Miners are leaving Ghash.io and switching to other services after a large rise in the pool’s hashrate.
According to Blockchain.info, the pool represented over 42% of the network’s hashrate yesterday, but the market share has dropped to 39% today.
Some bitcoin miners have voiced their concerns on social media over the fact that a single pool has such a high share. They say that if a pool with over 50% of the combined network hashrate could theoretically corrupt the blockchain.
A “>50% attack” could allow an attacker to prevent transactions from being confirmed, and prevent other users from mining blocks. An attacker could also send the same bitcoins twice, which results in double-spending.
If such an attack were to occur, it could result in irrevocable damage to the blockchain. However, this has not happened before.
Ghash.io, which is operated by cloud mining service CEX.IO, has been criticized by members of the community. Many users on the Bitcoin forum have advised others to switch pools.
Forum member Ximp said:
This is actually a really big threat to the security of bitcoin as a whole. The whole setup is supposed to solve the whole trust issue, but if 51% control is achieved and maintained, I don’t see any alternative to jumping aboard another coin, probably POS. Saying fingers crossed is not enough.
Ghash.io issued a press release yesterday to reassure miners and investors. The company stated that it would temporarily disallow new independent mining facilities to join the pool. The company also said that it would implement an option for CEX.IO users to mine on pools other than Ghash.io.
Ghash.io stated that it has nothing to gain from performing a 51% attack, because it would “do serious damage to the Bitcoin community” which the pool is a part of.