Control method, control system, first server, and data structure

1. A control method executed by a first server of a plurality of servers in a system including one or more Internet of Things (IoT) devices, the plurality of servers communicative with the one or more IoT devices via a network, and a terminal communicative with the plurality of servers via the network and used by the user, the control method comprising:

obtaining, from one IoT device of the one or more IoT devices, first transaction data including malfunction information indicating that the one IoT device is malfunctioning, and time information indicating a time when the one IoT device has obtained the malfunction information;

transferring the first transaction data obtained, to a plurality of second servers that are the plurality of servers other than the first server;

executing, together with the plurality of second servers, a first consensus algorithm for an agreement on an authenticity of the first transaction data;

recording a block containing the first transaction data in a distributed ledger of the first server, when the authenticity of the first transaction data is verified by the first consensus algorithm;

obtaining, from the terminal, second transaction data indicating a purchase of a right to use the one IoT device;

transferring the second transaction data obtained, to the plurality of second servers;

executing, together with the plurality of second servers, a second consensus algorithm for an agreement on an authenticity of the second transaction data;

recording a block containing the second transaction data in the distributed ledger of the first server, when the authenticity of the second transaction data is verified by the second consensus algorithm;

generating status information indicating whether the one IoT device is available based on the first transaction data and the second transaction data;

obtaining, from the terminal, a user request to unlock the one IoT device based on the purchase of the right to use the one IoT device;

in response to receiving the user request to unlock the one IoT device and when the one IoT device is determined to be available based on the status information, (i) performing unlock control to unlock the one IoT device, (ii) generating third transaction data indicating the unlock of the one IoT device, (iii) transferring the third transaction data to the plurality of second servers, (iv) executing, together with the plurality of second servers, a third consensus algorithm for an agreement on an authenticity of the third transaction data, and (v) recording a block containing the third transaction data in the distributed ledger of the first server, when the authenticity of the third transaction data is verified by the third consensus algorithm; and

in response to receiving the user request to unlock the one IoT device and when the one IoT device is determined to be unavailable based on the status information, sending, to the terminal, a signal indicating that the one IoT device is not permitted for use.

2. The control method according to claim 1 , further comprising:

reading out the first transaction data recorded in the distributed ledger;

generating the status information based on the first transaction data read out and the second transaction data obtained, and writing the status information on a memory of the first server; and

reading out the status information on the memory, when the user request to unluck the one IoT device is received from the terminal.

3. The control method according to claim 1 , wherein

the time information is a timestamp at a time of obtaining the malfunction information or a sequence number.

4. The control method according to claim 1 , further comprising:

executing a smart contract stored in the distributed ledger to obtain the first transaction data, when the malfunction information is obtained.

5. A control system, comprising:

one or more IoT devices;

a plurality of servers communicative with the one or more IoT devices via a network; and

a terminal communicative with the plurality of servers via the network and used by the user, wherein a first server of the plurality of servers:

obtains, from one IoT device of the one or more IoT devices, first transaction data including malfunction information indicating that the one IoT device is malfunctioning, and time information indicating a time when the one IoT device has obtained the malfunction information;

transfers the first transaction data obtained, to a plurality of second servers that are the plurality of servers other than the first server;

executes, together with the plurality of second servers, a first consensus algorithm for an agreement on an authenticity of the first transaction data;

records a block containing the first transaction data in a distributed ledger of the first server, when the authenticity of the first transaction data is verified by the first consensus algorithm

obtains, from the terminal, second transaction data indicating a purchase of a right to use the one IoT device;

transfers the second transaction data obtained, to the plurality of second servers;

executes, together with the plurality of second servers, a second consensus algorithm for an agreement on an authenticity of the second transaction data;

records a block containing the second transaction data in the distributed ledger of the first server, when the authenticity of the second transaction data is verified by the second consensus algorithm;

generates status information indicating whether the one IoT device is available based on the first transaction data and the second transaction data;

obtains, from the terminal, a user request to unlock the one IoT device based on the purchase of the right to use the one IoT device;

in response to receiving the user request to unlock the one IoT device and when the one IoT device is determined to be available based on the status information, (i) performs unlock control to unlock the one IoT device, (ii) generates third transaction data indicating the unlock of the one IoT device, (iii) transforms the third transaction data to the plurality of second servers, (iv) executes, together with the plurality of second servers, a third consensus algorithm for an agreement on an authenticity of the third transaction data, and (v) records a block containing the third transaction data in the distributed ledger of the first server, when the authenticity of the third transaction data is verified by the third consensus algorithm; and

in response to receiving the user request to unlock the one IoT device and when the one IoT device is determined to be unavailable based on the status information, sends, to the terminal, a signal indicating that the one IoT device is not permitted for use.

6. A first server of a plurality of servers in a system including one or more IoT devices, the plurality of servers communicative with the one or more IoT devices via a network, and a terminal communicative with the plurality of servers via the network and used by the user, the first server comprising:

a processor;

a memory that stores a program causing the processor to execute processing; and

a storage device that stores a distributed ledger storing a smart contract, wherein

the processor executes the smart contract stored in the distributed ledger to obtain, from one IoT device of the one or more IoT devices, first transaction data including malfunction information indicating that the one IoT device is malfunctioning, and time information indicating a time when the one IoT device has obtained the malfunction information, and

by executing the program stored on the memory, the processor:

transfers the first transaction data obtained, to a plurality of second servers that are the plurality of servers other than the first server;

executes, together with the plurality of second servers, a first consensus algorithm for an agreement on an authenticity of the first transaction data; and

records a block containing the first transaction data in the distributed ledger of the first server, when the authenticity of the first transaction data is verified by the first consensus algorithm; obtains, from the terminal, second transaction data indicating a purchase of a right to use the one IoT device;

transfers the second transaction data obtained, to the plurality of second servers; executes, together with the plurality of second servers, a second consensus algorithm for an agreement on an authenticity of the second transaction data;

records a block containing the second transaction data in the distributed ledger of the first server, when the authenticity of the second transaction data is verified by the second consensus algorithm;

generates status information indicating whether the one IoT device is available based on the first transaction data and the second transaction data;

obtains, from the terminal, a user request to unlock the one IoT device based on the purchase of the right to use the one IoT device;

in response to receiving the user request to unlock the one IoT device and when the one IoT device is determined to be available based on the status information, (i) performs unlock control to unlock the one IoT device, (ii) generates third transaction data indicating the unlock of the one IoT device, (iii) transforms the third transaction data to the plurality of second servers, (iv) executes, together with the plurality of second servers, a third consensus algorithm for an agreement on an authenticity of the third transaction data, and (v) records a block containing the third transaction data in the distributed ledger of the first server, when the authenticity of the third transaction data is verified by the third consensus algorithm; and

in response to receiving the user request to unlock the one IoT device and when the one IoT device is determined to be unavailable based on the status information, sends, to the terminal, a signal indicating that the one IoT device is not permitted for use.