KR20200009974A - Error-correction code based crypto currency system - Google Patents

Abstract

According to an embodiment of the present invention, a mining device performs a proof of work according to an improved proof of work algorithm to generate a block. More particularly, according to an embodiment of the present invention, the mining device comprises: a control unit configured to obtain a data value for proof of work from a current block header to be mined, obtain a first input value and a second input value based on the obtained value, obtain a hash function value for a particular nonce value based on the second input value and the third input value, obtain a mapped codeword value based on the hash function value and the first input value, determine whether the codeword value satisfies a condition set, and if so, generate a block to complete the proof of work; and a network unit for broadcasting the generated block to another mining device.

Description

Error-correction code based crypto currency system}

The present invention relates to a cryptocurrency system. In particular, the present invention relates to a cryptocurrency system including a mining device that generates a block through an improved proof-of-work algorithm and verifies it.

In 2009, blockchain-based cryptocurrency emerged from Bitcoin [1] developed by Satoshi Nakamoto. Blockchain is a distributed data processing technology for public distributed ledgers. Peer-to-Peer (P2P) transactional data is written into blocks, which form a linked list of blocks (in other words, chains). Each user on the network stores the entire data in a distributed manner without central authority. Since each block in the blockchain constitutes a blockchain that contains the hash value of the previous block, it makes it very difficult to manipulate transactions in blockchain-based cryptocurrencies.

Maintaining a single blockchain in a large P2P network requires a distributed consensus mechanism that ensures system integrity by mutually verifying results between peer nodes. This consensus mechanism should be able to determine who created the new block and whether the chain is valid.

Bitcoin is a representative cryptocurrency using Proof-of-work (PoW) algorithm. Proof of work is the most commonly used consensus algorithm in blockchain-based cryptocurrencies. In short, computing power is used to find and verify hash values that meet specific requirements to reach consensus. Proof of work is the process of finding a nonce that makes the block hash value less than the target value. The nonce is one of the information specified in the block header. A nonce set, which is a set of nonce values, is defined and assigned to a hash function by selecting nonce values one by one. At this time, the nonce value once used is excluded from the nonce set and is not used again. If a hash value satisfying the above requirement is found in a specific nonce value, the nonce value is recorded and inserted into the block header to generate a block. This series of processes is called proof of work. In the proof-of-work process, the target value represents the difficulty of calculating the nonce value and is adjusted to generate a single block every 10 minutes on average.

[1] Satoshi Nakamoto. Bitcoin: A peer-to-peer electronic cash system. Consulted, 1: 2012, 2008. [2] Dwork, Cynthia; Naor, Moni (1993). "Pricing via Processing, Or, Combatting Junk Mail, Advances in Cryptology". CRYPTO'92: Lecture Notes in Computer Science No. 740. Springer: 139-147. [3] Harald Vranken, in Current Opinion in Environmental Sustainability, 2017, 28: 1-9 [4] https://www.asicminervalue.com/miners/ebang/ebit-e10 [5] Henri Gilbert, Helena Handschuh: Security Analysis of SHA-256 and Sisters. en: Selected Areas in Cryptography 2003: pp175-193

The operation method of the mining device according to an embodiment of the present invention is intended to solve the re-centralization occurring in the existing proof-of-work cryptocurrency.

In addition, the operation method of the mining device according to an embodiment of the present invention is to solve the problem that a small number of mining operators monopoly hash power due to the appearance of ASIC.

In addition, the operation method of the mining device according to an embodiment of the present invention, to adjust the difficulty of the mining, and to propose a method of operation of the mining device that the input value is changed every block.

In accordance with an embodiment of the present invention, a method of operating a mining device includes: obtaining a data value for proof of work from a current block header. Generating a check matrix based on the first value included in the obtained data value, generating a hash tree based on the second value included in the obtained data value, a third value and the hash tree included in the obtained data value Generating an input set based on the method; applying an input set and a nonce value to a hash function to obtain a result vector; obtaining an output word based on the result vector and the check matrix; Determining whether the set condition is satisfied, and generating a new block or obtaining an output word again using another nonce value based on the determination result.

The operation method of the mining device according to an embodiment of the present invention can solve the re-centralization occurring in the cryptocurrency system based on the proof of work as an algorithm almost impossible to implement with an ASIC chip.

In addition, the operating method of the mining device according to an embodiment of the present invention, through the re-centralization solution to restore the nature of the blockchain-based cryptocurrency can recover the transaction credit and currency credit.

In addition, the operation method of the mining device according to an embodiment of the present invention can adjust the difficulty of the proof of work as necessary.

1 shows a general block and a block chain to which the blocks are connected.
2 is a flowchart illustrating an improved proof-of-work algorithm according to an embodiment of the present invention.
3 shows the codeword and condition set described above.
4 is a flowchart illustrating a verification process of a mining apparatus according to an embodiment of the present invention.
FIG. 5 is a diagram for explaining a method of controlling a mining difficulty in a proof-of-work algorithm according to an embodiment of the present invention through an 8 by 16 check matrix.
6 is a block diagram showing a mining apparatus according to an embodiment of the present invention.

Hereinafter, with reference to the drawings will be described in detail a specific embodiment of the present invention. However, the spirit of the present invention is not limited to the following embodiments, and those skilled in the art who understand the spirit of the present invention can easily add, change, delete, or add other components that fall within the scope of the same spirit. It may be proposed, but this will also be included within the scope of the present invention.

In the accompanying drawings, in order to easily express the spirit of the present invention, in describing the overall structure, minute parts may not be specifically described, and in describing the minute parts, the overall structure may not be specifically reflected. In addition, even if the specific parts, such as an installation position, are different, when the action is the same, the same name is given, and the convenience of understanding can be improved. In addition, when there exists a plurality of the same structure, only one structure is demonstrated, and the same description is applied about another structure, and the description is abbreviate | omitted.

Prior to describing the present invention, the proof of work performed on blockchain based cryptocurrency will be briefly described and related terms will be briefly defined.

1 shows a general block and a block chain to which the blocks are connected.

The block chain 2 has a form in which a plurality of blocks 1 are connected.

Block 1 is a bundle of a plurality of valid transaction information.

The block header 3 displays the information of the block. The block header contains the hash value of the previous block.

The block hash 4 is a value obtained by calculating a block header with a hash function. Here, the hash function is a function that maps data of arbitrary length to data of fixed length.

In the proof-of-work algorithm, as described above, the block hash and the target value are compared to determine whether the proof-of-work succeeds. Specifically, proof of work is performed in a so-called peer node. Each peer node performs a hash calculation while changing a nonce value of header information to determine whether a value smaller than a target value is obtained.

Here, the peer node is also referred to as a miner or a mining device, and means a computing device or a set of computing devices that performs proof of work. For example, a computing device could be a computer with a high performance graphics card and processor.

 The peer node changes the nonce until the block hash is smaller than the target value. If the block hash is smaller than the target value, the peer node determines that the proof of work is successful and confirms all transactions included in the block as valid transactions. And once a valid block is created, the peer node broadcasts the created block to the whole network, and when other peer nodes approve it and add it to the blockchain, the transaction is completed.

Here, a block may be generated at several peer nodes at the same time and the chain may branch, where peer nodes reach consensus using a predetermined consensus algorithm and extend the consensus chain. For example, the Bitcoin consensus mechanism only considers the longest chain as the right chain.

Bitcoin, the proof-of-work cryptography described above, has some problems.

First, it consumes too much power for proof of work [3]. The difficulty of crypto puzzles, called mining difficulty, is gradually increasing because the number of operators participating in bitcoin mining increases and the hash power of the mining network increases. The larger the hash power, the faster the proof-of-work and the faster the block generation. The Bitcoin protocol aims to fill the block creation time by one block every 10 minutes on average. To this end, the Bitcoin protocol reconstructs the hash difficulty every 2016 blocks [1]. Therefore, as the hash power increases, the difficulty increases. This consumes more power for mining.

The greater the number of miners in cryptocurrency, the better the protection against possible attacks, which helps to maintain blockchain immutability and credibility. In the early stages of the Bitcoin network (2010-2013), ordinary people using home computers were able to perform Bitcoin's proof of work.

However, over time, the computing power of home computers has not been able to quickly prove proof of work, and as the computing platform for bitcoin mining has recently reached ASICs from GPUs and FPGAs, a small number of miners have monopolized computing power. Is appearing. Through this, the Bitcoin network is centralized, moving away from the decentralization, which is the identity of the Bitcoin blockchain. Therefore, the possibility of blockchain being tampered by a few miners with overwhelming computing power is at the point where the public's trust in the blockchain is breaking down.

As a cause of the recentralization problem of all proof-of-work-based blockchain networks including Bitcoin, there is limited availability of crypto puzzles. The proof-of-work method in the bitcoin consensus mechanism is based on a fixed hash function (e.g. SHA-256) algorithm, resulting in an ASIC chip optimized for the bitcoin proof-of-work algorithm [4]. ASIC chips are relatively expensive, but the hash power of a few miners that are optimized for Bitcoin proof-of-work to perform mining through ASIC chips is a big part of the hash power of the entire network. I got it.

Therefore, a new proof-of-work algorithm is required to solve the re-centralization of such blockchain networks. The new proof-of-work algorithm is required to meet the following requirements.

1) Puzzles should be difficult to solve, but checkers should be easy.

2) Puzzles must have strong resistance to external attacks.

3) The nonce value of the solved puzzle is not reused.

4) The difficulty of the puzzle should be adjustable.

5) Anyone with a CPU should be able to participate in proof of work.

Hereinafter, an operation proof algorithm in an improved PoW-based blockchain network according to an embodiment of the present invention will be described. One of the improved requirements

6) The function used for proof of work must be able to change and change every block.

to be.

2 is a flowchart illustrating a proof-of-work algorithm that satisfies an improved condition according to an embodiment of the present invention.

The proof-of-work algorithm described in FIG. 2 may be performed through the mining apparatus described above, and specifically, may be performed by a processor such as a CPU provided in the mining apparatus.

The mining device obtains a data value for proof of work from the current block header (S1001). Here, the current block is a block that a miner is currently trying to make, and a block which is not yet connected to the chain because the proof of work is not completed. The block header included in the block chain may include one or more information about the block. The information included in the block header may include at least one of version information, difficulty information, time stamp information, nonce information, hash value information of a previous block, or transaction set information.

이고

이 될 수 있다. 채굴 장치는 현재 블록 인덱스 t (양의정수) 에서 이전 블록의 해쉬 값(h_t-1)을 이용하여 체크 매트릭스(F_t)를 생성할 수 있다. 여기에서 체크 매트릭스의 생성은 부호이론 분야에서 일반적으로 알려진 것을 사용할 수 있다.The mining device generates a check matrix based on the first value included in the obtained data value (S1003). Here, the first value used to generate the check matrix may be a hash value of the previous block. The check matrix may be an N _c -N _m by Nc matrix consisting of elements of Galois Field GF (q) (0 or 1 binary elements if q = 2). chamberlain

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This can be The mining device may generate the check matrix F _t using the hash value h _t-1 of the previous block at the current block index t (positive integer). Herein, the generation of the check matrix may be one commonly known in the field of sign theory.

The mining device generates a hash tree based on the second value included in the obtained data value (S1005). Here, the second value used to generate the hash tree may be transaction set information. In one embodiment, the mining device may generate a hash tree value based on the second value.

The mining device generates an input set S based on the third value included in the obtained data value and the generated hash tree (S1007). The third value used herein may be at least one of version information, difficulty information, or time stamp information of the previous block. In addition, other information included in the block header may additionally be used as the third value.

The mining device applies the input set to the hash function to obtain a result vector r (S1009). The hash function used here may be a SHA 256 [5] function, or another function whose security has been verified may be used. The mining device then generates a result vector that is the hash function output for a particular nonce value.

The mining apparatus applies the result vector r, which is the output of the hash function, and the check matrix generated in step S1003 as input values to the decoding function (S1011). The mining device may obtain an output word c ^ as an output value of the decoding function.

Here, the decoding function is a function that produces a unique output value for one input value, such as a decoder of error-correction code, a sphere-decoding signal receiver of communication theory, a sparse signal restoration algorithm of compression sensing, or an algorithm for solving inverse problems of mathematics. Can be used.

In a preferred embodiment, when a decoding function for error correction coding is used, an error-correction code is used when the transmitter and the receiver communicate between the noisy channels. The word received on the noisy channel is different from the transmitted word due to an error generated by the channel. Error correction codes are used to catch and correct this error. The transmitter generates a codeword by 1-to-1 mapping, ie, encoding the message vector, and transmits the generated codeword to the receiver instead of the message vector. The receiver may decode the received word including the received error and remove the error occurring in the channel. When the receiving word is input, the reconstruction function that solves the inverse problem of the encoding function and restores the transmitted codeword is called a decoder or decoding function.

To make room for error elimination, make the size N _c of the codeword vector longer than the size N _m of the message vector. R = N _m / N _c is called a code rate. Smaller code rates make it more robust to channel errors; However, it requires more computing to decode.

The present invention shows an embodiment of the invention to apply the decoder used in the Error-Correction Code to proof of work. We combine Decoder with cryptographic functions like SHA-256 to create a composite function. That is, the output value of the cryptographic function is put as one of the input values of the decoding function.

In the proof of work, it is very difficult to find the input value of the synthesized function, that is, the nonce value, in which the output word of the synthesized function satisfies the given condition. Therefore, the resulting synthesis function satisfies 1) of the proof-of-work algorithm. In a preferred embodiment, graph-decoder may be used as the decoding function. Additionally, the decoding function may use an algorithm capable of the fastest codeword mapping in the linear graph-decoder field.

The mining device determines whether the obtained output word of the decoder satisfies a preset condition (S1013). The mining device has a condition set related to the mapped output word in advance, and determines whether the output word value acquired in step S1011 is a codeword and whether the preset condition set is satisfied.

3 shows the codeword and condition set described above.

As illustrated in FIG. 3, there are 2 ²⁵⁶ vectors (eg, the output of the SHA function), of which there are about 2 ⁶⁴ codewords at a 1/4 code rate. When a vector is input to the decoding function Dec (), it is mapped to one output word. The mining device determines whether the mapped output word is a codeword included in a condition set.

Return to Figure 2 again.

As described above, when the mapped output word satisfies the condition set, the mining device determines that the proof of work is completed, generates a new block while recording the current nonce value and broadcasts it to another mining device (S1017). . Therefore, the process of verifying the output word value by using the decoding function is added to the existing bitcoin proof of work, instead of determining whether the proof of work is completed by the hash function output value alone. Recentralization).

In other words, in the proof-of-work algorithm by the synthesis function according to an embodiment of the present invention, since the check matrix, which is one of the inputs of the decoder part, may be changed every block, a different decoder puzzle for each block should be performed as proof of work. . The dependence of the check matrix on the previous block hash value also means that a different input value is used for each block, resulting in suppression of the appearance of the ASIC chip. That is, mining using ASIC chips makes it difficult for anyone to participate in proof-of-work even with a relatively low hash power CPU, thus satisfying the requirements of the new proof-of-work algorithm. In addition, the function used for decoding can also be changed to another kind of function having one-way characteristics, which also suppresses the appearance of the ASIC chip due to the fixed algorithm. In addition, even if a nonce value for a particular puzzle problem is found, a different input value is used to create a puzzle for each block, so the existing nonce value cannot be reused as the nonce value of a new block. That is, it satisfies the requirement 3) of the new working algorithm.

If the mapped output word does not satisfy the condition set, the mining apparatus excludes the used nonce value from the nonce set, selects a new nonce value not used in the nonce set, and returns to step S1009 again (S1015). . The mining apparatus repeats each step selecting a new nonce value until the mapped output word satisfies the condition.

4 is a flowchart illustrating a verification process of a mining apparatus according to an embodiment of the present invention.

Steps 2 to 3 described above are mining processes of the mining apparatus, and when the proof of work is completed, the mining apparatus broadcasts the newly generated block to another mining apparatus. If the mined device is recognized as a valid block by verifying the broadcast block, the mining device updates the block chain ledger by adding the block to the existing block chain.

The mining device obtains block header data of the broadcast block from another mining device that generated the block (S2001). Here, the block header data acquired by the mining device is the same as described above.

The mining device generates a check matrix based on the hash value included in the block header data (S2003). Here, the method of generating the check matrix is the same as described above.

The mining device obtains an output value of the hash function based on the block header data (S2005). Herein, obtaining the output value of the hash function is the same as described above.

The mining device obtains an output word using an output value of the hash function and a decoding function output value using the check matrix as an input value (S2007). The decoding function used here is the same as described above.

The mining device determines whether the output word satisfies the condition (S2009). Here, the conditions are set to the same conditions as those in the mining process. The set of conditions for verification may be set collectively for the entire mining device, or may be delivered together when the block is broadcast.

If the mining device determines that the output word satisfies the set of conditions, the mining device approves the broadcasted block and updates the ledger by extending it to the existing block chain (S2011).

On the contrary, when the output word does not satisfy the condition set as a result of the determination, the mining device determines that the broadcast block is not a valid block and rejects the broadcast block approval (S2013).

As a result, the above-mentioned verification method only needs to verify whether the condition set is satisfied by putting the value passed to a known (or preset) decoding function, and finds a codeword that matches the condition while changing the nonce value. Compared to the process of completing the verification, it is relatively simple and suitable for blockchain verification. Therefore, even if an external attacker manipulates the contents of the block, the verifier can easily know whether it has been manipulated.

FIG. 5 is a diagram for explaining a method of controlling a mining difficulty in a proof-of-work algorithm according to an embodiment of the present invention through an 8 by 16 check matrix.

5 (a) is an example of an 8 by 16 check matrix. In practice, a much larger check matrix is used, but for ease of explanation, the 8 by 16 check matrix is described as an example.

FIG. 5B is a table listing the codeword values based on the check matrix in (a). n represents the Hamming weight of the codeword, that is, the number of non-zero numbers included in the codeword. V _n represents a set of conditions that have 1 as the number of Hamming weights. p represents the ratio of the number of codewords included in the V _n condition set among the total number of codewords.

As shown in the table of FIG. 5 (b), it can be seen that the size of the condition set including n 1 is different, and the respective occupancy ratios thereof. Therefore, the hamming weight can be determined according to the difficulty of the cryptographic puzzle to be adjusted. For example, when the difficulty is lowered, the hamming weight may be set to 7 to 10. Conversely, if you want to increase the difficulty, you can set the Hamming weight to 3. In each case, the probability of selecting a codeword that satisfies a condition set is about 55% and 2.5%, respectively. In the latter case, more operations must be performed to obtain a codeword value that satisfies a condition set. As a result, the difficulty of proof of work increases. In other words, it is possible to flexibly adjust the difficulty of the puzzle by changing the code rate and adjusting the size of the matrix to solve the Decoder puzzle, thereby satisfying the requirements of the new proof-of-work algorithm.

6 is a block diagram showing a mining apparatus according to an embodiment of the present invention.

The mining device according to an embodiment of the present invention includes a control unit 110, a network unit 120 and a storage unit 130.

The controller 110 may refer to a processor and may include a microprocessor or a controller.

As shown in FIG. 6, the control unit 110 includes a current block header data obtaining unit 111, an input value generating unit 112, a hash function applying unit 113, a codeword obtaining unit 114, and a block generating unit. 115 may be included.

The current block header data obtaining unit 111 extracts a header of the current block to be mined to obtain data included in the header. Herein, the data acquired by the current block header data acquisition unit 111 may include at least one of version information, difficulty information, time stamp information, nonce information, hash value information of a previous block, or transaction set information.

The input value generator 112 generates a plurality of input values based on the current block header data. In an embodiment, the input value generator 112 may generate a check matrix based on a previous block hash value. In another embodiment, the input value generator 112 may generate a hash tree value based on a transaction set. In another embodiment, the input value generator 112 may generate a hash function input set based on a hash tree value and other header data. Herein, the other header data value may be at least one of version information, difficulty information, or time stamp information.

The hash function application unit 113 obtains a hash function output by using the input set generated by the input value generator 112 as an input value. Here, the hash function may be a SHA function, and other secured functions may be applied.

The output word obtainer 114 obtains an output word based on the check matrix and the hash function output value. According to an embodiment, the output word mapping algorithm may obtain an output word by searching for one codeword close to an input value. In another embodiment, graph codeword mapping may be used as the output word mapping algorithm.

The block generator 115 verifies the obtained output word and generates a block according to the verification result. The block generator 115 generates a nonce value and determines whether an output word corresponding to the nonce value satisfies a condition set. The block generator 115 stores a nonce value and generates a block when the obtained output word satisfies a condition set. On the other hand, if the output word does not satisfy the condition set, the block generator 115 changes the nonce value and receives a new output word value from the output word acquiring unit to perform verification.

The network unit 120 is a wired or wireless communication device. The network unit 120 connects with another mining device and broadcasts the generated block. In addition, the network unit 120 may receive a block generated by another mining device and transfer it to the current block header data acquisition unit 111.

The storage unit 130 stores various instructions used by the controller 110. In addition, the storage unit 130 stores the block chain ledger to which the blocks generated by the controller 110 are connected. The storage unit 130 may be a memory device.

The present invention described above can be embodied as computer readable codes on a medium on which a program is recorded. The computer readable medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable media include hard disk drives (HDDs), solid state disks (SSDs), silicon disk drives (SDDs), ROMs, RAMs, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and the like. There is this. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

Claims (11)

In the mining device that generates a block when a transaction occurs, and performs a proof of work through the proof-of-work consensus mechanism to form a block chain,
Obtain a data value for proof of work from the header of the current block to be mined, obtain a first input value and a second input value based on the obtained value, generate a check matrix based on the first input value, Obtain a hash function value for a particular nonce value based on the second input value and the third input value, obtain a mapped output word value based on the hash function value and the first input value, and output word value A control unit which determines whether or not the condition set is satisfied and generates a block to complete the proof of work if the condition set is satisfied; And
It includes a network unit for broadcasting the generated block to another mining device
Mining device. The method of claim 1,
The controller generates a hash tree based on a second input value among current block header data, and generates an input set based on the generated hash tree and a third input value.
Mining device. The method of claim 2,
The block header data value used for generating the third input value is at least one of version information, time stamp information, or difficulty information of the current block.
Mining device. The method of claim 1,
The controller generates a first input value based on a previous block hash value.
Mining device. The method of claim 1,
If the codeword value does not satisfy the condition set, the controller changes the nonce value to obtain the codeword value again.
Mining device. Obtaining a data value for proof of work from the current block header;
Generating a check matrix based on the first value included in the obtained data value;
Generating a hash tree based on a second value included in the obtained data value;
Generating an input set based on a hash value and a third value included in the obtained data value;
Applying an input set to a hash function to obtain a result vector;
Obtaining a codeword based on the result vector and the check matrix;
Determining whether the codeword satisfies a preset condition set; And
Generating a new block based on the determination result or obtaining a codeword again using another nonce value;
How mining device works. The method of claim 6,
Broadcasting the block to another mining device when a new block is generated;
How mining device works. The method of claim 7, wherein
Determining whether or not the codeword satisfies a preset condition set,
Adjusting a preset set of conditions for adjusting the difficulty of the proof-of-work process,
Broadcasting the block to another mining device,
Broadcasting the adjusted condition set information together with a block;
How mining device works. The method of claim 8,
To adjust the condition set,
Adjusting a hamming weight that refers to the number of 1s included in the codeword;
How mining device works. The method of claim 6,
Obtaining an output word based on the result vector and the check matrix,
And finding and mapping one output word corresponding to the result vector.
How mining device works. The method of claim 10,
The algorithm for finding the mapped output word is graph codeword mapping.
How mining device works.

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