JP2020088864A - Block chain system and server - Google Patents

Abstract

To establish both of stabilizing and smoothing of a transaction in a block chain.SOLUTION: A privilege node holds a secret key and a plurality of normal nodes hold a public key. Each normal node comprises: a transaction input unit for accepting input of transaction data; a transaction transmission unit for transmitting the transaction data; a transaction management unit for managing a transaction history as a block chain; and a block receiving unit for receiving a block from the privilege node. The privilege node comprises: a transaction receiving unit for receiving transaction data from the normal node; a block generation unit for generating a signature value on the basis of the secret key to generate the block as a data set including the transaction data and the signature value; and a block transmission unit for transmitting the block. The transaction management unit of the normal node couples the block with the block chain on the condition that authenticity of the signature value of the block received from the privilege node can be successfully confirmed using the public key.SELECTED DRAWING: Figure 4

Description

The present invention relates to blockchains, and more particularly to techniques for verifying authenticity of electronic transactions based on blockchains.

Blockchain is a mechanism that supports various virtual currencies such as Bitcoin and Ethereum (see Patent Document 1). A blockchain is a trading ledger shared by multiple communication nodes by peer-to-peer technology.

The transacting user broadcasts the transaction data to the communication network. A user called a miner inputs transaction data and an arbitrary nonce as variables of a hash function, and searches for a hash value satisfying a predetermined condition (hereinafter, referred to as an “appropriate hash value”). Multiple miners compete to find the correct hash value as soon as possible. When the correct hash value is found, the transaction data is registered on the blockchain. It is difficult to find a nonce that can produce a proper hash value, but it is easy to confirm whether or not the hash value is proper based on the found nonce. It is difficult to tamper with the blockchain because it is difficult to find the proper hash value and it is easy to confirm.

Japanese Unexamined Patent Application Publication No. 2018-160828

Since the blockchain is a decentralized system that is not subject to central (server) management, traders can trade without revealing their identity (name, etc.). On the other hand, since the blockchain does not have a "center", an event called "branch (fork)" may occur. Specifically, when miner A and miner B find two appropriate hash values for a block, two blocks are created and the block chain branches into two systems. It is assumed that the blockchain is a single road. Forks are usually resolved by surviving long chains and invalidating short ones. Possibility of forking can impair the stability of transactions, as the invalidation of short chains implies the invalidation of some transaction data.

In a general blockchain, in order to suppress the occurrence of forks, the difficulty level of the work of finding an appropriate hash value (hereinafter referred to as “mining difficulty level”) is increased. However, the higher the difficulty level of mining, the less smooth the transaction.

The present invention has been completed based on the above recognition of the problems, and its main object is to provide a technique for achieving both stabilization and smoothness of transactions in a block chain.
In addition, in order to clarify the gist of the present invention, a general blockchain mechanism and its problems will be described in detail later.

A blockchain system according to an aspect of the present invention includes a trading network including a plurality of ordinary nodes and a privileged node connected to the trading network.
The privileged node holds the private key. Further, the normal node has a public key corresponding to the private key in advance.
A normal node is a transaction input unit that receives the input of transaction data indicating the result of a commercial transaction using virtual currency, a transaction transmission unit that transmits the transaction data to the transaction network, a transaction management unit that manages the transaction history as a block chain, and a privilege. A block receiving unit that receives a block from the node.
A privileged node transacts a block with a transaction receiving unit that receives transaction data from a normal node, a block generation unit that generates a signature value based on a secret key, and generates a block as a data set including the transaction data and the signature value. A block transmission unit for transmitting to the network.
The transaction management unit of the normal node connects the received blocks to the block chain on condition that the authenticity of the signature value of the block received from the privileged node has been confirmed by the public key.

A server (privileged node) according to an aspect of the present invention is connected to a trading network including a plurality of ordinary nodes.
The normal node is a communication terminal that holds a public key corresponding to the secret key of the server in advance and manages the history of commercial transactions using virtual currency as a block chain.
This server generates a signature value based on a secret key and a transaction receiving unit that receives transaction data indicating the result of a commercial transaction using virtual currency from a normal node, and generates a block as a data set including the transaction data and the signature value. And a block transmission unit that transmits the block to the trading network.

ADVANTAGE OF THE INVENTION According to this invention, it becomes easy to make both the stabilization and smoothness of the transaction in a blockchain compatible.

It is a schematic diagram of a general block chain system. It is a schematic diagram for explaining a method of mining (block generation) in a general block chain system. It is a schematic diagram for explaining a mechanism in which a fork occurs in a block chain system. It is a schematic diagram of the block chain system in this embodiment. It is a data structure diagram of the block in this embodiment. It is a functional block diagram of a block chain system. It is a flowchart which shows the input process of transaction data. It is a flowchart which shows the process process of block generation. 7 is a flowchart showing a processing procedure when a normal node receives a block. It is a schematic diagram for demonstrating the usage method of the private key in a privileged node.

A general blockchain does not have a centralized privileged node (server) to centrally manage its operation. The blockchain will be extended by an unspecified number of miners competing to find the proper hash value. The process of finding an appropriate hash value is called "mining". Hereinafter, generating a new block such as “mining” will be referred to as “block generation”. In a general blockchain, a miner who wins a mining competition creates a block.

In the block chain shown in this embodiment, a privileged node (server) that plays a central role in its operation is installed. A single privileged node, rather than an unspecified number of miners, performs the block generation.
In the following, an outline of a general block chain will be described with reference to FIGS. 1 and 2. With reference to FIG. 3, we will point out the mechanism of "branching (fork)" in a general blockchain and the harmful effects that accompany it. The new block chain system in this embodiment will be described in detail with reference to FIG. 4 and subsequent figures.

FIG. 1 is a schematic diagram of a general block chain system 100.
In the blockchain system 100, a large number of ordinary nodes 110a, 110b... 110n (hereinafter referred to as “ordinary node 110”) and a large number of mining nodes 108a, 108b... 108n (hereinafter referred to as “mining node 108”). Are connected peer-to-peer via the trading network 102. The trading network 102 is formed in an open communication network such as the Internet.

The normal node 110 is a node that is a main body of transactions, and an individual wallet or a virtual currency exchange is assumed. The mining node 108 is a communication terminal used by a miner to perform block generation (mining). The normal node 110 may have the function of the mining node 108.

A block chain 104 is formed in the trading network 102. The data entity of the block chain 104 is locally stored in each of the normal node 110 and the mining node 108. When the blockchain 104 is updated, the update information is broadcast to the trading network 102. The normal node 110 and the mining node 108 update the block chain 104 stored by themselves according to the update information, so that the same block chain 104 is synchronously shared as a whole.

The block chain 104 has a data structure in which a large number of blocks 106 are linked as one chain. Block 106 is a data unit in which one or more transaction data are recorded. Each time the normal node 110 executes a transaction (remittance) using virtual currency, it broadcasts data indicating the transaction content (hereinafter referred to as “transaction data”) to the transaction network 102. The plurality of mining nodes 108 perform mining (block generation) on a collection of new transaction data. After mining, the new block 106 is connected to the existing block chain 104 (details will be described later). That is, it can be said that the block chain 104 is a long trading ledger in which a huge transaction history from the past is recorded. By referring to the block chain 104, past transaction details can be confirmed at any time. Further, since the normal node 110 can carry out a transaction with a temporary account, the anonymity of the transaction is maintained.
In the case of Bitcoin, there is an upper limit on the total amount of transaction data that can be written in one block 106 (the reason will be described later).

FIG. 2 is a schematic diagram for explaining a method of mining (block generation) in the general block chain system 100.
Here, a method of block generation (mining) of the (n+1)th block 106 (hereinafter referred to as “block 106(n+1)”) will be described. When generating the block 106(n+1), the proper hash value (n) based on the block 106(n) generated immediately before is used. Block 106(n+1) contains transaction data broadcast from a number of regular nodes 110. Hereinafter, a collection of various kinds of transaction data written in block 106 will be referred to as a “transaction data set”.

The mining node 108 calculates the hash value (n+1) by a predetermined hash function having the transaction data set (n+1), the hash value (n) and the nonce (n+1) as variables. In reality, the hash function includes variables other than these, but here, for the purpose of explaining the principle of block generation, the description will be made based on the above three variables.

The nonce (n+1) is arbitrary. When the generated hash value (n+1) satisfies the predetermined condition, specifically, when the hash value (n+1) is equal to or smaller than the predetermined threshold value W, the hash value (n+1) becomes the proper hash value. In order to find the proper hash value, the mining node 108 repeats the trial calculation while populating the hash function with various nonces (n+1). It can be said that mining work for finding a proper hash value is work for searching for a proper nonce. The mining node 108 that has found the proper hash value broadcasts the variable group including the nonce (n+1) and the hash value as the calculation result to the trading network 102. The other nodes (ordinary node 110 and mining node 108) connect the block (n+1) containing the proper nonce (n+1) to the block chain 104 if it can confirm that the calculation result is correct. The proper hash value (n+1) becomes a part of the next block 106(n+2).

If the transaction data of the block chain 104 is falsified later, the hash value will change. It takes some calculation cost to calculate the proper hash value, so it is difficult to rewrite all the transaction data and the proper hash value based on it. With such a mechanism, tampering with the block chain 104 is virtually impossible.

FIG. 3 is a schematic diagram for explaining a mechanism in which a fork occurs in the block chain system 100.
As described above, many mining nodes 108 compete for the proper hash value. Further, since there is no unique proper hash value, a plurality of mining nodes 108 may find a plurality of proper hash values. At this time, the block chain 104, which should be one chain, may be branched into two systems.

FIG. 3 shows a case where two types of proper hash values (H2A, H2B) are found based on block 106(2). The block 106 (3A) is generated based on the proper hash value (H2A) (hereinafter referred to as “A series”), and the block 106 (3B) is also generated based on the proper hash value (H2B) ( Hereinafter referred to as "B series".

It is assumed that the block 106 (3A) is generated in the A series, and the block 106 (4A) is subsequently generated. On the other hand, in the B series, a certain mining node 108x generates the block 106(4B), the block 106(5B), and the block 106(6B) after the block 106(3B) at a faster pace than the A series. It is assumed that the blocks 106 are collectively broadcast. As a result, the A series and the B series coexist. When the mining node 108x has overwhelming computing power, a "long chain", such as a B-series, can suddenly be thrown into the trading network 102.

The block chain system 100 is operated under the rule that "when a branch (fork) occurs, a long chain is officially adopted and a short chain is discarded." In the case of FIG. 3, the transaction data written in the block 106 (3A) and the block 106 (3B) in the A series is invalidated later. For example, it is assumed that a trader eats using virtual currency and writes the trade data in block 106 (3A). If the block 106 (3A) is invalidated subsequently, it means that the virtual currency has not been paid and the trading order is confused. In other words, if the 108x has overwhelming computational power, secretly creating a "long chain" can forcefully invalidate a "short chain" transaction.

With a popular virtual currency such as Bitcoin, it is difficult for one miner to overwhelm a large number of miners, so it is difficult to introduce such a “long chain” later. Forks are less likely to occur in popular currencies, but the likelihood of forking is not zero. On the other hand, the risk of a fork is increased in the case of a less popular virtual currency.

Bitcoin has introduced a mechanism for adjusting the mining difficulty level so that mining takes about 10 minutes. For example, the smaller the threshold value W described above, the more difficult it is to find an appropriate hash value. This mechanism makes it difficult for only one mining node 108 to outstrip another mining node 108 and steadily continue to make blocks 106. Instead, a waiting time of about 10 minutes is required from the input of transaction data to the official registration in the blockchain system 100.

In addition, in Bitcoin, an upper limit is set for the total data amount (size) of transaction data that can be registered in one block 106. Therefore, when the transaction is active, the transaction data may not be registered in the current block 106 and may be kept waiting until the next block generation. Hereinafter, the upper limit value of the transaction data amount that can be registered in one block 106 is referred to as “transaction upper limit value”.

Since the blockchain system 100 is not a centralized type, it is difficult to change the transaction upper limit value by design. In addition, due to the nature of the hash function, the difficulty of mining becomes higher when the transaction upper limit is increased. If the mining difficulty becomes too high, there is a dilemma that a general mining node 108 that has only normal computing power cannot win the mining competition.

In summary, in order to prevent forks, in other words, it is necessary to set a certain degree of mining difficulty to ensure the stability of transactions. This is to prevent one miner who is excellent in computing power from overtaking another miner and continuing to generate blocks. However, if the mining difficulty is set too high, the smoothness of transactions will be impaired. In the case of a popular virtual currency such as Bitcoin, it takes a long time to wait for a formal registration (hereinafter referred to as “transaction approval”) in the blockchain system 100 after executing a transaction (remittance). Is starting to stand out.

FIG. 4 is a schematic diagram of the block chain system 200 in this embodiment.
In the block chain system 200 according to the present embodiment, a single privileged node 120 takes charge of block generation instead of a large number of mining nodes 108. A plurality of ordinary nodes 110 are connected peer-to-peer via the trading network 102. The transaction network 102 is the same as FIG. 1 in that it is formed in an open communication network such as the Internet.

A block chain 104 is formed in the trading network 102. The data entity of the block chain 104 is locally stored in each of the normal node 110 and the privileged node 120.

Also in this embodiment, since the normal node 110 can carry out a transaction with a temporary account, the anonymity of the transaction is maintained. Also in this embodiment, the transaction upper limit value may be set in the block 106, but it is not essential to set the transaction upper limit value. Hereinafter, it will be described that the transaction upper limit value is not set in the block 106.

The privileged node 120 has a public key/private key pair. The public key is broadcast to the trading network 102, and all ordinary nodes 110 have the public key. The normal node 110 broadcasts the transaction data to the transaction network 102, and the privileged node 120 accumulates the transaction data in a local storage area (hereinafter referred to as “transaction pool”). Privileged node 120 reads transaction data from the transaction pool on a regular basis, such as once per second, and generates block 106 containing these transaction data. When generating the block, the privileged node 120 encrypts a part of the data included in the block 106 with the secret key to generate a signature value (details will be described later).

Privileged node 120 broadcasts block 106 containing the signature value to trading network 102. The ordinary node 110 verifies the authenticity of the signature value (block 106) by decrypting the signature value of block 106 with the public key. When the authenticity is confirmed, the normal node 110 adds a new block 106 to the block chain 104 (transaction approval).

In the present embodiment, the mining nodes 108 do not compete for mining (search for an appropriate hash value), and only the centralized privileged node 120 generates blocks. Since the privileged node 120 only generates the signature value, the processing cost associated with the block generation is low, and the block 106 can be generated at a high frequency of about once per second.

FIG. 5 is a data structure diagram of the block 106 in this embodiment.
The signature value (n) of the block 106(n) is a predetermined part of the transaction data set (n), for example, data obtained by encrypting 5-bit data from the 101st bit to the 105th bit with a secret key. is there. The privileged node 120 and the normal node 110 share (agree) information in advance from which part of the transaction data the signature value is generated. Hereinafter, the target data for generating the signature value is referred to as “original data”. Ordinary node 110 obtains the raw data from the transaction data set (n) of block 106(n) as well as the signature value (n). The normal node 110 decrypts the signature value (n) with the public key, and when the decrypted signature value (n) matches the original data, the block 106(n) is an authentic block generated by the privileged node 120. It is determined to be 106. Confirmation of the signature value is transaction approval.

FIG. 6 is a functional block diagram of the block chain system 200.
As described above, the blockchain system 200 includes a plurality of ordinary nodes 110 and privileged nodes 120.
(Normal node 110)
Each constituent element of the normal node 110 includes an arithmetic unit such as a CPU (Central Processing Unit) and various coprocessors, a storage device such as a memory and a storage, hardware including a wired or wireless communication line connecting them, and a storage device. It is realized by software that is stored and supplies a processing instruction to the arithmetic unit. The computer program may be configured by a device driver, an operating system, various application programs located in their upper layers, and a library that provides common functions to these programs. Each block described below is not a hardware-based configuration but a function-based block.
The same applies to the privileged node 120.

The normal node 110 includes a user interface processing unit 130, a data processing unit 132, a communication unit 134, and a data storage unit 136.
The communication unit 134 is in charge of communication processing for the transaction network 102. The user interface processing unit 130 receives operations from the user (trader) and is in charge of processing related to the user interface such as image display and audio output. The data storage unit 136 stores various data. The data processing unit 132 executes various processes based on the data acquired by the communication unit 134 and the user interface processing unit 130 and the data stored in the data storage unit 136. The data processing unit 132 also functions as an interface for the user interface processing unit 130, the communication unit 134, and the data storage unit 136.

The communication unit 134 includes a transaction transmission unit 146 and a block reception unit 148.
The transaction transmitter 146 broadcasts transaction data (remittance record) to the transaction network 102. The block reception unit 148 receives the block 106 generated by the privileged node 120.

The user interface processing unit 130 includes an input unit 138 and an output unit 140.
The input unit 138 receives various inputs from the user. The output unit 140 outputs various information to the user. The input unit 138 includes a transaction input unit 142. The transaction input unit 142 receives input of transaction details from the user when a transaction using virtual currency is performed.

The data processing unit 132 includes a transaction management unit 144. The transaction management unit 144 confirms the authenticity of the block 106 and updates the block chain 104.

The data storage unit 136 stores the block chain 104 and the public key.

(Privileged node 120)
The privileged node 120 includes a communication unit 150, a data processing unit 152, and a data storage unit 154.
Communication unit 150 is in charge of communication processing targeting transaction network 102. The data storage unit 154 stores various data. The data processing unit 152 executes various processes based on the data acquired by the communication unit 150 and the data stored in the data storage unit 154. The data processing unit 152 also functions as an interface between the communication unit 150 and the data storage unit 154.

The data processing unit 152 includes a block generation unit 160. The block generation unit 160 performs block generation by the method described above.

The communication unit 150 includes a transaction receiving unit 156 and a block transmitting unit 158.
The transaction receiving unit 156 receives the transaction data from the transaction network 102 and accumulates the transaction data in the transaction pool, which is the storage area of the data storage unit 154. The block transmission unit 158 broadcasts the generated block 106 to the trading network 102.

The data storage unit 154 stores the block chain 104 and the secret key. A transaction pool is formed in a part of the data storage unit 154, and transaction data is accumulated in the transaction pool.

FIG. 7 is a flowchart showing a process of inputting transaction data.
The process shown in FIG. 7 is executed in the normal node 110 when the user makes a transaction with virtual currency. The transaction input unit 142 first receives an input of transaction data from the user (S10). The transaction transmitting unit 146 immediately broadcasts the transaction data to the transaction network 102 (S12).

The transaction receiving unit 156 of the privileged node 120 acquires transaction data from a large number of ordinary nodes 110 and stores it in the transaction pool. Meanwhile, the ordinary node 110 that broadcasts the transaction data waits for the generation of the block 106 containing the transaction data.

FIG. 8 is a flowchart showing the process steps of block generation.
In the present embodiment, the block generation unit 160 of the privileged node 120 reads transaction data from the transaction pool (data storage unit 154) once a second. The process shown in FIG. 8 is executed at each read timing (block generation timing).

If the total amount of transaction data accumulated in the transaction pool is equal to or greater than the predetermined threshold T (Y in S20), the block generation unit 160 extracts the original data from a part of the transaction data set and keeps it secret. A signature value is generated by encrypting with a key (S22). The block generation unit 160 generates the block 106 including the signature value and the transaction data set (S24). The block transmission unit 158 broadcasts the block 106 including the signature value to the trading network 102 (S26).

When the total data amount of transaction data is less than the threshold value T (N of S20), the process after S22 is skipped. The block generation unit 160 periodically generates the block 106, and when transaction data is not much accumulated in the transaction pool, waits until the next read timing and then generates the block 106. By such a processing method, it is possible to prevent the block 106 having a small content (hereinafter referred to as “small block”) from being generated when the transaction is quiet.

FIG. 9 is a flowchart showing a processing procedure when the normal node 110 receives a block.
The block receiving unit 148 of the normal node 110 receives the block 106 broadcast by the privileged node 120. The transaction management unit 144 determines whether or not the block 106 is authentic by decrypting the signature value of the block 106 with the public key and comparing it with the original data included in the block 106 (S30). If the transaction is authentic (Y in S30), the transaction management unit 144 approves the transaction by adding the block 106 to the block chain 104 (S32). If not authentic (N of S30), the process of S32 is skipped. At this time, the communication unit 134 of the normal node 110 may warn the privileged node 120 that the illegal block 106 has been detected.
All ordinary nodes 110 update the blockchain 104 based on the received block 106.

FIG. 10 is a schematic diagram for explaining how to use the secret key 172 in the privileged node 120.
The premise of operation of the block chain system 200 is that only the privileged node 120 holds the secret key 172. If the private key 172 is illegally acquired by another node, the fake block 106 may be generated.

To protect the confidentiality of the private key, the privileged node 120 is locally connected to the databases A, B, and C. The secret key 172 is first encrypted by the encryption key 174. The encrypted secret key 172 is further divided into a first partial key 172a and a second partial key 172b. The database A stores the first partial key 172a. The database B stores the second partial key 172b. The encryption key 174 is stored in the database C. Normally, the privileged node 120 does not store the secret key 172 or the encryption key 174. Therefore, in a normal time, even if an unauthorized access to the privileged node 120 occurs, neither the private key 172 nor the encryption key 174 is leaked.

When the timing of reading from the transaction pool, that is, the timing of block generation is reached, the block generation unit 160 of the privileged node 120 reads the first partial key 172a from the database A and the second partial key 172b from the database B, and the built-in internal key is read. Load into volatile memory 170. The block generation unit 160 generates the secret key 172 on the volatile memory 170 by connecting the first partial key 172a and the second partial key 172b. At this stage, the private key 172 is still encrypted.

Subsequently, the block generation unit 160 reads the encryption key 174 from the database C, and decrypts the secret key 172 expanded in the volatile memory 170 with the encryption key 174. The block generation unit 160 generates a signature value based on the decrypted private key 172. After generating the block, the block generation unit 160 of the privileged node 120 deletes the secret key 172 from the volatile memory 170. The risk that the secret key 172 leaks from the privileged node 120 is reduced by configuring the privileged node 120 not to hold the secret key 172 only at an instant when the block is generated.

Each of the databases A, B, and C is locally connected to the privileged node 120, and is not connected to a public communication line such as the Internet. Therefore, unauthorized access to these databases is less likely to occur. Further, since the databases A and B store only part of the private key 172, the entire private key 172 will not be leaked even if an unauthorized access occurs to one of the databases. Furthermore, even if the first partial key 172a and the second partial key 172b are leaked, the private key 172 cannot be used without the encryption key 174.

The database C may have a plurality of encryption keys. For example, an encryption key A for decrypting the first partial key 172a and an encryption key B for decrypting the second partial key 172b may be prepared. Further, the block generation unit 160 may periodically change the plurality of encryption keys.

The privileged node 120 may be connected to the trading network 102 by a private communication line. Specifically, they may be connected by a secret line such as a VPN (Virtual Private Network), or may be connected by a dedicated wire line, and access to the privileged node 120 from the transaction network 102 side is restricted. A firewall may be provided for this purpose. According to such a control method, it becomes easier to more surely prevent unauthorized access to the privileged node 120 and the databases A, B, and C.

The blockchain system 200 has been described above based on the embodiment.
According to the present embodiment, since only the privileged node 120 generates the block 106, no branch (fork) occurs. In addition, since the block 106 is generated by creating a signature value with a secret key, the calculation cost associated with block generation is significantly smaller than that of a general block chain 104. In Bitcoin, it usually takes about 10 minutes to generate one block 106. According to the block chain system 200 in the present embodiment, the block 106 can be generated at a high frequency of about once per second, so that substantially immediate settlement is realized. Further, since the block 106 can be generated with high frequency, it is easy to prevent the total data amount of the transaction data included in one block 106 from increasing.

In the general block chain 104, the time required to generate one block 106 is set to about 10 minutes, so that the mining difficulty level is appropriately controlled. Since the frequency of block generation is statistically determined, it may be possible to wait for 10 minutes or more. On the other hand, in the present embodiment, since the privileged node 120 regularly generates blocks, the trader can more reliably estimate the time from the input of transaction data to the block generation (transaction authentication). Further, since the transaction upper limit value is not set, there is no need to wait for transaction approval.

Like the general blockchain 104, the normal node 110 can execute virtual currency transactions with a temporary account. The trader does not have to reveal his/her identity to the privileged node 120 or the like. Therefore, “anonymity”, which is the original appeal of the blockchain 104, can be maintained in the blockchain system 200 according to this embodiment.

The block chain system 200 according to the present embodiment is not based on the idea of increasing transaction safety depending on the difficulty level of mining. Therefore, the performance of block generation does not deteriorate even if the transaction upper limit is not set. Privileged nodes 120 may generate blocks 106 at the same pace as normal, even during periods of high trading activity (busy periods). The amount of transaction data included in one block 106 is small during periods when transactions are inactive (quiet periods), and the amount of transaction data included in one block 106 is large during busy periods. When a large number of transactions occur in a short period of time, a large amount of transaction data may be collectively recorded in one block 106. Since the total amount of transaction data that can be registered in the block 106 is variable, the activity of the transaction does not affect the pace of block generation.

In the case of a mining competition in a general blockchain 104, the calculation of the majority of mining nodes 108 that loses the competition is wasted. Mining requires a realistic cost such as electricity bills. In the present embodiment, since only the privileged node 120 generates blocks, it is possible to eliminate unnecessary costs associated with mining competition.

Further, in the present embodiment, when the total amount of transaction data accumulated in the transaction pool is less than or equal to the threshold value T, block generation is skipped (see FIG. 8). Therefore, the generation of small blocks can be suppressed. The threshold T may be several megabytes or zero. By setting the threshold T to zero, it is possible to prevent the generation of a wasteful block 106 that does not include transaction data at all. The general block chain 104 has no mechanism for suppressing the generation of small blocks. Small blocks not only cause unnecessary delays in remittance, but also place unnecessary load on the trading network 102. According to this embodiment, the block 106 can be generated at a reasonable pace while avoiding the generation of the small block in consideration of both transaction smoothness and transaction activity.

Not only the generation of the block 106, but also the confirmation of the signature value (transaction approval) at each normal node 110 requires some cost. Therefore, it takes some time to synchronize the block chain 104 (block 106) in all the normal nodes 110. From this point as well, it is preferable to suppress the generation of small blocks not only on the generation side (privileged node 120) but also on the reception side (normal node 110).

The privileged node 120 protects the private key 172 from unauthorized access by separating and encrypting it, as described with reference to FIG. Particularly, the secret key 172 is expanded in the volatile memory 170 only when the block is generated, and the secret key 172 is erased from the volatile memory 170 after the block generation is completed. This makes it easier to prevent the secret key 172 from leaking.

It should be noted that the present invention is not limited to the above-described embodiments and modifications, and the constituent elements can be modified and embodied without departing from the scope of the invention. Various inventions may be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments and modifications. Further, some constituent elements may be deleted from all the constituent elements shown in the above-described embodiments and modifications.

[Modification]
In the present embodiment, it is described that the transaction upper limit value is not set in the block 106. As a modification, a transaction upper limit value of several megabytes to about 1 gigabyte may be set. Assuming that block generation (mining) in bitcoin is performed once every 10 minutes and block generation in this embodiment is performed once per second, the block chain system 200 executes the block 106 at 600 times the speed of bitcoin. It can be generated. Therefore, even if a relatively small transaction upper limit value is set, the waiting time for block generation and transaction approval can be greatly shortened.

In the present embodiment, the transaction data is stored in the transaction pool of the privileged node 120, and the privileged node 120 periodically reads the transaction data from the transaction pool and generates a block. Alternatively, privileged node 120 may generate block 106 each time it receives transaction data from any regular node 110. Alternatively, the privileged node 120 may generate a block when the total amount of transaction data accumulated in the transaction pool becomes equal to or larger than a predetermined threshold K. According to such a control method, the block generation timing can be automatically adjusted according to the activity level of the transaction. Blocks are generated with high frequency in the busy season and blocks are generated with low frequency in the off-season. Further, it becomes easy to suppress the variation in the total amount of transaction data included in one block 106.

In this embodiment, the privileged node 120 has been described as adding one signature value to one block 106. Alternatively, the privileged node 120 may add multiple signature values to one block 106. For example, the block generation unit 160 of the privileged node 120 generates the first signature value based on the first original data from the 101st byte to the 105th byte, and the second signature value from the 1001st byte to the 1005th byte. The second signature value may be generated based on the original data. In this way, as the total amount of transaction data is larger, more signature values may be included. The normal node 110 approves the transaction on condition that the authenticity of all the plurality of signature values is confirmed. Such a control method makes it easier to more reliably prove the authenticity of the block 106.

The data processing unit 152 of the privileged node 120 may include a key changing unit (not shown) and a key transmitting unit (not shown). The key changing unit may change the private key and the public key periodically. The key changing unit may change the encryption key 174 periodically. The key changing unit may change the secret key or the like when an unauthorized access or an access suspected of being unauthorized is detected. The normal node 110 may notify the privileged node 120 of the existence of an illegal block when the block 106 whose authenticity cannot be confirmed based on the signature value is detected. At this time, the key changing unit of the privileged node 120 may change the secret key or the like. Further, the key changing unit of the privileged node 120 may change the secret key or the like even when the privileged node 120 or the databases A, B, and C are accessed from the outside. The privileged node 120 may prepare a plurality of types of secret keys/public keys in advance and change the secret key/public key pair when these change conditions are satisfied. For the change, the key transmission unit of the privileged node 120 may broadcast the newly adopted public key to the transaction network 102.

All or part of the databases A, B, and C shown in FIG. 10 may be a nonvolatile memory such as a hard disk built in the privileged node 120. Further, each database may be formed by dividing a partition in the non-volatile memory of the privileged node 120.

The privileged node 120 may disconnect the connection with the trading network 102 at the timing of block generation. After disconnecting the connection with the transaction network 102, the privileged node 120 generates a block from the transaction data accumulated in the transaction pool by the process described with reference to FIG. After generating the block, the private key 172 and the like are erased from the volatile memory 170. After clearing the private key 172, reconnect to the trading network 102 and broadcast block 106. According to such a control method, when the privileged node 120 uses the secret key 172, it can be completely offline, so that the risk of the secret key 172 leaking from the privileged node 120 can be further reduced.

In this embodiment, a part of the transaction data set is used as the original data, and the signature value is created from this original data. As a modification, the privileged node 120 may generate arbitrary original data and generate a signature value from this original data. The block 106 may include the original data and the signature value specified by the privileged node 120.

In the present embodiment, the block 106 generated by the privileged node 120 has been described as being connected to the block chain 104. In the case of the present embodiment, it does not necessarily have to be a “chain”. This is because it is not necessary to make a connection by the proper hash value as shown in FIG. For example, the privileged node 120 records the generation date and time (date and time information) in the block 106, broadcasts the block 106 to the trading network 102, and the normal node 110 confirms the authenticity of the signature value and then executes this block 106. It may be determined whether or not it is officially accepted. Since the block 106 includes date and time information, the order of transactions can be confirmed later by referring to the date and time information of a plurality of blocks 106.

In this embodiment, the description has been made on the premise that the transaction is performed using virtual currency. The transaction data registered in block 106 may be other than virtual currency transactions. For example, when the trader A gives the trader B a thing (tangible or intangible), the trade data may be registered in the block 106. In this case, the blockchain 104 can confirm that the ownership of the goods has been transferred from the trader A to the trader B. As described above, the block chain system 200 can be used not only for managing virtual currencies (money equivalents) but also for managing ownership of things and information.

100 block chain system, 102 trading network, 104 block chain, 106 block, 108 mining node, 110 ordinary node, 120 privileged node, 130 user interface processing unit, 132 data processing unit, 134 communication unit, 136 data storage unit, 138 input Section, 140 output section, 142 transaction input section, 144 transaction management section, 146 transaction transmission section, 148 block reception section, 150 communication section, 152 data processing section, 154 data storage section, 156 transaction reception section, 158 block transmission section, 160 block generation unit, 170 volatile memory, 172 secret key, 172a first partial key, 172b second partial key, 174 encryption key, 200 block chain system

Claims (11)

A trading network including a plurality of ordinary nodes, and a privileged node connected to the trading network,
The privileged node holds a private key,
The normal node has a public key corresponding to the secret key in advance,
The normal node is
A transaction input unit that accepts input of transaction data indicating the result of a commercial transaction using virtual currency,
A transaction transmitter for transmitting the transaction data to the transaction network,
A transaction management unit that manages transaction history as a blockchain,
A block receiving unit that receives a block from the privileged node,
The privileged node is
A transaction receiving unit for receiving transaction data from the normal node,
A block generation unit that generates a signature value based on the secret key and generates the block as a data set including the transaction data and the signature value;
A block transmission unit for transmitting the block to the trading network,
The transaction management unit of the normal node is
A block chain system, wherein the received block is connected to the block chain on condition that the authenticity of the signature value of the block received from the privileged node has been confirmed by the public key. In the privileged node,
The transaction receiving unit stores transaction data received from one or more ordinary nodes in a predetermined storage area,
The block chain system according to claim 1, wherein the block generation unit periodically reads the transaction data accumulated in the storage area and generates a block including the read transaction data and a signature value. In the privileged node,
The block generation unit reads transaction data collectively and periodically from the storage area regardless of the total amount of transaction data accumulated in the storage area, and has a variable size including the read transaction data and a signature value. The block chain system according to claim 2, wherein the block is generated. In the privileged node,
The transaction receiving unit stores transaction data received from one or more ordinary nodes in a predetermined storage area,
The block chain system according to claim 2, wherein the block generation unit skips block formation when the total amount of transaction data accumulated in the storage area at a read timing is less than or equal to a predetermined threshold value. .. In the privileged node,
The transaction receiving unit stores transaction data received from one or more ordinary nodes in a predetermined storage area,
The block generation unit reads transaction data from the storage area, generates a block including the read transaction data and a signature value, and adjusts the timing of block generation according to the activity level of the transaction. The block chain system according to claim 1. The transaction network is formed by an open communication line,
The blockchain system according to any one of claims 1 to 5, wherein the privileged node is connected to the transaction network by a non-public communication line. The private key is stored in a predetermined storage area in an encrypted state,
In the privileged node,
When the block is generated, the block generation unit reads the secret key from the storage area into a memory, decrypts the secret key, generates the signature value, and deletes the secret key from the memory after generating the block. The block chain system according to any one of claims 1 to 6. The secret key is divided into a plurality of parts and stored in a plurality of storage areas,
In the privileged node,
When generating a block, the block generation unit reads the parts of the secret key from each of the plurality of storage areas into a memory, synthesizes the secret key, and then generates the signature value. After the block is generated, the secret key is generated. 7. The block chain system according to claim 1, wherein the block chain system is deleted from the memory. Privileged nodes also
A key changing unit that changes the secret key when a predetermined changing condition is satisfied;
9. The block chain system according to claim 1, further comprising a key transmission unit that transmits a public key corresponding to the changed private key to the transaction network. Connected to a trading network containing multiple regular nodes,
The normal node is a communication terminal that holds a public key corresponding to the private key of the server in advance, and that manages the history of commercial transactions using virtual currencies as a block chain,
From the normal node, a transaction receiving unit that receives transaction data indicating the result of a commercial transaction using virtual currency,
A block generation unit that generates a signature value based on the secret key and generates a block as a data set including the transaction data and the signature value;
A block transmission unit that transmits the block to the transaction network. A function to receive transaction data showing the result of a commercial transaction with virtual currency from a normal node,
A function of generating a signature value based on a private key, and generating a block as a data set including the transaction data and the signature value,
A first program for causing a privileged node to exert a function of transmitting the block to a trading network including a plurality of ordinary nodes;
The ability to send transaction data to the privileged node,
The ability to receive blocks from the privileged node,
A function of confirming the authenticity of the signature value of the received block by the public key corresponding to the secret key,
A blockchain management program including a second program that causes the normal node to exhibit the function of connecting the received block to a blockchain on condition that the authenticity of the block has been confirmed.

Images