obviously it would take a lot of effort/money that probably only a government could pull off.
Right now you dont need a government, only a couple of tens of millions of dollars.
To put that in perspective, only in the USA right now, there are
1 million people that have a net worth of more than
10 million dollars. If a handfull of those wanted to harm bitcoin, they could.
Also the
supercomputer argument is a
known fallacy. Its a catchy phrase but does not make bitcoin less vulnerable to brute hashing attacks for the moment. The supercomputer argument is debunked in the thread above.
right, i should have said either a government or a person/corporation with substantial funds could do it