Question about 51% attack

[BlackHatCoiner]

Based on this: https://github.com/in3rsha/bitcoin-mining-distribution

Some pools have reached really closed on doing such an attack, but I have a question. Why anybody would want an attack like this? If he controls the network (that will not be forever) what can he achieve? He can't "destroy" the bitcoin, huh?

[joniboini]

He can show that the network is not strong enough, cash doubt over its users, and probably make them move to another chain that the attackers favor. Or he simply wanted people to stop using the network for whatever reason. An economic incentive might be another factor, as long as the attacker can move and liquidate the funds asap after he hijacks the network. But, considering how quick exchanges with detecting malicious funds right now, I don't think it is going to be as easy as it sounds. DEX is probably another choice.

But the profit does not guarantee that your profit outweighs your cost. It might be way more profitable to spam e-mail instead of doing 51% for the sake of making money.

[MicroGuy]

Based on this: https://github.com/in3rsha/bitcoin-mining-distribution

Some pools have reached really closed on doing such an attack, but I have a question. Why anybody would want an attack like this? If he controls the network (that will not be forever) what can he achieve? He can't "destroy" the bitcoin, huh?

Because when I control 51% of the network I can double-spend BTC.

[pooya87]

those are mining pools and if a pool starts acting shady or even if the possibility of them acting shady arises, miners switch to another pool and the hashrate of that malicious pool could fall down to zero. like the case with ghash.io couple of years ago where they weren't even shady they just started having around 60% hashrate then miners started migrating to other pools which dropped their hashrate.

when it comes to 51% attack it is always about cost and partly about the reward. the act of reversing a block is not profitable at all, in fact it would cost a lot of money. and it doesn't do anything since the same transactions that were in the confirmed block would either be in the new block or another block after it. it must be accompanied with an actual double spend with an amount equal to the cost of the attack to justify it. such high valued transactions will always demand more than 6 confirmation in which case the cost of the attack grows significantly more.

[Maus0728]

when it comes to 51% attack it is always about cost and partly about the reward. the act of reversing a block is not profitable at all, in fact it would cost a lot of money. and it doesn't do anything since the same transactions that were in the confirmed block would either be in the new block or another block after it. it must be accompanied with an actual double spend with an amount equal to the cost of the attack to justify it. such high valued transactions will always demand more than 6 confirmation in which case the cost of the attack grows significantly more.

This is a bit complicated to understand and I've read few articles to understand the concept.

As far as I understood, 51% attack is a scenario wherein a group of miners owns more than 50% of the overall networks' hashing power which gives them the ability to double spend and to prevent the incoming transactions to be confirmed.

But how can attackers benefit from this type of malicious intent if they need to spend more of their resources such as buying high end mining equipment like the Antminer S17 while the global hash rate they need to overcome is currently increasing (more miners)? They'll just suffer a greater financial loss. LOL

Furthermore, if there is an increasing number of miners in the bitcoin network then the possibility of conducting 51% attack is nearly impossible compare to the old days when the bitcoin is starting at an early age where no one is interested in mining.

[Baofeng]

Maybe you can find the answer is the following thread because this has been discussed before:

(1) How exactly would a 51% attack work?
(2) Is 51% attack a double-spending threat to bitcoin?
(3) Stopping 51% attacks
(4) 51% attack on Bitcoin
(5) Is the attack "51%" legal?
(6) 51% attack


Short answer is that if there are incentives, like double spending, then someone can 'try', but then again it will take a lot of money and in the long run, it's not worth to do it.

[Fundamentals Of]

Short answer is that if there are incentives, like double spending, then someone can 'try', but then again it will take a lot of money and in the long run, it's not worth to do it.

The incentives will not be worth the cost. From that perspective alone, there will be no one who will spend a lot just to try to attempt to double spend. That is like spending a whole lot of wealth in order to achieve something of equal value or even less.

In other words, the only possible aim left for someone doing it is merely to disrupt Bitcoin's adoption in general, to prove that Bitcoin is not as safe as it is being portrayed and aggressively promoted by its advocates.

[mycryptocoin]

If BTC is attacked 51%, the The system may be destroyed. As you know, Bitcon use Blockchain system to work, linked together by chains. Every info (with Bitcoin, It is transactions) is hashed on Block. All of Block is linked together and If 1 block is changed, all of Block is change.

So, You can imagine that If BTC is attacked 51%, the hacker will be change one or more Block, so all of chain of Bitcoin will be changed. It mean if before attacked, you have 1 BTC, after the attacked, you have nothing (this is only Example). In fact, the Blockchain of Bitcoin can be destroy

[pooya87]

when it comes to 51% attack it is always about cost and partly about the reward. the act of reversing a block is not profitable at all, in fact it would cost a lot of money. and it doesn't do anything since the same transactions that were in the confirmed block would either be in the new block or another block after it. it must be accompanied with an actual double spend with an amount equal to the cost of the attack to justify it. such high valued transactions will always demand more than 6 confirmation in which case the cost of the attack grows significantly more.

This is a bit complicated to understand and I've read few articles to understand the concept.

As far as I understood, 51% attack is a scenario wherein a group of miners owns more than 50% of the overall networks' hashing power which gives them the ability to double spend and to prevent the incoming transactions to be confirmed.

But how can attackers benefit from this type of malicious intent if they need to spend more of their resources such as buying high end mining equipment like the Antminer S17 while the global hash rate they need to overcome is currently increasing (more miners)? They'll just suffer a greater financial loss. LOL

Furthermore, if there is an increasing number of miners in the bitcoin network then the possibility of conducting 51% attack is nearly impossible compare to the old days when the bitcoin is starting at an early age where no one is interested in mining.

that's the general idea, to have high difficulty and a distributed hashrate (more number of independent miners) to make the cost of such attacks high enough to make them impossible. in fact a lot of other things in Bitcoin protocol rely on a similar concept. for example each time you create a private key and publish its public key or sign a transaction and publish your signature + public key, it works based on the idea that the cost of solving ECDLP (finding private key from public key) is so high (it takes a long time, more than our lifetime) that it is considered impossible.

[BlackHatCoiner]

Okay, so after I clarified some things in my mind I understood that you can't simply copy-paste blocks from your windows explorer (for example).

And that happens because nodes always accept the blockchain with the most difficulty summed. So if the attacker changes the difficulty to 1 to all of his blocks then the summed difficulty in the end will be equal to the number of blocks. Nodes will reject it because they will have much more difficulty summed.

The problem created to the attacker is that if he changes the difficulty to a big number (so he can fool the network) like 10^100 he needs to find the analogous hash that is below that tiny target. So the nodes will reject him again because they will see that the hashes of his blockchain are not valid to his difficulty. (Because... yeah... He won't find the hash with 10^100 difficulty, it's almost impossible...)

Am I getting this correctly?

[liverpool52]

I think in this case if such an attack happens and the truth is that there will be a high probability of losing your bitcoins.