What is a blockchain?

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What is the principle of blockchain?

Blockchain is essentially a distributed database. When many people mention blockchain, they naturally think of Bitcoin, but blockchain is not equal to Bitcoin. Blockchain is a technology, including asymmetric encryption, consensus algorithm, smart contract, distributed storage and many other underlying technologies. There are many applications of blockchain at present, and Bitcoin is just one of the well-known blockchain applications.

The chain of bitcoin is composed of many blocks containing bitcoin transaction information. The serial mode is that the blocks are generated in chronological order, and each block refers to the hash value of the previous block, and this block is stamped with time stamp and hashed to ensure the chronological order. The first block of Bitcoin was created and recorded by Satoshi Nakamoto in 2009. Bitcoin generates one block every ten minutes. Up to now, the whole network has generated nearly 700,000 blocks.

What is a node and what is distributed accounting?

Nodes are network nodes in the blockchain, generally referring to computers, servers or other devices connected to the network. Take Bitcoin as an example. In theory, only by downloading complete blockchain data and participating in mining and trading can it be called a node. But now, this kind of node is called a full node, while the node that only participates in trading is called a light node. At present, most of the bits in the network are light nodes, and a few are full nodes.

Light nodes refer to nodes that only participate in bitcoin transactions. They do not own complete blockchain data, and they need to rely on other information provided by the whole node to verify the transaction information. Light nodes are generally related to ordinary users.

A full node refers to a node that completely owns the data on the blockchain and can continuously synchronize. It can participate in bitcoin mining, completely verify the transaction and block information it receives, and send them to other full nodes after verification. Of course, it can also accept transaction information from light nodes, and when it finds that a transaction will affect the wallet controlled by a light node, the whole node will try to inform these light nodes, and the whole node is generally related to miners.

After knowing the nodes, it is necessary for us to know what distributed accounting is. Simply put, blockchain is a distributed ledger database that is jointly participated, verified and maintained by different nodes. Different from the traditional centralized way, the account book of blockchain is not in the hands of one person, but is openly placed in an organizational network maintained by many parties on an equal footing. Only when more than 51% of the participants approve a page account book, then the content of the page account book will be confirmed. Distributed bookkeeping has three main characteristics, each part can be executed in parallel, each part does not need a unified time, and any part error will not affect other parts.

We can learn more about distributed bookkeeping through an example.

In one class, all the income and expenditure of class fees are recorded by the monitor. Because he is the monitor, everyone naturally trusts him, and no one goes to audit the accounts. But one day, classmate Xiao A went to audit the accounts. He was surprised to find that the income and expenditure of the account books were completely different, and the personal problems of the monitor led to bad debts. This is a typical centralized bookkeeping method, but the disadvantage is that it relies too much on centralized bookkeepers, who are prone to evil and have opaque information.

So, everyone decided to change the bookkeeping method, that is, every student in the class holds a small ledger. Whenever the class fee changes, any student can record the class fee and broadcast it loudly to other students. After more than 51% of the students check it correctly, they can add this transaction to their own ledger, and this transaction will be confirmed. Because the students jointly maintain this account book, even if some of them remember or miss it, but because of the principle that the minority is subordinate to the majority, as long as they check with most of the students and update the account book again, everyone will be in a synchronized state, so the account book can keep its accuracy.

What are the characteristics of blockchain?

Typical characteristics of blockchain:

① Decentralization. Just like the example we gave above, all the data information is recorded in the distributed ledger, and no one can tamper with the data through the centralized server. If you intend to tamper with the data, you must control at least 51% of the database, which greatly increases the cost of the perpetrators and guarantees the data security to the maximum extent.

② Non-tampering. All the blocks used to record transaction information in the blockchain are arranged in chronological order from beginning to end. If you want to modify the data in any block, you need to regenerate all the data after this block. Take Bitcoin as an example. In theory, if you want to modify a certain data on Bitcoin, you need to master 51% of the computing power of the whole network, and the funds involved are basically astronomical figures. Moreover, if someone can master more than 51% of the computing power in Bitcoin network, the income from tampering with the data will be far lower than the income from maintaining the normal operation of this account book. It must be said that the design mechanism like Satoshi Nakamoto has a profound insight into human nature.

③ Anonymity. Take Bitcoin as an example. The transaction history of Bitcoin is completely open. Everyone can check the inflow/outflow of funds at an address in the blockchain browser, and can also trace the transactions of other addresses that have interacted with the address. But its anonymity lies in that we can only know the assets and flows of an address, but we don't know who is behind this address.

④ Traceability. Blockchain is composed of "block+chain", and all data are recorded in the blockchain network according to the sequence of occurrence time, which is interlocking, so each transaction data can be traced back to the source through the chain structure.