51% attack refers to an attack on a blockchain network by a group of miners who can control more than 50% of the network’s mining hash rate or computing power, which will give them the ability to halt the transactions on that network. It will also enable them to reverse the transactions that were completed while they were control of the network, allowing them to double-spend the bitcoin.
The crypto community has been speculating what if a government wants to get rid off bitcoin by using 51% attack strategy. It is clear that even if the government tries to ban bitcoin, they can not successfully do it as the cryptocurrency is not in hand of one individual or a group. However, 51% attack is the only way that government can use to demolish the bitcoin. It is very unlikely that a government would be able to pull off such a stunt in order to tackle bitcoin, but let’s entertain this thought.
If such an event happened, the bitcoin developers could modify the algorithm, effectively rendering the attacker’s hardware worthless. According to Greek-British bitcoin advocate Andreas Antonopoulos, it would take billions of dollars and covert operation of chip fabrication, then a coordinated assault that would give the government dominance over the next block for 10 minutes before they get flagged.
So chances of a successful 51% attack by the government are pretty much nill. It would require them to risk millions of dollars for an operation that is most likely to not go in their favour.