Arbitrum Nova logoArbitrum Nova

Arbitrum Nova is an AnyTrust Optimium, differing from Arbitrum One by not posting transaction data onchain.
Value Locked

$42.68 M

13.68%

Canonically Bridged
$42.68 M
Externally Bridged
$0.00
Natively Minted
$0.00
  • Tokens
  • Daily TPS
    8.2414.88%
  • 30D tx count
    47.61 M
  • Type
    Optimium
  • Purpose
    Universal
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    Milestones

    Mainnet for everyone

    2022 Aug 9th

    Whitelist got removed, there are no restrictions on who can transact with the network.

    Learn more
    Risk summary
    Fraud proof system is fully deployed but is not yet permissionless as it requires Validators to be whitelisted.
    Risk analysis
    Fraud proof system is fully deployed but is not yet permissionless as it requires Validators to be whitelisted.
    Sequencer failureState validationData availabilityExit windowProposer failure

    State validation

    Fraud proofs (INT)

    Fraud proofs allow 13 WHITELISTED actors watching the chain to prove that the state is incorrect. Interactive proofs (INT) require multiple transactions over time to resolve.

    Data availability

    External (DAC)

    Proof construction relies fully on data that is NOT published on chain. There exists a Data Availability Committee (DAC) with a threshold of 5/6 that is tasked with protecting and supplying the data.

    Exit window

    2d
    The Security Council can upgrade with no delay.

    Upgrades are initiated on L2 and have to go first through a 3d delay. Since there is a 1d to force a tx, users have only 2d to exit. If users post a tx after that time, they would need to self propose a root with a 6d 8h delay and then wait for the 6d 8h challenge window, while the upgrade would be confirmed just after the 6d 8h challenge window and the 3d L1 timelock.

    Sequencer failure

    Self sequence

    In the event of a sequencer failure, users can force transactions to be included in the project’s chain by sending them to L1. There is a 1d delay on this operation.

    Proposer failure

    Self propose

    Anyone can become a Proposer after 6d 8h of inactivity from the currently whitelisted Proposers.

    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 one of the whitelisted actors can submit a fraud proof that shows that the state was incorrect.

    • Funds can be stolen if none of the whitelisted verifiers checks the published state. Fraud proofs assume at least one honest and able validator (CRITICAL).

    1. How is fraud proven - Arbitrum documentation FAQ
    2. RollupUserLogic.sol#L288 - Etherscan source code, onlyValidator modifier

    Data is not stored on chain

    Users transactions are not published on-chain, but rather sent to external trusted parties, also known as committee members (DAC). Members of the DAC collectively produce a Data Availability Certificate (comprising BLS signatures from a quorum) guaranteeing that the data behind the new transaction batch will be available until the expiry period elapses (currently a minimum of two weeks). This signature is not verified by L1, however external Validators will skip the batch if BLS signature is not valid resulting. This will result in a fraud proof challenge if this batch is included in a consecutive state update. It is assumed that at least one honest DAC member that signed the batch will reveal tx data to the Validators if Sequencer decides to act maliciously and withhold the data. If the Sequencer cannot gather enough signatures from the DAC, it will “fall back to rollup” mode and by posting the full data directly to the L1 chain. The current DAC threshold is 5 out of 6.

    • Funds can be lost if the external data becomes unavailable (CRITICAL).

    • Users can be censored if the committee restricts their access to the external data.

    1. Inside AnyTrust - Arbitrum documentation
    Operator

    The system has a centralized sequencer

    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.

    1. Sequencer - Arbitrum documentation

    Users can force any transaction

    Because the state of the system is based on transactions submitted on-chain and anyone can submit their transactions there it allows the users to circumvent censorship by interacting with the smart contract directly.

    1. Sequencer Isn’t Doing Its Job - Arbitrum 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.

    1. Transaction lifecycle - Arbitrum documentation
    2. L2 to L1 Messages - Arbitrum documentation
    3. Mainnet for everyone - Arbitrum Blog

    Tradeable Bridge Exit

    When a user initiates a regular withdrawal a third party verifying the chain can offer to buy this withdrawal by paying the user on L1. The user will get the funds immediately, however the third party has to wait for the block to be finalized. This is implemented as a first party functionality inside Arbitrum’s token bridge.

    1. Tradeable Bridge Exits - Arbitrum documentation
    Other considerations

    EVM compatible smart contracts are supported

    Arbitrum Nova uses Nitro technology that allows running fraud proofs by executing EVM code on top of WASM.

    • Funds can be lost if there are mistakes in the highly complex Nitro and WASM one-step prover implementation.

    1. Arbitrum Nitro Sneak Preview

    Arbitrum DAO is in charge of upgrades

    Arbitrum DAO allows $ARB token holders to propose and vote on changes to the organization and the technologies it governs. The governance smart contracts are implemented on Arbitrum One rollup chain. The DAO can upgrade the Arbitrum One contracts on L2 with 3d delay and - using L2 --> L1 Governance Relay, update contracts on L1 with additional 3d delay + 6d 8h delay for all L2 --> L1 messages (in total a delay of 12d 8h). The Security Council can upgrade the contracts without any delay. It can also cancel any upgrades initiated by the DAO.

    • Funds can be stolen if a contract receives a malicious code upgrade. There is a 12d 8h delay on code upgrades.

    1. Arbitrum DAO
    Smart contracts
    A diagram of the smart contract architecture
    A diagram of the smart contract architecture

    The system consists of the following smart contracts:

    ProxyAdmin 1 0x71D7…7148

    This contract is an admin of most other contracts allowed to upgrade their implementations. It is owned by the Upgrade Executor.

    This contract can upgrade the system’s contracts. The upgrades can be done either by the Security Council or by the L1ArbitrumTimelock. Can cancel Timelock’s proposals.

    ProxyAdmin 2 0x5613…0678

    This contract is an admin of the Update Executor contract, but is also owned by it.

    Timelock contract for Arbitrum DAO Governance. It gives the DAO participants the ability to upgrade the system. Only the Nova counterpart of this contract can execute the upgrades.

    Main contract implementing Arbitrum Nova Rollup. Manages other Rollup components, list of Stakers and Validators. Entry point for Validators creating new Rollup Nodes (state commits) and Challengers submitting fraud proofs.

    Main entry point for the Sequencer submitting transaction batches to a Rollup.

    BatchPosterManagerMultisig 0xd0FD…679B

    It can update whether an address is authorized to be a batch poster at the sequencer inbox. The UpgradeExecutor retains the ability to update the batch poster manager (along with any batch posters).

    Entry point for users depositing ETH and sending L1 --> Nova messages. Deposited ETH is escrowed in a Bridge contract.

    Contract managing Inboxes and Outboxes. It escrows ETH sent to Nova. This contract stores the following tokens: ETH.

    Contract managing an interactive fraud challenge process.

    OneStepProofEntry 0xC6E1…4F7e

    Contract managing adjudication logic for EVM implementation in WASM used by the fraud proofs.

    ProxyAdmin 3 0xa8f7…e560

    Yet another proxy admin for the three gateway contracts below. It is also owned by the Upgrade Executor.

    Router managing token <–> gateway mapping.

    Main entry point for users depositing ERC20 tokens. Upon depositing, on Nova a generic, “wrapped” token will be minted. This contract can store any token.

    Main entry point for users depositing ERC20 tokens that require minting custom token on Nova.

    L1DaiGateway 0x97f6…A786

    Custom DAI Gateway, main entry point for users depositing DAI to Nova where “canonical” Nova DAI token managed by MakerDAO will be minted. Managed by MakerDAO.

    L1Escrow 0xA2e9…aAd3

    DAI Vault for custom DAI Gateway managed by MakerDAO. This contract stores the following tokens: DAI.

    The current deployment carries some associated risks:

    • Funds can be stolen if a contract receives a malicious code upgrade. There is no delay on code upgrades (CRITICAL).

    Knowledge nuggets
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