Fraud proofs allow actors watching the chain to prove that the state is incorrect. Single round proofs (1R) only require a single transaction to resolve.

Data availability

Onchain

All of the data needed for proof construction is published on Ethereum L1.

Exit window

∞

Users can exit funds at any time because contracts are not upgradeable.

Proposer failure

Self propose

Anyone can be a Proposer and propose new roots to the L1 bridge.

Rollup stage

Fuel v1 is a

Stage 2

Optimistic Rollup.

Learn more about Rollup stages

Please keep in mind that these stages do not reflect rollup security, this is an opinionated assessment of rollup maturity based on subjective criteria, created with a goal of incentivizing projects to push toward better decentralization. Each team may have taken different paths to achieve this goal.

Technology

Fraud proofs ensure state correctness

After some period of time, the published state root is assumed to be correct. For a certain time period, usually one week anyone can submit a fraud proof that shows that the state was incorrect.

Funds can be stolen if there is no one that checks the published state. Fraud proofs assume at least one honest and able validator.

Background - Fuel documentation

All data required for proofs is published on chain

All the data that is used to construct the system state is published on chain in the form of cheap calldata. This ensures that it will always be available when needed.

Background - Fuel documentation

State derivation

Node software

The node software source code can be found here.

Genesis state

The bridge contracts deployments are the genesis state of the rollup chain. The bridge contracts of mainnet and testnet (rinkeby) deployment block number are available here.

Data format

The data format details are documented in the Data Structure subsection here.

Operator

The system has a centralized sequencer

While forcing transaction is open to anyone the system employs a privileged sequencer that has priority for submitting transaction batches and ordering transactions.

MEV can be extracted if the operator exploits their centralized position and frontruns user transactions.

Users can force any transaction

Because the block production is open to anyone if users experience censorship from the operator they can propose their own blocks which would include their transactions.

Users can be censored if the operator refuses to include their transactions and users lack resources to propose blocks themselves.

Architecture: A High-Level View - Fuel documentation

Withdrawals

Regular exit

The user initiates the withdrawal by submitting a regular transaction on this chain. When the block containing that transaction is finalized the funds become available for withdrawal on L1. The process of block finalization usually takes several days to complete. Finally the user submits an L1 transaction to claim the funds. This transaction requires a merkle proof.