Ethereum contract loopholes

There is an essential difference between Ethereum and bitcoin. What is the difference? Bitcoin defines a set of currency system, while Ethereum focuses on building a main chain (which can be understood as a road) to allow a large number of blockchain applications to run on this road

from this point of view, Ethereum's application scenarios are more extensive, which is why we say that Ethereum marks a simple monetary system in the era of blockchain

1.0, and a transformation to other instries and application scenarios in the era of blockchain 2.0

however, there is no perfect thing in the world. Although Ethereum has expanded the application scope of blockchain in all walks of life and improved the speed of transaction processing, it also has some disputes and doubts

first, the solution to the lack of scalability of Ethereum: slicing technology and lightning network

the bottom design of Ethereum, the biggest problem is that Ethereum has only one chain and no side chain, which means that all programs have to run on this chain equally, consuming resources and causing system congestion. Just like last year's very popular Ethereum game "encryption cat", when this game was very popular, it once caused Ethereum network paralysis

to improve the processing capacity, Ethereum proposes two ways: shard and lightning network. Let's introce these two technologies respectively

(1) fragmentation technology

vitalik buterin, founder of Ethereum, believes that the reason why mainstream blockchain networks such as bitcoin process transactions very slowly is that every miner has to process every transaction in the whole network, which is actually very inefficient. The idea of fragmentation technology is: a transaction does not need to be processed by all nodes in the whole network, as long as some nodes (miners) in the network are allowed to process it. Therefore, Ethereum network is divided into many pieces. At the same time, each piece can handle different transactions. In this way, the network performance will be greatly improved

however, the slicing technology is also controversial. As we all know, the important idea of blockchain technology is decentralization. Only when the whole network witnesses (processes) the same transaction can it have the highest authority. The Ethereum slicing technology is similar to the group witness, not all nodes witness together. In this way, it will lose the absolute "decentralization" attribute, and can only achieve the purpose of high performance by sacrificing certain characteristics of decentralization

(2) lightning network

lightning network uses the way of transaction under the chain. What does that mean? It means: when the participants of lightning network transfer money to each other, they do not need to confirm the transaction through the main chain of Ethereum, but create a payment channel between the participants and complete it under the chain

however, lightning network is not separated from the main chain. Before establishing a payment channel, you need to use the assets on the main chain as collateral to generate a balance proof, which indicates that you can transfer the corresponding balance. In the case that both parties of the transaction hold the balance certificate, both parties can make unlimited number of transfers under the chain through the payment channel

only when the off chain transaction is completed and the assets need to be transferred back to the chain, the balance change information of the main chain account will be registered on the Ethereum main chain, and no matter how many transactions occur ring this period, there will be no record on the main chain

another real benefit of lightning network is that it can save the cost of miners for you. At present, when we trade on the main chain of Ethereum, we need to consume gas and pay for miners. Once we move the transaction to the lower chain, we can save this part of the cost

the above is the problem of insufficient scalability of Ethereum, as well as the two main solutions: fragmentation technology and lightning network

Second, there are loopholes in Ethereum's smart contract and the infamous Dao event

Ethereum's smart contract is very powerful, but there are loopholes in any code. The biggest controversy of Ethereum's smart contract lies in the so-called loopholes, that is, security issues. According to relevant research, 34200 (about 3%) of the nearly 1 million smart contracts based on Ethereum contain security vulnerabilities, which will allow hackers to steal eth, freeze assets or delete contracts, such as the infamous Dao incident

before introcing the Dao event, let's first introce what Dao is. Dao is the abbreviation of decentralized

autonomous organization, which can be understood as decentralized autonomous organization. From the perspective of Ethereum, Dao is a kind of contract or a combination of contracts on the blockchain, which is used to replace the government's review and complex intermediate proceres, so as to achieve an efficient and decentralized trust system. Therefore, Dao is not a specific organization, that is to say, there can be many Dao, all kinds of Dao

(2) the infamous Dao event

however, when we talk about Dao now, we basically refer to the Dao event, that is, the infamous hacker attack event we just mentioned. As we know, the English word "the" refers to "the Dao event". The Dao event

refers to "the Dao event", because we just said that Dao is not a specific organization, there can be many Dao, all kinds of Dao

in 2016, slock.it, a German company focusing on "smart locks", launched the Dao project on Ethereum in order to realize decentralized physical exchange (such as apartments and ships). Since April 30, 2016, the financing window has been open for 28 days

unexpectedly, this Dao project is very popular. It raised more than US $100 million in just half a month. By the end of the whole financing period, it raised a total of US $150 million. Therefore, it has become the largest crowdfunding project in history. However, it didn't last long. In June, hackers took advantage of the loopholes in the smart contract to successfully transfer more than 3.6 million Ethernet coins and put them into a Dao sub organization, which has the same structure as the Dao. At that time, the price of Ethernet currency fell directly from more than $20 to less than $13

this event shows that there are loopholes in smart contracts, and once the loopholes are exploited by hackers, the consequences will be very serious. This is why many people criticize Ethereum and say that its smart contract is not smart

to solve this problem, many foreign companies begin to provide code audit services in order to solve the vulnerability problem of smart contract. From a technical point of view, some teams are currently testing smart contracts. Most of these teams are led by professors from Harvard, Stanford and Yale, and some of them have obtained investment from leading institutions

in addition to the problems of insufficient expansibility and loopholes in smart contracts, the controversy over Ethereum lies in the POS consensus mechanism it pursues, that is, the proof of equity mechanism. Under the proof of equity mechanism, if anyone holds more money and holds it for a longer time, he will get more "rights" (interests) and have the opportunity to get bookkeeping power, Bookkeeping can also be rewarded. In this way, it is easy to create the oligarchic advantage of "the stronger the stronger"

The smart contract has been written for a long time

if they can add changes, the description is centralized

the contract is written into the Ethereum smart contract, which is a contradiction sentence

the financial customer service doesn't understand, which is very unreliable

community sites

1. with the recent sharp fluctuation of currency prices, a new profession, commonly known as "brick moving", is graally emerging in the circle. These brick moving workers pay close attention to the major bitcoin and Ethereum transactions every day. Once they find the price difference, they buy bitcoin and Ethereum from the low price and sell them from the high price to make profit

2. with the increasing number of bitcoin and Ethereum transactions, according to incomplete statistics, the number of current international mainstream bitcoin transactions is graally increasing. Different from A-share and other stock markets, the stock price is globally unified. For example, the stock price of technology has the only pricing in Hong Kong stock market. However, the prices of bitcoin and Ethereum are determined by the transaction itself. Because Ethereum has a large number of transactions and different transaction volumes, the transaction price is very likely to fall. When the price fall is large, it can even reach 8% ~ 10% of Ethereum's price. At this time, many porters have the opportunity to move bricks. The so-called "brick" of moving bricks refers to Ethereum. Porters buy Ethereum from the low price and then transfer it to the high price to get the price difference

3. for example, the recent sharp fluctuations in bitcoin and Ethereum markets are a good time to move bricks. Generally speaking, as long as there is a price difference of 5-50 yuan between bitcoin and Ethereum, it is worth moving bricks. However, moving bricks also requires certain transfer costs and labor costs. Sometimes, the withdrawal of bitcoin purchased from low price will not arrive so quickly. In order to speed up the transaction speed and rece the risk of price fluctuation, the porter usually has a turnover of bitcoin. For example, after purchasing bitcoin and Ethereum from a, he immediately transfers the same amount of bitcoin from his wallet to B for sale, After the completion of bilateral transactions, graally withdraw the funds into their wallets, waiting for the next time to move bricks. If you have both cash and bitcoin and Ethereum, it's the safest. You can pay at a low price and register at a high price, and then trade at the same time. The transaction can be completed in a few seconds. At this time, there is little risk in moving bricks, and what you get is pure profit. When the price of bitcoin fluctuates greatly, part of the price response is not so fast, and the profit of moving bricks is the highest

4. 2. Adopt large-scale high-end cloud computing, short or long currency transactions all over the world (low absorption and high selling), complete the transaction within 0.28 MS, and increase the value by floating trading point without upper limit, so as to ensure the dividend appreciation of each person

5. 3. They use the money of the participants to earn profits, and then give 50% to the participants, from Monday to Friday, and do not distribute on weekends. How much you earn depends on whether you have a big package or a small one

6. if you have any questions, please let me know. 5: 185 plus 654 and 39360
   

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Yes, refer to the interaction between contracts. digital currency exchange platform for example, I am trying to sign a smart contract from another factory contract and then redeploy the address of the new smart contract. However, the address it returns is the transaction hash, not the contract address. I believe this is because when the address is returned, the contract has not been exploited. When I deploy the smart contract with Web3, it seems that it will not output the contract address until the smart contract is deployed