After the halving, the cost of double-spending BCH and BSV is less than $10,000? There are two major misunderstandings

As BCH and BSV have completed their halvings and the computing power of related networks has plummeted, the topic of 51% attacks has been brought up for discussion again, and some people will cite data from crypto51 or NiceHash to show the cost of attacking these networks.

As shown in the figure above, the data displayed by crypto51 shows that the one-hour cost of attacking the BCH network is only US$8,983, while the one-hour cost of attacking the BTC network is only US$540,000. Is this really the case?

In fact, there are two major problems:

1. Data source: NiceHash. The computing power available for leasing is very limited. For example, the computing power available for leasing of the sha 256 algorithm is only 298 PH/s, accounting for about 16% of the current BCH network computing power.

2. Data source: NiceHash. The price of computing power is not fixed. If someone rents computing power in the short term to launch a 51% attack, the cost of renting computing power will also rise (this has happened in history).

Therefore, the actual cost of launching a 51% attack on the BCH and BSV networks is much higher than the value shown above, not to mention changing the target to BTC. Basically, for large PoW currencies whose NiceHash market cannot cover the computing power required for the attack (1/3 or slightly less than 1/3 for selfish mining, 1/2 for double spending), simply attacking through the computing power rental platform is basically a dead end.

So what is the real cost of double-spending attack on the BCH network? This can be divided into three situations, and it depends on whether you are a new miner or an old miner. If you do not have a mining machine, you need to rent all the available computing power on NiceHash (the cost is relatively negligible), and purchase a large number of mining machines. Taking S19 PRO as an example, this cost may exceed 100 million yuan. Alternatively, you can convince some miners to collude with you and let them provide computing power for the attack, then this cost is much less than the cost of purchasing a mining machine yourself (but still greater than the $8,983 mentioned above).

And if you are an old miner who has a lot of computing power and has already recovered the cost of the mining machine, then the cost of the attack is actually the electricity cost of running the mining machine. Although this possibility exists in theory, in reality, miners with sufficient resources (such as Bitmain) will not do anything that will harm themselves.

Of course, you might say, no matter what, I will attack, even at all costs.

(Photo from: tuchong.com)

Well, of course it is still possible to attack, but that doesn't necessarily mean there is no way around it.

In fact, even if a 51% attack does occur, it is possible to recover.

According to researchers from Harvard University and MIT, there was a case of anti-51% attack on the Bitcoin Gold blockchain in February 2020. After the attacker completed the attack, the defender continued to mine on the original chain and competed with the attacker, eventually forcing the attacker to abandon double spending.

Assuming that this mechanism is effectively used, it can greatly increase the cost of double spending, and attackers may be scared off.

Well, the purpose of this article is not to explain how safe BCH and BSV are, but to clarify some concepts that are easily misunderstood.

Related reading: "Anti-51% attack: Harvard MIT scholars propose a new theory to combat double spending"

Link to this article: https://www.8btc.com/article/580875
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