Topic: This 51% numbers kills everything! - page 2. (Read 1334 times)

Well, there are checkpoints in bitcoin-qt to minimize this.

He is a bit confused, but he is right when he says that a government has tons of money and CAN make such attack.

Yes it can, with a 51% attack bitcoin becomes instantly useless.

What? With a 51% attack you can replace the current blockchain with your! And that blockchain can for example start being modified since a year ago. This means that since a year ago all the blocks were found by the attacker. This means that he own all these bitcoins and that no other transaction has been confirmed since then. You mined your coin 6 months ago and spent them? No more, he mined these coins! Not you! So your transaction disappear. It never existed.

True 

This rely on your hope that the attack eventually would stop. Why it should? After a government start the computers, it can leave them attacking for whatever time it want!

Yes, if the attack stop then we can fix everything (lot of people keep a backup of the current blockchain). But that is a big if!

I wonder how much new users is commin from this direction. Since you are professional online poker player, can you provide some links and stats? Thanks.

There's really no loopholes besides the fact that multiple people can hoard thousands of BTC and make a huge profit off of it, kind of like gold or silver.

You've got some more reading to do.

The 51% attack cannot "collapse the whole system", and in fact attackers are very limited in what kinds of damage they can do. They can only fraudulently reverse or modify their own transactions, not anyone else's. They can (temporarily) prevent other people's transactions from being confirmed, but not modify them in any way or reverse transactions which were already confirmed before the attack. They cannot steal other people's coins (except for sending his own coins and taking them back), and cannot create coins out of thin air. Such an attack would also be extremely obvious and users would be warned not to perform any transactions until it is clear the attack has stopped.

Also, the attackers can only do anything during the time they are actively mining with 51% of the hashing power. As soon as they stop mining, or if legitimate miners summon enough resources to regain the majority of the mining power, the network will resume normal operation, all transactions which the attacker blocked would soon start being confirmed, and it'll be almost as though nothing had ever happened.

That's not to say such the 51% attack is nothing to worry about. It would cause a total (but temporary) disruption of all Bitcoin services and probably a loss of faith in the currency resulting in a massive price crash, and it may take a long time to recover, but it's not the end of the world either.

Except what you are saying, and what you are actually talking about are completely different and have nothing to do with who has how many coins.

https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_computing_power

I'm a professional online poker player. Life is tough for us as the US government keeps blocking online gaming transactions and bitcoins are popping up big on the poker forums as a way around this. I was thinking of investing in some bitcoins. I decided to do some research. 99% of everything I read blows way over my head. The one thing that got me was that if someone/organization could mine 51% of bitcoins, they could collapse the system.

It blows my mind that this system could be so creative and complex to me, but yet you could mine 51% and destroy it all.


Really the whole idea of this seems to undermine the government and banks which is great. But how the hell do you make it so easy for them to destroy the system considering they have endless amounts of money? How much money would it take to get a setup that mines 51%?


I love this digital currency thing, but I have a feeling this one will be destroyed a new one will take over. This is just waaaaaaaaaay too big of a loophole.