51% attack

[worldofcoins]

Not many people were mining with high-tech mining machines when Bitcoin was released (2009, if I'm not mistaken).
Thus, bitcoin was vulnerable to a 51% attack by a big company or an individual with huge resources.

But was there any such attack on Bitcoin around that time?

[lassdas]

Define "attack".

While in the early years there were no big companies at all involved in bitcoin
there have been times where one individual had the majority of hash-power.

In 2010 the user ArtForz was one of the first people using GPUs for mining and he used quite a lot of them, so for a while (a couple of weeks?) he had more than 51% iirc,
but he was just an honest miner and didn't "attack" the network.

After that I think there were some pools that came close, maybe some even got above the 51% fo some time, not sure about that.
The thing about pools is, that users (aka workers) can switch them anytime. So if any of them even tries to "attack" the network, it's probably not gonna be used much longer.

[worldofcoins]

Define "attack".

Unfair means to get an advantage over the network and abusing that advantage (more than 51% hash in this case)

I think you're right. If the people (individuals) started attacking the network at that time, then the adoption of Bitcoin could've been delayed, and we would be seeing a different market price of Bitcoin compared to now.

[The Cryptovator]

As far as I know, Bitcoin has never experienced a 51% attack & there were no reported 51% attacks on the Bitcoin network in its early days. Bitcoin's security relies on its decentralized nature and the significant computational power required to perform such an attack. While there have been 51% attacks on smaller and less secure blockchain networks, Bitcoin's popularity and widespread mining made it more resilient to such threats.

[pawel7777]

Not many people were mining with high-tech mining machines when Bitcoin was released (2009, if I'm not mistaken).
Thus, bitcoin was vulnerable to a 51% attack by a big company or an individual with huge resources.

But was there any such attack on Bitcoin around that time?

Why attack something that did not yet have any traction? After the release in 2009 Bitcoin had many vulnerabilities comparing to which 51% attack did not sound all that scary. For example, that one time, in the block 74638, 92 billion bitcoins came into existence, you can read more about that here:
https://bitcointalk.org/index.php?topic=822.0

I've never heard of any actual 51% attack on Bitcoin, but at one point (very briefly) a mining pool called ghash.io went above 50% of the total hashpower, but they had no intention of attacking the network and took steps to discourage individual miners from joining their pool.

[Casdinyard]

Not many people were mining with high-tech mining machines when Bitcoin was released (2009, if I'm not mistaken).
Thus, bitcoin was vulnerable to a 51% attack by a big company or an individual with huge resources.

But was there any such attack on Bitcoin around that time?

Don't think so. There's no merit to them in the past cause surprise, surprise, bitcoin's worth nothing back then. Only as the coin gradually increased in value and appreciation did people come to realize how bitcoin is vulnerable to 51% attacks but way back then we didn't have to worry cause why would a large corporation buy 51% of the total supply of a currency which doesn't even go as high as a dollar in value? Plus to add to this there's not even that much of users in the past so jacking the price up will be a herculean task which would require this company to fork out even more money in the process, yielding a negative payout for everyone who'd try this in 2009-2012. Of course as time goes by it became apparent that bitcoin is valuable and the idea of a 51% attack became more real, but as it stands today unless you have a trillion dollars just lying around, I don't think you'd be able to buy bitcoins to that degree that you'd have supreme control over it.

[thecodebear]

Not many people were mining with high-tech mining machines when Bitcoin was released (2009, if I'm not mistaken).
Thus, bitcoin was vulnerable to a 51% attack by a big company or an individual with huge resources.

But was there any such attack on Bitcoin around that time?

Nobody knew about Bitcoin in 2009. In early 2009 there was one person on the network (Satoshi), and then there were two (Hal Finney I believe). I would assume by the end of 2009 there were probably at most a few thousand people in Bitcoin, maybe only a few hundred.

And all these hundreds or at most few thousand people that were mining were mining with CPUs, "high-tech mining machines" didn't exist for years after this. I think GPU mining didn't even start until sometime in 2010? You're asking if companies or wealthy people attacked Bitcoin in 2009...nobody knew that Bitcoin existed in 2009. Probably only a few thousand people had even heard of Bitcoin. A 51% attack back then could have only been performed by one of the very few people that knew about Bitcoin back then and was actively engaged in Bitcoin, which means they had no incentive to do it. Also Bitcoin had no market value at that point either, it was still just an experiment back then so why would those few people involved with it bother to attack it?

It's sort of like asking if people were hacking ARPANET back in like 1970 when all it did was connect like 4 universities and nobody else knew about it.

Companies and wealthy individuals getting involved in mining or even just Bitcoin in general didn't happen until years later.

[decodx]

Define "attack".

Unfair means to get an advantage over the network and abusing that advantage (more than 51% hash in this case)

It is important to understand that having 51% hash power on the network does not necessarily imply abuse of that advantage. You should consider the context in which this was possible. During that time, there wasn't much traffic on the network, and there were no exchanges, casinos, or other services using Bitcoin transactions. Therefore, there was really nothing that could be abused.

[BenCodie]

Not many people were mining with high-tech mining machines when Bitcoin was released (2009, if I'm not mistaken).
Thus, bitcoin was vulnerable to a 51% attack by a big company or an individual with huge resources.

But was there any such attack on Bitcoin around that time?

There were close calls that caused very high potential bitcoin 51% attacks. I don't believe that any were successful (definitely none successful enough to hurt Bitcoin as we are still here today). I understand from memory reading that there was a pool who had more than 51% of the hash power at one stage, though miners reallocated themselves and the pool made steps to reduce the hash power, I believe dividing into two pools was the approach.

I don't believe that a 51% attack is still something to worry about today if Bitcoin maintains its ability to make the globe compete for it's supply and its hash power.

[Upgrade00]

I think you're right. If the people (individuals) started attacking the network at that time, then the adoption of Bitcoin could've been delayed, and we would be seeing a different market price of Bitcoin compared to now.

Bitcoin was attacked at the time, some of those attacks led to changes in the protocol and others were unsuccessful. A 51% attack will not have had a long term effect on the market price of Bitcoin, same way such an attack now will not have a long term effect.
In both cases it will have been far more profitable for such a miner to simply get new coins rather than attacking the network.

[seoincorporation]

Not many people were mining with high-tech mining machines when Bitcoin was released (2009, if I'm not mistaken).
Thus, bitcoin was vulnerable to a 51% attack by a big company or an individual with huge resources.

But was there any such attack on Bitcoin around that time?

Bitcoin has a lot of soft and hard forks, but it doesn't have 51% attacks yet, the closer we get to that was on January 2014.

Potential threat averted In January of 2014, a mining pool called Gash.io got so big that it neared 51% of the total mining power. This, of course, created some panic in the Bitcoin community but was fixed shortly after by miners who left the pool in order to balance things out. Additionally, the pool committed to a 40% limit for its future operations.

But there are some fresh examples of 51% attacks in the past years in other blockchains:

Bitcoin Cash (May 2019) Two Bitcoin Cash mining pools, BTC.com and BTC.top, carried out a 51% attack on the Bitcoin Cash blockchain in order to stop an unknown miner from taking coins that he wasn’t supposed to have access to, while the network forked. Even though some would argue the 51% attack was done to help the network, it still demonstrates the power these two mining pools have over the network.

Ethereum Classic (January 2019) Coinbase identified a “deep chain reorganization” of the Ethereum Classic (ETC) blockchain which included a double spend on Saturday, Jan. 5 2019. Subsequently, Coinbase halted all ETC transactions. Another exchange, Gate.io, also confirmed that it had picked up at least seven double spend transactions after conducting its own investigation into the attack.

Vertcoin (December 2018) 4 different attacks on the Vertcoin network (a relatively anonymous coin ranking below #200 in the cryptocurrency charts) concluded in the theft of around $100,000.

Bitcoin Gold (May 2018) More than $18 million were stolen through double spending in a Bitcoin Gold 51% attack conducted by an unknown malicious actor. Exchanges tried to fight off the attack by waiting for a longer amount of confirmations before approving transactions, but that did not seem to help a lot.

But you have a point there, we are talking about the old days, maybe satoshi did some test to verify the 51% attack, who knows. In the end the real risk for the 51% is the exchanges. just think about it, you send the cryptos to the exchange, sell them, then make the 51% attack and get back the coins. Sound easy but to get the 51% of the mining power isn't easy at all.

[jeraldskie11]

But was there any such attack on Bitcoin around that time?

Bitcoin can be possibly hit by 51% attack that time but there's no evidence that it was experienced such attack. We know that they can afford the hashing power before if we compared it today.

The current level of Bitcoin hash rate is around 437.01M TH/s and the 51% is 222.9M TH/s. The best Bitcoin miner which is Antminer S19 pro only has 110 TH/s and it cost 3000$ for one. Imagine, you have to get 2M Antminer S19 pro in order to make 222.9M TH/s, which is around $6B and that's too expensive. I think there's no bad organization want to take risks on that.

https://ycharts.com/indicators/bitcoin_network_hash_rate#
https://www.investopedia.com/terms/1/51-attack.asp

[dzungmobile]

Not many people were mining with high-tech mining machines when Bitcoin was released (2009, if I'm not mistaken).
Thus, bitcoin was vulnerable to a 51% attack by a big company or an individual with huge resources.

But was there any such attack on Bitcoin around that time?

There are times when some big pools have enough cumulative hashrate if they combine together but they did not do it. I have never read any report about past attacks and surely I can miss something.

My thinking is if in history of Bitcoin, there has ever been such attacks, Bitcoin would have never been continued to grow more like we are witnessing. Any successful attack will damage the reputation of Bitcoin blockchain and investor belief will vanish. Impossible to reclaim it and Bitcoin would have very cheap price.

• How many Bitcoin confirmations is enough?
• More important, if an attacker does such an attack, Bitcoin price will be dumped to the hell and even the attacker will not get much money from it.

Practice with Bitcoin confirmation risk calculators

• https://web.archive.org/web/20181231045818/https://people.xiph.org/~greg/attack_success.html
• https://jlopp.github.io/bitcoin-confirmation-risk-calculator/

https://petra.isenberg.cc/publications/papers/Tovanich_2020_VAO.pdf
http://organofcorti.blogspot.com/2016/11/november-6th-2016-block-maker-statistics.html?m=1
https://hal.archives-ouvertes.fr/hal-03610424/document

[Fundamentals Of]

I haven't read of any. I think there was really no 51% attack that happened. It has always been just a threat. Oftentimes the attack is merely in theory. But that became more serious and closer to reality in 2014 as mentioned by seoincorporation. But it didn't really become a problem.

First and foremost, there was no intention to attack. And that's common sense. The reason is simply that 51% attack is not cost-beneficial. Aside from the fact that it is an expensive undertaking, what you will get out of it if you are successful is close to nothing. And you're success will only be very short. So why do it then? You'd rather just contribute your computing power to the network and continuously make money.

[ranochigo]

After that I think there were some pools that came close, maybe some even got above the 51% fo some time, not sure about that.
The thing about pools is, that users (aka workers) can switch them anytime. So if any of them even tries to "attack" the network, it's probably not gonna be used much longer.

Generally, 51% attacks or the likes of it are one and done schemes. They are not intended to be sustained for very much longer than required and it wouldn't matter if the miners switch or not. Since 51% attack works by shifting the miners to work on an alternate chain simultaneously, the probability of the pool miners noticing it and shifting before the damage is done is pretty much zero.

The issue lies with the opportunity cost of executing such an attack. Most pool owners have a huge amount of Bitcoins and it is in their best interests to sustain the prices and keep them afloat. Any attack on the network would tank the price, destroy the mining economy and the probability of their pools ever being used again. It is simply not worth it to execute a 51% attack at any point in time.

[o_e_l_e_o]

There have been a number of occasions in the past where a single pool has controlled >51% of the hashrate, but they have not used this to attack bitcoin.

Deepbit in 2011 - https://bitcointalk.org/index.php?topic=26656
BTCGuild in 2013 - https://bitcointalk.org/index.php?topic=152296.0
GHash.IO in 2014 - https://bitcointalk.org/index.php?topic=645056.0

Obviously back then the total hashrate was a tiny fraction of what it is now.

The current level of Bitcoin hash rate is around 437.01M TH/s and the 51% is 222.9M TH/s. The best Bitcoin miner which is Antminer S19 pro only has 110 TH/s and it cost 3000$ for one. Imagine, you have to get 2M Antminer S19 pro in order to make 222.9M TH/s, which is around $6B and that's too expensive. I think there's no bad organization want to take risks on that.

That wouldn't be a 51% attack. If someone was to add new hashrate to the existing hashrate like that, then they would need to add more than all the already existing hashrate.

In your example, if there is 437 TH/s and a malicious party comes along with 223 TH/s, then now there is 660 TH/s altogether. Of that 660 TH/s, the malicious party owns 223 TH/s, which is only 33.8% - not enough to perform a 51% attack. The malicious party would instead need 438+ TH/s, at an even greater cost.

Your math is accurate only if you are taking hashrate which already exists (such as a mining pool) and turning it from honest to malicious, not if you are adding new hashrate.

[Wind_FURY]

But was there any such attack on Bitcoin around that time?

As far as we know, no.

Plus if there was, let's get the facts clear. There's a misstatement that's commonly accepted that if an entity "controls 51% or more of the total hashing power, that entity has total control over the Bitcoin network". That's actually wrong. An entity can have 100% of the total hashing power, but it still can't change the consensus rules and it still can't make invalid transactions into valid transactions. It can JUST censor transactions.

[stompix]

~

In your example, if there is 437 TH/s and a malicious party comes along with 223 TH/s, then now there is 660 TH/s altogether. Of that 660 TH/s, the malicious party owns 223 TH/s, which is only 33.8% - not enough to perform a 51% attack. The malicious party would instead need 438+ TH/s, at an even greater cost.

Your math is accurate only if you are taking hashrate which already exists (such as a mining pool) and turning it from honest to malicious, not if you are adding new hashrate.

But that's also not accurate since adding right now 200th/s would drop the revenue per th/s per miner from barely 7 cents as it is now in the 5 cents area and it will push a ton of hashrate out of business since they will be in the red.
And the prices of the hashrate needed he mentioned are also bad, he went for the s19pro at 110th/s for 3000, that's $27 per th/s when you can buy S19hydros at $11 per th/s or pros at $16 per th/s and I'm talking about new gear from Bitmain not used gear on the market. Even new with older models I saw Mikey selling at $9 per th.

But that aside, there is the thing of why doing it, and the best example is right here:
Bitcoin Scam Vision has around 600Ph/s, there are 7 companies I know of that have way more hash rate than the entire network yet none is doing anything against it. And why would they? And why would anyone do this to BTC also?

 

[Little Mouse]

it still can't make invalid transactions into valid transactions. It can JUST censor transactions.

Can't they make a valid transaction invalid? Isn't it double spending? If anyone can censor transactions, the network won't be any more decentralized. My bad if I have written something wrong, that's what I know. I'm not saying that's going to happen though.
Well, it doesn't make sense. Why would someone bother to attempt to do so by spending this huge amount in achieving this huge hash rate?

[Latviand]

I'm not sure of this but satoshi did answer this back then? I don't know if he exactly addressed this exact scenario or that he said that there should be a gentleman's agreement that no one should get much powerful miners so the beginner miners or newbies to bitcoin itself can mine without any problems. I might add the link to it later if I find it. 51% attack is not possible imo and many probably share the same answer with me, there's a lot of bitcoin mining corporations already and I don't think that they're merging anytime soon, not to mention that there's individual miners who has computing power too and there's more of them than those mining corporations, I think.