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Assume a hypothetical situation where a researcher was able to develop a computer capable of 2,000 PH/s (the current network hashrate). During his first 2 weeks of mining, he would strike it rich as he would win 50% of block generations with 5 minutes per block.

After 2 weeks, the difficulty target would readjust, and this miner would no longer have an advantage.

However, for this next 2 week period, the miner sits out, waits 2 more weeks, and allows the network to re-adjust back to a higher target, at which point he re-enters and sweeps the rewards once more.

He repeats this cycle in perpetuity.

A solo miner with 2,000 PH/s seems infeasible, but what if a powerful mining pool were to pull this stunt — withdraw from mining for 2 weeks, allow for the difficulty target to re-adjust, and re-enter with a much easier difficulty?

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  • I think you're mistaken. If the miner's own hash rate is equal to the combined rate of the rest of the network, that miner will on average take half the blocks, regardless of how the difficulty changes. Also, keep in mind that difficulty changes by at most a factor of 2 each 2016 blocks (if I recall correctly), so there won't be swings as dramatic as you seem to be suggesting. – Nate Eldredge Sep 3 '16 at 5:30
  • The maximum change is a factor 0.25 or 4. – Pieter Wuille Sep 3 '16 at 8:58
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No, for two reasons:

  1. His advantage is always the same. If he has 50% of the mining power, he makes 50% of the revenue when he's mining and 0% when he's not. The difficulty does not change this.

  2. In the on/off scheme, when he's mining, blocks are being found twice as quickly. So the difficulty adjustment comes twice as fast. When he stops mining, he has to wait twice as long for the difficulty to drop, so he's mining less than half the time. By forcing the difficulty up and then not mining, he has to wait an awfully long time before it comes back down -- during all that time, his mining hardware is depreciating.

I am assuming that the only thing he does is mine or not mine. I'm ignoring the possibility that he attempts to force reorganizations or does other "bad" things.

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  • Ah ok, I forgot to consider that difficulty changes happen every 2016 blocks, and not hardcoded to every 2 weeks. – Snowman Sep 3 '16 at 14:38
  • I understand the 2nd point, but not quite about the first. What did you mean by "he makes 50% of the revenue"? I think you meant he made 50% of the revenue statistically - say, if mining 10 blocks, he has 50% chance to mine 5 of them, hence 50% of the total revenue of the 10 blocks. Am I right? – yaobin Oct 17 '18 at 0:43
  • @yaobin Yes, precisely. While mining honestly, with 50% of the mining power, he gets 50% of the available mining reward. – David Schwartz Oct 17 '18 at 2:03

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