Data Availability Committee (DAC)

Overview

A Data Availability Committee supports systems such as validiums by keeping copies of transaction data outside the settlement chain. Committee members sign attestations that required data is available, allowing state commitments or proofs to proceed without publishing full data on-chain. The model reduces data costs but introduces trust in committee honesty, independence, and continued service. If enough members collude or disappear, users may be unable to reconstruct state or exit even when validity proofs prevent invalid transitions.

Evaluators should inspect membership, signature threshold, data-retention policy, geographic and operator diversity, replacement rules, and emergency publication mechanisms. Applications must verify attestations against the correct committee epoch and should disclose weaker availability assumptions compared with fully on-chain data.

A rollup or shard can continue producing commitments while users remain unable to reconstruct the information required for independent verification. Applications relying on Data Availability Committee (DAC) should identify how missing data is detected, how long data is retained, and what recovery path exists when normal providers fail. Monitoring should track publication delay, sampling success, reconstruction failures, provider diversity, and the relationship between availability evidence and canonical settlement. Capacity claims should be based on deployed parameters rather than projected roadmap throughput.

A commitment can authenticate data without ensuring that users or validators can obtain enough of it to verify state or produce an exit. Data Availability Committee (DAC) should be analyzed by separating data publication, commitment, sampling or retrieval, reconstruction, and final settlement. Implementation note: A DAC lowers publication costs by attesting to off-chain data, but users depend on its threshold remaining honest and available.