Both Proof of Work, and Proof of Stake are vulnerable to "bad-block" attacks. with proof of work, mining a block and changing your balance in the state to say 1 trillion... well that would be bad for that coin. with proof of stake, it is a bit harder, you would need 51% of all of the tokens(so mainly newer coins are vulnerable) to make said block. However, in what I will be calling Proof of Sender, the cryptography of a block would make it physically impossible to make new balance without removing some, or having an exeption(i.e block rewards) this is called Conservation of Coins or CoC(lol). but, the balance of an address is inaccessible without a private key. if it is possible to make an inaccessible private key, verifiable by the blockchain without revealing the key outside of the key's owner's computer(it is, I have made an implementation), then it would be impossible to make a fake block in the proper format(or at least a block with an invalidly altered state), the worst someone could do is exclude a transaction from a block. this can be fixed with a transaction minimum, so a block would need "x" amount of transactions on it to me created.
if you want to check out the implementation, go to
https://github.com/jordan69420/DefiSpace/releases/tag/663994.
keep in mind that the implementation uses a game to stop people from excluding transactions, not a tx minimum(you can't exclude and play at the same time lol)
