A group of Bitcoin miners briefly gained enough processing power to theoretically destroy the cryptocurrency. For a few hours last week, mining pool Ghash.io obtained control over 51% of all the processing power that keep Bitcoin secure. The security experts explain that if the pool had abused that power, it could have irreversibly take money from other users by rewriting the register of who owns which coins.

However, the pool reacted quickly – shortly after the threshold was breached, some of its members pulled their computing power from the group. This move helped to avert or maybe delay the catastrophe.

As you know, the Bitcoin network is based on peer participants who perform “mining”, i.e. spending large amounts of processing power to verify transactions. Miners are rewarded with Bitcoins, and their large number makes it impossible to force a fake transaction into the Bitcoin ledger, because to verify it you would need more than half the processing power of the entire network. That’s what the Ghash.io could do as a pool. Today many miners lump their processing power together to get more rewards. Although they can be understood from the financial prospective, such practice poses the threat of ending the decentralized nature of Bitcoin.

For that brief period when the pool controlled more than half of the network, the security of Bitcoin was ensured not by its mathematical background, but the mere trust that the members of the pool would notice what happens and respond. The observers point out that this is not the first time the “impossible” attack on cryptocurrency was so close. Five months ago, the same pool hit 45% of the network and was told to take steps in order to prevent the breach of the threshold. It looks like those steps appeared insufficient. In the meantime, Ghash made no attempt to abuse its position, and once some of its contributors pulled their computers, the pool’s proportion of the mining dropped to 40%.

It has to be noted that the 51% attack was the first headline news mentioning Bitcoin in a long time now. But it turned out that even though the media keeps silence about the cryptocurrency, its development continues. For example, users of Google Finance and Yahoo Finance can convert between Bitcoin and USD. Microsoft and Bloomberg added Bitcoin to their finance products four months ago. The first Bitcoin apps that comply with Apple’s new rules allowing cryptocurrencies on the App Store emerged a few days ago as well.