Hello cunicula,


There could be rational/malicious stakeholders who always provide the voluntary signatures to avoid the demurrage fee, but would be less willing to provide the mandatory signatures. To measure the participation level of a particular stakeholder we have to use voluntary signatures, because mandatory signatures that he failed to provide won't be recorded anywhere. Therefore the benefits of blacklisting become less straightforward, even if we do the lottery only among stakeholders who provided a heartbeat (whitelist). In other words, the voluntary signatures indeed force the stakeholder to maintain a full node that's always online, but it doesn't force the stakeholder to participate in generating mandatory blocks. So we overcome the concern of "lazy" stakeholders who aren't online, but not the concern of rational/malicious stakeholders who attempt to enrich themselves by denying service until their demands are met. Assuming that the would-be lazy stakeholders are honest (i.e. accept the recommended fee price as specified by the protocol), the voluntary signatures will push the fees downwards (compared to non-blacklisting protocol). But if the would-be lazy stakeholders are rational/malicious, the voluntary signatures wouldn't help in this regard.

Regarding the simple non-blacklisting protocol. Suppose that every (say) 5th block is the PoW block that derives the winning stakeholders who should create their mandatory block, and at the end of the difficulty retarget window we measure two difficulties: the regular pure-PoW difficulty, and the difficulty of the special 5th PoW blocks (by summing up the time differences between every 5th and 7th blocks in the retarget window, where the 6th block is the stakeholders block). Now we can have a separate difficulty re-adjustment for the special 5th blocks, which means that if too many stakeholders are greedy/malicious and deny service until their demands are met, then at the next retarget window it would be easier for the miners to generate the 5th PoW block, so more potential stakeholders would get a chance to participate (by re-solving the block when there aren't willing stakeholders available), which will hopefully push the stakeholders' fees downward toward the recommended fee that's used by honest clients?

Edit: The alternative is to have only PoW blocks that derive winning stakeholders (your post #134). Then there'd be only one re-adjusted difficulty that takes into account both the PoW hashrate and the stakeholders' participation level. This should also work in this regard, it just maximizes the reliance on stakeholders, so it has other implications. BTW, the protocol should probably split the txn fees between the PoW block that derives the winning stakeholders and the following stakeholders block, because near-instant stakeholders blocks wouldn't have many txns. If it's a protocol with 3 winning stakeholders, then it could specify that only the 3rd stakeholder includes txns in their block.

What about you idea of using mandatory fixed fees, say 0.1% fees? We could re-adjust the mandatory fixed fee at the next retarget window for example according to total txn volume (fewer total number of txns imply that we need higher fixed fee) ? This way it'd be futile for stakeholders (and miners) to demand higher fees, they could only refuse to generate blocks while not enough (high-paying) txns were broadcast. I think that you mentioned this idea in relation to bribe attacks?