The well-known Bitmain mining pool, Antpool, lost 12.5 bitcoins (about $150,000) due to a trivial error. According to a report by BitMEX Research, the research group of the BitMEX exchange, the mess occurred yesterday at 14:35 UTC.
Bitcoin had an invalid block at height 584,802, as spotted by @juscamarena
All 8 nodes at https://t.co/WKQ8hPDGON identified the block as invalid:
Bitcoin Core 0.18.0
Bitcoin Core 0.17.1
Bitcoin Core 0.16.2
Bitcoin Core 0.10.3
Bitcoin Knots 0.14.2
— BitMEX Research (@BitMEXResearch) July 10, 2019
When the miners add a block to the bitcoin blockchain they are normally rewarded with 12.5 BTC. This quantity will be reduced by half in about 300 days as a result of halving.
To obtain the reward, the miners must add a generation transaction (also known as a coinbase transaction) to the block. It is a transaction generated by the miner that adds the block to the blockchain. It allows to claim the reward and also to add 100 bytes of arbitrary data. The reward to be paid to the miners must be equivalent to the amount imposed by the Protocol, currently 12.5 BTC.
Bitcoin nodes automatically reject blocks that contain an incorrect reward value and that’s exactly what happened yesterday.
Antpool, wrong generation transaction: 12.5 bitcoins lost
All the work and resources spent by the pool to find the block have been completely wasted. It seems that instead of the canonical 12.5 BTC, those who mined the block mistakenly requested 13.26 BTC (about 155’000$).
This value is not random but is obtained by adding the generation transaction (12.5 BTC) and all associated fees. The value entered was incorrect and, consequently, the nodes rejected the block.
It seems that the error is due to the fact that the block in question was found only a few seconds after the previous block. There is probably a bug in the software generating the block template. It was not able to clean up the fees from the previous block template in time.