Bitcoin Forum

When reading about bitcoins, I came across the 51% attack concept. This is something that any entity with enough money can do. If Bitcoins really become a dominant force and threaten any of the major currencies, is it not possible that they would launch a 51% attack and control or destroy the bitcoin system? Or, is there a built-in protection available in the technology to prevent this?

Distributed mining is the defense against attack.

Which implies that it needs a defense. Sans that it can be brought down. Governments can ban GPUs, mining rigs etc. so the defense gets weak while they can have powerful hardware.

What does the technology have to prevent such a thing from occurring?

Bitch please, ban computer parts?
They don't need to make a PC revolution to make a 51% attack, they have lots of super-computers to make a lot of floating points operations that, if they want it today, they can make the 51% attack.

They are doing this right now in the Euro states. Legislation is being enacted to ban the sale of high-end graphics cards.

Hey now! That's to make the world a better, greener place. ;)

It's for your own good, now TAKE YOUR MEDICINE.

Miners are both the defenders of BTC and the minters of BTC.

ASICs are around the corner, but whether that makes the network safer or not is open for debate. I tend to think it does.

They're messing with my GAMES!  >:( Imma grab my raygun and shoot them all too kingdom come.  >:(*


* Disclaimer: There is no scientific evidence linking video games and propensity for violence. Now shut up about it before I kill you slowly and painfully.

http://www.nordichardware.com/Graphics/updated-eu-cripples-future-graphics-cards-exclusive.html

Come on guys, link articles etc. so people don't think your crazy.

Messing with video games won't make me violent, however if you touch my porn you better pray to whatever gods you believe in.

If you have 51% of the network hashing power, there are two things you can do with it:

• Secretly (but entirely legitimately) mine more bitcoins than the rest of the network combined, making you insanely wealthy; OR
• Do a 51% attack, which cannot be done without the rest of the network knowing about, causing a mass panic and a loss of faith in the system, greatly reducing the value of any coins you mine.

These options are mutually exclusive. You can either get rich or attack the network, but not both. There is a very strong economic incentive to not perform a 51% attack. A built-in bribe for potential attackers, if you will. Of course, a politically-motivated attacker might care more about disrupting the network than their own wealth, but really, what are the chances of that ever happening? ;D

...perhaps that's why there was no link? Just sayin'. ;p

Crap, now I'm gonna have to find a brand new way to seem crazy.

Maybe I could imitate usagi, that should work, shouldn't it?

Well, not so low...

Not really.

There are super computers, but generally they are already committed to tasks other than fucking with bitcoins and floating point operations also don't have much to do with SHA-2 hashing. There isn't a single supercomputer that could 51% the bitcoin network on its own. Traditional and even newer GPGPU supercomputers are actually a really shitty way to attempt a 51% attack.

When bitcoins threaten any major currency or the government control of economy, then they will have an incentive to make the 51% attack. That's when the chances of it happening go up.

I am still interested in knowing if there is anything in the technology that can thwart this.

What are you suggesting? That a political organisation might turn down a massive bribe? Maybe you're forgetting just how massive it is. We're talking about 51% of all transaction fees, plus 51% of all newly-created money, of a worldwide currency. That's a central banker's dream (well, they dream of complete control, but I think they're all aware that's never going to happen with a world currency). You really think anyone would rather try to destroy us (with no guarantee of success, I might add) than take a 51% cut? I don't.

You are mistaken.  If you can maintain 51% of the total hashing power on the network, you will acquire 100% of all transaction fees, plus 100% of all newly-created money.  For as long as you maintain 51% of the total network hashing power, you get to create ALL blocks.  Even if others happen to create a few blocks and get ahead of you for a bit, you will eventually overtake them orphaning their blocks and replacing them with your own.

Some would say that bitcoins already threaten all major currencies and the government control of the economy.

The technology is designed such that it becomes more difficult and more expensive to engage in a 51% attack as more people take up mining.  There is a cascading chain of events here...

The more mainstream bitcoin becomes, the more people want it.
The more people want bitcoin, the higher the exchange rate and the higher the value of the block reward and transaction fees.
The higher the value of the block reward and transaction fees, the more incentive there is for miners to try to get some of that money.
The more incentive there is for miners to try to get some of that money, the more mining equipment that enters the network.
The more mining equipment on the network, the higher the total network hashrate.
The higher the total network hashrate, the more money a government entity would need to spend to perform a 51% attack.

So, the current cost of a 51% attack is pretty expensive but not outside the realm of possibility for a well funded entitiy such as large government.  However, the future cost of a 51% attack is likely to be significantly higher.  Will it be high enough to prevent a government from attempting it if/when they decide to try?  We'll have to wait and see.

You're confusing nominal value with real value. A 51% attack can't be kept secret, it will be discovered pretty much instantly, and then who's going to buy your bitcoins or accept them as payment? Nobody, that's who. If there's ever a 51% attack, the attacker's coins (along with everyone else's) will be worthless, and if the attack continues for any length of time, they'll never recover their value as all faith in the security of the network vanishes. Alternatively, you could decide to not orphan everyone else's blocks, and then nobody will be the wiser, there'll be no drop in value, and you get to keep 51% of everything. I'd much rather have 51% of something valuable than 100% of something worthless, but maybe that's just me.

And? You don't even need a supercomputer for that. Just buy enough GPU (or ASIC once they are released) and ta-dah, 51% attack. Cost? You can do it today with less than 20 millions (probably with 10 millions, and i'm speaking about buying all the hardware, buying the building and the infrastructure to put that into, hire enough ppl and blablabla). 20 millions $ is CHEAP if you are a rich person/bank/government. Very cheap.

"massive"? Some millions $ is "massive" for you? Oh LOL. In case you don't know the guys i'm speaking about (banks, governments, etc) daily spend billions of $. Dozens of thousands of millions. The 51% cut is peanuts for them.
Also remember, if bitcoin become successfull they will lose billions.

I find it cheap. 20 millions? A soccer player gains more money in a year... clubs spend dozens of millions to buy one. Some years ago they bought Ronaldo for 90 millions.

Still much less than what is spent on wars. If they want to declare war on bitcoins then it entirely enters the realm of possibility.

How do you know this?  Do you have a magic crystal ball that predicts what the total network hashrate will be if/when a government decides to try a 51% attack?

Of course there isn't a single computer that could do the job. I said about he floating point operations because the main operation of a common GPU are floating point operations, since in our fake 3D games there are no integer numbers.

I know that every single supercomputer of a government already have a task, I'm just saying that they have enough power to easily make a 51% attack, but, why in the hell they would make it? BTC network is weak and they dont care about BTC, today.

If Bitcoin becomes successful, they stand to gain billions by working with it rather than against it (sure, it's not worth billions now, but it will be if it ever reaches the stage where it becomes a serious "threat"). And if it doesn't become successful, why go to the trouble?

The other thing is that as bitcoins increase in value, mining becomes more profitable, which means more people will mine, which makes it harder and more expensive to pull of a 51% attack. When Bitcoin is worth enough to pose even a slight threat to the banks and governments, it will have much, much, more security.

Working is the problem.

Why working when you can do all the debts you want and then print dozens of billions every month and "steal" value from everyone via inflation?

With bitcoin this is totally impossible. USA (and the rest of the world of course) would just collapse if they had to stop to print money

So why haven't any governments attempted a 51% attack yet?

Because they don't give a f*ck about BTC?

Probably. I still think Bitcoin is one of the biggest spit stirrers (both politically and socioeconomically, despite Bitcoin being a currency and apolitical) since JFK got the "red bills" printed up, though.

The future is a mystery = No one can know what tomorrow will bring, so there is no reason to worry about it.

In today's terms, the money needed to launch a 51% attack is insignificant compared to what is spent on wars. If needed, it is not inconceivable that money will not be a factor. Which returns me back to the original question. Does the technology have anything to prevent a 51% attack or is the bitcoin system helpless against such an attack? No one has addressed this. I believe this is the part that needs to be discussed, not whether governments will attack or whether they have resources to do so.

If the technology can have some way to prevent a 51% attack or a strategy can be formulated to prevent it, it is well worth discussing.

How so? From what I am reading, a 51% attack is all that is needed to cripple the system. Why an entity would do so or have the resources to pull it off is secondary. I am more interested in seeing if the technology can provide or it can be improved to prevent such a thing from occurring.

BTC Network is too small, that's why a 51% attack is so easy.
Want to prevent it? Wait for ASIC's and call more miners.

The government can also purchase ASIC's and mobilize miners. Not to mention bribing/coercing existing miners.

The idea of a future security, it's because every day the BTC can change it's code for block generation and many other things.
Godammit, we already said if the government wants it today, he can.
Now close the thread.

Well, if nobody is interested in discussing, I will close the thread.

Off to find Plato for some philosophical entertainment.

An entity with enough money can do a lot (but not anything). Go fishing, buy icecream, fly into the orbit, burn the money (https://en.wikipedia.org/wiki/K_Foundation_Burn_a_Million_Quid), start a war...

I've seen this concern many times, but never seen a satisfactory explanation as to how exactly Bitcoin would threaten anyone or anything more than any other technology.  After some struggle, the automotive industry is starting to embrace the electric car. The Internet is embraced by even most totalitarian regimes and corporations (for perfectly rational reasons), just like the printing press was embraced. If Bitcoin is a robust, effective, and disruptive technology, more smart people will recognize it than deny it - regardless of their ideological background.

***

As for the ease of >50% disruption (I wouldn't call it an attack) - hash rate, ASICs, etc. have nothing to do with it. Network security is simply determined by the total investment in Bitcoin mining. Assuming most miners use best available technology, and the same best technology available to a malicious entity, this malicious entity would need to invest at least that much money to claim >50% of the network. Current estimates are on the order of several tens of millions of USD. While this would disrupt validation of new payments, it would also become obvious to everyone. My coins would be perfectly safe, even if I am temporarily unable to spend them. I am not qualified to discuss counter measures, but I imagine the community could quickly set their nodes to only accept connections from known honest miners and nodes as a temporary fix.

bitcoins will survive

The concern here is that it is not just disruptive, it can threaten government control of money at which point they can consider destroying it. The purpose of this discussion is to see what can be done to prevent such a thing instead of just sitting and convincing ourselves that such a thing would not happen.

Thanks for providing the suggestion. This can indeed be one way. What else can be done?

You're so cute, how you all worry about 51% attacks and incredibly complex setups to achieve such an attack.

Wanna kill bitcoin? Here's how you kill bitcoin.

Wait for bitcoin conference, wait till all the movers and shakers are there, blow up the building, then claim it was a meeting of terrorists building doom machines, post pictures of mining rigs as evidence.

Remebers me of how some people failed at trying to kill Hitler, except the part of mining rigs.

There should be some thread locking program that scans for the word Hitler - it seems all threads eventually go there, one way or another.  Maybe "Hitler" can be a new term meaning "And now it's time to end the thread" = Hitler ?  Just a thought.

That's not new. It's called Godwin's Law and is about 20 years old or more.

Bitcoins will end when deflation finally becomes unmanageable enough to kill the economy. Deflationary currencies are not good.

It seems pretty unlikely that there would be a successful 51% attack.  I think even the richest people or governments in the world would have a hard time pulling it off.

I'd imagine that it wouldnt be overly difficult per se to carry out the 51% attack, i mean, everyone here is assuming they will just build a massive mining rig and take over the network, although if bitcoin was being targeted to be shut down i'm guessing it would be more than one government.

what would probably happen is all domain names linked to bitcoin, exchanges and mining pools would be turned off, as many servers as possible seized then every government that was aiming to shut it down turns on there own mining rigs and takes control of a lot more than 51%. If bitcoin was to threaten the monetary system then globally i'd be worried about a lot more than just a goverment pool harvesting 51% or more of the hashes.

Of course this would all happen after an official banning and some high profile arrests splashed all over the media to scare people into not doing it, under the pretence that bitcoin is used for buying drugs, building weapons (if they believed that dork who did that talk at the confrence in london i forget his name), and other such things that require money laundering.

Before they carried out a 51% attack they sure as hell would reduce the network hash rate a fair bit using more conventional methods (then probably use the impounded equipment to carry out the attack or fund it with money seized from accounts)

I do hope that you are right.

Meanwhile, "Iranians are resorting to virtual currency to move money into and out of the country in a way that Western authorities find hard to detect." http://www.businessweek.com/articles/2012-11-29/dollar-less-iranians-discover-virtual-currency

I also found this interesting article by Neil Fincham, the MineForeman: http://mineforeman.com/2012/12/10/want-to-destroy-bitcoin-i-am-going-to-tell-you-how/