The definition, classification and principle of blockchain
In "Bitcoin: A Peer-to Peer Electronic Cash System" written by Satoshi Nakamoto, the descriptive concept of Blockchain was first proposed, but this work mainly discusses the Bitcoin system. For blockchain However, there is no too in-depth summary and refinement, in fact, no definitions and concepts in an objective sense are proposed. In this book, the blockchain is a data structure used to record the history of Bitcoin transaction accounts.
Blockchain is a distributed shared ledger and database , which has the characteristics of decentralization, non-tampering, full trace retention, traceability, collective maintenance, openness and transparency. These characteristics ensure the "honesty" and "transparency" of the blockchain and lay the foundation for the creation of trust in the blockchain. The rich application scenarios of the blockchain are basically based on the ability of the blockchain to solve the problem of information asymmetry and realize the cooperative trust and concerted action between multiple subjects .
Blockchain is a new application mode of computer technology such as distributed data storage, point-to-point transmission, consensus mechanism, and encryption algorithm. Blockchain is an important concept of Bitcoin. It is essentially a decentralized database. At the same time, as the underlying technology of Bitcoin, it is a series of data blocks that are generated using cryptographic methods. Each data block Contains a batch of Bitcoin network transaction information, used to verify the validity of the information (anti-counterfeiting) and generate the next block.
Blockchain classification
In terms of participation methods, blockchain can be divided into: Public Blockchain, Consortium Blockchain, and Private Blockchain ; from the relationship between the chain and the chain, the blockchain can It is divided into main chain and side chain; different blockchains can also communicate with each other. This kind of interoperability between chains gives rise to the concept of interconnected chains .
1. Public chain The
public chain is completely open to the public and users can participate anonymously without registration, and can access the network and blockchain without authorization. Nodes can choose to access the network freely.
Public chain is completely decentralized to block chain in the true sense, it can not be tampered with by the transaction cryptographic assurance, as well as the use of cryptography to verify and encourage economic multiple nodes in a network environment to build consensus, to form the go Centralized credit mechanism .
The consensus mechanism in the public chain is generally Proof of Work (PoW) or Proof of Stake (PoS) . The proportion of resources owned by users in the network directly determines its influence on the formation of consensus.
Public chains are usually called Premissionless Blockchains . Typical public chains are Bitcoin and Ethereum ; public chains are generally more suitable for B2C, C2C, or C2B such as virtual currency, mass-oriented e-commerce, Internet finance, etc. Application scenarios.
2. Consortium chain
Consortium chain is limited to the participation of alliance members. Whether it is the read and write permissions on the blockchain or the permission to participate in accounting, it is determined by the rules of the alliance. For example, Hyperledger supported by the Linux Foundation belongs to the consortium chain architecture. Because the consortium chain is a blockchain that requires registration permission, it can also be called a permission chain (Premission Blockchain) .
The consensus process of the alliance chain is controlled by pre-selected nodes. It is suitable for B2B scenarios such as transactions, settlement or clearing between institutions. It should be noted that the alliance chain generally does not use the proof-of-work mining mechanism. The reason is nothing more than too few nodes participating in the consensus. Consortium chains generally use proof of rights or consensus algorithms such as PBFT and RAFT .
The number of transactions per second in the confirmation time of the consortium chain is quite different from that of the public chain, and the requirements for the security and performance of the transaction are much higher than that of the public chain.
3. Private chain The
private chain is different from the above. It is only used in private organizations. The read and write permissions on the blockchain and the permissions to participate in accounting are determined by the rules of the private organization. The usage scenarios of private chains are generally enterprise internal applications, such as database management and auditing. There are also some special circumstances, such as the application in the government industry: government budget and execution or government industry statistics. This is generally calculated by the government, but the public has the right to supervise.
The value of the private chain is mainly that it provides a safe, traceable, non-tamperable, automatic execution computing platform, and can prevent internal or external security attacks on data .
Similar to the consortium chain, the private chain is also a permission chain .
How blockchain works
The blockchain system is composed of data layer, network layer, consensus layer, incentive layer, contract layer and application layer .
Among them, the data layer encapsulates the underlying data blocks and related data encryption and time stamping and other basic data and basic algorithms; the network layer includes distributed networking mechanisms, data propagation mechanisms, and data verification mechanisms; the consensus layer mainly encapsulates network nodes The incentive layer integrates economic factors into the blockchain technology system, including the issuance mechanism and distribution mechanism of economic incentives, etc.; the contract layer mainly encapsulates various scripts, algorithms and smart contracts, which is a blockchain The basis of programmable features; the application layer encapsulates various application scenarios and cases of blockchain.
In this model, the chain block structure based on timestamp, the consensus mechanism of distributed nodes, the economic incentive based on consensus computing power and the flexible and programmable smart contract are the most representative innovations of blockchain technology.