Beginners' Notes | What is blockchain?

Blockchain (Blockchain) has been hot for a long time, and it will explode in 2021. Take the notes in the learning process and organize a content that novices can understand, and skip a lot of technical details. If there are experts passing by, please ask Whip a little harder!

Dismantling the blockchain, starting from the concept of block and chain:

What is a block (BlockK)?

block = transaction data + verification message

In the blockchain network, when someone sends transaction information, for example, A wants to pay B, A tells everyone on the Internet that he has a transaction to execute, and the accounting workers on the Internet, commonly known as "miners", will The transaction is packaged into a "block". In order to confirm that the information on this "block" is correct, this "block" contains three kinds of information:

The transaction data of this block, the unique identification code of this block, the identification code of the previous block

How does a block become a chain?

As mentioned above, each block contains a unique identification code, as well as the identification code of the previous block. These identification codes can be verified with each other through the mechanism of mathematics and cryptography. The identification code of the previous block is included, so the time series can be easily sorted out to ensure the order of transactions, and it becomes a whole chain of blockchains, like the picture below

Features of Blockchain

1. Disperse in each household (aka. "Decentralization")

In the past, our transaction data may have been stored in the data center of a company or bank. If this data center is damaged, hacked or made mistakes, all transaction records and results will disappear or the results will not be as expected. Think about the assets in the account returning instantly. Zero, isn't it scary?

But in the world of blockchain, every computer (or node) has records. If the data of one computer is wrong or disappears, there are other computers that record transaction information, which means there are many backups. file meaning

Some people will ask, if there are two different files, how do you know who is right and the latest?

2. Consensus mechanism

The operation of the blockchain is based on the fact that all nodes have the same consensus, so that they can cooperate with each other and ensure the correctness of the continuation data. One of them is the "longest chain consensus": as mentioned above, the block contains the previous block. When the new block uses A or B as the previous block, the chain becomes longer than the other fork, at this time, all nodes (the entire network) will be based on The "Longest Chain Consensus" recognizes that the one with new transactions is the main chain to be retained. It can be understood by the following diagram. When C appears after B, the following one becomes the longest chain that everyone agrees on, and A also becomes invalid. Now, if the data is still on the chain, the transaction message must be re-sent:

Is it possible to maliciously manipulate your data into the longest chain recognized by everyone?

It is possible, and this situation is the so-called "51% attack"; in the world of Bitcoin, using a high degree of computing advantages to allow yourself to dominate and quickly generate new blocks will be recognized by the entire network; but practical In addition to having strong computing power to master new blocks, all records can be checked. When everyone finds that the computing power is mastered by a specific person, the entire chain will have a crisis of information and life. collapse

In this note, the basic concept of blockchain will continue to be a series of notes for beginners entering the village~