All proof of work does is attach an irrecoverable cost to asserting multiple versions of the same claim.
The existence of these irrecoverable costs enables nodes in the network to choose which claim to respect via a very simple heuristic: pick the claim that would be most expensive to retract.
What proof of work does is very simple (deceptively simple). Trying to ascribe a bunch of extra properties to it is an exercise in chasing ghosts.
I think we have to look at why we need irrecoverable costs and why we pick a chain that would be the most expensive to retract.
In theory a well connected P2P network of honest nodes where nodes only accept the first transaction should be enough to determine the correct ordering of transactions (which is all the blockchain does). However there are problems, for example even in an honest network fragmentation can occur and separate groups of nodes that are weakly connected may develop different orderings and different versions of the truth. Then there are attacks by dishonest nodes.
What was needed to fix this was a central record of the "truth" for transaction ordering. The problem here is any central record maker becomes the weak link in the system and point for corruption, shutdown, gov control, etc.
Tying real world costs (that everyone has equal access to) to create blocks did several things: it ensures no one can know who will create the next block which prevents the opportunity for collusion with those who would double spend; it ensures no one can block specific transactions by withholding confirmation; it ensures the system is contained entirely within itself with no external dependencies ; and most importantly it ensures a consistent ordering that is expensive to reverse (making attempts to reverse the order more expensive than the rewards).
All of this put together allows for a central record to be created that does not have a central point to attack.
Another mechanism that achieves the same properties can also create a central record of truth for transaction orderings, but do so without spending real world
physical resources and instead spend economic resources. Blocks created by a random selection of BTC ownership can be made to do this as well. It's not a fair startup mechanism for coin distribution, but can work after coins are distributed.
Here there are real world costs just as with PoW. The costs are time value of money, votes are given by # of BTC held for X period of time. Attempts to reverse the order very high costs in the form of holding a significant percentage of total coins over a period of time, which is unlikely and expensive.
I know many on the previous thread did not like this mechanism before, but I fail to see how it does not achieve the same goals.
Re: alternatives to PoW mining
Mining has the benefit of being simple, whereas stake grinding might be harder to figure out how to optimize, making it analogous to security through obscurity (energy savings through obscurity), the tradeoff being that security modeling is weakened dramatically because whoever does figure out the more abstruse, optimal method of stake grinding will likely have an overwhelming advantage for a while - exactly the kind of centralization that mining seeks to avoid.
PoW mining had the exact same issue. Those who figured out GPU mining first had an unfair advantage for awhile, then those who created the first FPGA miners, then those who made the first ASICs had a crazy advantage and made an absurd amount of BTC.
Bitcoin did not suffer during this period. In fact it flourished since so many people were investing time and energy in the project.
Stake grinding optimization would be the same thing. People would spend significant resources figuring out various optimization strategies giving advantage, these strategies would slowly get out there and be used by most re-leveling the playing field.
BTW can you give an example of stake grinding optimization, it's always seemed fairly straightforward to me (at least the version I've toyed with)
