Edit: Here is my understanding of the proposed solution after watching the first part of the Pooling Zoom call
There has been this thing nagging my mind:
How can pool operators that want to distribute pool profits according to the degree of participation in the pool, verify that plots claimed by their pool participants actually exist as unique valid plots?
Let me elaborate based on my 20.000 ft level mental model.
Chia rewards are proportional to space and time. Of course, it can not really ‘see’ all the space dedicated by inspecting total netspace consists of valid plots, and it does not have to. It just relies on reward challenge that would be near impossible to complete without having expensively precomputed lookup tables (the plots). The construction of the table (plotting) is long and costly (otherwise you could just ignore it and do the challenge on the fly), but the production of the response (harvesting) is fast and cheap once you have the pre-computed lookup tables.
Now you could try to fudge the process, by in the extreme just participate in evry challange and instead of computing just guessing the correct response, but the solution space is made so large that you would never ever be able to guess a correct answer. In other words, you can pretend to have plots all you want, but they would never help you pass the test unless they where the real valid uncompressible lookup tables required to find the right response at the time of the challenge.
Chia really does not care whether you lie about having 1.000 plots that do not exist, as your imaginary plots will never win any Chia.
Now enter pools. The way most people think about pools is this: If a bunch of people that individually all have a very, very small chance of winning the Chia lottery anytime soon, all bundle their lottery tickets (plots), they together have a much higher chance of winning a lottery in the short term. If we then distribute the winnings fair amongst everyone participating in the pool according to their contribution to the effort, all would see a steady stream of fractions of Chia trickling into their wallets.
But here is the catch. Whereas before my fraudulent claim of having 1.000 plots did gain me nothing, now if I can convince a pool that I have them and put them in the pool, I’m enjoying a steady trickle of Chia without having to actually have any real space/time committed. Hey, I’m just unlucky, right? After all, the other guy with 1.000 real plots also isn’t winning. So as long as I don’t overplay my hand and stay under the statistical radar, I can free ride this game.
So pool operators now have a burden that Chia itself has not: How can you test that a plot is actually a real plot, not just once, but repeatedly to proof it still exists even though it is not passing any Chia challenges, and do so cheaply and in a non-fudgible way?
How do current unofficial pools solve this? HPool seems to detect some imposters, but I suspect not the ones that keep their fraud small enough to avoid statistical detection.
Bonus question: If such a verification function did exist, why did Chia not use this stronger proof themselves?