Blockchain belongs to the category of computer
The strict definition of blockchain refers to the distributed database technology that multiple nodes in peer-to-peer network jointly maintain a continuously growing list ledger constructed by time stamp and orderly record data blocks through consensus mechanism based on cryptography technology. This technical solution allows any number of nodes in the participating system to calculate and record all the information exchange data in the system in a period of time to a data block through cryptography algorithm, and generate the fingerprint of the data block for linking the next data block and checking. All participating nodes in the system jointly determine whether the record is true
blockchain is a technical solution similar to NoSQL (non relational database). It is not a specific technology, and can be implemented through many programming languages and architectures. There are many ways to realize blockchain, including pow (proof of work), POS (proof of stake), dpos (delegate proof of stake), etc
the concept of blockchain was first proposed in the paper "bitcoin: a peer-to-peer electronic cash system" by indivials (or groups) who call themselves Satoshi Nakamoto. Therefore, bitcoin can be regarded as the first application of blockchain in the field of financial payment
< H2 > [popular explanation]no matter how big the system or how small the website is, there is a database behind it. So who will maintain this database? In general, who is responsible for the operation of the network or system, then who is responsible for the maintenance. If it is wechat database, it must be maintained by Tencent team, and Taobao database is maintained by Alibaba team. We must think that this way is natural, but blockchain technology is not
if we think of the database as a book, for example, Alipay is a typical account book. Any change of data is bookkeeping. We can think of database maintenance as a very simple way of accounting. In the world of blockchain, everyone in the blockchain system has the opportunity to participate in bookkeeping. The system will select the fastest and best bookkeeper in a period of time, maybe within ten seconds or ten minutes. The bookkeeper will record the changes of the database and the account book in a block. We can think of this block as a page. After the system confirms that the records are correct, the system will record the changes of the database and the account book in a block, It will link the fingerprint of the past account book to this paper, and then send this paper to everyone else in the whole system. Then, over and over again, the system will look for the next person with fast and good bookkeeping, and everyone else in the system will get a of the whole ledger. This means that everyone as like as two peas in the system is called Blockchain. It is also called distributed account technology. P>
as like as two peas (computer) have identical accounting books, and everyone has the same rights, they will not collapse e to the loss of contact or downtime of a single person. As like as two peas, the data is transparent and everyone can see what changes are in every account. Its very interesting feature is that the data can't be tampered with. Because the system will automatically compare, it will think that the same number of books with the largest number are real books, and a small number of books with different numbers are false books. In this case, it's meaningless for anyone to tamper with his own account book, because unless you can tamper with most nodes in the whole system. If there are only five or ten nodes in the whole system, it may be easy to do so. However, if there are tens of thousands or even hundreds of thousands of nodes and they are distributed in any corner of the Internet, unless someone can control most computers in the world, it is unlikely to tamper with such a large block chain
< H2 > [elements]combined with the definition of blockchain, we think that we must have the following four elements to be called public blockchain technology. If we only have the first three elements, we will consider it as private blockchain Technology (private chain)
1, peer-to-peer network (power equivalence, physical point-to-point connection)
2, verifiable data structure (verifiable PKC system, non tampering database)
3, distributed consensus mechanism (Solving Byzantine general problem, solving double payment)
4 Game design of Nash equilibrium (cooperation is the strategy of evolutionary stability)
combined with the definition of blockchain, blockchain will realize four main characteristics: decentralized, trustless, collective maintenance and reliable database. And the other two will be derived from the four characteristics Features: open source Privacy. If a system does not have these characteristics, it can not be regarded as an application based on blockchain technology
Decentralized: there is no centralized hardware or management organization in the whole network. The rights and obligations of any node are equal, and the damage or loss of any node will not affect the operation of the whole system. Therefore, it can also be considered that the blockchain system has excellent robustnesstrustworthiness: there is no need to trust each other when participating in the data exchange between each node in the whole system. The operation rules of the whole system are open and transparent, and all data contents are also open. Therefore, within the specified rule range and time range of the system, nodes cannot and cannot cheat other nodes
collective maintenance: the data blocks in the system are maintained by all the nodes with maintenance function in the whole system, and these nodes with maintenance function can be participated by anyone
reliable database: the whole system will enable each participating node to obtain a of the complete database in the form of sub databases. Unless more than 51% of the nodes in the whole system can be controlled at the same time, the modification of the database on a single node is invalid, and the data content on other nodes cannot be affected. Therefore, the more nodes and computing power in the system, the higher the data security in the system
Open Source: since the operation rules of the whole system must be open and transparent, the whole system must be open source for the program
Privacy Protection: since there is no need to trust each other between nodes, there is no need to disclose the identity between nodes, and the privacy of each participating node in the system is protected
blockchain (English: blockchain or block chain) is a kind of distributed database . You may have heard about bitcoin, which is the core technology. Blockchain is a series of data blocks generated by cryptography. Each data block contains the information of a network transaction, which is used to verify the validity of the information and generate the next block. In a popular concept, blockchain is an account that everyone can keep. In a company or organization, most people only have the right to keep accounts, while only a few people with professional training have the right to keep accounts. Of course, blockchain is not an account book in the traditional sense. It has the following three key points in technical principle: first, decentralization. In a network practicing blockchain technology, each computer covered by it can read and add records. From the perspective of account book, they are the people who keep accounts together, and there is no authoritative person to guide and correct them. Second, asymmetric encryption. Although everyone can remember this account, they will not be able to read it unless they are in the Bureau. Because, in the accounting process, everyone follows the unified encryption rules, but when reading, they must use their own unique decryption method. Therefore, although everyone keeps this constantly updated account, the part they can read is only the one they can decrypt, that is, the part related to themselves. Third, time stamp. That is, time stamp (English: timestamp), refers to the string or coded information used to identify the recorded time and date. Each block on the blockchain is arranged in sequence according to the time it is generated, and is confirmed by collective authentication. Moreover, previous records cannot be modified. Just like in an account, we can index and verify the previous content through the records after a point in time. Once these contents are confirmed, it will be more difficult to tamper with them
blockchain technology is to maintain a growing distributed database of data records. These data are associated with all the data written before through cryptography technology, which makes it difficult for the third party or even the owner of the node to tamper with. Block contains the data that need to be saved in the database, and these data are written into the database through block organization. Chain usually refers to the use of Merkle tree and other methods to check whether all the current blocks have been modified. This is familiar to code farmers who have used git for a long time. Recall how to modify git's history
blockchain technology is mainly divided into three categories, which are open, collaborative and private
public blockchain
example: bitcoin, Ethereum frontier. The data on the public blockchain can be accessed by all people, and all people can issue transactions waiting to be written into the blockchain. Participants in the consensus process (corresponding to the miners in bitcoin) maintain the security of the database through cryptography technology and built-in economic incentives. Open blockchain is completely distributed
highlights and pain points: the open blockchain is completely distributed and has all the characteristics of bitcoin. However, it needs sufficient cost to maintain the system operation and relies on built-in incentives. At present, only bitcoin in the public blockchain is safe enough. If the algorithm is the same as bitcoin, it will be safe; There are no built-in rewards, but they are not; It's easy to concentrate on the attack of computing power (for example, as long as the raid sweeps goods and a large number of graphics cards), and take jujube pills. The more valuable the data on the open blockchain is, the more important it is to examine its security, transaction cost and system scalability
federated blockchain
example: audit system tried by hyperledger and Deloitte. The nodes participating in the blockchain are selected in advance, and there is likely to be a good network connection between the nodes. Other consensus algorithms without workload proof can be used on such a blockchain. For example, a blockchain has been established among 100 financial institutions, and more than 67 institutions must agree to reach a consensus. The data on such a blockchain can be public or internal to these node participants. Distributed in a partial sense
highlights and pain points: collaborative blockchain can achieve a good connection between nodes, only need a little cost to maintain operation, provide rapid transaction processing and low transaction costs, has good scalability (but the scalability will decline with the increase of nodes), and data can have certain privacy. Developers have the ability to change the protocol under the consensus. There is no problem with bitcoin hard fork, but it also means that everyone can tamper with the data together under the consensus. Collaborative blockchain also means that the application scope of this blockchain will not be too wide, lacking the network propagation effect of bitcoin
private blockchain
example: Eris instries. The participating nodes are only users themselves, and the access and use of data have strict authority management. Most of the blockchain technologies recently announced by some financial institutions for internal use are vague, but they are probably all within this scope
highlights and pain points: private blockchain is actually a confusing term. Such a system is nothing more than a shared database in the traditional sense. Merkle tree and other methods are used to try to show that the data in it is verifiable. There are already mature solutions for such databases, and Merkle tree is only one of many mature solutions. It's easy for these projects to be "like eggs". Because the user has the final say, the data inside can not be changed, and there is not much protection for the third party. Therefore, many private blockchains exist by attaching to bitcoin, such as recording system snapshots to bitcoin regularly
the core advantage of blockchain technology is decentralization, which can realize point-to-point transaction, coordination and cooperation based on decentralized credit in a distributed system without mutual trust by means of data encryption, time stamp, distributed consensus and economic incentive, so as to solve the high cost and low cost of centralized institutions Low efficiency and data storage insecurity provide solutions
the application fields of blockchain include digital currency, token, finance, anti-counterfeiting traceability, privacy protection, supply chain, entertainment, etc. with the popularity of blockchain and bitcoin, many related top domain names have been registered, which has a great impact on the domain name instry.
computer network technology
computer network technology is the combination of communication technology and computer technology. Computer network is a collection of scattered and independent computers connected to each other according to network protocol. The connecting medium can be cable, twisted pair, optical fiber, microwave, carrier or communication satellite. Computer network has the function of sharing hardware, software and data resources, and has the ability of centralized processing, management and maintenance of shared data resources. Computer network can be classified according to different standards, such as network topology, network scope and interconnection distance, network data transmission and network system owner, different service objects, etc. It is generally divided into: (1) local area network (LAN) 2) Man 3) Wide area network (WAN). The geographical scope of local area network is generally within 10 kilometers, which belongs to a small area network formed by a department or a group of groups, such as a school, a unit or a system. Wan covers a wide range, generally from tens of kilometers to tens of thousands of kilometers, such as a city, a country or an intercontinental network. At this time, the transmission devices and media used for communication are generally provided by the telecommunications department, which can achieve a wide range of resource sharing. Metropolitan area network is between LAN and WAN. It usually covers a city or an area, ranging from tens of kilometers to hundreds of kilometers.