That`s a problem because if a firm controls an total majority of the hash rate, it could execute a ‘51 percent attack‘, theoretically jeopardising the whole system. In a blockchain, each block have to be validated by a mining computer, which compete to do so. The only method for a miner to validate a block is to try combinations until one fits, that is, as it unveils the correct code, or ‘hash’. That hash is semi-random; partly randomly formed but also containing within it a reference to the previous hash in the chain. Thus all blocks are joined, and this is how we know that the blockchain is valid.
In a case when a new block is supplemented to the chain, all mining nodes are to validate the next block referencing that block. If there is more than one chain, the nodes will aim for the one with the longest history. But if one group regulates more than half of all the computational power on the system, it can choose an older block in the middle of the chain and begin re-mining everything from there. That chain will overtake the original chain and all original chain-transactions that had took place since the fork will become invalid. It can also deny to accept blocks created by others.
In July 2014 (when 1 bitcoin was estimated for about $550) a mining pool was named GHash.IO, really exceeded 51 percent. Actually, miners ceased mining with the pool. Responding to community concern, the firm voluntarily limited itself to 39.9 percent of the hashrate, and supposed that other groups follow suit.
The limit has already been surpassed by Bitmain, and it isn’t even devoting all of its computing power to Bitcoin mining, because it also mines Bitcoin Cash. Also, as the severeness of mining Bitcoin increase and the price falls (as it has recently), smaller firms are likely to be forced out of business.
The firm, originally from Beijing, has its offices in Amsterdam, Tel Aviv and Zug and has envolved funding from some big names, and by January of this year it already accounted for 41 percent of the computing power on the Bitcoin blockchain. It was strongly criticised in March for releasing a new mining machine that it would soon become obsolete.