Topic: How strong is Bitcoin against 51% attack ! (Read 475 times)

When accepting payments below $1 million dollars.. no one is going to 'Attack-The-Chain'. As you say, too expensive.

When accepting payments over $1 million, just wait a little longer..

If you did have 51% hash power, outrunning a 1 day chain, takes.. Yep.. 50 Days. No ones going to do that. (You only get a 1% boost - as the normal chain grows as per usual, but slower..)

I think to properly attack the network, what you need to do is remove 90% of the hashrate. But probably only a government could do that.. or BitMain (root kit) LOL..  China could just shut all the Chinese miners down. If you could do that, BTC would be in trouble. The blocks would take f-o-r-e-v-e-r-.. the retarget period would take 100's of days. You could hard fork your way to a simpler difficulty, but that's the only way. (But then I suppose they could turn the machines that go PING back on.. and attack properly.. with 90%..)

Anyway, I'd like to see a system introduced that could handle that sort of hash rate loss. Simply allowing the difficulty to trail off after 2 hrs.. has security issues..

It almost happened when BCH attacked the network.

..

The only people who could even think of doing this are those we pay to protect us.  Always the way (when you pay a third party to protect you).

I have made similar calculations about a year ago and came to the conclusion that Bitcoin could be 51% attacked with about 2-4% of the value of the "market cap" (with some variance because price/difficulty relation is not always the same). I based my calculations on rented hardware (cloud mining) but essentially the cost seems to be similar.

So I agree: Bitcoin is strong.

But Kakmakr's answer reminded me of a scenario I never was able to get out of my mind, where I guess it could be possible for an attacker to obtain large profits with his attack:


What if the attacker just wanted that -  to crash the price - for example, because he's massively shorting coins and would profit of a crash?

He would have to create a double spend to prove that he attacked the chain, but he can do that with his own addresses. So he would not even face charges of theft. (He could, however, face the charge of "damage to property" as he's interfering in the functioning of the Bitcoin system, or something similar.)

This attack scenario, however, depends massively on the amount of coins which can be shorted. Unfortunately, the new future markets would just allow these kinds of massive short operations.

Anybody able to "rebutt" that scenario?

This is one time investment.


And this is what the attacker would have to pay every day if they wanted to keep the attack alive.

With so much money involved I guess this could be pulled off only by the government (if we don't consider the most important miners currently mining bitcoin). Which would be hard to maintain long term, as the government presumably wouldn't be making any profit out of it. Also knowing that if they somehow managed to destroy bitcoin, there would be numerous other altcoins waiting to take its place, so it wouldn't be worth even contemplating.

Yes, new altcoins are more exposed to this kind of attack.


You are making wrong comparaison and this have no correlation, and this calculation will help other altcoin owners to check if they are exposed or not ... i made this example for Bitcoin but other can take note from this and make their own one on another coins.

If this seem for you useless, for others no, you can check the first comments on the top ... if you have good arguments and value to add to this topic you are welcome, if not do not speak to say nothing ...


You can read the first comments, this been already pointed before ... my intention is not to offend you.

And it is as useless and pointless as calculating 'how much I could earn if everyone who downloaded my homemade wideo on youtube would pay for watching it as if I were Dwayne Johnson and video were released by Universal'

All in all, 51% attacks are of little threat to well-established cryptocurrencies and will likely continue to fade into obscurity as decentralization increases. However, these attacks still pose a significant threat to new coins, particularly if the attack is being maintained for a significant period of time, at which point the changes may become irreversible. Moving forwards, rig operators should refrain from joining the largest pools, despite the obvious benefits, whilst remaining vigilant.

Around 6.3 billion without electricity cost (Around 3.9 millions $ per day - you imagine the power of eletricity required and how to get all that amount of antminer ? they must have their own power stations, and try to buy the plan of antminers and build them self as one user suggested above).


We already know this ... i just wanted to make the calculation to exploit this side too.

6.2 billion. Meh. That means anyone in the Forbes Top 50 could take it down whenever they want?

You can not 'hack' SHA-256. You can not hack any hash function.

Bitcoins 'security' is more dependent on the ECDSA, than on SHA. Read more about the discrete logarithm problem here.

Bitcoin is strong as its SHA 256, it will be strong untill there will be a sudden spike in computing power that will enable SHA 256 hack in minutes. Right now its not worth to try to attack bitcoin. The value would go to zero suddenly after such an attack.

As I already poited out in another similar puffy topic, there is no need to spend zillions of dollars for that (and then wait for delivery infinitly).

It's enough to pay much less to one or two biggest pool admin(s) for modifying their software (and you will get the entire hashpower immediately as a bonus).

Additional bonus for pool (i.e. miners) shall be a reward for all the 'overmined' (overriden) blocks.

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 -).

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

Thats pretty interesting how massive this thing is ..it would take over the entire planet .lol

In addition, if this kind of attack is performed ... a hard fork will solve this problem and all the amount of time, money, energy spent on this will go to zero.

The mining pool ghash.io briefly exceeding 50% of the bitcoin network's computing power in 2014, but as of now, there many new strong pools, bitcoin farms etc ... so it's really difficult to perform this kind of attack.

https://en.bitcoin.it/wiki/Comparison_of_mining_pools


Nice answer.

Good luck to spend over 3 million dollars per day just for the electricity, no matter if you have multiple locations to do it. A nuclear power plant can't even produce such amount of resource and a capital city surely uses less 5% of it

Considering the main motivations for such attack are market manipulation or loss of reputation. There is only a targeted type of people interested in doing it

We have been there before and when a huge Pool reached a percentage close to 51%, a lot of Pool members shifted their hashing to another Pool. Why would they willingly do that? Well the answer is simple.. If a double spend were done, investors in Bitcoin will question the security of this technology and the validity of the transactions.

A massive dump will follow and the price will take a nose dive. An attack of this magnitude will cause panic and the attackers will gain very little in the long run, because the price will keep going down. The cost to sustain such an attack, also outweigh the gains of doing this. 

The idea should also be based on the likelihood of all scenarios, including the possibility of these two or more current mining pools to collude. I find this highly unlikely. What would they gain? Several hundred thousand coins possibly before the attack is discovered and miners disconnect from their pools? Even if they found a way to sell those coins, what next for the colluding pools? Their losses would quickly eat up whatever gains they made from the attack. They wouldn't want to jeopardise a business model that already works for them, simply not enough golden eggs to make killing the goose worthwhile.

This makes the only possible motivation being a desire to see the world burn.

 

I think it would be easier if an attacker secretly bought up a load of bitcoin's over a long period of time and then proceeded to slowly crash the price, making mining unprofitable and reducing hashrate on the network so that it would be easier and cheaper to attack.

Unless.... the trading price drops to "mining unprofitable" value until the Pool operators themselves came up with an idea to earn "extra profits" by doctoring the next blocks.
As discussed in other threads, achieving more than 51% of the total hashrate isn't too far-fetched if two or more of the current mining pools merge together.
So if bitcoin's value became obsolete, this kind of possibility may happen...
Not saying that mining operators will revolt against Bitcoin but based on the statement: "How strong is Bitcoin against 51% attack".

The whole idea can't be based on the mining equipment/operation cost at all, but the whole setup including the price.
With the current setup, we are not that safe if a resourceful adversary plans it well, given that the Bitcoin trading price drops to an alarming value.