Picture of 147 blockchain

1.

The strict definition of blockchain refers to the distributed database technology that multiple nodes in peer-to-peer network jointly maintain a continuously growing list ledger constructed by time stamp and orderly record data blocks through consensus mechanism based on cryptography technology. This technical solution allows any number of nodes in the participating system to calculate and record all the information exchange data in the system in a period of time to a data block through cryptography algorithm, and generate the fingerprint of the data block for linking the next data block and checking. All participating nodes in the system jointly determine whether the record is true

blockchain is a technical solution similar to NoSQL (non relational database). It is not a specific technology, and can be implemented through many programming languages and architectures. There are many ways to realize blockchain, including pow (proof of work), POS (proof of stake), dpos (delegate proof of stake), etc

the concept of blockchain was first proposed in the paper "bitcoin: a peer-to-peer electronic cash system" by indivials (or groups) who call themselves Satoshi Nakamoto. Therefore, bitcoin can be regarded as the first application of blockchain in the field of financial payment

< H2 > [popular explanation]

no matter how big the system or how small the website is, there is a database behind it. So who will maintain this database? In general, who is responsible for the operation of the network or system, then who is responsible for the maintenance. If it is wechat database, it must be maintained by Tencent team, and Taobao database is maintained by Alibaba team. We must think that this way is natural, but blockchain technology is not

if we think of the database as a book, for example, Alipay is a typical account book. Any change of data is bookkeeping. We can think of database maintenance as a very simple way of accounting. In the world of blockchain, everyone in the blockchain system has the opportunity to participate in bookkeeping. The system will select the fastest and best bookkeeper in a period of time, maybe within ten seconds or ten minutes. The bookkeeper will record the changes of the database and the account book in a block. We can think of this block as a page. After the system confirms that the records are correct, the system will record the changes of the database and the account book in a block, It will link the fingerprint of the past account book to this paper, and then send this paper to everyone else in the whole system. Then, over and over again, the system will look for the next person with fast and good bookkeeping, and everyone else in the system will get a of the whole ledger. This means that everyone as like as two peas in the system is called Blockchain. It is also called distributed account technology. P>

as like as two peas (computer) have identical accounting books, and everyone has the same rights, they will not collapse e to the loss of contact or downtime of a single person. As like as two peas, the data is transparent and everyone can see what changes are in every account. Its very interesting feature is that the data can't be tampered with. Because the system will automatically compare, it will think that the same number of books with the largest number are real books, and a small number of books with different numbers are false books. In this case, it's meaningless for anyone to tamper with his own account book, because unless you can tamper with most nodes in the whole system. If there are only five or ten nodes in the whole system, it may be easy to do so. However, if there are tens of thousands or even hundreds of thousands of nodes and they are distributed in any corner of the Internet, unless someone can control most computers in the world, it is unlikely to tamper with such a large block chain

< H2 > [elements]

combined with the definition of blockchain, we think that we must have the following four elements to be called public blockchain technology. If we only have the first three elements, we will consider it as private blockchain Technology (private chain)

1, peer-to-peer network (power equivalence, physical point-to-point connection)

2, verifiable data structure (verifiable PKC system, non tampering database)

3, distributed consensus mechanism (Solving Byzantine general problem, solving double payment)

4 Game design of Nash equilibrium (cooperation is the strategy of evolutionary stability)

< H2 > [Characteristics]

combined with the definition of blockchain, blockchain will realize four main characteristics: decentralized, trustless, collective maintenance and reliable database. And the other two will be derived from the four characteristics  Features: open source  Privacy. If a system does not have these characteristics, it can not be regarded as an application based on blockchain technology

Decentralized: there is no centralized hardware or management organization in the whole network. The rights and obligations of any node are equal, and the damage or loss of any node will not affect the operation of the whole system. Therefore, it can also be considered that the blockchain system has excellent robustness

trustworthiness: there is no need to trust each other when participating in the data exchange between each node in the whole system. The operation rules of the whole system are open and transparent, and all data contents are also open. Therefore, within the specified rule range and time range of the system, nodes cannot and cannot cheat other nodes

collective maintenance: the data blocks in the system are maintained by all the nodes with maintenance function in the whole system, and these nodes with maintenance function can be participated by anyone

reliable database: the whole system will enable each participating node to obtain a of the complete database in the form of sub databases. Unless more than 51% of the nodes in the whole system can be controlled at the same time, the modification of the database on a single node is invalid, and the data content on other nodes cannot be affected. Therefore, the more nodes and computing power in the system, the higher the data security in the system

Open Source: since the operation rules of the whole system must be open and transparent, the whole system must be open source for the program

Privacy Protection: since there is no need to trust each other between nodes, there is no need to disclose the identity between nodes, and the privacy of each participating node in the system is protected

2. Basically, the principle is the same. Take baopin.com as an example, baopin.com's video blockchain authentication is actually DAPP. First, it takes a screenshot of the video's key frames per minute, then transcodes it into a string of unique numbers, and then uploads and records it into the Ethereum blockchain.

3. 1. Public chain, no official organization and management organization, no central server, participating nodes freely access to the network according to the system rules, not controlled, and work based on consensus mechanism among nodes Subversive: absolutely credible and open) < br > typical case: digital currency represents bitcoin < br > 2. The private chain is built within a group. The operation rules of the system are set according to the requirements of the group, and the modification or read permissions are limited to some extent, while maintaining the authenticity and partial decentralization of the blockchain Typical case: R3 < br > 3. Alliance chain, jointly initiated by several institutions, is between the public chain and the private chain, and has the characteristics of partial decentralization. The read permission on the fast chain in this area may be public or partially public, that is to say, multiple pre selected nodes are designated as bookkeepers internally, and the pre selected nodes compete for bookkeeping permission, Other access nodes can participate in the transaction, but not the accounting process The abilities of the candidates should not be uneven< Br > (relatively credible and open) < br > existing cases: Super ledger < br > example:? In the case of loan diversion, when the user jumps to the other party's website for registration through our link, the docking party can choose to cheat and say that it has not received the user's registration request. However, if we put the user registration behavior into the block, if the docking party wants to receive the user registration behavior, it must pay us at the same time.

4.

A: the basic characteristics of blockchain

I. decentralization
blockchain technology does not rely on additional third-party management institutions or hardware facilities, and there is no central control. In addition to the self-contained blockchain itself, each node realizes information self verification, transmission and management through distributed accounting and storage

Second, openness

the foundation of blockchain technology is open source. In addition to the private information of all parties involved in the transaction is encrypted, the data of blockchain is open to everyone. Anyone can query blockchain data and develop related applications through the open interface, so the information of the whole system is highly transparent

Third, independence

based on consensus specifications and Protocols (similar to various mathematical algorithms such as hash algorithm used by bitcoin), the whole blockchain system does not rely on other third parties, and all nodes can automatically and safely verify and exchange data in the system without any human intervention

Four, safety

as long as 51% of all data nodes cannot be controlled, the network data cannot be arbitrarily controlled and modified, which makes the blockchain itself relatively safe and avoids subjective and artificial data changes

5. Anonymity

unless there are legal requirements, technically speaking, the identity information of each block node does not need to be disclosed or verified, and the information transmission can be anonymous

5. 1. Radiation engineers have strong lethality to infantry and non armored combat vehicles
2. Radiation engineers have less damage to armored combat vehicles
3. Radiation engineers have no damage to spiders and mining vehicles
4. Radiation engineers have no damage to buildings

these are the original data

6. The solutions are as follows:
1. Regularly clean the st in the computer, turn off the computer, open the chassis, use a hair dryer and blow with cold air< At ordinary times, 360 guard, Jinshan guard and other tools should be used to clean up the system garbage and temporary files generated by the Internet, and check and kill malicious

Italian software
3. The computer configuration is poor, so try to set the virtual memory as large as possible, and install anti-virus software with less resources, such as NOD32, or only one

auxiliary anti-virus software
4. Try to set the IP to static IP, which can rece the startup time of the computer
5. Don't put too many files and icons on the computer desktop, which will slow down the reaction of the computer. Try not to install the software on disk C
6. Regularly defragment the disk. Open the drive of my computer to defragment - properties - tools

select the disk to be defragmented. Open the "disk defragmenter" window - Analysis - defragmentation - the system will start to defragment

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7. QQ coin is a kind of virtual currency issued by Tencent in order to facilitate users to purchase the virtual goods and services it provides. Its official price is: 1q coin = 1 yuan. However, if the amount of recharge is large, there will be a certain amount of discount on some recharge platforms
it should be noted that this is the recharge price. If it's selling q-coin, because q-coin recycling is now done by some third-party platforms, there will be a certain cost. Therefore, the recovery price of Q coin is generally lower than the recharge price, remember!

8. What is the longest chain? Why the right blockchain
according to the white paper of bitcoin, nodes always think that the longest chain is the right blockchain and will continue to extend on it. All miners are mining on the longest chain, which is concive to the uniqueness of blockchain ledger. If the bitcoin transaction transferred to you is not recorded on the longest chain, you may face property losses
what is the "longest blockchain"? Because the miners all over the world are mining at the same time, it is possible that two miners can work out the correct answer at the same time, then the blockchain will form a fork, and the remaining miners may continue to mine on any fork, extending the blockchain
therefore, we usually require that after the bitcoin transfer is packaged, we need to go through the confirmation of six blocks to ensure that the miners will not go back to the other branch to excavate, then the real transfer is successful.

9.

12.4km

take bus 857, pass 20 stops, and reach lianbanwai book city station

walk about 710 meters to the South of lianbanxin village