Antpool, the cryptocurrency mining pool controlled by Bitmain, has reportedly activated the controversial mining technique known as AsicBoost to increase its mining efficiency by up to 20%.

According to AsicBoost Block Explorer, the block #540032 was mined by Antpool using the AsicBoost which intends to exploit a flaw in Bitcoin’s Proof of Work algorithm to accelerate mining operation. Actually, the tracking website identified roughly 4% of blocks were mined utilizing the technology during the last week.

AsicBoost is best described as a “mathematical trick” which will narrow down miners’ choices of potential hashes. By reducing the amount of the computation required to mine blocks, this technology enables miners to increase mining efficiency and claim more bitcoin’s rewards.

Bitmain has been accused many times of using the questioned mining method over the past year. Blockstream CTO Greg Maxwell, among other critics, alleged some miners are engaged in the unfair practice to increase profits. Besides, many believed that AsicBoost drove the world’s leading crypto mining company to reject SegWit implementation last year.

Bitmain, however, has repeated for many times that they did not contribute to the development of AsicBoost and never used it on the mainnet. Jihan Wu,Bitmain CEO acknowledged that his company tested the technology on the testnet.

Antpool is the world’s second largest bitcoin mining pool with 13.5 of the total hash power on the network.Bitmain’s another subsidiary BTC.com represents 17.5% of the hash power, making it the biggest mining pool.

Why does Antpool adopt AsicBoot now to mine bitcoins? The initiative’s timing coincides with the mining giant’s declining mining revenue due to the ongoing crypto market and its impending IPO. Blockstream CSO Samon Mow posted a tweet yesterday, saying “ Why is Bitmain starting to mine with #AsicBoost now all of a sudden? Their hardware is getting obsolete and they need to squeeze as much out of it as possible. Need to try to look good for the IPO! #BitmainIPO”.