What Is the Difference between an “Optimistic Rollup” and a “ZK-Rollup”?
Both are Layer 2 scaling solutions. Optimistic Rollups assume transactions are valid by default and use a "fraud proof" system where a challenger has a time window to submit a proof if a block is invalid.
ZK-Rollups (Zero-Knowledge Rollups) use "validity proofs" (cryptographic proofs) to instantly prove the correctness of all off-chain transactions. ZK-Rollups have faster finality but are more computationally intensive to generate proofs.
Glossar
Optimistic Rollups
Rollup ⎊ Optimistic rollups represent a Layer-2 scaling solution for blockchains, primarily Ethereum, designed to enhance transaction throughput while inheriting the security of the underlying Layer-1.
Withdrawal Period
Duration ⎊ The Withdrawal Period defines the fixed, protocol-mandated length of time that assets must remain locked in a Layer 2 bridge contract before they can be claimed on the Layer 1 blockchain.