Blockchain multiple choice questions

1.

From the perspective of technology and architecture, I will tell you my understanding of blockchain in common language

what is blockchain? In a word, blockchain is a storage system. To be more specific, blockchain is a distributed storage system without an administrator and each node has all the data

What are the common storage systems like

first, how to ensure high availability

the common storage system usually uses "rendancy" to solve the problem of high availability. As shown in the figure above, if the data can be copied into several copies and rendant to multiple places, high availability can be guaranteed. The data in one place is hung, and there is data in other places. For example, the master-slave cluster of MySQL is the same principle, and the raid of disk is also the same principle

two points need to be emphasized in this place are: data rendancy often leads to consistency problems

1. For example, in the master-slave cluster of MySQL, there is actually a delay in reading and writing, which means there is a inconsistency in reading and writing in a short period of time. This is a side effect of data rendancy

The second point is that data rendancy often reces the efficiency of writing, because data synchronization also consumes resources. If you add two slave libraries, the write efficiency will be affected. The common storage system is to use rendancy to ensure the high availability of data

so the second question, ordinary storage system, can write more

the answer is yes, for example, take this graph as an example:

in fact, MySQL can do a master-slave synchronization of al masters, master-slave synchronization of al masters, two nodes can be written at the same time. If you want to do a multi room multi live data center, in fact, multi room multi live data synchronization. What we should emphasize here is that multi-point writing often leads to the consistency problem of writing conflicts. Take MySQL as an example, suppose that the attribute of a table is self incrementing ID, then the data in the database is 1234 now. If one of the nodes writes and inserts a piece of data, it may become 5, and then these 5 pieces of data are synchronized to another master node, Before synchronization, if another write node inserts a piece of data, a piece of data with self incrementing ID of 5 will be generated. Then, after the generation, synchronize to another node, and the synchronized data will conflict with the two local 5's after it arrives, which will lead to synchronization failure and write consistency conflict. This problem will occur in the case of multi-point writing

how to ensure consistency in multi-point writing

the reform "Swan class" gives you more technical work

2. Jinwowo analysis believes that blockchain mainly solves the trust and security problems of transactions. Once the information is confirmed and added to the blockchain, it will be permanently stored. Unless more than 51% of the nodes in the system can be controlled at the same time, the modification of data on a single node cannot be realized. Therefore, the data stability and reliability of blockchain are very high
e to the use of Distributed Accounting and storage, there is no centralized hardware or management organization, the rights and obligations of each node are equal, and the data blocks in the system are jointly maintained by the nodes with maintenance function in the whole system.

3. Is this the college entrance examination?

4. 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.

5. For example, I borrow money from you in a village. Normally, if I am afraid that you will not repay the money, I can find an intermediary recognized by everyone, such as the village head as the guarantor, and sign an IOU. In this way, if you default at that time, I can find an intermediary to prove that you really owe me money, But there are two problems: 1. What if the village head finds out that his long lost son colludes with him to cheat you on money? 2. What if the middleman dies on the spot the next day! This is about trust and security. If the method of blockchain is to provide you with the certificate of the whole village (distributed), so that everyone knows about it and the other party can't default on it. Second, even if a small number of people or village heads deny (some nodes commit crimes) that they have lost the IOU or tampered with the content, there will still be others to make the basis

in other words, blockchain solves the problem of trust and security