Fraud Proof
A fraud proof is how optimistic systems catch cheating: anyone watching can submit cryptographic evidence that a posted state transition was invalid, trigg
A fraud proof is how optimistic systems catch cheating: anyone watching can submit cryptographic evidence that a posted state transition was invalid, triggering re-execution on-chain and slashing the liar. Security assumes at least one honest watcher plus available data to check against.
Why it matters
The whole optimistic-rollup model (and week-long withdrawal windows) rests on this mechanism actually working in practice — funded watchers, published data, and users patient enough to wait. “Valid unless challenged” is only as strong as the challengers who show up.