Data Availability Committee (DAC)
A designated group of parties responsible for holding and attesting to the availability of a validium's off-chain transaction data, since the base chain itself doesn't store it.
A Data Availability Committee is a designated group of parties responsible for holding a validium's (see Kaavon's "Validium" glossary definition) off-chain transaction data and cryptographically attesting that it's genuinely available, since a validium, unlike a standard rollup, doesn't post its full transaction data directly to the base chain. Users and the system rely on the committee's attestation as evidence the data exists and can be retrieved if needed, such as for a user to prove their own balance or exit the system.
A DAC represents a specific, identifiable trust assumption within a validium's broader security model: validity proofs (see Kaavon's "zk-SNARK" glossary definition) guarantee that whatever state transition occurred was computed correctly, but they say nothing about whether the underlying data remains available — that assurance depends entirely on the DAC members behaving honestly and remaining operational. This is the specific tradeoff that distinguishes a validium's data-availability model from a rollup's stronger, base-chain-anchored data-availability (see Kaavon's "Data Availability" glossary definition) guarantee.
Examples
- A validium relying on a Data Availability Committee depends on that committee's members remaining honest and operational to guarantee users can retrieve the off-chain data needed to prove their balances.
- A DAC's attestation addresses data availability specifically, which is a separate concern from the validity proofs that already guarantee a validium's state transitions were computed correctly.