Topic: Almost no one understands the 51% Attack - page 4. (Read 789 times)

I don't understand the technical details, 'almost no one' fully does, but you can argue 'almost no one' understands how Bitcoin works in the back, this is literally how it is supposed to happen for a user technology. Does 'almost no one' understand how internet works? Does it stop 'the community' from preventing and fighting against attacks?

I propose anyone who thinks a 51% attack is easy to go ahead and try it. Make the hypothesis into theory. Then prove the theory, again and again. Then it becomes a fact.

though community might not be the right word
But when I said community I meant the collective honest miners, full nodes operators, exchanges, developers and users.


well as a decentralized system that operates on consensus there are no bad or good nodes.
It's based on consensus the biggest hash in this case 51% becomes the valid chain.

As a decentralized system with no central Authority, it is run by certain protocols and there are no human hands that can fix it
But we can mitigate the human problem
Once detected, miners who cares about network security in the supposed malicious pool would pull out which would reduce the hash power and full node operators may be able to fork it.


While Bitcoin might be decentralized and have no central Authority, it's continuous resilience relies on these stakeholders acting on its best interest.

It doesn't matter if the attacker is known or not unless you know a way of censoring a miner.


It is called a 51% attack because that is the threshold. With 51%, the attacker's chain will always be longer than any other over time. Even when the other 49% find a block, the attacker will eventually catch up and pass any competing branch with its own.

The reason that a pool is unlikely to take over with 51% is that the members of the pool will abandon it before that happens (we hope). No members, no hash power.

BTW, if an attacker successfully attains 51% and rejects all other blocks, then the other 49% might as well stop mining because they will never get another block reward.

How would the "community" respond? And what exactly do you mean by the "community".

And how would this "community" come to know that an entity has taken over 51% of the hashrate? How would the "community" know who the "attacker" is, and who the "defender" is? Is there some central entity that is going to dub certain nodes "bad" and certain nodes "good"? If so, how do they determine this? By what authority?

For me, one of the most common misconceptions about Bitcoin is that there are human beings involved in running it, and those humans can take action when they "see stuff" they don't like. But this isn't so. Bitcoin is just an algorithm. There are no human beings involved. A node as a vote with it's hashrate, and that's it. You can have whatever personal opinion about a node you want, the only recourse you have is to outvote that node with your own hashrate. Complaining here on Bitcointalk wouldn't do anything. Calling the police won't do anything (they would have no idea who to arrest).

I share the frustration that this author seems to have: lots of people--even a lot of people who seem to think they know a lot about blockchain and Bitcoin--don't seem to fully understand the implications of decentralized system. There is no central authority. There is no "community". There is no nothing except nodes running hashrate. Why is that so hard for people to understand? That's actually the central innovation of Satoshi's Bitcoin whitepaper, and to this day many people simply don't understand it.

It will be clearly visible for anyone, who will type "getchaintips" in their node.

Then why it is called "51% attack", and not "100% attack"? Note that if the group of honest miners still have remaining 49%, then they can still mine, on average, every second block. If it will be reorged, then people will notice that. First, because of chaintips. Second, because all miners in a given pool will suddenly see, that a pool is getting all of their blocks reorged.

So, doing a chain reorganization is not a silent thing. It is visible in logs. It is measured. It will be noticed. And people will take action (for example by leaving the 51% pool, because their reputation will be destroyed).

Even less serious reorganizations were noted, for example: https://bitcointalksearch.org/topic/error-connectblock-too-many-sigops-invalidchainfound-invalid-block-5447129

So, why do you think, that 51% attack will remain unnoticed, if even sigops limit violations were caught? And they are much more silent, because a block, which violates sigops limit, is simply invalid, so you have to receive it directly from a failing node.

This is not the case. If you have 51% mining power, then you can earn 51% rewards on average. Earning 100% rewards require 100% hashpower (or reorging all blocks, mined by everyone else, but then, it is very far from being "silent").

Also, there is one important thing: jumping from 51% to 60%, 70%, 80%, and so on, doesn't make much sense. Because then, you are basically raising your own difficulty, for no reason. And then, you can paradoxically get more coins, by going from 90% to 60%, because then, the difficulty can drop, so you will pay less for electricity.

The thread title is a biasly wrong induction.
Yes controlling 51% and making an attack on the Blockchain is more than double spending and could have way for an attacker to censor other miners by either including or excluding certain transactions in the Block
This gaining more benefit while other miners suffer the losses
But stating it would be 100% subtle is only theoretical
Bitcoin is quite transparent and as time goes someone would be on the abnormalities and a proper response would be taken by the community.
Same applies with miner centralization, though it poses it's risk and the way it's going we getting there since the top 2 mining pool already have a combined hash power of more than 51%.
But if the response of the community is swift the damage could also be mitigated.


Yes most of what the author stated was correct but I feel it overrated the ease in making a 51% attack undetected and Underrated The capabilities of the community.

https://www.reddit.com/r/Bitcoin/comments/197m0yc/almost_no_one_understands_the_51_attack/

I came across this thread on Reddit, and thought that community members here would be interested in it since we've discussed this same topic here before. I personally find the subject of the 51% on Bitcoin to be both fascinating and extremely relevant. If there is a systemic risk to the entirety of Bitcoin--even if is a relatively remote one--then this ought to be discussed thoroughly.

Here's the first part of it of the post: