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Blockchain learning summary 2

Time : 21/07/2021 Author : yleo32 Click : + -
        It is well known that bitcoin is the earliest and most successful application of the blockchain. Its tamperability and privacy protection are based on the hash algorithm. Merkle tree came into being to cater for the use of hash algorithm. Merkle tree is a special tree that replaces pointers with hash pointers. However, the record of bitcoin is based on transactions, so it is not easy to query the balance of a node at a certain time. Although all nodes in bitcoin also maintain a utxo, that is, the transaction light nodes that have not spent can also query the contents of utxo from all nodes to obtain the balance of a certain node. But the cost and time are unnecessary and contrary to our daily habits.
 
        Therefore, Ethereum proposes an account based block, that is, the block body in Ethereum includes the balance of each block. Then the question came. Whether we can use the Merkle tree structure in bitcoin to store account balances will be revealed later. The above is the storage structure of transactions in the block. First, each transaction Di generates a hash value, and then merges two by two from each layer to get a tree structure. Finally, the root hash value of the tree is stored in the block header as the unique identifier of all transactions. As long as any transaction on Merkle tree is tampered with, the corresponding hash will also be changed layer by layer. Just as the saying goes, the last root hash will also be changed.
 
        Therefore, the data structure based on Merkle tree can ensure the tamperability of transaction data. Secondly, there are many light nodes in the blockchain network, that is, the nodes that only store the blockchain header information. So what do these light nodes need to do when they want to check whether a transaction is recorded on the block. Does it need to request the node to download the complete information on the tree? Of course not. It only needs the whole node to provide other necessary hash values on the path from the transaction to the root. By generating hash along the path, the last light node will calculate a root hash value. Finally, it is only necessary to compare whether the calculated root hash is consistent with the root hash recorded on the block. If it is consistent, it indicates that the transaction is indeed recorded in the block; otherwise, it indicates that the transaction does not exist.
 
        In this way, each block will record transactions of about 10 minutes and all transactions will be traceable. The double flower problem can be solved through the verification of the transaction. Generally, in a transaction, for example, a needs to pay 10 bitcoins to B. Then a has to prove that it has obtained a certain amount of bitcoin in the previous block. This is called outputscript. For example, C paid 8 bitcoins to a and D paid 5 bitcoins to a. In this way, when a transfers money to B, it needs to be clearly pointed out that C and d once gave him 13 bitcoins in total, so that the transaction can be successfully completed. At the same time, the remaining three bitcoins need a to establish a new change account for storage, or they will be taken away by the miners as transaction fees.
 
        Do you think it's troublesome to prove that the money you have is legal every time you give money to others. Therefore, Ethereum established an account based block so that the balance of an account can be recorded explicitly without multiple verification like bitcoin. It has entered programmable applications and extended to asset types such as stocks, bonds and loans, and developed autonomous organizations and smart contracts. The most famous leader is. (blockchain) refers to the technical solution to collectively maintain a reliable database through centralization and distrust. This technical scheme allows any number of nodes participating in the system to calculate and record all transactions in the system for a period of time into a data block through a cryptographic algorithm, and generate the hash of the data block for use.
 
        One sentence explanation: a distributed accounting system based on cryptography algorithm, consensus mechanism, point-to-point transmission, mathematics, computer programming and other technologies. 1、 Yes. In 2008, a cryptographer named Satoshi Nakamoto published an article bitcoin: apeer to peer electronic cashsys. The system is used to record orderly and time stamped transaction records. It is mainly used to prevent double flower attacks and tampering with previous transaction records. Here, we need to pay attention to tampering prevention, not change prevention.
 
        actually. In, there is a phenomenon of redundant backup. That is to say, if all nodes need to save all transactions and other data information of the whole network, some disadvantages will inevitably occur, for example, users want to create their own. If the node carries out project development without participating in the consensus process, data synchronization will be a particularly huge task, which is time-consuming and resource consuming. All nodes: in. In, there is a kind of node called full node, that is, it stores the transaction data of the whole network, and can complete the relevant verification transactions and independently complete the connection with the peer nodes. In other words, this type of node stores a complete local.
 
        Reprinted from: introduction 1.1 overview merklepatricia tree (also known as merklepatricia tree) is an improved data structure that combines the advantages of Merkel tree and prefix tree. Is used to organize and manage account data and generate transaction set hash. MPT tree has the following functions: storing key value pair data of arbitrary length; Provides a. The basic workflow is summarized. In the process of executing the consensus algorithm, POW mechanism is taken as an example to explain. POW is the original.
 
        Various improvements have been made to the consensus algorithm. Among them, POS is the most important. Other dpos, POW + POS are all changes to pos. Nodes are used to develop DAPP, but they do not want to participate in the consensus. For this user, synchronizing a large amount of data is very time-consuming and consumes hard disk resources. Will. It was proposed in 2008 that its purpose is to build an electronic cash system that is completely realized through peer-to-peer technology, without any financial institutions. The main role of intermediary financial institutions is to:. Build a transit transaction bridge (ALT; gt; MLT; gt; b) between two trading parties who do not trust each other.
 
        The official account of information, but for more than half a year, most of them have scratched the surface of the water, tasted it, and surfaced on the surface, but they have no idea. Now I feel a little epiphany. Look. It is a popular new concept at present, which contains two concepts of technology and finance. From a technical point of view, this is a distributed database that sacrifices consistency efficiency and ensures final consistency. Of course, this is one-sided. From the perspective of economics, this kind of peer-to-peer network with strong fault-tolerant ability just meets a low-cost trusted environment required by the sharing economy. Let's share this time.
 
        
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