Block Withholding Attacks

• From the Proof of Work newsletter #71 (20-6-2019)

“A quick note about an attack on Bitcoin that’s been observed in the wild recently. Block witholding attacks have been discussed for a long time—the term refers to two different things, confusingly, but what we’re discussing here is when someone (often from a competing pool) joins a mining pool that pays out based on the average hashrate of the pool but withholds valid blocks, so the pool misses out on earnings and potentially becomes unprofitable.

Recently, F2pool mentioned on wechat that it was observable from hashrate distribution that this was actually happening a lot. Interestingly, there’s been a proposed fix for this from Luke Dashjr for a long time, but it would require a hard fork so it hasn’t been implemented yet. While it might not be a massively urgent problem, I would love to see increasing adoption of things at the pool level which make Bitcoin more decentralized (like Matt Corrallos BetterHash) “