Building a blockchain application from scratch

1.

From the current mainstream blockchain projects, blockchain projects are mainly divided into four categories: the first category: currency; The second is platform; The third category: application category; The fourth type: asset token

currencies mainly act as the "exchange media" in the field of blockchain assets, and the exchange media refer to general equivalents, such as gold and silver bills in the past< (currency exchange on trading blockchain assets)

platform projects refer to the establishment of technical platforms to meet the needs of various blockchain application development, which can rece the threshold of application development on blockchain

application projects cover a wide range of fields, including finance, social networking, games, property rights protection, etc., and are also the fastest growing fields of blockchain assets

asset token project refers to the blockchain mapping of physical assets, that is, the physical assets on the chain. At present, there are no more than 10 varieties

01 currency

the first category is currency project, which is also the earliest blockchain project. Currency projects mainly include bitcoin and lightcoin. In addition, there is another kind of asset with the characteristics of anonymity. Its main functions include protecting the privacy of both sides of payment while realizing payment. The well-known ones are dash, monero and zcash. Currency is mainly used as the "exchange medium" in the field of blockchain assets. The exchange medium is the general equivalent you use to exchange goods. For example, gold, silver and silver bills can be used as the exchange medium in the past. At present, there are more than 2100 types of digital assets in the world, and the number of currency blockchain projects has increased rapidly recently. As of June 2018, bitcoin is still the largest market value

02 platform type

the second type is platform type blockchain project. The main function of platform type blockchain project is to establish a technical platform to meet the technical requirements of various blockchain application development; In short, platform applications allow developers to directly issue digital assets and write smart contracts on the blockchain. Smart contract is a computer program running on the blockchain database, which can be automatically executed under the conditions of its source code setting

for example, you develop a smart contract based on the house rent protocol on the blockchain. When the owner receives the rent, it will trigger the automatic execution and give the security key of the apartment to the tenant

the main function of platform blockchain projects is to establish the underlying technology platform, so that developers can do application development on the underlying technology platform. A considerable number of platforms are still in the development state. As of June 2018, Ethereum has the largest market value

03 application

the third category is application blockchain projects. Application projects are blockchain projects based on blockchain development platform (such as Ethereum), which can solve many problems in various fields of the real economy

for example, augur, Golem, vechain, omisego, which provides asset exchange and transfer services. Using blockchain technology, these projects can better solve the problems of trust and cross-border circulation. At the same time, using smart contracts and tokens on the blockchain, they can better realize automatic execution and greatly improve the efficiency of social and economic activities. Application blockchain projects cover a wide range of fields, including finance, social networking, games, property rights protection and so on. It is also the field with the fastest market value increment of blockchain projects at present

04 asset token

the fourth category is the asset token blockchain project. Asset token refers to linking the blockchain assets to physical assets such as gold and US dollars, which is the blockchain mapping of physical assets. As of February 2018, there are no more than 10 varieties. The typical representatives are usdt against US dollars, digix Dao against gold, Digix each token represents 1 gram of Gold Certified by the London Bullion Market Association. Asset token has the advantages of convenient transaction and safekeeping. First of all, asset token is more convenient for transaction. Because blockchain assets can be split, it has better liquidity

for example, at present, real estate needs to be transferred as a whole. If the real estate can be token, it can be split and purchased, which is more convenient for transaction. Secondly, the token of physical assets is more concive to custody. Gold is easy to wear out and cause losses in physical transactions, but there is no need for physical transfer after the token of physical assets, which is more concive to the custody of physical assets

2.

Ten instry application scenarios of blockchain are listed on Oracle's website, including finance, proction, ecation, media, entertainment, government, retail business, health, medical care, supply chain, insurance and public utilities. Is it very tall? But what I want to say is that these application scenarios, in front of real high-energy blockchain applications, can only hide in the corner and shiver

now the real high-energy application scenario of blockchain is Ponzi application, commonly known as "Ponzi scheme". It is a smart contract type Qianbao, a blockchain game for rolling in and out of money, an ICO for trading, and a global pension platform

Ponzi scheme is one of the oldest application scenarios of our human beings. After Internet plus, the Ponzi scheme has upgraded the Internet + "Internet plus Ponzi scheme". The Internet enabled the Ponzi scheme, so there was an event similar to the 10 billion level of Qianbao. Before the Internet era, there were few Ponzi schemes on such a large scale. They were enabled through the Internet, and paid through mobile app. Finally, they rolled for several years and reached the 10 billion level

the Internet has broken the geographical restrictions, physical restrictions, capital flow restrictions and communication restrictions. As long as you have a mobile phone, you can play Qianbao app. Everyone participates in it, everyone gets into the money, and everyone gives out the money. According to the data of the people involved, it has reached the level of one million. Relatively speaking, the online pyramid scheme (Ponzi scheme 1.0), which still stays on the top of the list, has meetings every day, can't stop brainwashing, and uses violence and illegal means. It's simple and weak. With the rise of blockchain technology, the Ponzi scheme enabled by "blockchain +" can no longer be described as adding wings like a tiger. It is like a chicken changing into a tiger. Like the Internet, the "block chaining +" technology is a solid application to enhance the application scenario. Ponzi's fraud is further upgraded in the two generation of the Internet plus, because of the major improvement and improvement of the scene, turning into Ponzi scheme 3, whose characteristics are mainly in the following aspects:

1, centralization and no summit. The smart contract of blockchain runs automatically, and it does not need human intervention, nor can it be interrupted by human. Code rules are dead and cannot be tampered with. In terms of scene improvement, it solves the biggest pain point of Ponzi scheme for thousands of years, that is, the problem of head running away. Because the head is a program and code, the program of blockchain can exist forever, and no one can delete it. I think this is the biggest breakthrough. This virtual leader is always there. He can't run away, he can't run, he can't change. The rules will never change. He will stick to the Ponzi line for 100 years, 1000 years and 10000 years. It may be said that smart contracts can be iterated, and they can also be manipulated to leave a back door. Yes, but it can be done without iteration. Even if iteration is transparent and visible, it can be seen at a glance with a back door. This is the characteristic of the blockchain smart contract. If you cheat on it, you will get out a under the teacher's eyes. No one will participate in such a smart contract when it is online. Therefore, after technical review and verification, there is no backdoor, fair rules and irreversible smart contract, which can be realized by using blockchain technology. Such reliability, once verified, will never change. This is the certainty of the smart contract. A program or a character's code will not change. It will run one million times and one trillion times, and the result will be consistent and certain

2. The process was transparent. The number, address, account number, amount and time of deposit; Number, address, account number, amount and time of payment; All visible. Blockchain has a public ledger function, which can be viewed by everyone in the world, and the ledger data viewed by everyone is completely consistent. Why does Qianbao burst? Because we can't see his background account, how much money he goes in and how much money he comes out every day, and the details of each transaction. In this way, you can see the assessment of cashing ability before you pay in, and the assessment result is absolutely certain, that is, it will not change after you pay in

3. Complete anonymization. If you've ever heard of zero proof of knowledge. This part can be skipped. In short, some of the things we used to have in the mathematical knowledge base did not have application scenarios after many inventions. Later, it was found that it was easy to use these knowledge for anonymization. The cryptography technology in the blockchain can achieve identity hiding. As we all know, Zhihu can't achieve anonymity in a real sense in terms of technical structure, and blockchain can

The rules are open and fair to all. One yuan in gold, ten yuan in rebate. Everyone is the same rule. It will never change. If you pay one yuan, go to the front and pay for it, then the back will pay for it, and then pay for it. Fair, right? I have reflected on this many times, and I think it is fair

5. Sustainable iteration. In the low-level Ponzi scheme, the leader, proct designer, benefit distributor and benefit receiver are often four in one, while the blockchain Ponzi scheme can completely logically separate the four roles. Achieve sustainable iteration. Through collaboration based on socialization, these projects can be iterated on forever. There are now 400 senior engineers who are developing around bitcoin and constantly updating the code. These people can not know anyone. As long as the application is valuable, they can continue to iterate. Which centralized project can be achieved? Even bat level companies can't employ so many professionals scattered around the world. This kind of social iteration is not affected by the changes of a specific person or organization

"blockchain" enabled Ponzi scheme uses different range of blockchain technology, because the technology in this field is still constantly updated, and the application of smart contract has only increased in the past two years. The earliest application of blockchain is bitcoin. Some people think that bitcoin itself has the characteristics of Ponzi scheme. In 2013, I wrote a reply and implicitly pointed out that this new type of Ponzi scheme will have great lethality, because it has the characteristics of no head, open account book, no running away, open and fair rules. Later, I also found that many people around me like Ponzi scheme much more than blockchain technology. As soon as I hear that bitcoin is not a Ponzi scheme, before I start talking about blockchain technology, I usually walk away in silence. On the contrary, you tell him it's a Ponzi scheme, and then they will ask, where can I buy it? Of course, there is a lot of controversy about whether bitcoin is a Ponzi scheme, because the practical application scenarios of bitcoin have been expanding

in the ICO boom, there are a lot of air coins, such as the bogus Ponzi scheme, which has no application scenarios. The buyers probably know that these air coins are Ponzi schemes, but they buy them because the packaging is good. It is estimated that there are hundreds or thousands of such air coins. The scope of the case is all over the world, and the amount involved is more than 10 billion. These ICOS use smart contracts for subscription and distribution, and then circulate in the secondary market by themselves. In this case, there is no guarantee that the money will be paid out, and some people will lose all their money. Many people, blockchain professionals, have always wanted to draw a clear line with these applications, because although these air coins use part of the blockchain technology, they are still a centralized organization or indivial behind them. There are few network nodes, and users directly converge to a certain organization or indivial when they are paid (so they will be swept away), but there is no doubt that, Air money still uses blockchain to make money and raise funds, which solves part of the problem of running away and improves the scope and communication ability of Ponzi scheme. This is an objective situation

and from this year, with the development of technology, the Ponzi scheme, which uses smart contracts to achieve more decentralization, began to surface. Smart contract locking is used for fund in and fund out to complete a complete closed loop of fund in, fund subscription and fund out. It can already be a very pure blockchain application. Some blockchain games can freely admit that they are a Ponzi game after their release. He said: you see, the rules are transparent, the code is visible, the gold entry contract is locked, they can't run away, no one intervenes, and the gold is automatically paid. Early play, early gain. This is a key breakthrough. It's a way to publicly admit that you are a Ponzi scheme, which can't be done by Ponzi scheme 1.0 and Ponzi scheme 2.0 before. Great. It's simple and rough

this solves the major obstacles in the promotion process of Ponzi scheme, which used to rely on brainwashing, but now it depends on code. You see, "this program doesn't run on its own. There's no back door in it, right? Is the leader gone? The capture of Nakamoto does not affect the continued implementation of the program, does it Therefore, the first batch of blockchain Ponzi scams are hooked by code farmers who can understand the code, and then these code farmers stand up again and say that after technical verification, it is really such an effect, driving other people who do not read the code to join

in addition to realizing the Ponzi scheme application scenarios of entertainment, gambling and fraud, blockchain also has the opportunity to make a big show in the Ponzi scheme application scenarios involving the national economy and the people's livelihood and public utilities, which can even greatly enhance people's sense of gain and happiness, and actually improve people's life. For example, the application of national or global public pension platform based on blockchain can solve several major drawbacks of pension: fund misappropriation. The account book is open, the funds are not centralized and locked, and no one can unlock it, except the recipients who meet the rules can pay out the money. There is no possibility of misappropriation

2. Inflation. The current pension system adjusts the coefficient every year according to a series of complex algorithms such as inflation. After adjustment, the recipients are often dissatisfied because the total amount has increased, but the purchasing power has decreased. Using the feature that virtual currency can't be issued, we can control the inflation rate and ensure that we get real money

3. Unpredictable problems. It is very difficult for us to predict the pension payment after 30 years, and we can predict it in advance through smart contract. Stimulate the enthusiasm of paying

4. Policy loopholes and fairness. There will be unfairness in the diversification of groups that any pension policy faces. Everyone wants to pay less and get more, pay later and raise earlier. The transparency of blockchain is refined to each account, rather than a set of general policies to plug the loopholes in the implementation process. Everyone is the same, pay more, pay earlier, pay earlier. It can even be inherited and never lost

this has greatly reced the burden and cost of the state's pension management. What the existing pension system can do, after using the blockchain technology, can still be done, such as the state subsidies, just pay money into the contract, lock it in, there will be no fake, such as compulsory payment, and every record is real and traceable. In a word, all the existing systems and rules can be linked to the chain. On the basis of not affecting the existing effect, the efficiency and output level are improved, and fairness is guaranteed. Moreover, because the cost of the huge management system is reced, the absolute number that everyone can get may be increased by a large part. This has played a real effect on improving people's lives, and also has a positive effect

3.

Blockchain technology is widely used. Under the integration of new technologies, the main application scenarios of blockchain include finance and insurance, intelligent manufacturing, intelligent environmental protection, energy and power, health care, ecation, culture and innovation, smart city, social welfare, agriculture and many other fields

1. blockchain + finance

   blockchain can help financial institutions solve problems such as trust and data sharing

3. blockchain + right art

   Tianhe Guoyun's blockchain right system

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3. Blockchain + government

in statistics, voting, budget management and other aspects, blockchain can rece costs, improve efficiency, and increase transparency, so as to prevent the risk of failure of centralized system

4. Blockchain + insurance

fraud identification and risk prevention: by placing insurance claims under an unchangeable general ledger, blockchain helps to eliminate the common sources of fraud in the insurance instry

property insurance and accidental injury insurance: policies and shared ledgers recorded in the form of smart contracts can improve the efficiency of property insurance and accidental injury insurance

Health Insurance: blockchain technology enables medical records to be encrypted and shared among health service providers, thus improving the interoperability of the health insurance ecosystem

Reinsurance: the information security of reinsurance contracts on the blockchain platform can be ensured through the form of smart contracts, which can rece the amount of information and simplify the payment process between insurers and reinsurers

4. 1. What is blockchain? In a word
A: blockchain is an encrypted database chain, that is, the transaction data in multiple timestamps / events are encrypted and linked together, and the data can not be tampered with or shared
2. Performance and logic:
A. external operation forms: bank deposit and withdrawal, remittance, account in and out, shopping, currency issuance, capital transaction, etc
B. internal logic processing (software program): after human operation, the data will be encrypted first and then stored in the database. After the program, the data will be divided into regions, such as the data in the event and time stamp will be classified and put together into a region. Multiple events and data in timestamps are associated to form a blockchain. The encrypted data can be shared, but not tampered with
C. forms of sharing: querying personal information, auditing, etc. Query permission / sharing permission: different permissions can query different data. For example, the bank can query the information of all people, and the indivial can only query the indivial
3. Most of the examples are different, but the logic processing ideas are the same, but the implementation methods and operations are different
4. Blockchain: it has the characteristics of encrypted data, tamperable data and shared data
5. Blockchain Technology: the technology of encrypting, partitioning and sharing data with editing programs
there are suggestions for guidance
application fields: finance, it, commodity sales, online shopping, etc.

5. The development of blockchain can be divided into three stages. Melanie Swann, founder of blockchain Science Research Institute, in her book blockchain: blueprint and guide to new economy, according to the application and development of blockchain, it can be divided into three stages: blockchain 1.0, 2.0 and 3.0< br /> 
I. blockchain 1.0 cryptocurrency era (2008-2013)
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in 2008, Nakamoto first proposed the concepts of bitcoin and blockchain, and then in January 2009, the first blockchain came out. At this stage, people pay more attention to the transaction of cryptocurrency, and blockchain is only used as the underlying technology to act as a "public account book"< br /> 
2. Blockchain 2.0 smart contract era (2014-2017)
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in 2014, & quot; Blockchain 2.0 "has become the pronoun of decentralized blockchain database. At this stage, people mainly focus on the application of the platform. Anyone can upload and execute the smart contract on the blockchain, and will be rewarded automatically after the execution. Because this transaction process does not need any intermediary, so people's privacy has been greatly protected< br /> 
III. blockchain 3.0 large scale application era (2018 -)
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at this stage, people begin to build a completely decentralized data network, and the application of blockchain technology is no longer limited to the economic field, but expanded to the fields of art, law, real estate, hospital, human resources and so on.

6. 1. Work hard [Pinyin]: F è n f ā chu ō l ì Explanation: work hard and be energetic [source]: it comes from the epitaph of Liu Zihou written by Han Yu of Tang Dynasty: "to discuss the evidence of the present and the ancient times, to go in and out of history, to be vigorous and resolute, and to lead the people who often bow to it." No matter who the first emperor is, he can't help Su Xin. The second part of Chen Tianhua's on the history of Chinese revolution in Qing Dynasty: ffcl: go all out, go all out, go all out; It refers to a person's mental outlook è n f ā d ǎ o l ì Explanation: Struggle: cheer up; Hair: encourage; Step: step, extend to do, implement; Li: fierce and quick. Be inspired and act fast [source]: Han Yu's epitaph of Liu Zihou in Tang Dynasty said: "to discuss the evidence of the present and the ancient times, one can go back and forth through the history of the hundred scholars, who are vigorous and resolute, and often yield to the people in his seat." There are thousands of young women going out of their families and going to the front line to prevent their male compatriots from focusing on beauty. In Zou Taofen's ten million youths who have worked hard since the Anti Japanese War, FFDL is used as the predicate; It refers to people's mental outlook è n f ā t ú qi á Ng [explanation]: figure: seeking. Cheer up for strength [source]: Guo Moruo's spring of Science: "I wish the middle-aged generation of scientific workers to work hard, make revolution and work hard, and bravely climb the world's scientific peak." Young people should work hard and contribute to the construction of the motherland Phonetic code: fftq [synonym]: to be angry and strive for success [antonym]: to abandon oneself [usage]: as predicate, adverbial and attribute; Go all out to make the country strong: in the Western Han Dynasty, Sima Qian traveled all over the cultural relics of the motherland, accumulated a lot of historical materials, and began to compile historical records as an imperial edict. He was involved in the crime of Li Ling and sentenced to court punishment. After he was released from prison, he enred great mental and physical torture. Through unremitting efforts, he finally completed 130 great works historical records. 4. Work hard è n f ā xi à ng sh à He is in high spirits [source]: Deng Xiaoping's "emancipating the mind, seeking truth from facts, United and looking forward" said: "in all fronts, we have formed an atmosphere of catching up with each other, striving to be advanced, and striving to make progress." Phonetic code: ffxs: used as attributive and adverbial; For people's mental state 5 è n f ā y ǒ u w é I [explanation]: work hard: cheer up. Cheer up and make a difference Source: Wang Chong of Han Dynasty's Lun Heng Chu Chen Pian: "courage, nature." If you can work so hard, what is not easy to do in the future! The 35th chapter of Li Baojia's the appearance of officialdom in Qing Dynasty [pinyin code]: ffyw [synonym]: to be angry and to be strong [antonym]: to abandon oneself [usage]: as predicate and attribute; Energetic and promising

7. Generally, there is only one approximate time cycle for the development of blockchain application app. For example, starting technology mainly depends on its functions and complexity. Generally, the development time is about 2-3 months. The specific time is estimated according to the customer's needs, mainly the development time. If the functions are multiple and more complex, there will be more things to develop and design, and the time will be longer. For example, in another case, the existing source code can meet the requirements, and only need to add or modify some functions will be very fast.

8. Triporg travel: it is a travel service application built by blockchain, which can provide travel booking services such as train tickets.