Getting started with blockchain | From the perspective of attack energy and defensive energy, who is more secure with PoW and PoS?

The security issue in the blockchain field has always been the focus of discussion. Peter believes that before designing a more secure system, we must first define the definition of security. This article is my own point of view. My academic background is electrical automation engineering, and the professional background is a programmer, so the point of view is definitely the technical worldview. Based on the security definitions given here, I can explain why I am a supporter of a POW and why I have doubts about certain POS projects.

The definition of security is defined by my own security.

The ratio of defensive energy to attack energy.

Let me explain it below.

First of all, security is an energy issue. The wall is repaired to be thicker. If there is enough gunfire, it can be smashed. The defensive energy here is the energy to build the wall. The more energy you spend, the higher the wall can be repaired. The attack energy is the energy stored in the shell. Another example, if you understand cryptography, you know that there are no passwords that cannot be cracked in the world. Just because many passwords need to be spent on the energy that the attacker can't afford, there is a temporary security password that is considered to exist.

Second, security is a ratio. There is a concept in the project called safety factor, the safety factor is high enough, we think the system is safe. Specifically, the safety factor refers to the coefficient of safety and is the ratio of the ultimate stress to the allowable stress. To give a simple example, a manned lift, the ultimate capacity of the rope is 10,000 kg, the total allowable weight of the general manned work is 1000 kg, and the safety factor is 10. Here, the defensive energy is the gravitational pull between the particles of the rope, which ensures that the rope is constantly. Attack energy is the gravity brought by the human body.

Third, a system with a negative return on investment is considered safe. Safety is a relative concept. Engineering believes that if the rope is used to carry people, the safety factor should be 10, and if the goods are transported, a safety factor of 5 is sufficient. An ordinary iron cabinet, it is safe to save my personal belongings, but if it is to save a pile of gold, it is not safe enough. The principle can still apply the idea that security is a ratio. If the attack potential is profitable, then the attack energy is considered to be great, so the defensive energy must also be improved to ensure security.

To sum up, security is an energy ratio, and the system with negative attack returns is considered safe.

Can multiple POW systems coexist in the world?

Based on the previous security definition, I myself support the use of POW to ensure system security. At the same time, I also believe that there can be multiple POW blockchains in the world at the same time.

The security of POW comes from the comparison of offensive and defensive energy. The most famous POW system is definitely Bitcoin. Bitcoin will use the longest chain as the final consensus result, and which miner adds a block to the fork is equivalent to supporting the fork to become the longest chain. This is the process of voting with blocks, and each block is energy lost. In this way, the attacker must attack the bitcoin network, and it also costs energy. The attacker will succeed when the attacker's energy level is higher than the sum of the energy of other honest nodes in the whole network. In combination with what we said before, security is the idea of ​​attack energy and defensive energy confrontation. It can be seen that Bitcoin's POW mechanism is fully consistent with the definition of security in this article. Therefore, the energy consumption of the POW is not in vain, and its return is safe.

Another point, our Andreas said

Maybe we can only afford a POW system in this world.

I also thought so at first, I think everything should be done on Bitcoin, and don't open a new chain of POWs. But in fact, stacking too many features into Bitcoin will reduce the security of Bitcoin. So everyone started a lot of POW chains. Based on the logic of this article, this is acceptable for the following reasons. If there is only one POW blockchain in the world, that is, bitcoin, then the value of bitcoin is the world, then use more than 50% of the world's electricity to protect her, because the success of the attack is the world. However, if there is another POW chain that carries a part of the value, and the value of the bitcoin bearer is low, then the corresponding power can of course be distributed to another chain. Bitcoin no longer carries the world, which means that the attack revenue is low, and the corresponding attack energy will be low, so reducing some defensive energy will not affect the security of Bitcoin.

Summarizing this part, it is not a waste of POW to use energy for safety. Building multiple POW chains will not reduce the security of any one.

Is POS safe?

Let me discuss my point of view from the opposite side. POS is a consensus mechanism similar to shareholder voting, which is characterized by no need to consume energy. It can be inferred from the previous discussion that POS is definitely worth studying, but the mechanism that does not consume energy is destined to be independent of security.

Let's start by talking about why POS is not guaranteed to be secure. The POS system spends 0 for security, meaning that the defensive energy is 0, so the security is 0 regardless of the attack energy. POS systems are often very complicated to design. The reason is that it is not good to do evil. Since there is no cost in voting, the attacker can vote freely for the maximization of their own interests. On this basis, setting up various reviews and punishments is also a symptom. The root of the disease.

The practical significance of POS should be there, and you can build a complete system based on trust or the security of the POW system. However, the POS itself does not provide security, and the POS system must find its own safety corner. At present, many chains use POS itself as a cornerstone of security, and then build various functions on it. Personally, this idea is debatable.

in conclusion

The blockchain system is complex. If you change a preset condition, the conclusion may change, so I will also reserve the right to modify the conclusions of this article. The purpose of writing this article is to communicate with you on ideas, and hope that my thinking process can be instructive.