If you do change the chain id, then by definition your chain is the new and different one, because it has a different id.
Genuine question: how does that work? How does ETH mainnet know that my validator is also voting on a different chain?
Don't cite me on the details, but that is the idea
Assume I could have obfuscated the move through the many means availible.
> Slashing is triggered by the evidence of the offence being included in a beacon chain block. Once the evidence is confirmed by the network, the offending validator (or validators) is slashed.
It is a powerless mechanic if the majority of validates don’t want to play along.
A chain is defined by a set of rules that everyone on the chain agrees to abide by. Braking the rules damages the economic utility of the chain, so the Ether on the chain where the validators colluded to break the rules would be worth less, as a result of their actions. The validators are locked on that chain (as they can't prevent a fork from excluding them), so they have a strong incentive against harming the chain. Ethereum is not majoritarian. I don't have to abide by the will of the majority. I only need to come to a consensus about the rules and state of the chain with the people with whom I want to share the chain.
PoS makes it much easier to escape a malicious majority compared to PoW where the hashing power majority can follow the minority anywhere unless the minority is willing to switch to a different hashing algorithm. Even then, the majority could sell their mining equipment and buy new equipment that will work on the new chain on the same terms as that chain's honest minority can. With PoS, the malicious majority would need to buy new Ether from the honest minority who can then just fork again after having made a profit on the attack, and can continue to do that until the malicious majority runs out of resources or realizes that they cannot censor a fork in Ethereum's PoS system.
So you’re going to create a new fork, remove the money from the majority of the wealthy stakeholders who are governing the system, and expect this one to be be seen as legitimate? The one that is explicitly giving the finger to the wealthy?
Good luck!
While I don't think it's meaningful to say that one chain is more legitimate than another, if I was forced to make such a deamination in this case, I would consider the chain where the rules are consistently and predictably enforced in a way that leads to predictable outcomes more legitimate than a chain where validators have colluded to arbitrarily subvert the enforcement of the rules.
The majority of validators could perhaps block this by all running forks of the various consensus client software, with some code changed to set the reward to zero, but why would they do that?
[1] https://github.com/ethereum/consensus-specs/blob/dev/specs/p...
If we imagine a 90/10 split of opinions that leads to a hard fork, the 90 majority can either be satisfied and with their fork and be nice or they can stonewall the 10% fork and refuse to approve any blocks that supports the idea that they deserve to be slashed. Because the only thing that can punish the majority is the approval of the majority. And because allowing another fork to exist reduces the value of the other forks. And because it would just be nicer if instead of having two forks we just kicked out all those annoying validates we don’t agree with.
If the 10% wants to fork off and do a completely different blockchain, what happens to the folks who aren’t colluding either way? I mean, while we’re down to just throw away people’s stakes, why not do so for everyone who isn’t explicitly on our side?
For example: migrating to a new chain ID and restarting with a validator set limited only to the public keys of the 10% who are acting honestly, and loosening that restriction slowly over time.
The attack would end up being extremely costly: not only because it makes the original chain’s token price worthless (who wants to be on a malicious chain?), but because the attacker may also have their deposit slashed in the new chain by the now-majority of honest users defending it.