Definitely not impossible, but a quick check at the moment suggests that with the best available ASICs, it'd cost about $376M retail (or perhaps less wholesale) to buy hashing power equivalent to the current network. (And that assumes sufficient supply to do so, though it might be possible to scale that better.) So, definitely in the range for states to accomplish, but not trivial; it'd have to be extremely critical to do so. (And an attempt to do so would likely get noticed, and there are ways to work around it.)

The U.S. threw ~$80M worth of missiles into Syria several days ago, just to damage an airfield. No one would blink at half a billion to take out bitcoin, and that's assuming that the NSA/CIA don't already have billions' worth of codebreaking hardware that could be applied to that purpose (they almost certainly do.) Taking control of bitcoin is probably "fun weekend project" level work for them.

>Taking control of bitcoin is probably "fun weekend project" level work for them.

What if they created Bitcoin?

We've all read about the CIA running drugs to raise cash for black ops... why not take it a step further and create your own currency?

My personal theory is it was an intel agency, or a criminal group.

Keep in mind Truecrypt was also written by criminals: https://magazine.atavist.com/he-always-had-a-dark-side

Damn that's a chilling thought

The cost ($80M) is not the interesting metric - consider the press coverage, positive poll results and resulting political engagement. The power gained is the interesting result.

Currently there is no power to be gained in wiping out bitcoin when half of the constituents have never even heard of it. Never mind the cost.

Agreed. The point is that USGOV could 100% do it, for pocket change. It would be pocket change for a bunch of countries, really, and expensive but doable for a whole lot more.

I would assume the only reason we haven't done it has nothing to do with the cost, its simply that bitcoin is just not interesting enough to them (yet). I can't imagine that some USGOV and probably >1 non-us-gov have plans already and could rapidly build out an ASIC farm, if asked to do so (and funded, of course).

The NSA has its own fab (IC fabrication plant). That makes rapidly building out an ASIC farm even easier.

China doing so to halt capital flight is far more likely.

Agreed. China doing it is way more likely in general because they could walk in and take over enough capacity to reduce the capex required for takeover (by combining stolen capacity + new capacity) by perhaps 75%. It would also make it way harder to notice, because a massive new mining pool trying to pull things in a new direction would be obvious. Several established mining ops shifting direction would be less obvious.

rsync is right. There's a lot of factors at play to make those missiles worthwhile to those in power. Whereas, they won't waste effort on bitcoin until they get similar gains or it's similarly a threat. Right now it's definitely not a major threat in their eyes. It's barely even a minor threat with all the crooks using stolen credit cards, money mules, Western Union, etc. Vast majority of damage done on that end of things. Their big investment to deal with finance is the same they'd use on Bitcoin transactions: mass surveillance of Internet and financial system. A multi-use technology that helps in more goals. ;)

If the top 2-3 miners are in China, it would cost the Chinese state zero dollars to issue an ultimatum to these organizations - say, requiring them run X modified software or do whatever.

China's legal system already contains provisions which could be summarized as "all your data belongs to us".

> they could either just buy some thousand Bitcoin and spam the network with transactions

Marginal loss on each transaction + "spamming transactions" = essentially paying people to run their machines at 100% for a while for you, which to the tune of "some thousand bitcoin" would be money to their ears

> just [..] buy enough hardware to get over 50% hashing power

'just'

> Especially China only needs to take down the 2 or 3 top miners and can cut the mining power in half within a day

If that is true (and I'm not convinced that it is) you don't think those '2 or 3' entities aren't large and financially self-interested enough to work to secure themselves, divest their resources, or so on?

I highly doubt any sort of subversive action could be taken sub-rosa to the tune of 51% of a network of paraniod individuals who'd either fork or move out given any whiff of subversion, especially by state actors.

> Marginal loss on each transaction + "spamming transactions" = essentially paying people to run their machines at 100% for a while for you, which to the tune of "some thousand bitcoin" would be money to their ears

If the network is unusable for 6 months or so because confirmations take dozens of blocks or need very high fees, what do you think would happen? Everybody just waits for it to blow over and continues like nothing happened? The costs don't matter if the control over the monetary system is at stake. Defend now or the $/€/¥/£/etc will lose value anyways. Not that I expect it to come this far but don't underestimate the monetary power of large states. Bitcoins often quoted market cap is only a very, very small blip on their radar right now.

> 'just'

Okay, you are right. They would most likely confiscate the miners' hardware and will mine with that. So they kill two birds with one stone.

> If that is true (and I'm not convinced that it is) you don't think those '2 or 3' entities aren't large and financially self-interested enough to work to secure themselves, divest their resources, or so on?

China regularly takes down party members for "corruption" (more likely not enough corruption). So if not even party members are safe, how could anybody be safe that threatens the power of the whole government?

As the supply goes down, so too does the price rise. They will become more expensive the more governments try to do this. This is like saying that "a government can buy all the gold in the world to prevent this" .. inherently false and shallow statement ignoring the complexity of the issue

And again a novelty account pops up and talks about how complex Bitcoin is and how Bitcoin is like gold despite both not sharing similarities. Bitcoin is not gold. It never was and never will be.

The anarcho-capitalists who think that Bitcoin exists outside of government control and will be able to replace national currencies are wrong. China can at any point order the top miners to shut down their pools. Bitcoin is simply not relevant enough to be attacked by more than the local police that is underfunded for those endeavors anyways.

Always remember this old XKCD: https://xkcd.com/538/

The difficulty is according to the amount of miners, right? So it's supposed to not matter if China shuts down their pools. And local police? Complete speculation, my friend.

You obviously don't know enough about Bitcoin to argue the way you did.

If there is X hashing power and you need X/2 to control the network, then reducing X by 50% means that you only need X*0,5/2 to control the network. The difficulty is only adapted every 2010 blocks which equals around 2 weeks but if you suddenly cut the hashing power in half, this will take up to around 4 weeks and slow the network down immensely.