Ethereum Proof of Stake FAQ
Ethereum was supposed to have every feature under the sun from the start, proof-of-stake perhaps being the second most hyped. (Turing completeness being the clear first, which is problematic given the halting theorem and all that, so it's now rich statefullness instead.) And PoS is one of those ideas that most people looking at cryptocurrencies end up trying some variant of. PoW is obviously wasteful and it would be nice to improve on that. The problem is that it doesn't have the same properties as PoW have, and that are hard to do without.The problems are the basic ones, how to avoid colluding stakers, how to neuter the market for consumed stakes, how to deter chain splits. There is a constant flow of new coins that try various approaches, but the ones that have survived have all had to resort to some variant of checkpoints where a trusted third party decides on regular intervals which chain is valid. This has obvious implications for a supposedly trustless digital currency, where you don't really need that complicated blockchain anymore.This Ethereum PoS FAQ is much like other documentation from the Ethereum Foundation quite dense where most paragraphs introduce terms not seen elsewhere (economic finality? slashing? weak subjectivity?). If you want the interesting bit, the TL;DR, then skip to the part about weak subjectivity. Read it, and then read it again and bear in mind how other coins solved this problem.Tell me I'm wrong, but I think this bit with the key part being that the node "authenticate out of band", involve a certain third party with a Very Important Key. In which case the rest of the theory in the document doesn't matter much, does it?