An anonymous reader writes "Bitcoin transactions are confirmed by performing complex calculations, also known as "mining". If a single mining pool gains 51% of the overall computational power in the network, various forms of transaction manipulation become possible. Only a few years into Bitcoin's existence, this existential threat appears to be at hand, with Bitcoin mining pool ghash.io approaching 51% of mining power. ghash.io has now assured the Bitcoin community in a press release: "GHash.IO does not have any intentions to execute a 51% attack, as it will do serious damage to the Bitcoin community, of which we are part of." But can a network relying on such assurances survive in the long run?"