Blockchain database issues

1. 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 />}
}

2. In one sentence, it is decentralization
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
in a narrow sense, blockchain is a kind of chain data structure that combines data blocks in chronological order in a sequential way, and it can not be tampered with and forged by cryptography
broadly speaking, blockchain technology is a new distributed infrastructure and computing method, which uses blockchain data structure to verify and store data, uses distributed node consensus algorithm to generate and update data, uses cryptography to ensure the security of data transmission and access, and uses intelligent contract composed of automated script code to program and operate data< Advantages:
1) the algorithm is simple and easy to implement
2) there is no need to exchange additional information between nodes to reach a consensus
3) it takes a lot of cost to destroy the system< Disadvantages:
1) waste of energy
2) it is difficult to shorten the block confirmation time
3) the new blockchain must find a different hash algorithm, otherwise it will face bitcoin attack
4) it is easy to generate bifurcation and needs to wait for multiple confirmations
5) there is no finality, and checkpoint mechanism is needed to make up for it.

3. Chongqing jinwowo: as for how to build a rigorous database, the method of blockchain is to innovate the structure of the database, divide the data into different blocks, link each block to the back of the previous block through specific information, and present a complete set of data in sequence, which is also the source of the three words "blockchain".

4. That's ten times the survival rate he set. If you lose one, you'll get ten. It's set in the game

5. This scoring trading platform has servers, wallets,
blockchain,
and the price is not expensive. Hundreds or thousands of yuan are OK

6. No

bitcoin trading platform has many running platforms, such as mtgox in Japan, bitcoin in China and so on
therefore, investors need to choose a reliable bitcoin trading platform. The reference factors are: 1. The longer the running time, the better; 2. The bigger the instry reputation, the better; 3. The larger the team size, the better; 4. Being able to visit<

it is suggested that China choose "fire coin net", which is cooperated by Wukou School of finance of Tsinghua University. Sequoia Capital has invested 10 million US dollars; The choice of coinbase in foreign countries is an important choice for Silicon Valley banks to invest.

7. Chongqing jinwowo analyzes and solves problems in the following ways:
first of all, by using all data chains in the blockchain for prediction and analysis, the regulatory authorities can timely discover and prevent possible systemic risks. The decentralized characteristics of the blockchain can eliminate the information island in big data risk control, and improve risk control through information sharing

secondly, the distributed database of blockchain can improve the poor quality of big data risk control data, and solve the problems of data format diversification, data form fragmentation, lack of effective data and incomplete data content

finally, blockchain can prevent data leakage. Because the blockchain database is a decentralized database, any node's operation on data will be found by other nodes, thus strengthening the monitoring of data leakage.

8. Big data refers to the data set that can not be captured, managed and processed by conventional software tools within a certain period of time. It is a massive, high growth rate and diversified information asset that needs new processing mode to have stronger decision-making power, insight and process optimization ability. 5V features of big data (proposed by IBM): Volume (large amount), velocity (high speed), variety (diversity), value (low value density), veracity (authenticity)