51% attack | Bitcointalksearch.org

seoincorporation

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Quote from: o_e_l_e_o on December 30, 2019, 02:41:20 PM

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You misunderstand what a 51% attack can achieve.

A successful 51% attacker would mine and build a secondary blockchain in secret, with whatever transactions they like included in it. Once their own secret blockchain is longer than the main chain, they broadcast it to the network. Since they now have a longer chain with more proof of work, the rest of the network would automatically switch to this secondary chain, and the previous main chain would be abandoned. Any transactions which were included in the previous main chain but not in the newly accepted secondary chain would be reversed. This can happen after theoretically any number of confirmations, although with each confirmation it becomes exponentially harder and more expensive. However, a successful 51% attack would, at a minimum, be able to reverse or double spend transactions with 1 confirmation.

Most exchanges wait for at least 3 confirmations before confirming bitcoin, and some still wait for 6.

Thanks for the explanation o_e_l_e_o, after reading your comment i read more from other sources about the topic. You are right, it is not about a double-spend problem, it is a full block replace and a chain replacement.

squatter

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Quote from: takingthis4 on December 29, 2019, 08:42:14 PM

Quote from: HeRetiK on December 29, 2019, 08:33:50 PM

You mean the Chinese government? The majority hashrate is already located in China:
https://www.coindesk.com/highest-in-2-years-65-of-bitcoin-hash-power-is-in-china-report-finds

We're still talking about private companies running these mining operations, not the government. The confiscation of private mining facilities to launch a 51% attack seems rather unlikely as China knows better than to kill their own cash cows.

Well depends what their intentions are, they might confiscate all the farms to launch the attack and destroy btc to be able to force on public their own "cryptocurrency".

Then they might cripple the ASIC manufacturing industry, which China overwhelmingly dominates. China is trying to boost its exports, not restrict them.

Quote from: takingthis4 on December 29, 2019, 08:42:14 PM

In this way, they would have the best of both worlds, the biggest competitor would be gone, and everyone in china would have no other choice but to use their centralized government shitcoin. It's actually scary what countries as powerful as china can do to bitcoin.

It wouldn't be gone. A 51% attack only allows attackers to perform double spend attacks and censorship. The costs are absurd and users can simply wait out the attack. Worst comes to worst, the network can hard fork to brick SHA-256 miners and introduce a new POW algorithm.

With the DCEP project, I don't think they are necessarily trying to dethrone Bitcoin. Rather, they are putting their fiat currency under tighter controls and surveillance.

o_e_l_e_o

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Quote from: seoincorporation on December 30, 2019, 11:25:01 AM

Even if someone use this attack to make a double spend that will not work at all because the different services who accept bitcoin always ask for 1 confirmation. So, the double-spend isn't a risk at all nowadays.

You misunderstand what a 51% attack can achieve.

A successful 51% attacker would mine and build a secondary blockchain in secret, with whatever transactions they like included in it. Once their own secret blockchain is longer than the main chain, they broadcast it to the network. Since they now have a longer chain with more proof of work, the rest of the network would automatically switch to this secondary chain, and the previous main chain would be abandoned. Any transactions which were included in the previous main chain but not in the newly accepted secondary chain would be reversed. This can happen after theoretically any number of confirmations, although with each confirmation it becomes exponentially harder and more expensive. However, a successful 51% attack would, at a minimum, be able to reverse or double spend transactions with 1 confirmation.

Most exchanges wait for at least 3 confirmations before confirming bitcoin, and some still wait for 6.

seoincorporation

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Quote from: pooya87 on December 29, 2019, 10:10:31 PM

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you aren't considering a couple of important things here.
first is that no "company" or mining farm owns anywhere close to 51% of the hashrate, even combinations of multiple one of them don't come to a summation of 51%. the high hashrate percentages you see are mining pools. if a government took control of a pool, the miners connecting to that pool will simply switch to another pool or create a new one.
second is that owning 51% of hashrate or even performing the attack isn't going to damage bitcoin at all. the only thing that can damage it is if they actually perform double spends. which isn't going to be easy not to mention the high cost that it has.

Even if someone use this attack to make a double spend that will not work at all because the different services who accept bitcoin always ask for 1 confirmation. So, the double-spend isn't a risk at all nowadays. Y the coins never confirm then they never get accredited on balance.

ranochigo

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Quote from: takingthis4 on December 29, 2019, 08:42:14 PM

Well depends what their intentions are, they might confiscate all the farms to launch the attack and destroy btc to be able to force on public their own "cryptocurrency". In this way, they would have the best of both worlds, the biggest competitor would be gone, and everyone in china would have no other choice but to use their centralized government shitcoin. It's actually scary what countries as powerful as china can do to bitcoin.

It isn't necessary for them to launch a 51% attack against Bitcoin at all. Launching a 51% attack against Bitcoin wouldn't actually kill off Bitcoin but it could just spin off another fork of Bitcoin for the community to use; one that is ASIC resistant. In addition, there isn't actually any incentive to take the efforts to amass such a huge amount of computing power from the ASIC farms to attack Bitcoin. If they want to push for their own currency, they could easily just continue what they're doing right now, to block off Bitcoin related sites using their firewall and promote their own online currency.

The motivation behind a 51% attack for a state attacker isn't huge given that the gains is largely intrinsic.

pooya87

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Quote from: takingthis4 on December 29, 2019, 08:42:14 PM

Quote from: HeRetiK on December 29, 2019, 08:33:50 PM

Quote from: Kahan848 on December 29, 2019, 07:46:16 PM

But what would happen if one state (you know which one) could actualy gain control over more than 51% hash rate though?

You mean the Chinese government? The majority hashrate is already located in China:
https://www.coindesk.com/highest-in-2-years-65-of-bitcoin-hash-power-is-in-china-report-finds

We're still talking about private companies running these mining operations, not the government. The confiscation of private mining facilities to launch a 51% attack seems rather unlikely as China knows better than to kill their own cash cows.

Well depends what their intentions are, they might confiscate all the farms to launch the attack and destroy btc to be able to force on public their own "cryptocurrency". In this way, they would have the best of both worlds, the biggest competitor would be gone, and everyone in china would have no other choice but to use their centralized government shitcoin. It's actually scary what countries as powerful as china can do to bitcoin.

you aren't considering a couple of important things here.
first is that no "company" or mining farm owns anywhere close to 51% of the hashrate, even combinations of multiple one of them don't come to a summation of 51%. the high hashrate percentages you see are mining pools. if a government took control of a pool, the miners connecting to that pool will simply switch to another pool or create a new one.
second is that owning 51% of hashrate or even performing the attack isn't going to damage bitcoin at all. the only thing that can damage it is if they actually perform double spends. which isn't going to be easy not to mention the high cost that it has.

bitcoindusts

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Quote from: takingthis4 on December 29, 2019, 08:42:14 PM

Quote from: HeRetiK on December 29, 2019, 08:33:50 PM

Quote from: Kahan848 on December 29, 2019, 07:46:16 PM

But what would happen if one state (you know which one) could actualy gain control over more than 51% hash rate though?

You mean the Chinese government? The majority hashrate is already located in China:
https://www.coindesk.com/highest-in-2-years-65-of-bitcoin-hash-power-is-in-china-report-finds

We're still talking about private companies running these mining operations, not the government. The confiscation of private mining facilities to launch a 51% attack seems rather unlikely as China knows better than to kill their own cash cows.

Well depends what their intentions are, they might confiscate all the farms to launch the attack and destroy btc to be able to force on public their own "cryptocurrency". In this way, they would have the best of both worlds, the biggest competitor would be gone, and everyone in china would have no other choice but to use their centralized government shitcoin. It's actually scary what countries as powerful as china can do to bitcoin.

I believe Chinese government is not that savage. They are bound by laws, let us not overthink things. If they are against mining, they would release notice of shutting them down but not confiscating the mining equipment unless these mining company won't heed their notice. Aside from that, I believe company based on China will never unite just to create a 51% attack to the network where they get their earnings.

takingthis4

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Quote from: HeRetiK on December 29, 2019, 08:33:50 PM

Quote from: Kahan848 on December 29, 2019, 07:46:16 PM

But what would happen if one state (you know which one) could actualy gain control over more than 51% hash rate though?

You mean the Chinese government? The majority hashrate is already located in China:
https://www.coindesk.com/highest-in-2-years-65-of-bitcoin-hash-power-is-in-china-report-finds

We're still talking about private companies running these mining operations, not the government. The confiscation of private mining facilities to launch a 51% attack seems rather unlikely as China knows better than to kill their own cash cows.

Well depends what their intentions are, they might confiscate all the farms to launch the attack and destroy btc to be able to force on public their own "cryptocurrency". In this way, they would have the best of both worlds, the biggest competitor would be gone, and everyone in china would have no other choice but to use their centralized government shitcoin. It's actually scary what countries as powerful as china can do to bitcoin.

HeRetiK

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Quote from: Kahan848 on December 29, 2019, 07:46:16 PM

But what would happen if one state (you know which one) could actualy gain control over more than 51% hash rate though?

You mean the Chinese government? The majority hashrate is already located in China:
https://www.coindesk.com/highest-in-2-years-65-of-bitcoin-hash-power-is-in-china-report-finds

We're still talking about private companies running these mining operations, not the government. The confiscation of private mining facilities to launch a 51% attack seems rather unlikely as China knows better than to kill their own cash cows.

Kahan848

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But what would happen if one state (you know which one) could actualy gain control over more than 51% hash rate though?

greatr

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Quote from: enhu on December 29, 2019, 02:59:14 PM

51% attack would be pointless unless those miners are willing to spend their energy without mining BTC. That's a horrible decision to do for them. It had never happen because these miners won't commit to plan on doing it. And I guess this will be the reason why it will remain decentralize even when a pool has the capacity to do it.

Unless, bitcoin hashrate drops in the future if the price doesn't go up and many miners quit. In that case, it would become easier and cheaper to commit a 51% attack. Also, there has already been such attacks on some altcoins such as bitcoin gold or ethereum classic. This means that if things fall into place it might be possible in the future, but at least at the moment if bitcoin continues like it does now, it shouldn't be a problem.

rizkyalhabsy

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i've come to crypto world since 2 years ago, and when i see this thread,i try to find info about 51% attack,and so far i didn't see any info regarding atk 51% to bitcoin network .Also for now,i guess its imposibble to do that, the pool stats seems stable,even the rank 1 just have 18-19% network power.

NeuroticFish

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Quote from: Bitcoin_bullish on December 29, 2019, 02:14:20 PM

Basically every chain except Bitcoin Ethereum and Litecoin was 51% attacked in the past, but I prefer to ridicule BCash most!

Afaik Dogecoin, although there was for a while a pool with more than 50% hash rate, was not attacked. The pool played fair.
And afaik that was the reason it implemented merged mining with Litecoin. After that the hash rate went up and got splitted between much more pools and there were no more problems.

So if an attack means that funds are stolen, maybe the "except" list can be much bigger.

Also I don't think that Monero ever had 51% attack problems either...

o_e_l_e_o

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Quote from: hknot on December 29, 2019, 12:19:22 PM

has it ever happened that some pool had exceeded 51% of Bitcoin hash-rate?

Yes. Most recently in July 2014, GHash.IO exceeded 51% of the hashrate. It didn't perform a 51% attack, however, and quickly voluntarily reduced its mining power, vowing to stay below 40% in the future.

It's worth noting that in July 2014, the hashrate of the entire network was around 100,000 TH/s, meaning GHash.IO controlled around 50,000 TH/s. Current hashrates are around 1000x higher at 100,000,000 TH/s, so the amount of power GHash.IO controlled back in 2014 is currently equivalent to 0.05% of the hashrate. Performing a 51% attack now would require enormous amounts of hash power at a huge cost.

Prior to this, when the overall hashrate was even smaller (and so obtaining 51% of it easier), mining pools Deepbit in July 2011 (thread here: https://bitcointalksearch.org/topic/deepbit-at-about-49-26656) and BTCGuild in March 2013 (thread here: https://bitcointalksearch.org/topic/danger-51-attack-possibility-152296), also crossed the threshold.

koinsever

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i remember something about that but not sure. which pool i dont remember exactly. cex.io bitmain antpool or other i dont remember really. anyway they reach %50+1 but they didnt do anything. because they are all know if somebody do that shit on BTC. this ll be end for everything.

enhu

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51% attack would be pointless unless those miners are willing to spend their energy without mining BTC. That's a horrible decision to do for them. It had never happen because these miners won't commit to plan on doing it. And I guess this will be the reason why it will remain decentralize even when a pool has the capacity to do it.

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Quote from: hknot on December 29, 2019, 12:19:22 PM

Hello guys, has it ever happened that some pool had exceeded 51% of Bitcoin hash-rate? I tried to find some information on the Internet, but there are many articles which are not in the contrast so I am not able to find out which of them are correct and which are just hoaxes. Thank you

I don't think it's possible now. I mean, there is one company that dominates the market, but to get 51% it still needs some consolidation if I remember correctly. Moreover, it's something that will ruin the company's business and reputation, so fortunately it's very unlikely to happen. Profits drove the companies, and losing everything is not in their interests. It seems that this has never happened, though, and would not destroy something as big as bitcoin right away anyway.

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Quote from: DooMAD on December 29, 2019, 01:47:00 PM

Quote from: Bitcoin_bullish on December 29, 2019, 01:31:51 PM

Quote from: hknot on December 29, 2019, 12:19:22 PM

Hello guys, has it ever happened that some pool had exceeded 51% of Bitcoin hash-rate? I tried to find some information on the Internet, but there are many articles which are not in the contrast so I am not able to find out which of them are correct and which are just hoaxes. Thank you

Only on Bitcoin Cash.

Bitcoin Gold had one too. The coin that claimed it was going to be ASIC-resistant. I see that worked out well for them. Roll Eyes

Also Feathercoin and EthereumClassic. Probably a few others no one cares about.

Basically every chain except Bitcoin Ethereum and Litecoin was 51% attacked in the past, but I prefer to ridicule BCash most!

DooMAD

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Quote from: Bitcoin_bullish on December 29, 2019, 01:31:51 PM

Quote from: hknot on December 29, 2019, 12:19:22 PM

Hello guys, has it ever happened that some pool had exceeded 51% of Bitcoin hash-rate? I tried to find some information on the Internet, but there are many articles which are not in the contrast so I am not able to find out which of them are correct and which are just hoaxes. Thank you

Only on Bitcoin Cash.

Bitcoin Gold had one too. The coin that claimed it was going to be ASIC-resistant. I see that worked out well for them. Roll Eyes

Also Feathercoin and EthereumClassic. Probably a few others no one cares about.

hv_

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Quote from: hknot on December 29, 2019, 12:19:22 PM

Hello guys, has it ever happened that some pool had exceeded 51% of Bitcoin hash-rate? I tried to find some information on the Internet, but there are many articles which are not in the contrast so I am not able to find out which of them are correct and which are just hoaxes. Thank you

For PoW, where miners have a very high grade of long term investments like in asics and plants, contracts, datacenters, leased lines.... any attack doesn't make much sense.

Open competition is much more important cause that will allow any sort of innovation and change & break any bigger players in the long.

Any attack is lowering price and reputation. What long term Investor would like to risk such ever?

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