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Blockchain crisis! Dangerous consensus algorithm, depth

Time : 15/06/2021 Author : dur3xt Click : + -
        Just a few days ago, Neo, known as "China Ethereum", experienced a serious situation that the whole platform was down and the whole network was suspected to be paralyzed due to the failure of blocking. Ericwall, a foreign cryptocurrency researcher, pointed out that the underlying design of Neo's dbft algorithm has fatal shortcomings, and even roast said that the project party has no experience in designing consensus algorithms. But at the same time, we asked relevant insiders of Neo, and the answer was that it was caused by the problem of P2P communication protocol, and the crisis had been lifted one hour after the problem appeared. Let's put aside these unclear insides and think about a new question: have you ever thought that there may be security risks in the lowest technology of blockchain?.
        A popular saying in the industry is that bitcoin is the first application of blockchain, which is actually equivalent to admitting that there is blockchain before bitcoin. Bitcoin is the product of the development of blockchain technology. I wonder if Nakamoto had a complete blockchain technology idea in mind when he first thought about creating bitcoin?. However, in fact, we can't find a word called blockchain in the white paper bitcoin:apeer-to-peer electroniccashsystem written by Nakamoto Cong that year. But later, people regarded the principle of creating bitcoin as a new technology, which has been many years later.
        Blockchain technology can be seen as a technology to create a point-to-point public ledger. It uses consensus algorithm (POW: proof of work is used in bitcoin) to motivate miners and maintain the security of the network. For this kind of public ledger system, consensus algorithm is particularly important, which involves some of the most important concepts of blockchain. After bitcoin, different consensus algorithms have emerged, such as proof of stack (POS), proof of burn (POB), etc. However, people have been asking: where does the value of bitcoin come from? Does it have strong endorsement like legal currency? Will it become worthless overnight?.
        First of all, we won't discuss how the actual price of bitcoin is formed, which is not the focus of our discussion, but there is one point we can't get around:. If the network that provides this virtual currency has security problems, such as double blossom, theft, and being controlled by a third party, no matter how much value is added to it, it will vanish in an instant. The security of blockchain network is largely determined by consensus algorithm. POW is the most secure consensus algorithm proved by practice so far; Since the birth of bitcoin 10 years ago, there has been no security accident caused by consensus algorithm. However, despite this, it does not mean that pow is absolutely safe.
        At present, the industry is generally worried that the future quantum computer will bring great challenges to the cryptography technology used in bitcoin. In addition, the most important thing is that if blockchain is applied in specific industries, it also needs to solve some fundamental technical problems. The two biggest technical difficulties are security and scalability. Vitalik is also working hard to improve Casper algorithm and plans to completely transfer Ethereum to pos. Casper can be regarded as holding democracy. Whether it is the most primitive POS algorithm or dpos algorithm used by peercoin, it is a consensus algorithm without strict mathematical proof in the eyes of scholars in the field of cryptography, and there are great doubts about its security.
        Just from the incident of "suspected paralysis of the whole Neo network" mentioned at the beginning of the article (regardless of whether it is caused by consensus algorithm or not), we can imagine how serious the catastrophic consequences will be if this security hazard breaks out. In order to better understand POS consensus algorithm, we can understand that the core of consensus algorithm design is to design a random number generator to prevent anyone from guessing who is the packer of the next block. POW has natural defects in this regard. Due to network delay, the former blockpacker has certain advantages in competing for the packaging rights of the next blocker, and the POS scheme largely avoids this defect because of different design mechanisms, but the previous POS algorithm has other problems.
        In the design of consensus algorithm, there is a famous trilemma (trilemma problem), which is that secure (Security), scalability (scalability) and Decentralization (decentralization) cannot have both. At least at present, almost all blockchain projects encounter this challenge. Vitalik criticized the design of EOS for sacrificing decentralization to obtain the capability of so-called millions of TPS (txpersecond). Dpos adopted by EOS seems to be the preferred choice for many other projects at present, but dpos also has the problems mentioned above and faces many criticisms.
        Let's first look at its security: in the dpos mechanism, once a "representative" (node) who does evil is found, it will be removed and cannot participate in the election of this "representative" in the future, but because the "representatives" themselves do not need to take a stake, the loss is not large; However, there is a possibility that if it is a premeditated ambush, the attacker can select a large number of his own "representatives" who usually perform well, and at a specific time, these "representatives" attack together, which may lead to the possibility of controlling the entire network;. Or most people do evil at the same time (such as being extremely dissatisfied with the project party or official developers), and this extreme situation cannot be avoided.
        In addition, this kind of POS design cannot avoid the impulse of bifurcation, because users can get rewards on both chains at the same time. At the same time, there is a problem of "the rich are always rich and the poor are always poor" in the early design of POS algorithm, because the principle of classic POS algorithm is "Whoever has more money has a greater say". Of course, this can be sophistry. For example, you can also buy a lot of money to compete, and you can also raise the price, because there are more and more people in demand, which seems to be a win-win situation. Is it possible to raise the price of money indefinitely? Because everyone holds money to "bet", in order to get the corresponding reward, and the currency flowing in the market is less and less.
        In extreme cases, if several people or organizations have more than 80% of tokens, they can control the whole network? This problem is particularly prominent in some projects where teams have most of the tokens. If a public blockchain platform is controlled by several such big players, it is contrary to the decentralized concept of blockchain. In addition, such a platform will lose credibility, and people will choose to leave after a long time, which will return its value to its original form. Ethereum Casper also has the same problem. It even sets a minimum amount of participation: 1250eth! That means that the poor can't count on it.
        Based on the above security risks, the industry began to seek a more secure consensus algorithm, trying to remove the inherent defects in blockchain technology. It is reported that gö Engineers of the dellabs project are developing a consensus algorithm known as the next generation of POS or pos2.0 consensus algorithm: wujipos. According to insiders, wujipos is a provable secure consensus algorithm protocol, which is used to create a scalable and secure blockchain network. In the future, it will be applied to a new computing platform, tangrum (about tangrum, will report in another article).
        Return to Sohu to see more.
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