Alex connects to Ethereum private network

1. Eth is a kind of digital token of ethereum, which is regarded as "bitcoin version 2.0". It adopts the blockchain technology "Ethereum", which is different from bitcoin. It is an open-source public blockchain platform with intelligent contract results, and a resonance network composed of tens of thousands of computers around the world. Developers need to pay eth to support the application. Like other digital currencies, ether currency can be bought and sold on the trading platform

warm tips: the above explanations are for reference only, without any suggestions. There are risks in entering the market, so investment should be cautious. Before making any investment, you should make sure that you fully understand the nature of the investment and the risks involved in the proct. After a detailed understanding and careful evaluation of the proct, you can judge whether to participate in the transaction
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2. When it comes to money, mining is indispensable. In Ethereum network, if you want to get Ethereum, you also need to mine it. When it comes to mining, there must be a consensus mechanism
do you remember what the consensus mechanism of bitcoin is? The consensus mechanism of bitcoin is pow. To put it simply, the more work you do, the higher the amount of computation you pay, the more likely you will be the first to find the correct hash value, and the more likely you will be rewarded with bitcoin
however, there are some defects in the pow of bitcoin, that is, it is too slow to process transactions, and miners need to constantly collide hash values through calculation, which is costly and inefficient. Friends who are interested in blockchain knowledge should see such a saying:
in order to make up for the deficiency of bitcoin, Ethereum has proposed a new consensus mechanism, called POS (this is the abbreviation of English, which means "proof of equity", also translated into "proof of equity")
POS simply means the same as its literal meaning: equity, equity. The more currency you hold, the more equity you have, the higher your equity
Ethereum's POS means that the more money you hold, the longer you hold it, the less difficult it will be to calculate and the easier it will be to mine
in the initial setting of Ethereum, Ethereum hopes to build a relatively stable system by using POW in the early stage, then graally adopt POW + POS, and finally completely transition to POS. So, it's true that the consensus mechanism of Ethereum is POS, but POS is only a plan or goal at the beginning of Ethereum's release. At present, Ethereum has not yet transitioned to POS, and the consensus mechanism adopted by Ethereum is still pow, that is, the pow of bitcoin, but it is slightly different from the pow of bitcoin
the amount of information here is a bit large,
the first information point is that the consensus mechanism currently adopted by Ethereum is also pow, but it is slightly different from the pow of bitcoin. So, what's the difference between the pow of Ethereum and bitcoin: in short, the mining difficulty of Ethereum can be adjusted, but the mining difficulty of bitcoin can't be adjusted. Just like our college entrance examination, because the teaching situation and the number of students in different provinces are not the same, so the college entrance examination is divided into national papers and provincial independent proposition
Ethereum said that I am in favor of the topic by region. Bitcoin said: No, it must be the same volume in the whole country. The difficulty is the same for everyone
the popular explanation is that bitcoin uses computer computing power to do a lot of hash collisions, enumerate various possibilities to find a correct hash value. The Ethereum system has a special formula to calculate the difficulty of each block. If a block is verified faster than the previous block, Ethereum protocol will increase the difficulty of the block. By adjusting the block difficulty, the time needed to verify the block can be adjusted
according to the Ethereum protocol, the dynamic adjustment method of difficulty is to make the time interval of creating new blocks in the whole network 15 seconds, and the network uses 15 seconds to create blockchain. In this way, because the time is too fast, the synchronization of the system is greatly improved, and it is difficult for malicious participants to launch 51% (that is, more than half) of the computing power to modify historical data in such a short time
the second information point is: in the initial setting of Ethereum, we hope to achieve the transition from POW to
POS through phased upgrade
dating back to 2014, at the beginning of Ethereum's launch, the team announced that the launch of the project would be divided into four stages, namely, Froniter, homestead, metropolis and serenity. In the first three stages, the consensus mechanism adopts pow (workload proof mechanism), and in the fourth stage, it switches to POS (equity proof mechanism)
on July 30, 2015, the first phase "frontier" of Ethereum was officially released. This phase is only suitable for developers. Developers can write smart contracts and decentralized application DAPP on Ethereum network, and miners begin to enter Ethereum network to maintain network security and get Ethereum coins. The leading-edge version is similar to the beta version, proving whether the Ethereum network is reliable or not
on March 14, 2016, Ethereum entered the second stage of "homeland". In this stage, Ethereum provides the wallet function, so that ordinary users can easily experience and use Ethereum. There is no obvious technology improvement in other aspects, but it shows that Ethereum network can run smoothly
in September 2017, Ethereum has reached the third stage of "metropolis"“ "Metropolis" is composed of Byzantine and Constantinople. The goal of this stage is to introce the hybrid chain mode of POW and POS, so as to prepare for the smooth transition from POW to POS. This is the latest popular "Ethereum Constantinople upgrade". In the Constantinople upgrade, Ethereum will make some changes to the underlying protocols and algorithms to lay a good foundation for the implementation of POW and
POS
how much reward will Ethereum get for mining? Miners who win the block creation competition will get the following income:
1. Static reward, 5 ethereums
2. The fuel cost in the block, i.e. gas, we talked about in the last issue
3. As a part of the block, it includes the extra reward of "Uncle block". Uncle is uncle of uncle, and each uncle block can get 1 / 32 of the mining reward as a reward, that is, 5 times 1 / 32, which is equal to 0.15625 ethereums. Here, let's briefly explain the concept of "TERT block". The concept of "TERT block" was proposed by Ethereum. Why should we introce the concept of TERT block? This also starts with bitcoin. In the bitcoin protocol, the longest chain is considered absolutely correct. If a block is not part of the longest chain, it is called a "orphan block". An isolated block is a block, which is also legal, but it may be found later, or the network transmission is slower, and it does not become part of the longest chain. In bitcoin, the solitude is meaningless and will be discarded later, and the miners who find the solitude will not receive mining related rewards
however, Ethereum does not think that isolated blocks are worthless, and Ethereum system will give rewards to miners who find isolated blocks. In Ethereum, isolated blocks are called "Uncle blocks", which can contribute to the security of the main chain. Ethereum's ten second block interval is too fast, which will rece the security. By encouraging the use of tertiary blocks, the main chain can obtain more security guarantees (because the isolated block itself is legal). Moreover, paying the tertiary block can also stimulate the miners to actively mine and actively use tertiary blocks. Therefore, Ethereum thinks that it is valuable.

3.

Ethereum is an implementation of blockchain. In Ethereum network, many nodes are connected with each other to form Ethereum network:

Ethereum node software provides two core functions: data storage and contract code execution

in each Ethereum node, complete blockchain data is stored. Ethereum not only saves the transaction data on the chain, but also saves the compiled contract code on the chain

At the same time, a virtual machine is provided to execute the contract code

Ethereum virtual machine

Ethereum blockchain not only stores data and code, but also contains a virtual machine (EVM) in each node to execute contract code - it sounds like a computer operating system

in fact, this is the core difference between Ethereum and bitcoin: the existence of virtual machine has brought blockchain into the era of 2.0 and made blockchain a friendly platform for application developers for the first time

the above content comes from the introction course of Ethereum DAPP development

4. If it's me, I'll choose ash and only do the application layer. Of course, the easier I get to know, the better

5.

Link

< H2 > 1. Introction

link is the erc20 standardized token based on Ethereum blockchain, which is used to pay the chainlink node operators, so as to retrieve data from the data of the chain off, format the data into the readable format of the blockchain, calculate the chain off and ensure the normal running time. Chainlink token, as a part of the running node, can prevent undesirable participants

< H2 > 2. Project introction

the first distributed Oracle network, which allows anyone to safely provide smart contracts, access key external data, offline payment and any other API functions. Any user with a data feed, offline service (such as local payment) or any other API can directly provide it to a smart contract in exchange for a link token. Chainlink network is a distributed network of chainlink nodes, which directly transport specific data, API and various offline payment functions to smart contracts. Chainlink network is composed of two independent parts, on chain and off chain, which must interact to provide services. The network is built in such a way that it can be upgraded, so that it can replace its different components when better technologies and technologies emerge. The chain components of the network filter Oracle through service level agreement (SLA) based on the measurement of one party's request of smart contract. Using these metrics, chainlink collects responses to SLA queries, sorts them using reputation and aggregation models, and provides final set results of chainlink queries that may be implemented in smart contracts. The out of chain components of the network are composed of Oracle nodes connected to the Ethereum network, which independently collect responses to offline requests. These off link nodes can be located in any instry. For example, the off link nodes operated by the New York stock exchange can provide real-time and accurate transaction information for the chainlink network, or the off link nodes of the visa network can solve transactions and interact with consumers and suppliers through the chainlink network. Chainlink technology aims to integrate nodes from all these instries into a common network, which itself acts as a (low-cost) middleman, interpreting and allocating data correctly as needed. The chainlink system will ensure that the results obtained from the Oracle are accurate and allow the oracle to remain independent of the data they provide. Any data, payment, e-signature or other API providers and personal developers can easily join the chainlink network by connecting their familiar API to the network. Once the API is connected to the chainlink, the user becomes the chainlink node operator and is responsible for connecting the API to the chainlink network. In order to motivate operators to provide API information, they are compensated in the link token to successfully complete the online link request. The project currently provides a fully distributed Oracle network compatible with bitcoin, Ethereum and hyperledger. It is expected that other blockchains will be supported in the future, which will allow cross chain connections between smart contracts and any other public or private chains, and allow anyone in the world to use the chainlink network, regardless of its platform. All service providers will be able to securely provide smart contracts to access critical external data and possibly even non chained payments

< H2 > 3. Comment

chainlink (link) is a decentralized network, which can provide information (Oracle) for smart contracts. Chainlink was established by Sergey Nazarov and Steve Ellis in 2017, aiming to solve the problem of information procurement under the chain through smart contract for its execution parameters. Smart contract is designed to execute automatically when some parameters are satisfied. However, when these parameters exist under the chain, it depends on the information source (called Oracle) to provide the necessary information. Off chain predictors are often centralized and rely on third parties to provide critical information in a reliable and time-consuming manner. Chainlink aims to break this dependence by providing information to smart contracts through a decentralized prediction network. These predictions work together on the link blockchain to verify and forward key information to these contracts. Chainlink network allows users with data feeds or information hosting APIs to easily provide information to smart contracts in exchange for link tokens< memorabilia September 2017 - chainlink ICO. November 2018 - acquisition of town crier (smart contract and data privacy project). June 13, 2019 - announced cooperation with Google utility link network to provide timely and accurate information to smart contracts through Oracle's distributed network (data sources and APIs). This information is very important for the effective and accurate execution of smart contracts, because the required information exists under the chain, and there must be a reliable way to obtain the information on the chain. The link token is used as payment for smart contracts that use the data provided by the link network, in which the oracle that provides accurate information will be rewarded in proportion to the link< important functions partnership with major instry players such as swift and Google, integration of Ethereum side chain, such as harmony, celer and matic. Average block time n / A; The total supply is 1 billion link; Write Oracle consensus to Ethereum blockchain through threshold signature

related links: https://chain.link/

https://en.bitcoinwiki.org/wiki/ChainLink

https://everipedia.org/wiki/lang_ en/chainlink-cryptocurrency

https://blog.chain.link/threshold-signatures-in-chainlink/

https://blockonomi.com/chainlink-guide/

 

6. There is no problem at all, but relatively speaking, we must buy some reliable ones, because we must pay attention to them.

7.

CDC is the Centers for Disease Control (CDC) and China Center for Disease Control and Prevention (CDC). It is a public welfare institution organized by the government to implement national disease control and prevention and public health technology management and service

The mission of CDC is to create a healthy environment, maintain social stability, ensure national security and promote people's health through the prevention and control of diseases, disabilities and injuries; Its purpose is to rely on scientific research, talent as the foundation, disease control as the center. Under the leadership of the Ministry of health, we should give full play to the functions of technical management and technical services, focus on the key tasks of national disease prevention and control, strengthen the research on the strategies and measures of disease prevention and control, and do a good job in the organization and implementation of various disease prevention and control work plans

to carry out the management of food safety, occupational safety, health-related proct safety, radiation hygiene, environmental hygiene, women's and children's health care and other public health services, vigorously carry out applied scientific research, strengthen the technical guidance, training and quality control of national disease prevention and control and public health services, and improve the quality of health services The national team plays a role in the construction of public health information capacity