2022 Review of Zero-Knowledge Rollups and Validiums

Zero-knowledge rollups (ZKRs) utilize advanced cryptographic techniques to generate a validity proof that ascertains the validity of a particular state. Compared to its counterpart, Optimistic Rollups (ORs), ZKRs typically offer higher security while requiring more computation and blockspace, thereby being more costly.

One unique feature of scaling solutions that utilize validity proofs is that they can leverage off-chain data availability, though there is a different classification for such solutions: Validiums, a term coined by StarkWare. This is because submitting a valid validity proof on-chain is considered highly improbable without a valid execution trace, meaning that a malicious attacker would find it nearly impossible to submit a validity proof for a fraudulent state. As such, the data used in the generation of the validity proof can be hosted off-chain with a marginal trade-off in security.