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This article is a prelude, originally intended to introduce the Azure Blockchain Service on Azure, found that we need to start from what is the blockchain.

What is a blockchain? Let's start with Bitcoin. In November 2008, Satoshi Nakamoto presented a Bitcoin white paper, and there have been no major security incidents in the Bitcoin system since 2009.

1. The underlying technology of Bitcoin is blockchain.

two。 Bitcoin is a peer-to-peer electronic cash system (payment field)

3. The system is based on block chain technology.

4. Through the block chain technology, the system makes peer-to-peer electronic transactions without intermediate verification.

5. It has the nature of experiment and has been running for 10 years, without major problems.

To simply understand the blockchain, start with a story:

The story of Zhang San transferring 1000 yuan to Li Si:

1. Zhang San gave a roar. I transferred 1000 yuan to Li Si.

two。 The villagers near Zhang San heard the cry and confirmed that Zhang San had enough balance.

3. After the villagers checked, each villager recorded in his own ledger:

Zhang San transferred to Li Si 1000, Zhang San 3000-1000 million 2000; Li Si 200-1000 years 1200

4. The villagers near Zhang San told the neighboring village about the transfer, and the neighboring village told the neighboring village that people all over the world knew about it and recorded it in their own books.

How many questions?

Li Si's question: will the account book be tampered with?

Villager A's question, why bother to record the transaction for Zhang San?

Who remembers the questions of all the villagers?

Will the ledger be tampered with?

It is generally understood that transactions over a period of time are put into a block, and the block is hashed (hash operation is understood as Hash algorithm can convert a data into a flag, which is closely related to every byte of the source data. Another feature of Hash algorithm is that it is difficult to find the inverse rule. If there is any change in the original data, the result of the hash operation will change), the hash value of the block will be generated, and if there is any change in the block, the hash value of the block will change greatly, and the result of the hash algorithm will be written to the next block. string the two blocks together.

If the previous billing (block) data is modified, its data fingerprint (hash) will change and will not correspond to the hash recorded in the next billing. All players will be able to recognize that this is a tampered invalid chain and discard it.

Therefore, through the block + chain way, the account can not be tampered with.

As Pucun A, why bother to keep accounts?

Because there are benefits, that is, the so-called miners' incentives, the first person who gets the right to keep accounts will be rewarded.

Who remembers?

Proof of workload (PoW). Whoever first calculates the answer to a question will be based on his ledger, and others will copy it. The answer to a question is actually a random number in the block.

Several characteristics of block chain:

1. Decentralized decentralized system, there is no intermediary, the rights and obligations of all nodes are equal, any node stops working will not affect the operation of the system as a whole

two。 All the nodes in the Trustless system can trade without trust, because the operation of the database and the whole system is open and transparent, and within the rules and time frame of the system, nodes cannot deceive each other.

3. The collective maintenance (Collectively Maintain) system is jointly maintained by all the nodes with maintenance functions, and all people in the system participate in the maintenance work.

4. Reliable database (Reliable Database) system each node has the latest complete copy of the database, it is not valid to modify the database of a single node, because the system will automatically compare and assume that the same data records that appear the most times are true.

Blockchain is not a new technology, but a combination of a set of technologies:

Core technology-distributed ledger

Send the correct ledger to others through P2P.

Core Technology-Cryptography

Mainly in the next block, the hash value of the previous block is stored.

Core technology-block composition

Core Technology-distributed consensus

Core Technology-Intelligent contract

Technological Evolution of Block chain

It is generally believed that the block chain has gone through three stages:

Encrypted currency stage: it refers to the encrypted currency stage represented by the bitcoin system.

Digital assets, encrypted finance: in 2013, ethernet founder Vitalik Buterin released the first edition of etherfang white paper in the context of the development of bitcoin into universal mining. Yi Tai Fang introduces the concept of intelligent contract, which, in a real sense, can meet the needs of commercial application release. Unlike the first stage, which only serves cryptocurrencies such as Bitcoin, blockchain 2.0 relies on Ethernet Square, which can be used to program, distribute, guarantee and trade anything, thus realizing the spread and expansion of blockchain + applications. Most blockchain applications are based on Ethernet Square, such as Ethernet cats, block chain games such as meta-chain galaxies, various encryption dogs, and so on.

With the further development of blockchain technology, its "decentralization" function and "data anti-counterfeiting" function have been paid more and more attention in other fields. People begin to realize that the application of blockchain may not only be limited to the financial field, but also can be extended to any field where there is demand. Therefore, outside the financial field, blockchain technology has been applied to notarization, arbitration, audit, domain name, logistics, medical care, e-mail, authentication, voting and other fields, and the scope of application has been extended to the whole society.

In the three stages, the first two are mainly open block chains, which also become public chains. At the beginning of the third stage, there are private chains, alliance chains and other forms.

Classification of block chains:

Public chain refers to the block chain that anyone can read, anyone can send the transaction and the transaction can be effectively confirmed, and anyone can participate in the consensus process.

Public chain adopts the methods of workload proof mechanism (POW), equity proof mechanism (POS), share authorization proof mechanism (DPOS), and combines economic reward with encrypted digital verification, and establishes a principle that the economic reward that everyone can get from it is proportional to the workload. These blockchains are generally considered to be completely decentralized.

A private chain is a block chain whose write permission is in the hands of only one organization. Read permissions are either open to the public or are restricted to any extent. Related applications include database management, auditing, and even a company, although in some cases it is expected to be publicly auditable, but in many cases, public readability is not necessary.

The degree of openness and decentralization of the alliance chain is limited. Its participants are filtered out in advance or specified directly, and the read permissions of the database may be public, or they may be limited to the participants of the system just like write permissions.

Typical application of block chain: currency ring + chain ring

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