Rather than “genuine” rollups, systems that depend on external data availability are validiums, according to Buterin.
In reaction to a post on X made by Taiko’s creator Daniel Wang—who offers an Ethereum rollup solution—Buterin said that a system loses its rollup status when it depends on other chains, since users are unable to withdraw their assets unconditionally in the event that operators conspire against them.
In spite of the categorization, validiums are nonetheless appropriate for a wide variety of additional uses, as Buterin points out. Modular blockchain Celestia and other systems that depend on external data availability (DA) are validiums, not “genuine” rollups, as Buterin points out in his tweet.
In order to alleviate congestion and gas expenses, scaling solutions for Ethereum such as validiums and rollups enable more transactions to be executed off-chain.
Rollups provide scalability by compressing data and batching transactions off-chain, all while sending data to Ethereum for security. Similarly, validiums permit off-chain transactions; but, instead of posting transactions on-chain, they use zero-knowledge proofs to ensure their validity.
The accessibility of data is the key distinction between the two. The data is accessible on-chain in a rollup, but in a validium, it is stored off-chain with just a hash kept on-chain.
Validiums are more efficient and flexible than rollups because of this difference, but there is a possibility that data availability providers may collude, censor, or go down, which might affect the data. Mainnet hosts a set of smart contracts that manage Validiums. Among these contracts are a data availability committee and a verifier contract.
While validators purportedly provide greater privacy, rollups make transactions more trustworthy and secure by publishing all relevant data on-chain.
Buterin suggests major changes to how layer-2 solutions are categorized. He proposes a new taxonomy of layer-2 solutions using the more flexible “strong” label for rollups and “light” label for validiums. “Strong” labels “security-favoring” solutions and “light” labels “scale-favoring” L2s.
When it comes to scalability, rollups provide compression by batching transactions, which guarantees security that is passed down from layer 1. The throughput is limited, nevertheless, by procedures for data storage and verification. To get around this, Validiums use zero-knowledge proofs, which verify off-chain actions without disclosing on-chain transaction data. Because of this, validiums may grow to larger quantities.
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