It may be somehow premature, but I'm concluding that the most concerning issue according to you guys is centralization of mining to be leveraged by governments for interventional purposes, most importantly censorship purposes. Yes?
P2Pool exist and it just need more promotion/contribution, so it's not most concerning issue to me.
I'm afraid that P2Pool has failed its mission as a historical fact, and it is not going to improve ever because of the core idea suffering inherent flaws.
I'm not aware of any serious critical review of P2Pool, actually I didn't bother looking for such reviews because once I started learning about it (with good faith just like you), I became deeply disappointed in the very first steps.
For P2Pool, the idea is to run a separate p2p network with lower difficulty than the actual Bitcoin network where miners adjust the coinbase transaction such that it allocates rewards to (multiple) peers on a Pay-Per-Last-N-Shares, PPNLS, convention. Obviously
shares have to be propagated to
and verified by all participating miners.
Although P2Pool is a highly crafted protocol with lots of built-in mechanisms to resist malicious actions and attacks, it fails to help with pooling pressure flaw in bitcoin because of one brutal fact:
it is not scalable!
Current implementation sets a rough 20 times constant as the order by which the actual Bitcoin network difficulty is considered to be
lowered while bad news is: you can't touch this number to cover actual small/medium size miners, they need ways more reduced difficulties to keep paying their costs, for current network, difficulty should be adjustable in ranges between 10,000 up to 1,000,000 and further for any practical purpose. Unfortunately, P2Pool can't approach anything like that, 20 times difficulty reduction is the best it can offer!
In P2Pool, the so-called
sharechain is supposed to generate a
share every 30 seconds (in average) which is a complete block that needs
both propagation and verification just like the original network blocks, as I've mentioned earlier. The 30 seconds round time is a direct result of the magical
20 times easier rule. The number,
20, is not an arbitrary number for P2Pool, it is the limit the protocol is bound to because it is not feasible to have any shorter round time.
Tragic, isn't it? But there is still hope:
What about implementing the idea recursively, like in a hierarchical model, say in 5
layers redirecting miners to 2
5 partitions having difficulty being reduced up to millions of times? Sounds nice, doesn't it? But here comes another bottleneck built into the protocol: reward distribution.
I'm not going to discuss more details here, the conclusion is obvious anyway: p2Pool is not ready for the job operationally, nor it is matured enough theoretically.
P.S. since there are many technical challenge/issue, IMO there'll be more discussion if a thread is created each challenge/issue.
I started this to stress on the escalating consequences of the latest price rally, spotting the most critical challenges, it is ok to have separate threads for each issue, respectively and I think we have a candidate right now: centralized mining scene.