Data Availability Committee (DAC)

Overview

How it works

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.

What matters in practice

A data availability committee is a selected set of parties entrusted to store or attest that transaction or state data can be recovered. A committee may reduce costs compared with publishing all data on an L1, but introduces trust, membership and liveness assumptions. An attestation is only as meaningful as the committee's actual access and retention obligations. If data disappear, users may struggle to reconstruct state even if the execution commitment remains visible. A merchant assessing a payment network should ask who runs the committee, what a failure does to withdrawals and whether independent users can audit data retrieval.

Related glossary concepts

Data Availability; Transaction Data