Next, the transaction management device 55 instructs the additional area network 20 to transfer the asset token from the user device 3 to the user device 4 (S402). Here, the transaction management device 55 transmits the transfer instruction to the additional area network 20 via an application programming interface (API). In another example, the transaction management device 55 may instruct a specific communication device, such as a gateway or operator device 25, to transmit the transfer instruction in the additional area network 20. In this case, the communication device that receives the instruction transmits the transfer instruction to the additional area network 20. The transfer instruction generates blockchain transaction information in the additional area network 20.

[0041] When each node in the additional area network 20 detects an instruction to transfer the asset token, it verifies the transaction information and executes an approval process (S403). In the verification and approval process of the transaction information, the owner of the coin token in the additional area network 20 is changed from the account corresponding to the user device 4 to the account corresponding to the user device 3, and the transfer process is executed. If the account corresponding to the user device 4 does not have the amount of coin tokens instructed to be transferred, the transfer process is terminated without completion, and the subsequent transfer of the asset token is not executed. If the account corresponding to the user device 4 has the amount of coin tokens instructed to be transferred, transaction information is generated, and the transfer of the coin token is executed by being verified and approved by a communication device in the additional area network 20. When the transfer of the coin token is completed, the asset token is transferred from the user device 3 to the user device 4 in the additional area network 20 (S404). In this way, by executing the transfer of the coin token and the subsequent transfer of the asset token in one transaction in S402, the settlement process in accordance with the instruction to transfer the asset token can be easily executed.

[0042] This prevents asset token transfers when the coin token balance is insufficient, making it possible to prevent transaction failures where only coin tokens are transferred and no asset tokens are transferred. It also eliminates the need for cumbersome processing such as reversing asset token transfers when only asset tokens are transferred and the coin token transfer fails.

[0043] When the relay device 15 detects the transfer of the coin token from the transaction information, it instructs the common area network 10 to transfer the ownership of the coin linked to the transferred coin token from the account of the user device 4 to the account of the user device 3, just like the coin token (S405). The transfer of the coin is also realized by verifying and approving the transaction information generated by the relay device 15 from the communication device in the common area network 10.

[0044] In this embodiment, the relay device 15 instructs the transfer of colored coins according to the additional area network 20, that is, it specifies the type of coin to be transferred according to the type of additional area network 20.

[0045] As described above, according to this embodiment, it is possible to easily operate electronic currency associated with cash currency in response to the transfer of asset tokens. Also, from the user's perspective, asset tokens can be purchased with tokens associated with electronic currency, and the number of payment methods for purchasing asset tokens can be increased, thereby improving user convenience.

[0046] (Variation 1) In the above description, an example has been described in which the transfer of asset tokens and coins is processed when the transfer of coin tokens is performed. However, conversely, the transfer of coin tokens and coins may be executed when the transfer of asset tokens is performed.

[0047] In this case, in S302, the transaction management device 55 instructs the operator device 25 to transfer the asset token, and upon receiving the instruction to transfer the asset token, the operator device 25 instructs the additional area network 20 to transfer the asset token before instructing the coin token to transfer. Then, when it detects that the asset token transfer has been completed, the operator device 25 may instruct the additional area network 20 to transfer the coin token.

[0048] (Variation 2) In the above description, one common area network 10, one additional area network 20, and one external network 50 are associated with each other. However, a plurality of additional area networks 20 may be associated with each common area network 10, a plurality of external networks 50 may be associated with each additional area network 20, or a plurality of common area networks 10 may be associated with one external network 50. Furthermore, the coin token and the asset token may be operated on different blockchain networks.

[0049] 5 illustrates a case where two additional area networks 20A and 20B for managing coin tokens are associated with one additional area network 30 for managing asset tokens, and an external network 50 is associated with the additional area network 30. Note that the same reference numerals are used for configurations and functions similar to those in FIG. 1, and descriptions thereof will be omitted. Relay devices 15A and 15B have the same configuration as relay device 15, and operator devices 25A and 25B have the same configuration as operator device 25.

[0050] In the asset management system 1 shown in Figure 5, two first additional area networks 20A and 20B are connected to one common area network 10, and one second additional area network 30 is connected to the first additional area networks 20A and 20B. The second additional area network 30 is a blockchain network for transferring asset tokens traded on an external network 50. The common area network 10 and the first additional area networks 20A and 20B are connected by first relay devices 15A and 15B, respectively, and the first additional area networks 20A and 20B and the second additional area network 30 are connected by second relay devices 35A and 35B, respectively. In the example of Figure 5, the common area network and the first additional area network and the first additional area network and the second additional area network are shown as being connected by different devices, but a single relay device may connect the common area network, the first additional area network, and the second additional area network.

[0051] Alternatively, two first additional area networks 20A and 20B may be connected to one common area network 10, and two second additional area networks 30 (referred to as 30A and 30B) may be connected to each of the first additional area networks 20A and 20B. In this case, a relay device connecting the first additional area network 20A and the second additional area network 30A, a relay device connecting the first additional area network 20A and the second additional area network 30B, a relay device connecting the first additional area network 20B and the second additional area network 30A, and a relay device connecting the first additional area network 20B and the second additional area network 30B may be installed. This allows each first additional area network 20 to support multiple second additional areas.

[0052] In this way, by connecting multiple first additional area networks to one second additional area network, it is possible to switch which first additional area network to use when operating asset tokens traded through the second additional area network 30.

[0053] For example, when a transaction involving the transfer of a digital asset is concluded on the external network 50 (S501), the transaction management device 55 instructs the second additional area network 30 to transfer an asset token (S502). Here, in the transaction, the type of coin token is specified as the payment method accompanying the transfer of the asset token, and the transaction management device 55 includes information capable of identifying the type of coin token in the instruction of S502. This allows the relay devices 35A and 35B to transmit instructions to the first additional area networks 20A and 20B to which they are respectively connected to transfer the coin token accompanying the transfer of the asset token. In the example of FIG. 5, the relay device 35A transmits an instruction to transfer the coin token to the additional area network 20A (S503).

[0054] The relay device 15A, which has detected the instruction to transfer the coin token, transmits the instruction to transfer the coin in association with the transfer of the coin token over the common area network 10 (S504), and the coin is transferred. This allows settlement associated with the transfer of digital assets. Furthermore, by switching the type of coin token used to transfer digital assets, the user can select from multiple payment methods for the digital assets, thereby improving the convenience of payments.

[0055] In this processing example, the transfer of coin tokens in response to an instruction to transfer asset tokens is illustrated as occurring only in one first additional area network. However, in response to an instruction to transfer one asset token, the transfer of coin tokens may occur in multiple first additional area networks. In this case, the transaction management device 55 includes, in the instruction to transfer asset tokens, information specifying two or more types of coin tokens to be transferred and the amounts of each of the multiple types of coin tokens to be transferred.

[0056] This allows asset tokens to be combined with multiple coin tokens for settlement, improving user convenience.

[0057] As described above, in this embodiment, in response to an instruction to transfer an asset token, the transfer of a coin token, as well as the transfer of an asset token and the transfer of a coin are automatically executed. As a result, in response to the transmission of an instruction to transfer a digital asset in the additional area network, settlement is completed with coins associated with cash currency, improving the convenience of management associated with the transfer of digital assets.

[0058] <Other embodiments> The instruction to transfer asset tokens issued from the transaction management device 55 may include parameters other than the type and quantity of asset tokens. For example, the instruction to transfer asset tokens may include information specifying the timing to transfer asset tokens. The information specifying the timing may be information specifying a date and time, such as one day later or the end of the month, or information instructing the transfer to occur after the occurrence of a specified event, such as after the transfer of coin tokens or coins. This allows the transfer of digital assets to be executed at the timing determined in the transaction, further improving the convenience of the digital asset management system.

[0059] It is also possible to realize the process of supplying a program that realizes one or more functions of each of the above-mentioned embodiments to a system or device via a network or storage medium, and having one or more processors in the computer of that system or device read and execute the program. [Explanation of symbols]

[0060] 1: Digital asset management system, 3, 4: User device, 5: Issuer device, 10: Common area network, 15: Relay device, 20: Additional area network, 25: Operator device, 50: External network, 55: Transaction management device

Claims

1. 1. A digital asset management system, comprising: A common area blockchain network that operates coins associated with fiat currencies; a first additional domain blockchain network that operates a first token associated with the coin; A detection means for detecting an instruction to transfer a second token associated with the digital asset; a first execution means for executing the transfer of the first token after the detection means detects an instruction to transfer the second token; second execution means for executing the transfer of the second token after the detection means detects an instruction to transfer the second token; a transfer means for transferring the coins associated with the first token within the common area blockchain network in response to the transfer of the first token in the first additional area blockchain network; A digital asset management system comprising:

2. The digital asset management system according to claim 1 , wherein the second execution means executes the transfer of the second token when the completion of the transfer of the first token is detected.

3. The digital asset management system according to claim 1 , wherein the first execution means executes the transfer of the first token when it detects completion of the transfer of the second token.

4. The digital asset management system of claim 1 , wherein the second token is operated on the first additional domain blockchain network.

5. The digital asset management system according to claim 1 , wherein the first additional domain blockchain network receives an instruction to issue the second token from an external device.

6. The digital asset management system of claim 1, wherein the second token is operated in a second additional domain blockchain network different from the first additional domain blockchain network.

7. The digital asset management system of claim 6, wherein the first execution means, when detecting an instruction to transfer the second token, determines in which of a plurality of additional domain blockchain networks to execute the transfer of the first token based on the instruction.

8. The digital asset management system of claim 1 , wherein the second token includes digital certificate data.

9. The digital asset management system according to claim 1 , wherein the instruction to transfer the second token specifies the timing to transfer the second token.

10. A method for controlling a digital asset management system, comprising: The digital asset management system includes: A common area blockchain network that operates coins associated with fiat currencies; a first additional domain blockchain network that operates a first token associated with the coin; Equipped with The control method includes: Detecting an indication of a transfer of a second token associated with the digital asset; executing the transfer of the first token after detecting an indication to transfer the second token; performing the transfer of the second token after detecting an indication of the transfer of the second token; and In response to the transfer of the first token in the first additional domain blockchain network, transferring the coins associated with the first token within the common domain blockchain network; A control method comprising:

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