Sorry I don’t know the meaning of the proof of ancestry and ‘GRADPA’.
Thank you guys for helping me understand how casper will work.
According to what we discussed, we all agree that:
- if 2/3 of the validators are honest and
- honest validators don’t switch from a finalized checkpoint to a conflicting one, then the blockchain is safe(i.e., no two finalized checkpoints conflicts each other)
- we believe the 2/3s are honest.
So the blockchain will be safe.
I have no problem with it. But please allow me to argue something.
1)If we ONLY think about the reasoning in the Theorem One, which is about the safety(without additional ‘honest action’, since as a mathematical proof, it is supposed to be logical self-contained without any external hypothesis), I would say the two slashing conditions could be not adequate and the proof itself might not be very correct.
2)The philosophy behind the casper I guess is to turn the hypothesis of ‘honest people’ to ‘rational people’(I guess that’s why we call casper is based on the cryptoeconomy), which implies that as soon as the action is to weaken the blockchain and validators will get benefit from the it, the action will get punished, so the expectation of profit of this kind of actions will be negative, preventing rational validators to take it. For example slashing condition one is to prevent the ‘vote with no stake’.
If the ‘cross-fork’ votes get no slashed, rational validators will probably do it if there is for example some kind of double-spending benefits the validators. The cost is zero anyway why not have a try?
On the contrary if we assume 2/3 are honest, I would argue that the two slashing conditions can also be removed since 2/3 are honest.
- I think the fork rule is based on the rationale that no finalized checkpoint will be reverted unless 1/3 validators’ deposit get slashed, and which is based on the Theorem of the Safety, not based on the honesty.
The reason I insist arguing about this is that as soon as we have some flaw in the logic which we thought is right, someone will use it to attack the blockchain probably.