Fuel aims to be a complete optimistic rollup with low transaction costs, high speed and high throughput.
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.
All of the data needed for proof construction is published on chain.
The code that secures the system can never change.
In the event of a sequencer failure, users can force transactions to be included in the project’s chain by sending them to L1.
Anyone can be a Proposer and propose new roots to the L1 bridge.
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.
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.
The node software source code can be found here.
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.
The data format details are documented in the Data Structure subsection here.
While proposing blocks 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.
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.
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.