0 sats \ 2 replies \ @_b_o_n_e_s_ 24 Oct 2023 \ on: The BitVM Primer: A Non-technical Explanation of BitVM bitcoin
nice work. thank you. the papers abstract talks about optimistic rollups, are they different from zk rollups?
Yes, optimistic rollups operate differently from zk rollups.
If we start with the similarities, both optimistic and zk rollups:
- execute transactions "off-chain" (i.e. not on the L1)
- post transaction data back to the main chain
The difference comes in when we consider how they verify that a transaction on the rollup was valid.
Optimistic rollups assume all transactions are valid (hence "optimistic"). They rely on actors searching for invalid transactions in the transaction data that is posted back to the main chain. If an invalid tx is found, whoever found it can post a "fraud proof" that demonstrates it is invalid. If their fraud proof is successful, then the validator that included the invalid tx gets slashed.
Zk rollups operate differently. They rely on zero-knowledge proving systems to ensure that transactions on the rollup are valid. Through some cryptography wizardry, zk proving systems produce a "proof" to go along with each tx that shows it was executed correctly. Given the start state, the end state, and a proof, a verifier can validate that each tx was executed correctly.
So, the big difference is that zk rollups verify every transaction on the rollup whereas optimistic rollups only verify transactions when a fraud proof is submitted.
If you want to dive more into these two topics, I recommend Ethereum's developer docs on each:
reply
Just a minor point though:
Most ZK-Rollups are not really Zero-Knowledge. The mistake comes from the confusion between Validity proofs (assures computational integrity) and Zero-Knowledge proofs (assures no information is revealed). (source)
reply