Definition
A state commitment is a compact cryptographic value that uniquely represents the entire state of a blockchain or rollup at a specific point in time. It is typically derived from a data structure such as a Merkle tree that encodes all accounts, balances, contract storage, and other state elements. By publishing state commitments, a system provides a canonical reference against which individual state elements and transitions can be efficiently verified.
In rollup architectures, state commitments are often posted from a sequencer to a base layer chain to anchor the rollup’s state. These commitments serve as the basis for mechanisms like fraud proof and validity proof systems, which check whether the transitions between successive state commitments are correct. As a result, state commitments are central to ensuring that off-chain or layer-2 execution remains cryptographically tied to an on-chain security model.
Context and Usage
Within a rollup, the sequencer typically aggregates transactions, computes the new state, and then derives a state commitment that is submitted to a more secure base layer. This commitment allows external verifiers and light clients to confirm the integrity of the rollup’s state without needing to process every transaction themselves. In systems that rely on state sync, these commitments can be used to synchronize state views across different components or chains.
Fraud proof schemes treat state commitments as claims about the system’s state and attempt to show that a claimed transition between two commitments is invalid, while validity proof schemes provide cryptographic evidence that the transition is correct. In both cases, the security of the design depends on the binding property of the state commitment: any deviation in underlying state must produce a different commitment. This makes state commitments a foundational concept for scalable, trust-minimized blockchain and rollup designs.