Bitmain’s Mining Pools Now Control Nearly 51 Percent of the Bitcoin Hashrate

Bitcoin mining pools controlled by China-based industry giant Bitmain now account for more than 40 percent of the total Bitcoin hashrate, raising new concerns about miner centralization.

According to data from CoinDance, bitcoin mining pools BTC.com and Antpool have mined 25.5 percent and 16.5 percent, respectively, of all bitcoin blocks over the past seven days.
Both of these mining pools are owned by Bitmain — the world’s largest producer of application-specific integrated circuit (ASIC) miners — meaning that the firm now has influence over at least 42 percent of the Bitcoin hashrate. The two pools also control a combined 21.3 percent of the Bitcoin Cash hashrate, which operates on the same algorithm (SHA-256) as Bitcoin.

At this level, Bitmain is dangerously close to controlling 51 percent of the Bitcoin hashrate, a mark that would theoretically allow it to attempt a 51 percent attack against the network. Such attacks have recently been successfully deployed against a number of smaller altcoins, including Litecoin Cash, Bitcoin Gold, Verge, Litecoin Cash, and Monacoin.There is far less financial incentive to attack Bitcoin, but some in the community nevertheless worry that — given CEO Jihan Wu‘s support for bitcoin cash and controversial scaling proposal SegWit2x — Bitmain might launch a malicious attack against the network anyway. That’s a very unlikely scenario, but critics argue that the fact that it is a discussion at all means that bitcoin mining is too centralized.

It’s not clear what percentage of the hashrate belongs to devices physically-operated by Bitmain, but that point is somewhat moot since pool operators control the block templates for the entire pool. This means that, as long as those devices are pointed at Antpool or BTC.com, Bitmain can decide what transactions the pool will process (and which, if any, it won’t).