If the resources of all governments combined were brought to bear on the problem of demolishing BTC, what would be a way to accomplish that?
Making it illegal won't work. Neither will buying it – that will just raise the price. 51% attacks aren't effective because all they can do is double-spend coins, not arbitrarily reassign wealth.
But it will likely never go away until/unless you could find an unfixable flaw. For example, a flaw in the hashing algorithm that permits you to double-spend. Unfortunately there's effectively an enormous bounty on that particular defect that no one has yet claimed. If someone did, another coin with another hashing algorithm would take bitcoin's place.
More importantly -- what is your motivation? Let's please enumerate the evils going on in the world and rank bitcoin appropriately. It's not worth your time.
If you are really in a huff over the energy consumption I think your consternation is poorly focused. Again, let's rank our concerns here. In any case, the best way to "destroy" proof-of-work coins is to invest and promote coins that are similarly effective without proof-of-work. e.g. proof-of-stake coins like Raiblocks.
However, if China or some other government compelled miners to sign invalid transactions, this would have a big impact. This is a weakness of proof-of-work secured coins (note that they also have many strengths that proof-of-stake coins lack).
EDIT: I was unclear what I meant by "this is a weakness of PoW" -- the energy signature of concentrated mining operations make them easy for governments to find.
* Create exchange(s), get users, then implode them ("oops, bad code / we got hacked") (bonus: free $ for black ops)
* Create competing coins, either crappy ones just to suck away mindshare or legit one(s) backed by the gov't that grants some stability through gov't capability. Or heck just designed well enough that people want to actually use it for spending.
Or just go the more traditional / direct route and create regulations or make it outright illegal, and shut down exchanges and throw people in jail (probably the most effective)
BTC is gearing up to be the biggest financial disaster in history, and it's better to start planning for it now.
I can see how one can arrive at this sentiment based on how quickly the price has increased, but I wonder how bad it would really be since the vast majority of Bitcoin investment is not debt based. Additionally most people I've talked to on the matter, only invest what they are willing to lose.
Now, if a significant amount of investors get in via margin and other debt-based approaches, then that could be problematic. BTC have seen huge drops in value in the past, how individuals new to the space react is unknown.
Lots of value evaporating doesn't necessarily make for a disaster. It only does that when it interacts with the larger financial universe in unexpected ways. In countries where people will start missing their mortgage payments as a result of Bitcoin losses, yes, there are systemic risks. In the United States, we're still far from that point.
And there's no way for society to decide that should change. They can act as evil as they want with no fear of losing their coins.
https://www.theguardian.com/global-development/2017/jan/16/w...
It's one thing if hedge funds are pouring in, another if housewives in Japan (if the press stories are to be believed), but at the end of the day there's a finite amount of capital that will be pumped into it, as capital wants to go to other investments, too.
This is my best guess, and I'm legitimately curious if it's a believable threat.
But you could just do the DDOS, then blocks would stop being confirmed and the value would plummet.
The only problem Bitcoin solves is double spending. Without this ability it’s worthless.