Quote from: BenOnceAgain on June 11, 2018, 03:05:38 AM

Quote from: btj on June 09, 2018, 10:28:24 PM

In the current state of things, it's near impossible to attack Bitcoin ! This show how this coin is strong now.

I agree: Bitcoin is strong.

As others in the thread have noted, a group of miners that collectively control 51% or more of hashrate could decide this second to implement some change to Bitcoin's code, consensus rules, and/or presumably do all sorts of nefarious things to the blockchain. If they started running new code, their blocks would be accepted, at least, by them (unless they don't know how to code and somehow break their fork, and I seem to recall a problem with exactly this in a certain fork that occured just under a year ago).

As of right now, there are currently 9938 nodes on the network, two of which are mine. However, I do not mine (see what I did there?). So, from one perspective, I have no say in what my nodes choose to accept into their local copies of the blockchain. From another perspective, however, I also control those servers and can choose to stop running Bitcoin Core or upgrade the software as new releases are available. So, in that way, the plurality of users do "have a say" in what happens to Bitcoin.

From this link, it looks like the three largest pools control 51% of hashrate. So if they chose to collude, they could change the rules. On the other hand, if at least one of those three did not participate in some fork, the rest of Bitcoin miners could not cause an "attack".

I trust Bitcoin Core. Not just the software itself, I also trust the people that are involved with the project. This could change, of course, but I don't expect that with the present contributors and the project as a whole. If a nefarious attack threatened the viability of Bitcoin, I am virtually certain that they'd take countermeasures. There exists at least one "emergency hardfork" repo to change the PoW algorithm if it's ever needed. I'm confident they could ship such an update in hours if necessary. I believe Core would treat certain circumstances with the same level of attention that they would treat security vulnerabilities, and implement, test, and ship mitigations as quickly as possible.

Other thoughts...

If I was a miner, I don't think it'd be in my best interest to mess up Bitcoin, so I doubt I'd go along with any concocted scheme to attack/fork/etc. the chain. Confidence in a technology as well as in the integrity of the people behind it can be difficult to gain but very easy to lose. Why risk it?

I strongly support measures to increase the resilience of Bitcoin. My personal belief is that mining effort is too centralized and hope that problem is resolved in time. I believe that multiple approaches to increasing resilience are merited for Bitcoin, given that it is the world's premier cryptocurrency. I believe a sufficient number of nodes should be run in nuclear-hardened bunkers on multiple continents and that mining should be done in areas where it might just "break even" and that other, cheaper mining operations should work together as a collective (not any formal organization as that is more centralization) to share the costs and profits for these resilience pools, not to make a huge profit--but to ensure the continued resilience of Bitcoin (which also is part of profitability). Measures of this type may sound elaborate or excessive, but I believe they are crucial to a technology that is digital money. They are the type of things that instill the confidence that I previously mentioned.

In conclusion, even if you had the 6.2 billion dollars that you estimated it would cost to conduct a 51% attack, good luck getting the equipment necessary manufactured. I believe you'd have to set up your own production facility to come up with enough ASIC's to get the job done. And as LeGaulois said, good luck finding the necessary electricity. I suppose with the money you saved from running your own ASIC shop, you could also build your own power plants.

There are far more profitable ways to invest 6.2 billion dollars and all of the work required to successfully 51% attack Bitcoin. And in the end, for that reason, it is very unlikely to occur.

(Incidentally, I hope that last section stands the test of time and that I do not eat those words--that would be a shame. Why would someone choose to focus on negatives, attacks, division? There's so much good that can be accomplished through peer to peer, decentralized yet collaborative work towards greater goals.)

Best regards,
Ben

Nice reading, thank you for your contribution !

It's pratically almost impossible to perform this kind of attack on Bitcoin, even if someone succeed to do it (A simple hard fork and he lose 6.2 like nothing, even without hard fork he will never get back the money spent on the attack since no one will buy bitcoin in that case and everyone will SELL - Panic SELL -).