Parallel logoParallel

Parallel is an Ethereum L2 solution utilizing Arbitrum Nitro technology.
Value Locked

$214.40 K

9.42%

Canonically Bridged
$214.40 K
Externally Bridged
$0.00
Natively Minted
$0.00
  • Tokens
  • Daily TPS
    0.144.96%
  • 30D tx count
    196.70 K
  • Stage
    Stage 0
  • Type
    Optimistic Rollup
  • Purposes
    Universal, DeFi
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    Milestones

    ArbOS v20 upgrade

    2024 Apr 10th

    Introduces EIP-4844 data blobs for L1 data availability and Dencun-related opcodes on L2.

    Learn more

    Parallel Mainnet closed launch

    2024 Jan 5th

    Parallel Mainnet is open for developers.

    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)

    No actor outside of the single Proposer can submit fraud proofs. Interactive proofs (INT) require multiple transactions over time to resolve. The challenge protocol can be subject to delay attacks. There is a 6d challenge period.

    Data availability

    On chain

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

    Exit window

    None

    There is no window for users to exit in case of an unwanted upgrade since contracts are instantly upgradable.

    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.

    Rollup stage
    ParallelParallel is a
    Stage 0
    Optimistic Rollup.
    The requirement for available node software is under review
    Stage 0
    3 requirements met
    1 under review
    Stage 1
    3 issues need fixing
    Stage 2
    3 issues need fixing
    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, one of the whitelisted actors can submit a fraud proof that shows that the state was incorrect. The challenge protocol can be subject to delay attacks.

    • 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. Arbitrum Glossary: Challenge Period
    3. RollupUser.sol - Etherscan source code, onlyValidator modifier
    4. Solutions to Delay Attacks on Rollups

    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 blobs or calldata. This ensures that it will be available for enough time.

    1. Sequencing followed by deterministic execution - Arbitrum documentation
    2. SequencerInbox.sol - Etherscan source code, addSequencerL2BatchFromOrigin function
    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. Anyone can become a Proposer after approximately 6d 8h (45818 blocks) of inactivity from the currently whitelisted Proposers.

    1. SequencerInbox.sol - Etherscan source code, forceInclusion function
    2. 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

    Autonomous exit

    Users can (eventually) exit the system by pushing the transaction on L1 and providing the corresponding state root. The only way to prevent such withdrawal is via an upgrade.

    Other considerations

    EVM compatible smart contracts are supported

    Arbitrum One 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. Inside Arbitrum Nitro
    Permissions

    The system uses the following set of permissioned addresses:

    ProxyAdmin 0x6d4b…Fb4d

    Admin of UpgradeExecutor, RollupEventInbox, ChallengeManager, Outbox, L1CustomGateway, L1ERC20Gateway, Bridge, L1GatewayRouter, Inbox.

    Validators/Proposers 0x56D3…b7de

    They can submit new state roots and challenge state roots. Some of the operators perform their duties through special purpose smart contracts.

    Sequencers 0x5eAD…F2D4

    Central actors allowed to submit transaction batches to L1.

    ConduitMultisig 0x4a49…A746

    Multisig that can execute upgrades via the UpgradeExecutor. This is a Gnosis Safe with 4 / 7 threshold.

    Used in:

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    Those are the participants of the ConduitMultisig.

    EOA that can execute upgrades via the UpgradeExecutor.

    Smart contracts
    A diagram of the smart contract architecture
    A diagram of the smart contract architecture

    The system consists of the following smart contracts:

    Router managing token <–> gateway mapping.

    Main contract implementing Arbitrum One 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.

    Implementation used in:

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    Contract managing Inboxes and Outboxes. It escrows the native token used for gas on the chain. This contract stores the following tokens: ETH.

    Can be upgraded by: ProxyAdmin

    Upgrade delay: No delay

    Implementation used in:

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    Main entry point for the Sequencer submitting transaction batches.

    Entry point for users depositing ETH and sending L1 -> L2 messages.

    Can be upgraded by: ProxyAdmin

    Upgrade delay: No delay

    Implementation used in:

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    Contract that allows L2->L1 calls, i.e. messages initiated on L2 which eventually resolve in execution on L1.

    Can be upgraded by: ProxyAdmin

    Upgrade delay: No delay

    Implementation used in:

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    Contract allowed to upgrade the system.

    Can be upgraded by: ProxyAdmin

    Upgrade delay: No delay

    Implementation used in:

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    Contract that allows challenging invalid state roots. Can be called through the RollupProxy.

    Can be upgraded by: ProxyAdmin

    Upgrade delay: No delay

    OneStepProofEntry 0x57EA…C221

    Contract used to perform the last step of a fraud proof.

    OneStepProverMemory 0x8b73…a22f

    Contract used to perform the last step of a fraud proof.

    OneStepProverMath 0x90eC…9F38

    Contract used to perform the last step of a fraud proof.

    OneStepProverHostIo 0x17e7…8010

    Contract used to perform the last step of a fraud proof.

    OneStepProver0 0x72B1…5a62

    Contract used to perform the last step of a fraud proof.

    Value Locked is calculated based on these smart contracts and tokens:

    Main entry point for users depositing ERC20 tokens. Upon depositing, on L2 a generic, “wrapped” token will be minted.

    Main entry point for users depositing ERC20 tokens that require minting custom token on L2.

    Contract managing Inboxes and Outboxes. It escrows ETH sent to L2.

    Can be upgraded by: ProxyAdmin

    Upgrade delay: No delay

    Implementation used in:

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    Escrow for WETH sent to L2.

    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).