Ideal properties of rollup escape hatches

Abstract

A rollup is a type of popular "layer two" scaling solution for slow-but-secure blockchains like Ethereum. A rollup perfoms computation of blockchain state updates off-chain but posts the inputs and the data to the underlying blockchain in order to benefit from its security. However, if rollup operators go offline, further state updates are no longer possible through the rollup; instead, state updates to the layer two state must be forced on the underlying blockchain. Such a mechanism is called an escape hatch as it allows state, and in particular digital assets, to escape from an inoperative rollup. We review the approaches from rollups developed by the community and highlight potential issues. We also establish a wish-list of properties that an escape hatch mechanism should have to be considered trustworthy and compatible with decentralization.