The dreaded 51% attack is one of the dangers that are latent in all blockchains, especially those based on the PoW protocol.

LBlockchain technology since its inception has had a weakness by design that its developers seek to avoid, it is called 51% attack. This attack allows one or more malicious agents that control at least 51% of the network to do what they want with it. There are no limits to the actions they can take on the blockchain. They are majority and as such they can rewrite or even perform a DoS attack on the network.

This weakness is related to the way in which blockchain networks are structured. These are but a series of nodes distributed. All of them driving a consensus protocol It is based on the trust and work offered by a majority group of participants. This is to avoid that the existence of a low percentage of malicious nodes can create chaos on the network.

However, the story completely changes when malicious actors come to have 51% or more of the network's power. At this point, as we have said before, they can do whatever they want. From there derives the name of the attack, because that percentage of power is the minimum necessary to carry it out.

How are these attacks carried out?

Performing a 51% attack is not technically complex. It is enough to have a mining node and have the majority participation in the blockchain network. That is all that is really needed, and this situation might sound worrisome, but it is not. Well, the problem lies in having that majority participation. A situation that depending on the blockchain can cost a few thousand dollars or cost millions.

Take for example the case of Bitcoin. With its consensus protocol PoW and algorithm SHA-256 It is technically quite easy to make such an attack. There are powerful machines ASIC y FPGA that can facilitate the task of obtaining computing power. However, the size and total distributed computing power of the Bitcoin network make the attack difficult. It would not take thousands of these teams to successfully carry out our attack. A situation that would raise costs to millions of dollars. An economic expense that might not be rewarded for the profits that the malicious actor could obtain for his successful attack.

But if instead of Bitcoin we take a smaller blockchain like LeaCoin, the story changes. With the same consensus protocol and Bitcoin hash function, LeaCoin It is a small and easily attachable blockchain. With a total computing power that barely exceeds 1 TH / s, a current ASIC team would be enough and more than enough to carry out this attack. If the attacker could take financial advantage of the situation, he would undoubtedly be a prime target. The reality is that LeaCoin has very little value and is considered a shitcoin.

The history of these attacks is repeated over algorithms like PoS y DPoS, each of them with their difficulties and particularities.

How much do you know, cryptonuta?

Is a 51% attack simple and cheap?


51% attacks are a fairly complex and can be a very expensive form of attack on cryptocurrencies. The truth is that the more miners and people participate in the network, the more complex and costly this type of attack becomes. Hence the great advantage of networks such as Bitcoin or Ethereum, whose size and potential protect them from this type of malicious action.

What consequences can a 51% attack have?

First, such an attack would allow the attacker to obtain the most mining rewards on the net. This is because it controls most of the mining power, and therefore the system will reward you proportionally.

Another case that may take place is the attacker's ability to perform double-spending attacks. That is, the ability to modify the history of the blockchain to recover spent coins and have the ability to spend them again. These first two actions are the main reasons to control most of the mining power of a blockchain. They allow you to make completely dishonest profits and no one can stop you from that goal.

A more extreme case of this type of attack is to carry out a DoS attack that leaves the network out of service. All in order to negatively affect the economic ecosystem of said network, which would lead to millions of losses depending on the market value of the cryptocurrency.