Blockchain create node directory

1. Nodes are the places where the blocks are connected, and the blocks need to be chained to be useful
core analysis:
1. Transparency, 2. Openness, 3. Information can not be tampered with, 4. Decentralization,
5. Detailed analysis
blockchain is a new application mode of distributed data storage, point-to-point transmission, consensus mechanism, encryption algorithm and other computer technologies. The so-called consensus mechanism is a mathematical algorithm to establish trust and obtain interests between different nodes in the blockchain system
1. In a narrow sense, blockchain is a kind of chained data structure composed of data blocks connected in sequence according to the time sequence, and it can not be tampered with and forged by cryptography
2. Broadly speaking, blockchain technology uses blockchain data structure to verify and store data, uses distributed node consensus algorithm to generate and update data, and uses cryptography to ensure the security of data transmission and access It is a new distributed infrastructure and computing method to program and operate data by using intelligent contract composed of automated script code.

2. const SHA256 = require(crypto-js/SHA256);< br />class Block{
constructor(index,timestamp,data,previousHash='&# 39;)< br />{
this.index=index;< br />this.timestamp=timestamp;< br />this.data=data;< br />this.previousHash=previousHash;< br />$this.hash=this.calculateHash();< br />}

calculateHash(){
return SHA256(this,index+this.previousHash+this.timestamp+JSON.stringify(this.data)).tostring();< br />}
}
class Blockchain{
constructor(){
this.chain=[this.createGenesisBlock()];<
}
/ / create a generated information block
creategenesis block() {
return new block (0, & quot; 01/01/2019",& quot; Genesis block", 0);
/ / the date is the user's data. In fact, it is the hash value obtained by adding several values together. Here, the information is encrypted and the picture is encrypted. Then the data is still stored in the database, but all the data are hash values. To get this data, you must know the hash value of the previous data block. Then, if the hacker needs to crack all the nodes, the hash value is decrypted, Then all the blocks from the first node to the last node can be decrypted to get the real data. So the security of data stored in the blockchain depends on whether the data is encrypted. If the plaintext is not encrypted, then it is not a blockchain
}
/ / get the last block
getlatesblock() {
return this.chain [this.chain. Length-1]
}
/ / create block
addblock (newblock) {
newblock. Previoushash = this. Getlatesblock(). Hash< br />newBlock.hash=newBlock.calculateHash();< br />this.chain.push(newBlock);< br />}
}

3. Blockchain mainly solves the trust and security problems of transactions, so it proposes four technological innovations to solve this problem:
(1) distributed ledger, that is, transaction bookkeeping is completed by multiple nodes distributed in different places, and each node records complete accounts, so they can participate in monitoring the legitimacy of transactions, At the same time, they can testify together
different from traditional distributed storage, the uniqueness of distributed storage of blockchain is mainly reflected in two aspects: one is that each node of blockchain stores complete data according to block chain structure, while traditional distributed storage generally stores data in multiple copies according to certain rules. Second, the storage of each node in the blockchain is independent and has the same status, which relies on the consensus mechanism to ensure the consistency of storage, while the traditional distributed storage generally synchronizes data from the central node to other backup nodes[ 8]
no single node can record the account data separately, so as to avoid the possibility that a single bookkeeper is controlled or bribed to record false accounts. In theory, unless all the nodes are destroyed, the accounts will not be lost, so as to ensure the security of the account data
(2) asymmetric encryption and authorization technology, the transaction information stored on the blockchain is public, but the account identity information is highly encrypted, which can only be accessed under the authorization of the data owner, thus ensuring the data security and personal privacy
(3) consensus mechanism is how to reach a consensus among all accounting nodes to determine the validity of a record, which is not only a means of identification, but also a means of preventing tampering. Blockchain proposes four different consensus mechanisms, which are suitable for different application scenarios and achieve a balance between efficiency and security
the consensus mechanism of blockchain has the characteristics of "the minority is subordinate to the majority" and "everyone is equal", in which "the minority is subordinate to the majority" does not completely refer to the number of nodes, but also can be the computing power, the number of shares or other characteristics that can be compared by computers“ "Everyone is equal" means that when the nodes meet the conditions, all nodes have the right to put forward the consensus results first, and then directly recognized by other nodes, and finally may become the final consensus results. Taking bitcoin as an example, the workload proof is adopted. Only when more than 51% of the accounting nodes in the whole network are controlled can a nonexistent record be forged. When there are enough nodes in the blockchain, this is basically impossible, thus eliminating the possibility of fraud.
(4) smart contract, which is based on these trusted and tamperable data, can automatically execute some pre-defined rules and terms. Take insurance as an example. If everyone's information (including medical information and risk occurrence information) is true and reliable, it is easy to carry out automatic claim settlement in some standardized insurance procts

4. Bitcoin blockchain is a bitcoin blockchain? No, the block stores the transaction. In the early stage, you will get a coin if you successfully build a block. In the later stage, you can only get the fees paid by the exchange. A currency is a string of digital signatures. It is a digital signature sent by the last owner to the receiver. Everyone can see who owns the currency from the transaction
does each node have complete blockchain data? You mean a user node? A user node needs to keep the of the block head of the longest workload proof chain, so it knows the data of all the block heads. It can move forward to know all the data on the block chain, but not all of them are saved. A block header is very small, only 80 bytes, which can be saved completely, because the generation of nodes is very slow. Even with the passage of time, the amount is not too large now.

5. The decentralized nodes in Chongqing jinwowo analysis blockchain technology are as follows:
every central node can generate blocks and write data, so every point is a central node, or the blockchain is decentralized. In order to control the whole system, more than half of the nodes must be controlled in order to control voting, so there is no administrator in this system.

6. It contains complete blockchain and network routing nodes, which are only used to synchronize blocks, participate in verification, and maintain connection with peer nodes.

7. Jinwowo analysis: a node is actually a computer (server) connected to the blockchain. Any connected computer can access the blockchain, so there are countless nodes on the blockchain; However, the number of blocks on the blockchain is limited, that is, one block is generated every 10 minutes, and no new blocks will be added after reaching a certain number.

8. What are the characteristics of public chain, private chain and alliance chain
according to the access mechanism, blockchain can be divided into three categories: public chain, private chain and alliance chain. Other types of blockchains may be born in the future
the public chain is open and transparent. Any indivial or group in the world can send transactions on the public chain, and the transactions can be effectively confirmed by the blockchain. Everyone can compete for bookkeeping rights. Bitcoin blockchain is a typical representative of public chain
the alliance chain is semi open. It is a blockchain used within a group or organization. Several nodes need to be designated as bookkeepers in advance. The generation of each block is decided by all preselected bookkeepers. Other nodes can trade, but they have no bookkeeping rights
the private chain is completely closed. Only the blockchain technology is used for bookkeeping, and the bookkeeping right is not open, and only internal transactions are recorded, which are exclusively enjoyed by companies or indivials.