[jhall1468]

You're off by a factor of 20. The current hash rate is 17.5 million terahashes per second. Ant Antminer S9 goes for $2800 and produces 13.5 terahashes per second. In order to get to 51%, you'd need a $2 billion dollar investment.

[loceng]

How much is spent on war directly (that we know about) every year globally?

[jhall1468]

The US military budget is $600B. Not sure what your point is though. A 51% attack doesn't give a government control, it just allows it to double spend. And that's until a hot patch to increase the required number of confirmations resolves the issue.

Besides there's a huge supply problem here. ASICs need to be manufactured. You can't just buy several hundred thousand of them. The whole point of Bitcoin is that it's prohibitively expensive to just perform a 51% attack and impossible to entirely regulate.

[once_inc]

A simple fork invalidating coins originating from the double spend would be enough. You've just spent $2B to achieve something that the network can invalidate with a dozen lines of code. It would set a bad precedent, but it did cost you a lot of money.

[wellboy]

So, you can undo any 51% attack with just a quick hardfork with a few lines of code?

[jhall1468]

One hell of a straw man. Bitcoin isn't going to do that. It isn't Ethereum.

[tuxxy]

If I'm not mistaken, too, the $2Bn investment is just the beginning. The attacker would also have to cover the costs of at least 51% of the energy used in the network - much less find somewhere they can use that much energy without someone noticing.

The idea that a 51% attack on Bitcoin is plausible just isn't sound, imho.

[wellboy]

Interesting, how much would it be say on Bitcoin Cash?