JP2024048265A - Block chain verification method and block chain verification system - Google Patents

Abstract

To detect falsification in a block chain.SOLUTION: In a block chain verification system 1, an administrator node 2 is configured to: execute processing to generate an electronic signature of a block 30 from an electronic signature of a previous block 30 and the block 30, for each of the blocks 30 included in a block chain 3; generate, after generating an electronic signature of the last block 30b, an electronic signature of a new block 30a from the electronic signature of the last block 30b and the new block 30a; and transmit the electronic signature or the like, of the new block 30a to a secure element 4. The secure element 4 generates an electronic signature of the new block 30a from the electronic signature of the last block 30b stored in the secure element 4 and the new block 30a transmitted by the administrator node 2, and verifies validity of the electronic signature of the new block 30a received from the administrator node 2 using the electronic signature of the new block 30a generated by the secure element 4.SELECTED DRAWING: Figure 5

Description

This application relates to technology for detecting tampering in blockchain.

Blockchain, which was developed as a distributed ledger technology for implementing virtual currencies, is rapidly becoming popular (for example, see Patent Document 1). In this application, blockchain does not refer to the broad definition of blockchain as defined by the Japan Blockchain Association, but rather to a ledger that records blocks that compile transaction histories (transaction data) in a chronological order.

Blocks stored in the blockchain contain a hash value calculated from the previous block. This allows blocks recorded in the blockchain to be linked in chronological order, making it difficult to tamper with blocks contained in the blockchain. In addition, the blockchain is managed in a distributed manner across many nodes in a P2P (Peer to Peer) blockchain network, making it even more difficult to tamper with the blockchain.

In addition to public blockchains, which have no administrator, there are permissioned blockchains, which have administrators. Permissioned blockchains are divided into private blockchains and consortium blockchains depending on the number of administrators. A permissioned blockchain with a single administrator is called a private blockchain. A permissioned blockchain with multiple administrators is called a consortium blockchain.

Permissioned blockchains are said to have a higher risk of blockchain tampering than public blockchains. This is because the blockchain can be tampered with if approved by a limited number of administrators. This is particularly likely to be a problem in private blockchains with a single administrator.

JP 2021-105680 A

The present invention aims to make it possible to detect tampering in a permissioned blockchain.

The first invention disclosed in this application is a blockchain verification method executed between an administrator node that manages a blockchain and a secure element connected to the administrator node.
In the blockchain verification method of the first invention, when the administrator node generates a new block to add to the blockchain, the administrator node executes a process of generating an electronic signature of the block from the electronic signature of the previous block and the block using an electronic signature generation algorithm shared with the secure element, for each block included in the blockchain, to generate an electronic signature of the last block, which will be the last block in the blockchain, and a step b of generating an electronic signature of a new block from the electronic signature of the last block and the new block using the electronic signature generation algorithm, and sending the electronic signature of the new block and the new block to the secure element.
In the blockchain verification method of the first invention, the secure element executes step c of generating an electronic signature of a new block from the electronic signature of the last block stored in the secure element and the new block sent by the administrator node using the electronic signature generation algorithm, and verifying the validity of the electronic signature of the new block received from the administrator node using the electronic signature of the new block generated by the secure element; and if the validity verification of the electronic signature of the new block is successful, step d of updating the electronic signature of the last block stored in the secure element to the electronic signature of the new block whose validity verification has been successful, and then notifying the administrator node of the success of the validity verification of the electronic signature of the new block.

The second invention disclosed in this application is a blockchain verification system that includes an administrator node that manages a blockchain and a secure element connected to the administrator node.
In the blockchain verification system of the second invention, which is a system invention, the administrator node has a blockchain verification unit that executes, when it generates a new block to be added to the blockchain, a process of generating an electronic signature of the block from the electronic signature of the previous block and the block using an electronic signature generation algorithm shared with the secure element, for each block included in the blockchain, to generate an electronic signature of a last block, which will be the last block in the blockchain, and a step b of generating an electronic signature of a new block from the electronic signature of the last block and the new block using the electronic signature generation algorithm, and sending the electronic signature of the new block and the new block to the secure element.
In the blockchain verification system of the second invention, the secure element comprises an electronic signature verification unit that executes step c of generating an electronic signature of a new block from the electronic signature of the last block stored in the secure element and the new block sent by the administrator node using the electronic signature generation algorithm, and verifying the validity of the electronic signature of the new block received from the administrator node using the electronic signature of the new block generated by the secure element, and step d of, if the validity verification of the electronic signature of the new block is successful, updating the electronic signature of the last block stored in the secure element to the electronic signature of the new block whose validity verification has been successful, and then notifying the administrator node that the validity verification of the electronic signature of the new block has been successful.

The invention disclosed in this application is configured so that an administrator node that manages a blockchain can detect tampering in a permissioned blockchain by using a secure element connected to the administrator node.

Diagram of the blockchain verification system. Block diagram of the blockchain verification system. A diagram explaining the mechanism for chaining block digital signatures. A diagram explaining the initial processing performed in the blockchain verification system. FIG. 1 is a diagram explaining the blockchain verification process performed in the blockchain verification system.

From here, an embodiment of the invention disclosed in this application will be described. This embodiment is intended to facilitate understanding of the invention disclosed in this application. The invention disclosed in this application is not limited to this embodiment. Furthermore, unless otherwise specified, the drawings are schematic diagrams drawn to facilitate understanding of the invention disclosed in this application.

Figure 1 is a configuration diagram of a blockchain verification system 1 according to this embodiment. The blockchain verification system 1 disclosed in this application is a system that is applied to a permission-based blockchain in which there is one or more administrators and only participants authorized by the administrators can participate.

The blockchain verification system 1 illustrated in FIG. 1 is composed of at least a blockchain 3, an administrator node 2 that manages the blockchain 3, and a secure element 4 connected to the administrator node 2. Furthermore, the blockchain verification system 1 illustrated in FIG. 1 includes a blockchain network 5 in which only participants authorized by the administrator can participate.

The blockchain network 5 is a P2P network consisting of an administrator node 2 that manages the blockchain 3 and participant nodes 50 that are participants who are permitted to participate in the blockchain network 5. If the blockchain 3 is a private blockchain, there will be one administrator node 2. If the blockchain 3 is a consortium blockchain, there will be multiple administrator nodes 2. In either case, the functions of the administrator node 2 remain the same, so in Figure 1, the number of administrator nodes 2 is one. Note that the nodes of the blockchain network 5 are computer devices such as servers. A cloud system consisting of multiple servers can also be a node of the blockchain network 5.

The blockchain verification system 1 illustrated in FIG. 1 includes a blockchain 3 that records blocks 30, each of which summarizes a transaction history 301, in a chronologically linked manner. In this embodiment, the blockchain 3 is a permission-based blockchain. Therefore, in this embodiment, only the administrator can add a new block 30a to the blockchain 3. With this in mind, FIG. 1 illustrates only the blockchain 3 that is connected to the administrator node 2. In an actual system, multiple copies of the blockchain 3 that are connected to the administrator node 2 are managed in a distributed manner by participant nodes 50 included in the blockchain verification system 1.

In a permissioned blockchain, only the administrator can add new blocks 30a to the blockchain 3, so permissioned blockchains are said to have a higher risk of tampering with the blockchain 3 compared to public blockchains that have no administrator.

Therefore, in this embodiment, the blockchain verification system 1 includes a secure element 4, which is a device used to verify the validity of the blockchain 3 to which the new block 30a is added. In the blockchain verification system 1 according to this embodiment, the secure element 4 is connected only to the administrator node 2, and is not connected to other participant nodes 50. When adding a new block 30a to the blockchain 3, the administrator node 2 has the function of verifying whether the blockchain 3 to which the new block 30a is added has been tampered with by using the secure element 4 to verify the validity of the blockchain 3 connected to the administrator node 2.

Figure 2 shows a block diagram of the blockchain verification system 1. The blockchain 3 included in the blockchain verification system 1 records blocks 30 that are linked together in chronological order, each block 30 consolidating transaction history 301 (transaction information, electronic signature, and public key) related to transactions that occurred in the blockchain network 5. The transaction history 301 recorded in the block 30 is transaction history 301 related to transactions that occurred within a certain period of time in the blockchain network 5, or a certain amount of transaction history 301 that occurred in the blockchain network 5. In the blockchain 3, the first block 30 is the genesis block 30G.

A block 30 recorded in the blockchain 3 includes a previous hash value 300, which is the hash value of the previous block 30, and one or more transaction histories 301. In the case of a block 30 with block number "n", the previous block 30 is the block 30 with block number "n-1". A hash value calculated from the block 30 with block number "n-1" is stored as the previous hash value 300 in the block 30 with block number "n". The transaction history 301 includes transaction information describing the contents of the transaction, a digital signature of the transaction information, and the public key of the person who generated the digital signature. In addition to this, the block 30 can include a timestamp indicating the date and time when the block 30 was generated, a nonce for making the hash value satisfy certain conditions, and the like.

In this embodiment, the only node that can add a new block 30a to the blockchain 3 is the administrator node 2. The administrator node 2 has a blockchain verification unit 20 that uses a secure element 4 to verify the validity of the blockchain 3 to which the new block 30a is added. The blockchain verification unit 20 provided in the administrator node 2 is a function realized by the processor of the computer device used as the administrator node 2 and a computer program that operates this processor.

In this embodiment, the blockchain verification unit 20 provided in the administrator node 2 verifies the validity of the blockchain 3 using the electronic signature of the block 30. In the blockchain 3, the previous hash value 300 is included in the block 30, so that the multiple blocks 30 stored in the blockchain 3 are chained in chronological order. Therefore, in this embodiment, the electronic signature of the block 30 is chained by generating the electronic signature of the block 30 from the electronic signature of the previous block 30 and the block 30. By chaining the electronic signatures of the blocks 30, the electronic signature of the last block 30b, which is the last block in the blockchain 3 (the newest in chronological order), depends on all the blocks 30 stored in the blockchain 3. If at least one of the blocks 30 stored in the blockchain 3 is tampered with, the electronic signature of the last block 30b changes to a different value.

The digital signature generation algorithm for generating the digital signature for block 30 may be any algorithm that can generate the digital signature for block 30 from the digital signature for the previous block 30 and block 30. In this embodiment, a CBC (Cipher Block Chaining) block cipher using a common key is used as the digital signature generation algorithm. Other algorithms that can be used include SHA (Secure Hash Algorithm).

This will be explained with reference to FIG. 3. FIG. 3 is a diagram for explaining the mechanism for chaining the electronic signature of block 30. As described above, in this embodiment, the electronic signature of block 30 is generated from the electronic signature of the previous block 30 and block 30 by a predetermined electronic signature generation algorithm (indicated as f(x) in FIG. 3). In FIG. 3, the block 30 immediately preceding block 30 with block number "1" is the genesis block 30G. Therefore, the electronic signature of block 30 with block number "1" is generated from the electronic signature of the genesis block 30G and block 30 with block number "1". Note that since the genesis block 30G does not have a previous block 30, the electronic signature of the genesis block 30G is generated from initial data that can be determined arbitrarily and the genesis block 30G. The electronic signature of block 30 with block number "2" is generated from the electronic signature of block 30 with block number "1" and block 30 with block number "2". By performing this process in the order of the blocks 30 included in the blockchain 3, a digital signature is generated for the block 30 with block number "n", which is the last block in the blockchain 3. The digital signature for the block 30 with block number "n", which is the last block in the blockchain 3, is data based on all blocks 30 stored in the blockchain 3. Therefore, if at least one of the blocks 30 stored in the blockchain 3 is tampered with, the digital signature for the block 30 with block number "n" will have a different value.

In this embodiment, taking this into consideration, the digital signature of the new block 30a is used to verify the validity of the blockchain 3 to which the new block 30a is to be added. The digital signature of the new block 30a is generated from the digital signature of the last block 30b in the blockchain 3 to which the new block 30a is to be added and the new block 30a. The digital signature of the new block 30a depends on the digital signature of the last block 30b in the blockchain 3 to which the new block 30a is to be added. Therefore, verifying the validity of the digital signature of the new block 30a equates to verifying the validity of the blockchain 3 to which the new block 30a is to be added.

In this embodiment, the validity of the blockchain 3 is verified using the electronic signature of the new block 30a in order to enable the electronic signature of the last block 30b stored in the secure element 4 to be updated. After the validity of the electronic signature of the new block 30a is successfully verified, the electronic signature of the new block 30a whose validity has been successfully verified becomes the electronic signature of the last block 30b. If the secure element 4 is made to verify the validity of the electronic signature of the new block 30a, the secure element 4 can store the electronic signature of the new block 30a that was the subject of the validity verification as the new electronic signature of the last block.

The secure element 4 refers to an IC chip equipped with a security function. In this embodiment, the secure element 4 is a device that verifies the validity of the electronic signature of the new block 30a generated by the administrator node 2. The secure element 4 has an electronic signature verification unit 40 as a function for verifying the validity of the electronic signature of the new block 30a generated by the administrator node 2. The electronic signature verification unit 40 provided in the secure element 4 is realized by the processor of the secure element 4 and a computer program that operates this processor.

In this embodiment, the electronic signature verification unit 40 provided in the secure element 4 stores the electronic signature of the last block 30b so that the electronic signature of the new block 30a can be generated from the new block 30a sent by the administrator node 2. Then, when the electronic signature verification unit 40 provided in the secure element 4 successfully verifies the validity of the new block 30a received from the administrator node 2, it updates the electronic signature of the last block 30b stored in the secure element 4 to the electronic signature of the new block 30a whose validity has been successfully verified.

In the case of FIG. 3, the blockchain 3 stores blocks from the genesis block 30G to the block 30 with block number "n". In this case, the electronic signature verification unit 40 provided in the secure element 4 stores the electronic signature of the block 30 with block number "n" as the electronic signature of the last block 30b. When the validity verification of the electronic signature of the block 30 with block number "n+1", which becomes the new block 30a, is successful, the electronic signature verification unit 40 provided in the secure element 4 updates the electronic signature of the block 30 with block number "n" stored as the electronic signature of the last block 30b to the electronic signature of the block 30 with block number "n+1" whose validity has been successfully verified.

From here, we will explain the operation of the blockchain verification system 1 according to this embodiment. The explanation of the operation of the blockchain verification system 1 according to this embodiment also includes an explanation of the blockchain verification method, which is a method-related invention. Figure 4 is a diagram explaining the initial processing performed by the blockchain verification system 1. Figure 5 is a diagram explaining the blockchain verification processing performed by the blockchain verification system 1.

First, the initial processing performed by the blockchain verification system 1 will be described with reference to FIG. 4. In the initial processing performed by the blockchain verification system 1, a sharing process (step S1) is first executed between the administrator node 2 and the secure element 4 to share items required for verifying the validity of the new block 30a.

Items required for verifying the validity of the new block 30a include an electronic signature generation algorithm (e.g., CBC block cipher, SHA-256, etc.) for generating an electronic signature. In an electronic signature generation algorithm that uses a common key, the common key used in the electronic signature generation algorithm is shared. Any method can be used to share items required for verifying the validity of the block 30 between the administrator node 2 and the secure element 4. For example, a method of sharing an encryption key using an elliptic curve is known as a method of sharing an encryption key.

When the sharing process (step S1) is completed, the administrator node 2 generates an electronic signature for the genesis block 30G (step S2). The electronic signature for the genesis block 30G is generated from the initial data and the genesis block 30G by the electronic signature generation algorithm shared with the secure element 4 in the sharing process.

After generating the electronic signature of the genesis block 30G, the administrator node 2 transmits a request to register the electronic signature of the genesis block 30G to the secure element 4 (step S3). When the secure element 4 receives the request to register the electronic signature of the genesis block 30G from the administrator node 2, it stores the electronic signature of the genesis block 30G included in the request to register the electronic signature of the genesis block 30G as the electronic signature of the last block 30b (step S4), and the procedure in FIG. 4 ends.

Next, the blockchain verification process performed by the blockchain verification system 1 will be described with reference to FIG. 5. The blockchain verification process is a process executed between the administrator node 2 and the secure element 4 when the administrator node 2 generates a new block 30a.

In the blockchain verification process performed by the blockchain verification system 1, first, the administrator node 2 generates a new block 30a to be added to the blockchain 3 (step S10). The new block 30a is a block 30 that includes transaction history 301 related to transactions that occurred within a certain period of time in the blockchain network 5, or a block 30 that includes a certain amount of transaction history 301 that occurred in the blockchain network 5.

When a new block 30a to be added to the blockchain 3 is generated, the blockchain verification unit 20 of the administrator node 2 executes a process for each block 30 included in the blockchain 3 to generate an electronic signature for the previous block 30 and an electronic signature for block 30 from block 30 using an electronic signature generation algorithm shared with the secure element 4, and generates an electronic signature for the last block 30b, which will be the last block in the blockchain 3 (step S11).

After generating the electronic signature for the last block 30b, the blockchain verification unit 20 generates an electronic signature for the last block 30b, which is the block immediately before the new block 30a, and an electronic signature for the new block 30a from the new block 30a using an electronic signature generation algorithm shared with the secure element 4 (step S12).

When the digital signature of the new block 30a is generated, the blockchain verification unit 20 of the administrator node 2 sends a request for verifying the validity of the digital signature for the new block 30a to the secure element 4 (step S13). This request for verifying the validity of the digital signature includes the digital signature of the new block 30a generated by the administrator node 2 and the new block 30a to be added to the blockchain 3.

When the electronic signature verification unit 40 of the secure element 4 receives the electronic signature verification request from the administrator node 2, it uses the new block 30a included in the electronic signature verification request to generate an electronic signature for the new block 30a (step S14). The electronic signature verification unit 40 generates an electronic signature for the new block 30a from the electronic signature of the last block 30b stored in the secure element 4 and the new block 30a received from the administrator node 2, using an electronic signature generation algorithm shared with the administrator node 2.

When the electronic signature verification unit 40 of the secure element 4 generates the electronic signature for the new block 30a, it uses the electronic signature for the new block 30a generated by the electronic signature verification unit 40 to verify the validity of the electronic signature for the new block 30a received from the administrator node 2 (step S15). In this embodiment, when the electronic signature for the new block 30a received from the administrator node 2 matches the electronic signature for the new block 30a generated by the electronic signature verification unit 40, the electronic signature verification unit 40 determines that the verification of the validity of the electronic signature for the new block 30a received from the administrator node 2 has been successful.

The electronic signature verification unit 40 of the secure element 4 branches the process depending on the result of verifying the validity of the electronic signature of the new block 30a sent by the administrator node 2 (step S16).

If the electronic signature of the new block 30a sent by the administrator node 2 does not match the electronic signature of the new block 30a generated by the secure element 4, the electronic signature verification unit 40 of the secure element 4 notifies the administrator node 2 that the verification of the validity of the electronic signature of the new block 30a has failed (step S17). When notified by the secure element 4 that the verification of the validity of the electronic signature of the new block 30a has failed, the blockchain verification unit 20 of the administrator node 2 stops the process of adding the new block 30a to the blockchain 3 (step S18), and the procedure in FIG. 5 ends.

If the electronic signature of the new block 30a sent by the administrator node 2 matches the electronic signature of the new block 30a generated by the secure element 4, the electronic signature verification unit 40 of the secure element 4 updates the electronic signature of the new block 30a stored in the secure element 4 to the electronic signature of the new block 30a whose validity has been successfully verified (step S19). Then, the electronic signature verification unit 40 of the secure element 4 notifies the administrator node 2 that the validity of the electronic signature of the new block 30a has been successfully verified (step S20). When notified by the secure element 4 that the validity of the electronic signature of the new block 30a has been successfully verified, the blockchain verification unit 20 of the administrator node 2 executes a process of adding the new block 30a to the blockchain 3 (step S21), and the procedure of FIG. 5 ends.

In the procedure described using FIG. 5, if the blockchain 3 to which the new block 30a is to be added is tampered with before the new block 30a is added, the electronic signature of the last block 30b generated by the administrator node 2 in step S11 of FIG. 5 will have a different value from the electronic signature of the last block 30b stored in the secure element 4 at this time. For this reason, in this case, the electronic signature of the new block 30a generated by the administrator node 2 using the electronic signature of the last block 30b generated by the administrator node 2 in step S12 of FIG. 5 will have a different value from the electronic signature of the new block 30a generated by the secure element 4 using the electronic signature of the last block 30b stored in the secure element 4 in step S14 of FIG. 5. Therefore, in the invention disclosed in this application, the administrator node 2 that manages the blockchain 3 can detect tampering in the permission-based blockchain 3 by using the secure element 4 connected to the administrator node 2.

REFERENCE SIGNS LIST 1 Blockchain verification system 2 Administrator node 20 Blockchain verification unit 3 Blockchain 30 Block 30a New block 30b Last block 30G Genesis block 300 Previous hash value 301 Transaction history 4 Secure element 40 Digital signature verification unit 5 Blockchain network 50 Participant node

Claims (2)

A method executed between an administrator node that manages a blockchain and a secure element connected to the administrator node, comprising:
When the administrator node generates a new block to be added to the blockchain, a process of generating a digital signature of the block from the digital signature of the previous block and the block using a digital signature generation algorithm shared with the secure element is executed for each block included in the blockchain to generate a digital signature of the last block that will be the last block in the blockchain.
a step b in which the administrator node generates a digital signature of a new block from the digital signature of the last block and the new block using the digital signature generation algorithm, and transmits the digital signature of the new block and the new block to the secure element;
a step c in which the secure element generates a digital signature for a new block from the digital signature of the last block stored in the secure element and the new block transmitted by the administrator node, using the digital signature of the new block generated by the secure element, and verifies the validity of the digital signature of the new block received from the administrator node;
a step d in which, when the secure element has successfully verified the validity of the electronic signature of the new block, the secure element updates the electronic signature of the last block stored in the secure element to the electronic signature of the new block whose validity has been successfully verified, and then notifies the manager node that the validity of the electronic signature of the new block has been successfully verified;
A blockchain verification method comprising: The system includes an administrator node that manages a blockchain and a secure element that is connected to the administrator node,
the administrator node comprises a blockchain verification unit that executes step a, when generating a new block to be added to the blockchain, a process of generating a block's electronic signature from the electronic signature of the previous block and the block using a digital signature generation algorithm shared with the secure element for each block included in the blockchain to generate a digital signature of a last block that will be the last block in the blockchain, and step b, of generating a digital signature of a new block from the digital signature of the last block and the new block using the digital signature generation algorithm, and transmitting the digital signature of the new block and the new block to the secure element;
the secure element comprises an electronic signature verification unit that executes step c of generating an electronic signature of a new block from the electronic signature of the last block stored in the secure element and the new block transmitted by the administrator node, using the electronic signature of the new block generated by the secure element, and verifying the validity of the electronic signature of the new block received from the administrator node; and step d of, if the verification of the validity of the electronic signature of the new block is successful, updating the electronic signature of the last block stored in the secure element to the electronic signature of the new block whose validity has been successfully verified, and then notifying the administrator node of the success of the verification of the validity of the electronic signature of the new block.
A blockchain verification system.

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