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Natively Minted Tokens

Arbitrum (ARB)
GMX (GMX)
USD Coin (USDC)
Gains Network (GNS)
Hydranet (HDN)
Dream Machine Token (DMT)
Externally Bridged Tokens

JoeToken (JOE)
SmarDex (SDEX)
beefy.finance (BIFI)
Bitcoin (BTC.b)
Canonically Bridged Tokens (Top 15)

Ether (ETH)
Tether USD (USDT)
USD Coin (USDC.e)
Wrapped BTC (WBTC)
Wrapped liquid staked Ether 2.0 (wstETH)
Dai Stablecoin (DAI)
ChainLink Token (LINK)
Rocket Pool ETH (rETH)
Dopex Governance Token (DPX)
Dopex Rebate Token (rDPX)
Wootrade Network (WOO)
Uniswap (UNI)
Balancer (BAL)
LUSD Stablecoin (LUSD)
Lyra Token (LYRA)

Milestones

ARB token airdrop

2023 Mar 23rd

ARB token launched as a governance token for Arbitrum DAO.

Learn more

Nitro Upgrade

2022 Aug 31st

Upgrade is live, introducing new architecture, increased throughput and lower fees.

Learn more

Odyssey paused

2022 Jun 29th

Due of the heavy load being put on the chain, Odyssey program got paused.

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Odyssey started

2022 Jun 21st

Incentives program to onboard new users has started.

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Mainnet for everyone

2021 Aug 31st

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

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Description

Fraud proof system is fully deployed but is not yet permissionless as it requires Validators to be whitelisted.

Arbitrum One is an Optimistic Rollup that aims to feel exactly like interacting with Ethereum, but with transactions costing a fraction of what they do on L1. Centralized Sequencer receives users’ transactions and regularly sends the transaction batch to mainnet Ethereum. Independent Proposers (currently whitelisted) read transaction batches from L1, execute them and submit a resulting L2 state root to L1. Any Validator (currently whitelisted) can challenge the state root within the challenge window (6d 8h 43m 36s). The challenge will result in an interactive fraud proof game that will be eventually settled by L1. As long as there is at least one honest Validator, users are guaranteed that eventually correct L2 state root will be published to L1. If Sequencer is censoring users transactions, it is possible to force the transaction via L1 queue. If no Proposer publishes L2 state root within 6d 8h 43m 36s (45818 blocks), the whitelist is dropped and anyone can take over as a new Proposer or Validator.

If you find something wrong on this page you can submit an issue or edit the information.

Risk analysis

Sequencer failureState validationData availabilityUpgradeabilityProposer failure

State validation

Fraud proofs (INT)

Fraud proofs allow WHITELISTED actors watching the chain to prove that the state is incorrect. Interactive proofs (INT) require multiple transactions over time to resolve. The challenge protocol can be subject to delay attacks.

Data availability

On chain

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

Upgradeability

~12d 9h or no delay

There is a 12d 8h 43m 36s delay for upgrades initiated by the DAO that can be canceled by the Security Council multisig. This multisig can also upgrade with no delay.

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 43m 36s of inactivity from the currently whitelisted Proposers.

Rollup stage

Arbitrum OneArbitrum One is a
Stage 1
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, 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#L288 - Etherscan source code, onlyValidator modifier
  4. Solutions to Delay Attacks on Rollups

All transaction data is recorded on chain

All executed transactions are submitted to an on chain smart contract. The execution of the rollup is based entirely on the submitted transactions, so anyone monitoring the contract can know the correct state of the rollup chain.

  1. Sequencing followed by deterministic execution - Arbitrum documentation
  2. SequencerInbox.sol#206 - Etherscan source code, addSequencerL2BatchFromOrigin function

State derivation

Node software

The rollup node (Arbitrum Nitro) consists of three parts. The base layer is the core Geth server (with minor modifications to add hooks) that emulates the execution of EVM contracts and maintains Ethereum’s state. The middle layer, ArbOS, provides additional Layer 2 functionalities such as decompressing data batches, accounting for Layer 1 gas costs, and supporting cross-chain bridge functionalities. The top layer consists of node software, primarily from Geth, that handles client connections (i.e., regular RPC node). View Code

Compression scheme

The Sequencer’s batches are compressed using a general-purpose data compression algorithm known as Brotli, configured to its highest compression setting.

Genesis state

They performed a regenesis from Classic to Nitro, and that file represents the last Classic state. To sync from the initial Classic state, instructions can be found here.

Data format

Nitro supports Ethereum’s data structures and formats by incorporating the core code of the popular go-ethereum (“Geth”) Ethereum node software. The batch is composed of a header and a compressed blob, which results from compressing concatenated RLP-encoded transactions using the standard RLP encoding.

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 43m 36s (45818 blocks) of inactivity from the currently whitelisted Proposers.

  1. SequencerInbox.sol#L125 - 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

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 43m 36s delay for all L2 --> L1 messages (in total a delay of 12d 8h 43m 36s). 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 43m 36s delay on code upgrades.

  1. Arbitrum DAO

Permissions

The system uses the following set of permissioned addresses:

SecurityCouncil 0xF06E…3F85

The admin of all contracts in the system, capable of issuing upgrades without notice and delay. This allows it to censor transactions, upgrade bridge implementation potentially gaining access to all funds stored in a bridge and change the sequencer or any other system component (unlimited upgrade power). It is also the admin of the special purpose smart contracts used by validators. This is a Gnosis Safe with 9 / 12 threshold.

ArbitrumProxyAdmin 0x5547…2dbD

This contract is an admin of SequencerInbox, RollupEventInbox, Bridge, Outbox, Inbox and ChallengeManager contracts. It is owned by the Upgrade Executor.

UpgradeExecutorAdmin 0x5613…0678

This contract is an admin of the UpgradeExecutor contract, but is also owned by it. Can cancel Timelock’s proposals.

GatewaysAdmin 0x9aD4…0aDa

This is yet another proxy admin for the three gateway contracts. It is owned by the Upgrade Executor.

Sequencer 0xC1b6…47cc

Central actor allowed to set the order in which L2 transactions are executed.

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

Smart contracts

A diagram of the smart contract architecture
A diagram of the smart contract architecture

The system consists of the following smart contracts:

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.

Can be upgraded by: UpgradeExecutorAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

Contract managing Inboxes and Outboxes. It escrows ETH sent to L2. This contract stores the following tokens: ETH.

Can be upgraded by: ArbitrumProxyAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

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

Can be upgraded by: ArbitrumProxyAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

Entry point for users depositing ETH and sending L1 --> L2 messages. Deposited ETH is escrowed in a Bridge contract.

Can be upgraded by: ArbitrumProxyAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

Arbitrum’s Outbox system allows for arbitrary L2 to L1 contract calls; i.e., messages initiated from L2 which eventually resolve in execution on L1.

Can be upgraded by: ArbitrumProxyAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

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

Can be upgraded by: UpgradeExecutorAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

Timelock contract for Arbitrum DAO Governance. It gives the DAO participants the ability to upgrade the system. Only the L2 counterpart of this contract can execute the upgrades.

Can be upgraded by: UpgradeExecutorAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

Router managing token <–> gateway mapping.

Can be upgraded by: GatewaysAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

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

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

Can be upgraded by: GatewaysAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

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

Can be upgraded by: GatewaysAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

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

Can be upgraded by: ArbitrumProxyAdmin

Upgrade delay: 12d 8h 43m 36s or 0 if overridden by Security Council

Escrow for DAI 0xA10c…9400

DAI Vault for custom DAI Gateway. Fully controlled by MakerDAO governance.

wstETH Vault for custom wstETH Gateway. Fully controlled by Lido governance.

Tokens: ARB

The current deployment carries some associated risks:

  • Funds can be stolen if a contract receives a malicious code upgrade. There is a 12 days delay on code upgrades unless upgrade is initiated by the Security Council in which case there is no delay.

Knowledge nuggets