51% attack not pow cracking attack
You have mentioned quantum computers.
If they would exist (they don't) they would be used to attack the ECDSA... not mining.
ASIC's are made for mining.
please ignore the quantum reference as it takes away from the point.
You have mentioned quantum computers.
Most basic computers can mine/become a full node and/or connect to a minning pool, so as long as the have computing power it will only require plugging in a supercomputer or two.
1 or 2 'supercomputers' won't achieve as much hashing power as bitmain, for example.. with all their ASIC farms.
If you want to mine bitcoin efficiently, you need an ASIC.
Because thats what they do. Thats the only thing they can. They are made for the only purpose of calculating sha256 hashes.
SO they dont actually have to break algorithms of security but simply outperform total current network and destroy the confidence in the coin.
Theoretically, maybe.
Practically not going to happen.
and if the banks/govts way of life is threatened they will dedicate a project of the like. because the door is their or am I missing something.
Or they rather choose to ban the possession/usage of cryptocurrencies, instead of investing billions into trying to stop something which won't be stopped.
Imagine governments spending all their money on building the biggest mining factory. A simple hardfork would completely destroy their whole 'investment'.
A backdoor is a backdoor anyhow you sugar coat it.
How is that now related to a backdoor?