Quote from: instagibbs on February 20, 2015, 01:41:21 PM

That's not clear at all.

https://gist.github.com/oleganza/8cc921e48f396515c6d6

Quote

"Message X should be provably recent and alternatives should be practically impossible to produce."

Practical impossibility can be reframed in terms of "opportunity cost": there are limited physical resources and those should have been largely allocated to X than to Y so we can see that X sucked in all resources from any alternatives. Because if it didn't, then there is a huge uncertainty about whether remaining resources are used for alternative Y or they do not interfere with the voting process. Is it possible that X did not suck in a lot of resources while alternatives are still not possible? Then it would mean that X logically follows from whatever previous state of the system and there is no voting process needed.

Therefore: message X should be provably recent and should have employed provably big amount of resources, big enough that there are not enough resources left for any alternative Y to produce in a reasonably short time frame. Also, the message X should be always "recent" and always outcompete any alternative. Because we cannot reliably compare "old" messages: is Y an "old" one that was just delivered now, or was it produced just now after resources spent on X were released?

This logically leads us to the following: we should accept only the messages with the biggest Proof-of-Work attached, and that proof-of-work should be the greatest possible ever, so there would not be any possibility for any alternative to be produce in the short window of time. And that proof-of-work must be constantly reinforced or the value of previous consensus begins to fade quickly as the opportunity for alternatives grows.

If most of the planet's double-SHA256 capability is being used to mine Bitcoin, then choosing messages with the most accumulated proof of work satisfies the requirements for consensus.

Quote from: instagibbs on February 20, 2015, 01:41:21 PM

We need, at a minimum, a majority of *active* hashrate to not "attack" the network.

You're trying to accomplish more than what is possible.

The best achievable guarantee for mining is: "ought to find it more profitable to play by the rules."

There is no technical solution available to counteract attacks by highly-resources entities who do not care about profit.

The only thing we can do is to make Bitcoin so valuable that the opportunity cost of not playing by the rules is high enough to deter such attackers.