Need an explanation over 51% attack.

[Westingcote]

Guys, why is this 51% (or the majority) attack so popular?
It only allows double spend once, and some "censorship" while 51% hash-rate sustained, right?
Even they have 51% hash-rate, miners cannot violate protocol rules, right?

Thanks

Its not what you can do with transactions but the capability of causing massive amounts of panic and pushing the price down of Bitcoin as a result. If all the mining pools which have more than 10% merged together in an attempt of pushing prices down because of the panic which would result as soon as a 51% attack happens then it could both be lucrative for them and a lot of profit could be made.

The price would be pushed down because of the amount of people willing to now sell their coins in fear that Bitcoin is dying. Resulting in more people willing to lower their prices until they find a buyer and eventually the Bitcoin market would crash. Depending on the amount of time spent on the 51% attack depends on the profit that could be generated.

The attacker would have to time it perfect in order to not spend too much money on the resources required to have that amount of computational power directed towards a 51% attack.

Right now is actually a prime time for an attack to do just this. The Bitcoin market would eventually recover once everything evens out and the attack has stopped.

However a lot of trust would be lost with the pools mentioned and I'm not sure what the consequences of this would be.

who have the major hashrate and how much is this hashrate? I don't know...is it possible that right now someone owns more than 10% ot total hashrate?

This is definitely possible. Especially since there are pools with more than 10% hashrate each.
The majority of hashrate is being provided by Bitmain/BTC.com. You can find a graph containing pools with their hashrate here.

thank you for your help!

BTC.com have more than 27% of the hashrate!
We are still far away from 51%, but what happened if one day two or three big pool decide to join? Or maybe they know that something like that can bring the death of btc?

Even if pools which combined have a total over 50% hash rate combined (which is unlikely due to different goals and agendas) it would not be the death of Bitcoin unless they would be able to continually  keep the hash rate above 51%. Well to be honest they would have to have more hash rate than that to be able to control the vast majority of the network. Something like 75% would likely render the network useless for the time it was being attacked.

51% attack is only effective for the time it is taking place. No one in the world has the motives or funds to tackle this 24/7. Its literally on the spectrum of nuclear war and flying pigs. Its just not worthwhile to anyone other than government operators that wish to take down Bitcoin because its a threat to politics and the banking system.

But then you have a huge amount of people which would be converted into hashing power that would be willing to combat it. These pools could be the ones to defend the network rather than the ones attacking it.

[asdlolciterquit]

Guys, why is this 51% (or the majority) attack so popular?
It only allows double spend once, and some "censorship" while 51% hash-rate sustained, right?
Even they have 51% hash-rate, miners cannot violate protocol rules, right?

Thanks

Its not what you can do with transactions but the capability of causing massive amounts of panic and pushing the price down of Bitcoin as a result. If all the mining pools which have more than 10% merged together in an attempt of pushing prices down because of the panic which would result as soon as a 51% attack happens then it could both be lucrative for them and a lot of profit could be made.

The price would be pushed down because of the amount of people willing to now sell their coins in fear that Bitcoin is dying. Resulting in more people willing to lower their prices until they find a buyer and eventually the Bitcoin market would crash. Depending on the amount of time spent on the 51% attack depends on the profit that could be generated.

The attacker would have to time it perfect in order to not spend too much money on the resources required to have that amount of computational power directed towards a 51% attack.

Right now is actually a prime time for an attack to do just this. The Bitcoin market would eventually recover once everything evens out and the attack has stopped.

However a lot of trust would be lost with the pools mentioned and I'm not sure what the consequences of this would be.

who have the major hashrate and how much is this hashrate? I don't know...is it possible that right now someone owns more than 10% ot total hashrate?

This is definitely possible. Especially since there are pools with more than 10% hashrate each.
The majority of hashrate is being provided by Bitmain/BTC.com. You can find a graph containing pools with their hashrate here.

thank you for your help!

BTC.com have more than 27% of the hashrate!
We are still far away from 51%, but what happened if one day two or three big pool decide to join? Or maybe they know that something like that can bring the death of btc?

Even if pools which combined have a total over 50% hash rate combined (which is unlikely due to different goals and agendas) it would not be the death of Bitcoin unless they would be able to continually  keep the hash rate above 51%. Well to be honest they would have to have more hash rate than that to be able to control the vast majority of the network. Something like 75% would likely render the network useless for the time it was being attacked.

51% attack is only effective for the time it is taking place. No one in the world has the motives or funds to tackle this 24/7. Its literally on the spectrum of nuclear war and flying pigs. Its just not worthwhile to anyone other than government operators that wish to take down Bitcoin because its a threat to politics and the banking system.

But then you have a huge amount of people which would be converted into hashing power that would be willing to combat it. These pools could be the ones to defend the network rather than the ones attacking it.

thank you for these more informations!

So in few words, they have to keep to have more than 51% for a long period...but in that period they can put what they want in the blocks that they mine...correct? And they block will be approved becouse they owns the majority of the hashpower of the network correct?

Well, if it's correct, i think that even few hours like that can be a real problem for the future of btc..

[goddog]

So in few words, they have to keep to have more than 51% for a long period...but in that period they can put what they want in the blocks that they mine...correct? And they block will be approved becouse they owns the majority of the hashpower of the network correct?

No, they can, "only", doublespend transactions recently spent . They can not put what they want. their transactions have to be valid. The only thing they can do: is start an hidden(secret) longer chain, so they, or their friends can spend bitcoin and recover them when the secret longer chain will be publicated.

[asdlolciterquit]

So in few words, they have to keep to have more than 51% for a long period...but in that period they can put what they want in the blocks that they mine...correct? And they block will be approved becouse they owns the majority of the hashpower of the network correct?

No, they can, "only", doublespend transactions recently spent . They can not put what they want. their transactions have to be valid. The only thing they can do: is start an hidden(secret) longer chain, so they, or their friends can spend bitcoin and recover them when the secret longer chain will be publicated.

ok, now it's more clear.
So if someone have more than 51% of hashpower for a long period they can only gain more money but they can't make other people lose their btc...!

correct?

[goddog]

So in few words, they have to keep to have more than 51% for a long period...but in that period they can put what they want in the blocks that they mine...correct? And they block will be approved becouse they owns the majority of the hashpower of the network correct?

No, they can, "only", doublespend transactions recently spent . They can not put what they want. their transactions have to be valid. The only thing they can do: is start an hidden(secret) longer chain, so they, or their friends can spend bitcoin and recover them when the secret longer chain will be publicated.

ok, now it's more clear.
So if someone have more than 51% of hashpower for a long period they can only gain more money but they can't make other people lose their btc...!

correct?

I hope someone better that me will reply this.
if you get paid in the meantime, when the longest chain is publicated, it can include that transaction or not. if not, you have to rebroadcast that transaction and hope for some miner to include it asap, or the sender of that transaction can try to doublespend it.
Miners will not directly gain from this, but the situation will be unstable and your incoming transaction is not really safe until it is included in the longest chain.

[mu_enrico]

<...>
ok, now it's more clear.
So if someone have more than 51% of hashpower for a long period they can only gain more money but they can't make other people lose their btc...!
correct?

<...>
I hope someone better that me will reply this.
if you get paid in the meantime, when the longest chain is publicated, it can include that transaction or not.
<...>

I'm not better than @goddog but I'll try to answer based on various aantonop youtube video
As I said:

<...>
It only allows double spend once, and some "censorship" while 51% hash-rate sustained , right?
Even they have 51% hash-rate, miners cannot violate protocol rules , right?
<...>

They cannot steal BTC because, in order to do that, they need to rework the previous POW blocks which are impossible. Actually, this censorship could be damaging. Let's say xxxwallet has 51% hash-power behind it and thus only include transaction from xxxwallet and discard all transaction from other wallets. This way xxxwallet can monopolize BTC and set high transaction fees for their own benefit.

[ranochigo]

They cannot steal BTC because, in order to do that, they need to rework the previous POW blocks which are impossible.

No. No matter what you do, you cannot steal BTC. Spending BTC requires the correct signature to spend it. If the signature doesn't tally with the conditions for the inputs to be spent, then it isn't possible for anyone to spend any BTC. You can steal money in a sense that you can "re-spend" coins that were in another blockchain that is recognised by the merchant by essentially replacing that blockchain.

Actually, this censorship could be damaging. Let's say xxxwallet has 51% hash-power behind it and thus only include transaction from xxxwallet and discard all transaction from other wallets. This way xxxwallet can monopolize BTC and set high transaction fees for their own benefit.

Bitcoin would be dead already before they start to censor transactions. No one would use a coin for which someone obviously has the say to which transactions they like.