This property is crucial to the 'proof of work' algorithm involved in mining: to successfully 'solve' a block, miners try to combine all of the inputs with their own arbitrary piece of input data in such a way that the resulting hash starts with a certain number of zeroes.
As a basic demonstration, we could try 'mining' with our Python hash function by manually adding exclamation points after "CoinDesk rocks! Of course, solving the hash for a bitcoin block — which at the time of writing must start with 18 zeros — requires an extremely large amount of computation and so the combined processing power of all the computers in the network still takes approximately 10 minutes to solve a block.
It's the need for this large amount of processing power that means new bitcoins get mined over a long period of time, not all at once. In order to earn bitcoins through mining, you need to put in the huge amount of work necessary to solve a block — and by earning that reward, you're locking in all of the new transactions into a block, which is added to the permanent record of all previous transactions: the blockchain.
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CoinDesk journalists are not allowed to purchase stock outright in DCG. The industry is down bad, but is that more about the Federal Reserve or crypto institutional failures? The NFT was given to the country in March near the start of its crypto fundraising campaign.
First mover. By Sam Reynolds James Rubin. Jun 20, at p. While they are considered cryptographically "weak" because they can be solved in polynomial time, they are not easily decipherable. Cryptographic hash functions add security features to typical hash functions, making it more difficult to detect the contents of a message or information about recipients and senders.
A hash function turns an input for example text into a string of bytes with a fixed length and structure. Any hash value created from data using a specific hashing algorithm is always the same length and one-way - it cannot be reversed. Image by Wikipedia. Blockchains rely heavily on hash functions for generating cryptographic keys and hashing the transaction blocks. For input of any length, the function will always generate a fixed-length output. This property allows us to hash any file whether it is a text document, image or even a video file and get the output of the same length.
For example, Bitcoin platforms largely rely on SHA it takes in the input of any length and converts it into bytes. This means that you can literally hash an entire movie into just bytes. Deterministic : For a given input, the output will always be the same. Efficiently Computed : the hashing algorithm should be so efficient that you can compute hashes on an ordinary Laptop or PC using just your CPU cores.
Preimage Resistance : given the output of the hash function hash digest , you cannot determine the input. Therefore, if someone hashes a message and sends it to another, then even if they get a hold of the hash digest, they will not be able to decrypt what the original message was. Collision Resistance : for two distinct inputs, the output of the hash function should not be the same.
Avalanche Effect : it means that for a small change in the input, there will be a significant change in the output of the hash function. Puzzle Friendliness : even if you get hold of the initial bytes, you cannot determine the next 56 bytes from it.
With the introduction of hash functions out of the way, now let's look at how they are used in leading cryptocurrencies. A cryptographic hash function should be computationally efficient : it must be quick in performance to create the hash value. It has to be deterministic - every time you put in a certain input, it has to produce the same output and to be pre-image resistant which means it cannot reveal any information about the input in the output.
Finally, a hash function has to be collision-resistant which ensures that it has to be impossible for two different inputs to produce the same output. It is the deterministic feature, pre-image resistance and collision-resistance that constitute the three most important properties of hash functions in the Bitcoin mining process. A hash function has to be collision-resistant which ensures that it has to be impossible for two different inputs to produce the same output.
Any block is bundled and contains several transactions as well as information on the previous block. This means if someone wanted to change the ledger or double-spend the risk that a cryptocurrency is used twice or more a transaction, they would have to change the hash in all previous blocks. In order for the bundled block to be added to the blockchain, miners need to find a hash that meets the target difficulty.
The purpose of a nonce is varying the input to a cryptographic hash function, that is increased randomness, in computation during the mining process. The node checks whether a hash meets the criteria of difficulty. The hash must start with the correct number of zeroes.
The time consumption of the SHA operation is mainly in the iteration part of Step 4, and the most time-consuming part is the calculation of A and E values. Therefore, adopting the method of critical path segmentation and combining with the parallel characteristics of FPGA computing resources can effectively shorten the time consumption. Therefore, the critical path of the algorithm is divided into the following formulas:.
In this way, A and E values will be updated and shortened from the original and to and , where denotes the time consumption of addition operations. FPGA is suitable for bit operation. Carry-Save Adders CSA strategy can reduce addition operation, minimize critical path length, and ensure pipeline throughput. For n -bit binary numbers a, b , and c , the CAS operations are as follows:.
By dividing the critical paths, it takes , , and to calculate , , and , respectively. Since the addition operation consumes a lot of time on the FPGA, the CSA method should be used to increase bit operation and reduce the addition operation, in order that the total time consumption can be reduced. The critical path segmentation method and the CSA strategy reduce the operation of and to only , thus improving the efficiency of the algorithm.
After the optimization of critical path partition, the time consumption of the longest path is reduced. For serial computing, the total time consumption does not decrease. Therefore, it is necessary to use the parallel characteristics of FPGA and pipeline method for optimization, so as to truly reduce the total time consumption of computing.
According to the characteristics of the SHA algorithm and the optimization of critical path, the core processing of the algorithm is divided into three modules: W module, split S module, and update module. The pipelining technology reduces time consumption by increasing resource utilization. Therefore, each module needs 64 computing units and a total of computing units.
While data are being calculated, in the first clock cycle, the first data are input to the computing unit for processing in the first clock cycle. In the second clock cycle, the output of W 0 is taken as the input of S 0, and W 1 is calculated. At the same time, the second data are input to W 0. In the third clock cycle, three computing units are processed in parallel, and so on.
Until the 66th clock cycle, when all units are running, the output of the first data is completed. When there is a large amount of data to be computed, one type of data is computed in a clock cycle, which reduces the time consumed by 64 iterations in the algorithm. Therefore, the throughput and resource utilization of the algorithm are greatly improved. The pipeline structure of the SHA algorithm is shown in Figure 6.
The core processing module of hash computing is mainly responsible for hash calculation of blockchain data, which is implemented in full-pipeline mode and supports hash calculation of SHA1, SHA, and so forth. The data communication interface circuit based on 10, Mega mainly includes 10, Mega MAC interface, data buffer, and interface of module on the same chip.
The module is mainly responsible for the input of data to be processed and the recovery of calculation results. The data communication interface circuit based on DDR3 mainly includes DDR3 interface, data buffer, and interface of on-chip module.
This module is mainly responsible for data memory reading. This module is mainly responsible for data memory writing. The processor-based on-chip processing control core is mainly responsible for reporting the running state of the mimic computer and processing the control information. Data communication interface based on Gigabit Ethernet interface is mainly used for communication of control information. It uses FIFO interface to communicate with external devices [ 15 ].
In the process of transmitting control messages, if the receiver does not have an ARP response, the system will issue a timeout error because ARP does not respond; if there is a timeout transmission, the system will show the number of times of timeout transmission. If the transmission succeeds, the successful message will be returned; if the transmission fails, the error message which is retransmitted overtime will be returned.
If there is a timeout and no information is received, the system will send out the wrong signal of communication channel, according to which the user will take appropriate action accordingly. The whole structure is shown in Figure 8. The highest bit indicates whether the data transmission is the last one. If more than bytes of data are to be transmitted, multiple transfers are required. The sending status FIFO is used to identify whether there is an error in the data transmission.
If there is an error like the timeout in the process of data transmission, all subsequent contents will be read out until the last one. Each data transmission corresponds to a state FIFO write. The highest bit indicates whether the data transmission is the last frame of data, and the data received is identified by index number.
Read-write memory is implemented by four groups of FIFOs in burst mode. If it is a writing operation, the data will be written to memory through the DDR write module. The process of reading memory data is similar to that of writing.
When it begins reading and writing memory, the address of memory will be counted according to the length of writing, and the reading and writing of the whole data will be completed. After the reading and writing operation is completed, it will jump to the idle state and wait for the next operation.
Public and private keys in blockchains are a pair of keys obtained by a kind of algorithm. It will be encrypted with public key and decrypted with corresponding private key. After three times of SHA computation and one time of RIPEMD computation for the public key, a public key hash can be obtained, and the address can finally be obtained through base58 encoding [ 16 ].
Merkle tree is a kind of tree structure. In trading with blockchains, every transaction is hashed, and the final root is Merkle root [ 17 ]. Proof-of-work PoW is called mining in blockchains. CPU calculation uses the complexity of hash operation to determine PoW, and it will produce a value smaller than the specified target [ 18 ].
Block filter proposed in the blockchain is a fast search based on hash function, which can quickly determine whether a retrieved value exists in the searched set [ 19 ]. The application of hash algorithm in blockchain is shown in Figure In this paper, the communication equipment and network are optimized. In a relatively safe environment, a relatively simple and lightweight hash algorithm is chosen to replace the complex hash algorithm, so as to improve the running speed of the system and reduce the energy consumption of the system.
Meanwhile, multiple hash algorithm is used to reduce the attack of length expansion and ensure the integrity and tamper-proofing of information, which reflects the security performance of blockchain. In this paper, proactive reconfigurable computer is used for experiments. The software platform is ISE software integrating design, simulation, integration, wiring, and generation.
First, the comparison of CPU running speed and resource utilization is given by optimizing the hash algorithm deeply. Second, the collision resistance of proactive reconfigurable hashes is analyzed. Finally, the security of this scheme is analyzed from many aspects.
The configuration information of each computing unit used in the experiment is shown in Table 1. Their resource occupation, frequency, and throughput are shown in Table 2. From Table 3 , it can be seen that the proactive reconfigurable computer can realize the parallelism of multiple modules and can fully meet the application requirements of hash computing in blockchain.
Taking Bitcoin three hash as an example, three SHA combinations are connected in series to form a cascade pipeline. The data can be directly input into the pipeline without waiting, and the results are output sequentially by the end, which is very efficient. Contrastively, CPU can only rely on multithreaded concurrency to improve computing performance, and its essence is still serial execution, which will not be competent for blockchain applications requiring large amounts of computing.
As each clock cycle can transmit 8 bytes of data, the clock frequency is Two memory modules are configured: one is responsible for writing operation of 10G network and reading operation of hash module, and the other is responsible for writing operation of hash module and reading operation of 10G network.
The two memory modules work independently, which improves the efficiency of data transmission. Hash operation is irreversible and gets different values for different contents. Any change of input information will lead to significant changes in hash results. Moreover, hash operation is also anticollision; that is, two pieces of information with the same hash result cannot be found, which can effectively prevent differential attack [ 20 ].
Assuming that the output value of hash function is uniformly distributed and the message digest has m bits, the hash value has possible outputs. If , that is, , then ; this means. Table 4 gives the threshold of hash function conflict. Bitcoin obtains hash data through the SHA algorithm and runs two iterations in block trading to mitigate the length expansion attack.
The multiple phases of have many different hash combination schemes and can be represented by at time t , which is dynamic, diverse, and random. The hash algorithm of PRCA blockchain system is dynamically reconfigurable. After negotiation, the hash algorithm can be reconstructed dynamically and partially to complete the switching of different algorithms. Obviously, the blockchain based on PRCA not only improves the complexity of internal hash operation but also combines the hash to increase the length of output, which greatly hinders the attackers from extending the blockchain and reduces the probability of collision.
Encryption of information is the key link of blockchain, which mainly includes hash function and asymmetric encryption algorithms [ 21 ]. Asymmetric encryption uses private key to prove the ownership of the node and is implemented by digital signature. Hash algorithm is used to transform the input of any length into an output of fixed length consisting of letters and numbers, which is irreversible and tamper-proofing.
From the perspective of information security, the main advantages of this scheme are as follows: i Multiple hash algorithms are jointly used to ensure the integrity and nontampering of information ii There is a pseudorandom dynamic selection and the hash algorithm is updated to increase the difficulty of attack in time dimension iii By using the hardware implementation of proactive reconfigurable computer, the attack surface is expanded and the attack threshold is raised. Obviously, the blockchain based on PRCA enhances the confidentiality, authenticity, and integrity of data and enhances the overall security of blockchain transactions with its reliability, security, and tamper-resistance.
In order to improve the efficiency and security of blockchain hash algorithm, a scheme of blockchain hash algorithm optimization based on PRCA is proposed in this paper. This scheme combines blockchain with proactive reconfigurable computer to improve the performance of blockchain hash function. In terms of security performance, several lightweight hash algorithms are used to exchange information to ensure the integrity and tamper-proofing of information.
The proactive reconfigurable computer hardware is used to expand the attack surface, improve the attack threshold, and ensure the security of blockchain. Blockchain security is the most important part of the system, which includes data, intelligent contract, privacy protection, and application risk. Meanwhile, the data of blockchain is unique. Under the condition of its own security, data writing cannot be changed.
Based on the security problem of data immutability, the data structure, cryptography technology, and communication network at the bottom of blockchain are improved to promote the healthy development of blockchain application. The data used support the findings of the study are available from the corresponding authors upon request. The authors declare that there are no conflicts of interest regarding the publication of this paper.
This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Article of the Year Award: Outstanding research contributions of , as selected by our Chief Editors.
Read the winning articles. Journal overview. Special Issues. Academic Editor: Yuan Yuan. Received 12 Mar Revised 14 Apr Accepted 23 May Published 14 Sep Abstract Blockchain is widely used in encrypted currency, Internet of Things IoT , supply chain finance, data sharing, and other fields. Introduction Blockchain is a kind of distributed general ledger technology, originated from the literature [ 1 ].
Proactive Reconfigurable Computing Architecture 2. Definition of Proactive Reconfigurable Computation PRCA is an operation mechanism based on multidimensional reconstructed functional structure and dynamic multibody. Figure 1. Figure 2. Principle prototype structure of the proactive reconfigurable computer. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7.
Figure 8. Figure 9. Figure Table 1. Table 2. Table 3. Table 4. References Q. Lu and X. Padmavathi and R. Bentov and R. View at: Google Scholar P. Xia, E. Sifah, K. Asamoah, J. Gao, X. Du, and M. Liang, S. Weller, F. Luo, J. Personal Finance. Your Practice. Popular Courses. Investing Cryptocurrency. What Are Cryptographic Hash Functions? Key Takeaways Hash functions are mathematical functions that transform or "map" a given set of data into a bit string of fixed size, also known as the "hash value.
Hash functions are used for cryptocurrency, password security, and message security. Article Sources. Investopedia requires writers to use primary sources to support their work. These include white papers, government data, original reporting, and interviews with industry experts. We also reference original research from other reputable publishers where appropriate. You can learn more about the standards we follow in producing accurate, unbiased content in our editorial policy.
Compare Accounts. The offers that appear in this table are from partnerships from which Investopedia receives compensation. This compensation may impact how and where listings appear. Investopedia does not include all offers available in the marketplace. Related Terms. Understanding Hash A hash is a function that converts an input of letters and numbers into an encrypted output of a fixed length. Encryption Encryption is a means of securing digital data using an algorithm and a key.
Proof of Work PoW Proof of work describes the process that allows the bitcoin network to remain robust by making the process of mining, or recording transactions, difficult. ZCash ZEC is a decentralized and anonymous payment system. It is an enhanced, transaction-shielded fork of Bitcoin. Bitcoin Mining Breaking down everything you need to know about Bitcoin mining, from blockchain and block rewards to proof of work and mining pools.
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