AnyTrust Protocol
AnyTrust is a variant of Arbitrum Nitro technology that lowers costs by accepting a mild trust assumption.
The Arbitrum protocol requires that all Arbitrum nodes, including validators (nodes that verify correctness of the chain and are prepared to place a bond on correct results), have access to the data of every child chain Transaction in the Arbitrum chain's inbox. An Arbitrum rollup provides data access by posting the data (in batched, compressed form) on parent chain Ethereum as calldata. The Ethereum gas to pay for this is the largest component of cost in Arbitrum.
AnyTrust relies instead on an external Data Availability Committee (DAC) to store data and provide it on demand. The DAC has N
members, of which AnyTrust assumes at least two are honest. This means that if N - 1
DAC members promise to provide access to some data, at least one of the promising parties must be honest. Since there are two honest members, and only one failed to make the promise, it follows that at least one of the promisers must be honest — and that honest member will provide data when it is needed to ensure the chain can properly function.