Bitcoin Forum

Gavin Andresen about the 51% problem

https://bitcoinfoundation.org/2014/06/13/centralized-mining/

The hashing power of GigaHash comes from users that work for them - how easy would it be to direct the users to hash a double-spending transaction? Has GigaHas full power over what the user machines hash?

The only solution would be to penalize pools who produce too much hashrate. There should be a limit, like 5% or total network rate or more gets penalized harshly. It needs to be kept very low, but not so low that some of the bigger individual users are shut out of the network. Some individuals are currently producing a few petahashes on their own, and they should be allowed to do so. But nobody or thing should ever be allowed to come anywhere close to even 10% of network hashrate. This is destroying GHash.io's reputation quickly.

there is nothing in the bitcoin protocol that would allow to determine that two coinbase transactions came from the same pool. assuming we know what the identity of the "pool" is in the first place.

I realize 5 years isn't very long in this world, but even the three years of legit experience has pushed me towards believing if it could have been done... it would have been done by now...

Anything that can happen will happen. The biggest problem I see is that you don't have to buy mining equipment with more than the current mining power to do a 51% attack. All you need to do is start a few pools that pays slightly better than the current pools, and wait until their total mining power is more than 51%. It's also sad that Gavin seems to think that the safety of the Bitcoin network ultimately depends on the ability of the established banking network to verify their customers.