validium

Validium is a layer-2 scaling solution for blockchains such as Ethereum that uses zero-knowledge proofs to verify state transitions while keeping transaction data off-chain. In validium, data availability does not rely on the main chain; instead, data is stored off-chain in a separate data availability layer, often a data availability committee or dedicated storage. This arrangement enables higher throughput and lower on-chain data load but introduces trust assumptions about data availability.

How it works: An operator collects user transactions, computes a new state, and produces a zero-knowledge proof that the transition is valid. The proof is posted to the main Ethereum chain to secure finality, while the actual transaction data remains off-chain. The off-chain data must stay accessible to reconstruct the state and allow withdrawals; this is provided by a data availability layer or DAC.

Security and trade-offs: Validium offers higher throughput and lower gas costs compared with on-chain data models, but relies on external data availability providers. If data is withheld or the data layer is compromised, users may face withdrawal or verification risks, and censorship becomes a concern. The security model therefore depends on the reliability of the off-chain data ecosystem.

Relation to other layer-2 approaches: Validium contrasts with zk-rollups, where transaction data is posted to the layer-1 chain along with proofs, ensuring data availability by the L1 contract. Validium favors throughput at the expense of on-chain data assurance. Some StarkWare deployments provide both validium and rollup modes.

Applications: Validium has been deployed in StarkWare’s StarkEx-enabled apps, such as DeversiFi and dYdX, to enable high-throughput trading and other use cases, as well as in NFT and payments platforms. The technology continues to evolve with ongoing research into data availability schemes and cross-chain interoperability.