Validity Proof
A cryptographic proof that a batch of transactions is correct, used by zk-rollups to guarantee integrity upfront.
A validity proof is a zero-knowledge proof that mathematically certifies a batch of transactions was executed correctly, without revealing or re-running each one. ZK-rollups post this proof to the base chain, which verifies it cheaply — guaranteeing the rollup’s state is correct by mathematics rather than by trust or challenge periods.
The distinction from fraud proofs is fundamental: a validity proof proves correctness before finalizing (no waiting, no assumption of honest watchers), while a fraud proof catches errors after the fact. Validity proofs enable fast withdrawals and stronger security guarantees, at the cost of the computational work to generate them — a cost that specialized hardware and better algorithms keep driving down.