1. Background
One daily transfer
The hidden dangers of the tripartite secured transaction model:
Transactions in daily life rely on third-party guarantee institutions, such as banks, WeChat, Alipay, etc. The trust of third-party guarantee institutions collapses. In a completely anonymous decentralized network, how do users transfer money?
2. What is blockchain
On October 31, 2018, Satoshi Nakamoto demonstrated and solved this problem with a 9-page paper.
Core Definition: A special kind of distributed database. Distributed databases are not new inventions, there are already such products on the market. However, blockchain has a revolutionary feature.
The blockchain has no administrator, it is completely centerless. Other databases have administrators, but blockchains do not. If someone wanted to add auditing to the blockchain, it wouldn't be possible, as it was designed to prevent the emergence of a central authority. It is precisely because it cannot be managed that the blockchain can be uncontrollable. Otherwise, once the big companies and groups control the management, they will control the entire platform, and other users will have to obey them.
The next transaction behavior in the blockchain scenario:
Everyone has a ledger of all transaction records that are created from the blockchain. Whenever a transaction occurs, everyone will verify whether the transaction is OK through the broadcast electronic signature (transfer behavior data). After the verification is successful, the transfer is recorded in the ledger, and the transaction is completed.
The ledger is the block, and when the blocks are connected, it is the blockchain. The blockchain records all the transaction records of Bitcoin from its creation to today. As of 2020, there will be about 60W blocks, and each block has about two or three Thousands of transactions; in the blockchain network, everyone holds the same account book that is updated in real time, so when I want to transfer 100 yuan to Jack Ma, all the books will start to backtrack the transaction records to check whether you have 100 block, if not, the transfer is invalid, which raises two problems:
Who will do the accounting for you?
In a decentralized scenario, everyone has the right to keep accounts, so the transactions and transaction sequences contained in each block may be different, so who should keep accounts for a transaction? Satoshi Nakamoto's plan is to do the problem (POW, Proof of Work). Simply put, whoever does the math quickly listens to the other, and the first person who successfully calculates will receive a reward.
How to ensure that the ledger is not tampered with?
The flow of a billing behavior is shown in the following figure:
Simply put, it is guaranteed by the hash value in the block. Each block stores the hash value of the previous block. If someone tampers with the transaction data, the hash value of the current block and all subsequent blocks need to be recalculated. The block hash value, the current probability of successful calculation of each block is 1 in 755 trillion, calculated with a NVIDIA latest 2080TI graphics card, it will take about 1407 years.
Find a random number to calculate the hash value that finally meets the conditions. This process is mining. As long as you calculate the hash value, everyone can instantly verify whether the calculation is correct or not. If there is no problem with the block, everyone will This block is added to the ledger and the calculation of the next block begins, so that everyone in the network has an identical and real-time updated ledger.
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