Bitcoin’s infrastructure is more centralized than ever before --raising alarms about the security and viability of what is championed as a decentralized network.

Transactions on the Bitcoin network are processed by so-called miners -- mostly companies operating vast arrays of computers. As competition increased, many smaller participants became unprofitable and dropped out, while the larger operations have entered into various partnership agreements. As a result, five mining entities -- all of them based in China -- control 49.9% of all computing power on the network, the highest concentration of mining power ever, a new analysis from TokenAnalyst found.

The five mining entities -- AntPool, BTC.com, BTC.top, F2 Pool and ViaBTC -- are available via BitDeer, which lets consumers rent mining power without buying or setting up crypto mining hardware. BitDeer acts effectively as the connective tissue between the five mining pools, each of which allows individual miners to pull their resources and to share the freshly minted Bitcoins that serve as rewards. Problem is, a miner with more than 50% of hash power can potentially wreck havoc on the network, raising the likelihood of double-counted coins, stopped payments and stalled transactions.”

“Once a consumer has paid BitDeer for a plan, they can assign that hashrate to any partnership mining pool,” TokenAnalyst said in the report released Friday. “Does it really make a difference anymore? What is to stop the entities merging into a single large entity that maintains a degree of separation” only by having separate addresses where they receive rewards.

Bitcoin’s main attraction has always been its lack of centralization -- its lack of dependence on a particular government or bank. But in recent years, the bulk of trading has become controlled by a handful of exchanges. Now network operations appear to have become highly centralized, too.