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Xai

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Xai is an Ethereum Layer-3 that leverages Arbitrum AnyTrust to enable open trade in the next generation of video games.


  • Total Value SecuredTVS
    $693.54 K9.53%
  • Past day UOPSDaily UOPS
    1.006.91%
  • Gas token
    XAI
  • Type
    Other

  • Purposes
    Universal, Gaming
  • Host chain
    Arbitrum One
  • Chain ID
    660279

  • Tokens breakdown

    Sequencer failureState validationData availabilityExit windowProposer failure

    Badges

    About

    Xai is an Ethereum Layer-3 that leverages Arbitrum AnyTrust to enable open trade in the next generation of video games.

    Why is the project listed in others?

    There are less than 5 external actors that can submit challenges

    Consequence: projects without a sufficiently decentralized set of challengers rely on few entities to safely update the state. A small set of challengers can collude with the proposer to finalize an invalid state, which can cause loss of funds.

    The data availability committee threshold is too low

    Consequence: projects with a low DAC threshold rely on the honesty of few entities to safely attest data availability on Ethereum. These entities can collude with the proposer to finalize an unavailable state, which can cause loss of funds.

    Learn more about the recategorisation here.


    Total
    Canonically BridgedCanonically Bridged ValueCanonical
    Natively MintedNatively Minted TokensNative
    Externally BridgedExternally Bridged ValueExternal

    ETH & derivatives
    Stablecoins
    BTC & derivatives
    Other
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    Past Day Ops count
    Max. UOPS
    Past day UOPS/TPS Ratio
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    Mainnet Launch

    2024 Jan 9th

    XAI launches on Arbitrum One.

    Learn more
    There are 3 additional risks coming from the host chain Arbitrum One logoArbitrum One
    Fraud proof systemThe infrastructure that allows projects to verify their state transitions. It is composed by onchain verifiers and offchain provers. The main two flavors are optimistic and ZK proof systems, but they can be combined in a hybrid model. In general though, if a system is able to accept state roots optimistically, even if it has a ZK component, it is considered an optimistic proof system. is fully deployed but is not yet permissionlessAnyone willing should be able to join and leave the network at any time, without causing significant disturbance to the network or being detrimental to the party in question. No single entity should have the power to allowlist or blocklist participants. as it requires ValidatorsIn the context of L2s, a Validator is an actor that validates the correctness of state transitions. For optimistic rollups this corresponds to challengers, and for ZK rollups this corresponds to the onchain verifier to be whitelisted.
    The L3 risks depend on the individual properties of L3 and those of the host chain combined.
    Fraud proof systemThe infrastructure that allows projects to verify their state transitions. It is composed by onchain verifiers and offchain provers. The main two flavors are optimistic and ZK proof systems, but they can be combined in a hybrid model. In general though, if a system is able to accept state roots optimistically, even if it has a ZK component, it is considered an optimistic proof system. is fully deployed but is not yet permissionlessAnyone willing should be able to join and leave the network at any time, without causing significant disturbance to the network or being detrimental to the party in question. No single entity should have the power to allowlist or blocklist participants. as it requires ValidatorsIn the context of L2s, a Validator is an actor that validates the correctness of state transitions. For optimistic rollups this corresponds to challengers, and for ZK rollups this corresponds to the onchain verifier to be whitelisted.
    SEQUENCER
    FAILURE
    STATE
    VALIDATION
    DATA
    AVAILABILITY
    EXIT WINDOWPROPOSER
    FAILURE
    Arbitrum One
    L2
    Self sequenceFraud proofs (INT)OnchainNoneSelf propose
    Xai
    L3 • Individual
    Self sequenceFraud proofs (INT)External (DAC)NoneSelf propose
    Xai
    L3 • Combined
    Self sequenceFraud proofs (INT)External (DAC)NoneSelf propose
    L2 & L3 individual risks
    Sequencer failureState validationData availabilityExit windowProposer failure
    L3 combined risks
    Sequencer failureState validationData availabilityExit windowProposer failure

    L3 combined risks
    The information below reflects combined L2 & L3 risks.
    Sequencer failure
    Self sequence

    In the event of a sequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs. failure, users can force transactions to be included in the project’s chain by sending them to L1Layer 1 (L1) is a blockchain that is self-reliant on its validator set for its security and consensus properties. Ethereum is an example of a layer 1. Blockchains started receiving the moniker of layer 1 once layer 2 became a meaningful area of development.. There can be up to a 2d delay on this operation.

    State validation
    Fraud proofs (INT)

    Fraud proofs only allow 2 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. There is a 6d 8h challenge periodIn optimistic rollups, the window of time wherein network participants can assert that some fraud was included in a prior block. Most optimistic rollups currently specify a challenge window of 7 days. By extending the period, there is more time for participants to guard against fraud (invalid state transitions), but also more time until withdrawals gets enabled..

    Data availability
    External (DAC)

    Proof construction relies fully on data that is NOT published onchain. There exists a Data Availability Committee (DAC)A set of members whose task is attesting and ensuring that the data is available for the public. An onchain DAC verifier checks that a threshold of signatures from the DAC members is reached before considering a data commitment as available and therefore valid to be used in the system. with a threshold of 3/5 that is tasked with protecting and supplying the data.

    Exit window
    None

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

    Proposer failure
    Self propose

    Anyone can become a ProposerIn the context of L2s, the actor that proposes a claimed state root on L1. The term is also used in the context of Ethereum to refer to the actor that proposes a new block. after 12d 17h of inactivity from the currently whitelisted Proposers.

    Xai
    Xai is not even a
    Stage 0
    project.
    The requirement for available nodeA software client that participates in the network. software is under review.

    Learn more about Stages
    Please keep in mind that these stages do not reflect project security, this is an opinionated assessment of project 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.

    Set of parties responsible for signing and attesting to the availability of data.

    Economic security
    Public committee

    There are no onchain assets at risk of being slashed in case of a data withholding attack. However, there is indirect economic security derived by the committee members being publicly known, and their reputation is at stake should they behave maliciously.

    Fraud detection
    None

    There is no fraud detection mechanism in place. A data withholding attack can only be detected by nodes downloading the full data from the DA layerAn infrastructure that is used to make publish data so that it's available to the public. They take the form of Data Availability Committees (DACs) or blockchains. Not to confuse with the layer responsible with ordering, since ordering and DA can be separated..

    Committee security
    3/5

    The committee does not meet basic security standards, either due to insufficient size, lack of member diversity, or poorly defined threshold parameters. The system lacks an effective DA bridgeSystem that verifies that data has been made available. It takes the form of a smart contract verifying a consensus or, if the data is verified directly by either downloading the full data or sampling, of an enshrined bridge. and it is reliant on the assumption of an honest sequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs., creating significant risks to data integrity and availability.

    Upgradeability
    No delay

    There is no delay in the upgradeabilityThe ability for rollup smart contracts and parameters used in a rollup to be updated by holders of an admin key. Upgradeability represents a vector of risk for users, and should be decentralized and combined with time delays for greater security guarantees. of the bridgeA message-passing protocol between two blockchains. At its most basic, a token bridge consists of a smart contract which can escrow funds on one side of the bridge, and instruct the release or minting of corresponding assets on the other side, but bridges could also support arbitrary messages. How these instructions are validated is a critical factor in assessing the trust assumptions of a bridge.. Users have no time to exit the system before the bridge implementation update is completed.

    Relayer failure
    No mechanism

    The relayer role is permissioned, and the DA bridgeSystem that verifies that data has been made available. It takes the form of a smart contract verifying a consensus or, if the data is verified directly by either downloading the full data or sampling, of an enshrined bridge. does not have a Security CouncilA Security Council is a sufficiently decentralized set of members that is able to upgrade a system. A properly set up Security Council consists of at least 8 members with a threshold greater than 75%. What 'sufficiently decentralized' means is fundamentally subjective and L2BEAT evaluates each case individually. A Security Council is allowed to instantly upgrade Stage 1 rollups. or a governance mechanism to propose new relayers. In case of relayer failure, the DA bridge will halt and be unable to recover without the intervention of a centralized entity.

    Architecture

    Anytrust architecture

    The DAC uses a data availabilityThe property of a rollup's data being reachable by any node retrieving the data that were rolled up and executed to reach the proposed state. Data availability (DA), specifically decoupling it from the rollup nodes themselves, is one of the preeminent factors which allows a rollup to scale securely. A rollup is faced with a decision of what to use as a DA layer to guarantee that any node can retrieve this data--permissionlessly under any circumstance. For this reason, using Ethereum for DA currently provides the strongest security guarantees. If data is stored somewhere other than a permissionless L1, then the project is not a rollup, but rather a validium or an optimium. solution built on the AnyTrust protocol. It is composed of the following components:

    • SequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs. Inbox: Main entry point for the Sequencer submitting transaction batches.
    • Data Availability Committee (DAC)A set of members whose task is attesting and ensuring that the data is available for the public. An onchain DAC verifier checks that a threshold of signatures from the DAC members is reached before considering a data commitment as available and therefore valid to be used in the system.: A group of members responsible for storing and providing data on demand.
    • Data Availability Certificate (DACert): A commitment ensuring that data blobsThe data that a rollup publishes to its L1/data availability (DA) layer. They consist of the L2 transactions that are rolled up, along with some metadata. Blobs are introduced as a new transaction type within Ethereum with EIP-4844, and has rollup scaling specifically in mind. Blobs persist on Ethereum’s Beacon Chain ephemerally. are available without needing full data posting on the L1Layer 1 (L1) is a blockchain that is self-reliant on its validator set for its security and consensus properties. Ethereum is an example of a layer 1. Blockchains started receiving the moniker of layer 1 once layer 2 became a meaningful area of development. chain.

    Committee members run servers that support APIs for storing and retrieving data blobs. The Sequencer API allows the rollupA blockchain that inherits consensus and data availability from another blockchain called L1. Rollups enable trust minimized bridges with the base layer via proof systems, either optimistic or zero-knowledge. A rollup without a bridge, or without considering the bridge, is called a sovereign rollup. Sequencer to submit data blobs for storage, while the REST API enables anyone to fetch data by hashA fixed-length fingerprint of variable-size input, produced by a hash function.. When the Sequencer produces a data batch, it sends the batch along with an expiration time to Committee members, who store it and sign it. Once enough signatures are collected, the Sequencer aggregates them into a valid DACert and posts it to the L1 chain inbox. If the Sequencer fails to collect enough signatures, it falls back to posting the full data to the L1 chain as calldata.

    A DACert includes a hash of the data blockAn ordered list of transactions and chain-related metadata that gets bundled together and published to the L1/DA layer. Nodes execute the transactions contained within blocks to change the rollup chain’s state. Protocol rules dictate what constitutes a valid block, and invalid blocks are skipped over., an expiration time, and proof that the required threshold of Committee members have signed off on the data. The proof consists of a hash of the Keyset used in signing, a bitmap indicating which members signed, and a BLS aggregated signature. L2Layer 2 (L2) is a category of technical solutions aimed to scale the base layer in a trust minimized way. This category includes solutions like rollups as well as state channels and plasma. Other solutions are able to scale further, but with the introduction of additional trust assumptions, which are therefore not trust minimized. Sometimes the term Layer 2 is used to refer to include these solutions too, like validiums and optimiums, but to distinguish between trust minimized and non trust minimized solutions they are often referred to as "light" L2s, opposed to "strong" L2s like rollups. nodes reading from the sequencer inbox verify the certificate’s validity by checking the number of signers, the aggregated signature, and that the expiration time is at least two weeks ahead of the L2 timestamp. If the DACert is valid, it provides a proof that the corresponding data is available from honest committee members.

    DA BridgeSystem that verifies that data has been made available. It takes the form of a smart contract verifying a consensus or, if the data is verified directly by either downloading the full data or sampling, of an enshrined bridge. Architecture

    Anytrust bridge architecture

    The DA commitments are posted to the destination chain through the sequencer inbox, using the inbox as a DA bridge. The DA commitment consists of Data Availability Certificate (DACert), including a hash of the data block, an expiration time, and a proof that the required threshold of Committee members have signed off on the data. The sequencer distributes the data and collects signatures from Committee members offchain. Only the DACert is posted by the sequencer to the destination chain inbox (the DA bridge), achieving destination chain transaction ordering finalityStrongest confirmation rule that can be given on the ordering of transactions. On Ethereum, a transaction is finalized when the corresponding epoch becomes final, which currently takes around 15 mins from transaction inclusion. A rollup transaction can be said to be final when the corresponding data is published to L1 and its ordering cannot be reverted. If outputs, i.e. state diffs are published, then also a proof proving their correctness must be verified to consider the transaction final. in a single onchain transaction.

    • Funds can be lost if a malicious committee attests to an invalid data availability certificate.

    • Funds can be lost if the bridge contract or its dependencies receive a malicious code upgrade. There is no delay on code upgrades.

    1. Inside AnyTrust - Arbitrum Docs
    A diagram of the state validation
    A diagram of the state validation
    Fraud proofs

    After some period of time, the published state rootA cryptographic hash succinctly representing a state using a Merkle tree. is assumed to be correct. For a certain time period, one of the whitelisted actors can submit a fraud proofAlso referred to as a fault proof, it is the construction of an assertion that fraud was perpetrated on an optimistic rollup. More concretely, that an invalid state transition took place according to the protocol rules. The submitter of a fraud proof would expect a reward from the optimistic rollup protocol for helping maintain the integrity of the system. that shows that the state was incorrect. The challenge protocol can be subject to delay attacks. After the state root is published, there is also a trusted entity, called Challenger, that signs it and submits the signature to a Referee smart contract. The signatures submitted to the referee are used then verified by sentry nodes. The role of sentry nodes is to verify (assert) the submitted state root after it has been submitted. There is no integrated way to flag an invalid state root, sentry nodes will have to raise the alarm by external means, making them just observation nodes.

    • 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. Referee.sol - Etherscan source code, submitChallenge function
    5. Referee.sol - Etherscan source code, submitAssertionToChallenge function
    6. Solutions to Delay Attacks on Rollups

    Program Hashes

    Name
    Hash
    Repository
    Verification
    Used in
    0xdb69...b69a
    SX Network logoCapx logoXai logoAppchain logoEverclear Hub logo

    Projects used in

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    Past upgrades

    The metrics include upgrades on the currently used proxy contracts. Historical proxy contracts and changes of such are not included.

    Count of upgrades
    47
    Last upgrade
    1y 3mo ago
    Avg upgrade interval
    5mo 4d
    2026 September 07, 21:35 UTC
    8changes

    SafeL2 owning the ProxyAdmin of the Sentry contracts: member added; threshold lowered 4/6 → 3/7. XaiFundsReiceiverMultisig: 3 members removed; threshold 3/7 → 2/4. Team Secret removed from the listed DAC members: its key left the keyset on 2025-01-12; the current 3/5 keyset is Xai, Ex Populus, LayerZero, Alt Layer and Offchain Labs.

    contract SafeL2 (arb1:0x754286508D57Fae1256bC288461E075552175CBa) [GnosisSafe] {
    +++ description: None
    values.$members.0:
    + "arb1:0x194654c631686077d3C34a0e7c1856E4BE2E2705"
    values.$threshold:
    - 4
    + 3
    values.multisigThreshold:
    - "4 of 6 (67%)"
    + "3 of 7 (43%)"
    }
    contract XaiFundsReiceiverMultisig (arb1:0xFCF7248C495d6fd3641eE43F861c48Ebe402c878) [GnosisSafe] {
    +++ description: The designated fundsReceiver in the NodeLicenseRegistry. Receives all ETH from 'Sentry Node License' mints.
    values.$members.1:
    - "arb1:0x739bd9Ed651d200dc84d0b0dF444CA47CBFf520f"
    values.$members.2:
    - "arb1:0x90D77E3a3B660E54E04cD622937765d2375FB2e3"
    values.$members.5:
    - "arb1:0xE529a3271f9CC84B1FE9107ab4764a8dF177782a"
    values.$threshold:
    - 3
    + 2
    values.multisigThreshold:
    - "3 of 7 (43%)"
    + "2 of 4 (50%)"
    }
    2026 July 09, 09:59 UTC
    3changes

    XaiFundsReiceiverMultisig (receives ETH from Sentry Node License mints) added a new 1-of-3 SafeL2 ( 0x1946…2705 ) as a member. Top-Safe per-member share drops: 3/6 (50%) → 3/7 (43%).

    contract XaiFundsReiceiverMultisig (arb1:0xFCF7248C495d6fd3641eE43F861c48Ebe402c878) [GnosisSafe] {
    +++ description: The designated fundsReceiver in the NodeLicenseRegistry. Receives all ETH from 'Sentry Node License' mints.
    values.$members.0:
    + "arb1:0x194654c631686077d3C34a0e7c1856E4BE2E2705"
    values.multisigThreshold:
    - "3 of 6 (50%)"
    + "3 of 7 (43%)"
    }
    + Status: CREATED
    contract SafeL2 (arb1:0x194654c631686077d3C34a0e7c1856E4BE2E2705) [GnosisSafe]
    +++ description: None
    2025 October 03, 09:01 UTC
    2changes

    Upgrade to ArbOS v40.

    contract RollupProxy (arb1:0xC47DacFbAa80Bd9D8112F4e8069482c2A3221336) {
    +++ description: Central contract for the project's configuration like its execution logic hash (`wasmModuleRoot`) and addresses of the other system contracts. Entry point for Proposers creating new Rollup Nodes (state commitments) and Challengers submitting fraud proofs (In the Orbit stack, these two roles are both held by the Validators).
    +++ description: ArbOS version derived from known wasmModuleRoots.
    values.arbOsFromWmRoot:
    - "ArbOS v32 wasmModuleRoot"
    + "ArbOS v40 wasmModuleRoot"
    +++ description: Root hash of the WASM module used for execution, like a fingerprint of the L2 logic. Can be associated with ArbOS versions.
    values.wasmModuleRoot:
    - "0x184884e1eb9fefdc158f6c8ac912bb183bf3cf83f0090317e0bc4ac5860baa39"
    + "0xdb698a2576298f25448bc092e52cf13b1e24141c997135d70f217d674bbeb69a"
    }
    2025 September 03, 10:26 UTC
    2changes

    msig changes.

    contract ProxyAdmin (arb1:0xD88c8E0aE21beA6adE41A41130Bb4cd43e6b1723) {
    +++ description: None
    values.owner:
    - "arb1:0x7C94E07bbf73518B0E25D1Be200a5b58F46F9dC7"
    + "arb1:0x754286508D57Fae1256bC288461E075552175CBa"
    }
    + Status: CREATED
    contract SafeL2 (arb1:0x754286508D57Fae1256bC288461E075552175CBa)
    +++ description: None
    2025 August 18, 10:36 UTC
    3changes

    DAC key changed.

    contract SequencerInbox (0x995a9d3ca121D48d21087eDE20bc8acb2398c8B1) {
    +++ description: A sequencer (registered in this contract) can submit transaction batches or commitments here.
    values.dacKeyset.blsSignatures.1:
    - "YBnmxAj50xHWx74c8TEJQ4hMxDc8au4r/8ZjDdm9VZZeVz30yudFDkKd5gzt/bnDkxL/fS3uO/uyV5IK/x5g53D7ZBMcrVJF3UMriIitIvf/jriRsnCi1TSZVG+RpGoMNAAji+ipTEVV5YnQPi/AVGQIGwmoEzhA/giQH7evlxzC1Q876MQqHTwwfIrX63UZ5hPEs84OyTq5gHvR71UYbI7TEzHRNi3RJTfgsidx8Q1v2jndA5HfYUq2pxmmPPkIoxHSK+Syt24Fe9q/6dIMN76BXMDpbXu1+r0QdQMPLEfSWm/aquMI6sN1ljaa958XThaluC1z+iqrR9b5e8LoEq1OliZf2qCHnv9MFX51KCF42zEQiz493XQrf0HUJIfCag=="
    values.dacKeyset.blsSignatures.4:
    + "YAs1+BYgCS8HZ5vbTRT1nbt71wSvrFO3cFKUzWPXaud5V0ErIbWmk4ITu7VxEdDGnAyGmwwfVf2KjZXtsmDHYvXqED6z2fWva8RuY8wTrK5DYRVrPFpZxyFvfkO6j5TXyBPelZmJQzpQlFjx0eMoq4HFloDG1utysJywf3SqUuZKoU074I8pfkz4DSA8gomp6ACZNDBe+1rzvo4jFyzIKbhzveNanj9UWNEBJcrorD+ajWHW/Mrwn0P9RY5MeBt/CQQdCeHvOxTp95aWg2dXYv3iEB3WgH0i06da5gyjit809RYytX2x5I8pbgzugpsieBf8RrKq9FZujcdJJVAVtYJf/hWdptqcwEDdhfZTE2uMOVNJGFnwQ95wYdMT1jQpHA=="
    values.keySetUpdates:
    - 8
    + 9
    }
    The section considers only the L3 properties. For more details please refer to Arbitrum One logoArbitrum One

    The system has a centralized sequencer

    While forcing transaction is open to anyone the system employs a privileged sequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs. 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 the underlying host chain and anyone can submit their transactions there it allows the users to circumvent censorship by interacting with the smart contract on the host chain directly. After a delay of 1d in which a SequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs. has failed to include a transaction that was directly posted to the smart contract, it can be forcefully included by anyone on the host chain, which finalizes its ordering.

    1. SequencerInbox.sol - source code, forceInclusion function
    2. Sequencer Isn't Doing Its Job - Arbitrum documentation

    Delayed forced transactions

    To force transactions from the host chain, users must first enqueue “delayed” messages in the “delayed” inbox of the BridgeA message-passing protocol between two blockchains. At its most basic, a token bridge consists of a smart contract which can escrow funds on one side of the bridge, and instruct the release or minting of corresponding assets on the other side, but bridges could also support arbitrary messages. How these instructions are validated is a critical factor in assessing the trust assumptions of a bridge. contract. Only authorized Inboxes are allowed to enqueue delayed messages, and the so-called Inbox contract is the one used as the entry point by calling the sendMessage or sendMessageFromOrigin functions. If the centralized sequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs. doesn’t process the request within some time bound, users can call the forceInclusion function on the SequencerInbox contract to include the message in the canonical chain. The time bound is hardcoded to be 1d.

    The section considers only the L3 properties. For more details please refer to Arbitrum One logoArbitrum One

    Regular messaging

    The user initiates L2Layer 2 (L2) is a category of technical solutions aimed to scale the base layer in a trust minimized way. This category includes solutions like rollups as well as state channels and plasma. Other solutions are able to scale further, but with the introduction of additional trust assumptions, which are therefore not trust minimized. Sometimes the term Layer 2 is used to refer to include these solutions too, like validiums and optimiums, but to distinguish between trust minimized and non trust minimized solutions they are often referred to as "light" L2s, opposed to "strong" L2s like rollups.->L1Layer 1 (L1) is a blockchain that is self-reliant on its validator set for its security and consensus properties. Ethereum is an example of a layer 1. Blockchains started receiving the moniker of layer 1 once layer 2 became a meaningful area of development. messages by submitting a regular transaction on this chain. When the blockAn ordered list of transactions and chain-related metadata that gets bundled together and published to the L1/DA layer. Nodes execute the transactions contained within blocks to change the rollup chain’s state. Protocol rules dictate what constitutes a valid block, and invalid blocks are skipped over. containing that transaction is settled, the message becomes available for processing on L1. The process of block finalization usually takes several days to complete.

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

    Autonomous exit

    Users can (eventually) exit the system by pushing the transaction on L1Layer 1 (L1) is a blockchain that is self-reliant on its validator set for its security and consensus properties. Ethereum is an example of a layer 1. Blockchains started receiving the moniker of layer 1 once layer 2 became a meaningful area of development. and providing the corresponding state rootA cryptographic hash succinctly representing a state using a Merkle tree.. The only way to prevent such withdrawal is via an upgrade.

    EVM compatible smart contracts are supported

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

    1. Inside Arbitrum Nitro
    A dashboard to explore contracts and permissions
    Go to Disco
    Disco UI Banner

    The DA committee has the following members:

    Arbitrum One

    Actors:

    XaiMultisig0x4972…495E

    A Multisig with 3/5 threshold.

    • Can upgrade with no delay
      • UpgradeExecutor
      • Outbox
      • GatewayRouter
      • RollupEventInbox
      • ChallengeManager
      • BridgeA message-passing protocol between two blockchains. At its most basic, a token bridge consists of a smart contract which can escrow funds on one side of the bridge, and instruct the release or minting of corresponding assets on the other side, but bridges could also support arbitrary messages. How these instructions are validated is a critical factor in assessing the trust assumptions of a bridge.
      • SequencerInbox
      • Inbox
      • ERC20Gateway
      • RollupProxy
    • Can interact with RollupProxy
      • Pause and unpause and set important roles and parameters in the system contracts: Can delegate SequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs. management to a BatchPosterManager address, manage data availabilityThe property of a rollup's data being reachable by any node retrieving the data that were rolled up and executed to reach the proposed state. Data availability (DA), specifically decoupling it from the rollup nodes themselves, is one of the preeminent factors which allows a rollup to scale securely. A rollup is faced with a decision of what to use as a DA layer to guarantee that any node can retrieve this data--permissionlessly under any circumstance. For this reason, using Ethereum for DA currently provides the strongest security guarantees. If data is stored somewhere other than a permissionless L1, then the project is not a rollup, but rather a validium or an optimium., DACs and the fastConfirmer role, set the Sequencer-only window, introduce an allowList to the bridge and whitelist Inboxes/Outboxes

    A Multisig with 3/7 threshold.

    • Can upgrade with no delay
      • PoolProxyDeployer
      • GasSubsidy
      • NodeLicenseRegistry
      • RefereeCalculations
      • PoolFactory
      • SentryReferee
    XaiMultisig20x000d…E871

    A Multisig with 1/3 threshold. Member of XaiMultisig.

    Participants (3):

    EOA 6EOA 3EOA 5

    A Multisig with 1/3 threshold. Member of SafeL2, XaiFundsReiceiverMultisig.

    XaiFundsReiceiverMultisig0xFCF7…c878

    A Multisig with 2/4 threshold. The designated fundsReceiver in the NodeLicenseRegistry. Receives all ETH from ‘Sentry NodeA software client that participates in the network. License’ mints.

    • Can interact with RollupProxy
      • Can propose new state rootsA cryptographic hash succinctly representing a state using a Merkle tree. (called nodes) and challenge state roots on the host chain

    Member of XaiMultisig2.

    • Can interact with SequencerInbox
      • Add/remove batchPosters (Sequencers)
    • Can interact with SequencerInbox
      • Can submit transaction batches or commitments to the SequencerInbox contract on the host chain
    A dashboard to explore contracts and permissions
    Go to Disco
    Disco UI Banner
    Note: Contracts presented in this section had their implementations updated since the last time our team looked at this project. The information presented may be inaccurate.
    A diagram of the smart contract architecture
    A diagram of the smart contract architecture

    Arbitrum One

    Contract that allows challenging state rootsA cryptographic hash succinctly representing a state using a Merkle tree.. Can be called through the RollupProxy by ValidatorsIn the context of L2s, a Validator is an actor that validates the correctness of state transitions. For optimistic rollups this corresponds to challengers, and for ZK rollups this corresponds to the onchain verifier or the UpgradeExecutor.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
    Can be upgraded by:

    Escrow contract for the project’s gasA virtual fuel used to execute smart contracts on a rollup. The EVM (or other VM within the rollup) uses an accounting mechanism to correspond the consumption of gas to the consumption of computing resources, and to limit the consumption of computing resources. token (can be different from ETH). Keeps a list of allowed Inboxes and Outboxes for canonical bridgeA message-passing protocol between two blockchains. At its most basic, a token bridge consists of a smart contract which can escrow funds on one side of the bridge, and instruct the release or minting of corresponding assets on the other side, but bridges could also support arbitrary messages. How these instructions are validated is a critical factor in assessing the trust assumptions of a bridge. messaging.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
    The following tokens are included in the value secured calculation:
    XAI token logo
    Can be upgraded by:

    A sequencerA party responsible for ordering and executing transactions on the rollup. The sequencer verifies transactions, compresses the data into a block, and submits the data related to it to enable state reconstruction to Ethereum L1 as a single transaction. The data can be either transaction data or state diffs. (registered in this contract) can submit transaction batches or commitments here.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
      • batchPosterManager: XaiMultisig2; ultimately EOA 3, EOA 5, EOA 6
      • batchPosters: EOA 4
    Can be upgraded by:
    Implementation used in:

    Central contract for the project’s configuration like its execution logic hashA fixed-length fingerprint of variable-size input, produced by a hash function. (wasmModuleRoot) and addresses of the other system contracts. Entry point for Proposers creating new RollupA blockchain that inherits consensus and data availability from another blockchain called L1. Rollups enable trust minimized bridges with the base layer via proof systems, either optimistic or zero-knowledge. A rollup without a bridge, or without considering the bridge, is called a sovereign rollup. Nodes (state commitments) and Challengers submitting fraud proofs (In the Orbit stack, these two roles are both held by the ValidatorsIn the context of L2s, a Validator is an actor that validates the correctness of state transitions. For optimistic rollups this corresponds to challengers, and for ZK rollups this corresponds to the onchain verifier).

    • Roles:
      • admin: UpgradeExecutor; ultimately XaiMultisig
      • owner: UpgradeExecutor; ultimately XaiMultisig
      • validators: EOA 1, EOA 2
    Can be upgraded by:

    Central contract defining the access control permissions for upgrading the system contract implementations.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
      • executors: XaiMultisig
    Can be upgraded by:
    Implementation used in:

    Facilitates L2Layer 2 (L2) is a category of technical solutions aimed to scale the base layer in a trust minimized way. This category includes solutions like rollups as well as state channels and plasma. Other solutions are able to scale further, but with the introduction of additional trust assumptions, which are therefore not trust minimized. Sometimes the term Layer 2 is used to refer to include these solutions too, like validiums and optimiums, but to distinguish between trust minimized and non trust minimized solutions they are often referred to as "light" L2s, opposed to "strong" L2s like rollups. to L1Layer 1 (L1) is a blockchain that is self-reliant on its validator set for its security and consensus properties. Ethereum is an example of a layer 1. Blockchains started receiving the moniker of layer 1 once layer 2 became a meaningful area of development. contract calls: Messages initiated from L2 (for example withdrawal messages) eventually resolve in execution on L1.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
    Can be upgraded by:

    Facilitates sending L1Layer 1 (L1) is a blockchain that is self-reliant on its validator set for its security and consensus properties. Ethereum is an example of a layer 1. Blockchains started receiving the moniker of layer 1 once layer 2 became a meaningful area of development. to L2Layer 2 (L2) is a category of technical solutions aimed to scale the base layer in a trust minimized way. This category includes solutions like rollups as well as state channels and plasma. Other solutions are able to scale further, but with the introduction of additional trust assumptions, which are therefore not trust minimized. Sometimes the term Layer 2 is used to refer to include these solutions too, like validiums and optimiums, but to distinguish between trust minimized and non trust minimized solutions they are often referred to as "light" L2s, opposed to "strong" L2s like rollups. messages like depositing ETH, but does not escrow funds.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
    Can be upgraded by:
    Implementation used in:

    Escrows deposited ERC-20 assets for the canonical BridgeA message-passing protocol between two blockchains. At its most basic, a token bridge consists of a smart contract which can escrow funds on one side of the bridge, and instruct the release or minting of corresponding assets on the other side, but bridges could also support arbitrary messages. How these instructions are validated is a critical factor in assessing the trust assumptions of a bridge.. Upon depositing, a generic token representation will be minted at the destination. Withdrawals are initiated by the Outbox contract.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig

    All supported tokens in this escrow are included in the value secured calculation.

    Can be upgraded by:
    Implementation used in:

    This routing contract maps tokens to the correct escrow (gateway) to be then bridged with canonical messaging.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
    Can be upgraded by:
    Implementation used in:
    ProxyAdmin0x041F…8485
    • Roles:
      • owner: UpgradeExecutor
    OneStepProverHostIo0x33c1…06D4

    One of the modular contracts used for the last step of a fraud proofAlso referred to as a fault proof, it is the construction of an assertion that fraud was perpetrated on an optimistic rollup. More concretely, that an invalid state transition took place according to the protocol rules. The submitter of a fraud proof would expect a reward from the optimistic rollup protocol for helping maintain the integrity of the system., which is simulated inside a WASM virtual machine.

    Helper contract sending configuration data over the bridgeA message-passing protocol between two blockchains. At its most basic, a token bridge consists of a smart contract which can escrow funds on one side of the bridge, and instruct the release or minting of corresponding assets on the other side, but bridges could also support arbitrary messages. How these instructions are validated is a critical factor in assessing the trust assumptions of a bridge. during the systems initialization.

    • Roles:
      • admin: ProxyAdmin; ultimately XaiMultisig
    Can be upgraded by:
    OneStepProver00x54E0…0881

    One of the modular contracts used for the last step of a fraud proofAlso referred to as a fault proof, it is the construction of an assertion that fraud was perpetrated on an optimistic rollup. More concretely, that an invalid state transition took place according to the protocol rules. The submitter of a fraud proof would expect a reward from the optimistic rollup protocol for helping maintain the integrity of the system., which is simulated inside a WASM virtual machine.

    Manages beacon addresses for the v2 staking pools.

    • Roles:
      • admin: ProxyAdmin; ultimately SafeL2
    Can be upgraded by:
    ValidatorUtils0x6c21…867b

    This contract implements view only utilities for validatorsIn the context of L2s, a Validator is an actor that validates the correctness of state transitions. For optimistic rollups this corresponds to challengers, and for ZK rollups this corresponds to the onchain verifier.

    Implementation used in:
    • Roles:
      • admin: ProxyAdmin; ultimately SafeL2
    Can be upgraded by:
    • Roles:
      • admin: ProxyAdmin; ultimately SafeL2
    Can be upgraded by:
    ProxyAdmin0xD88c…1723
    • Roles:
      • owner: SafeL2
    OneStepProofEntry0xD89d…8049

    One of the modular contracts used for the last step of a fraud proofAlso referred to as a fault proof, it is the construction of an assertion that fraud was perpetrated on an optimistic rollup. More concretely, that an invalid state transition took place according to the protocol rules. The submitter of a fraud proof would expect a reward from the optimistic rollup protocol for helping maintain the integrity of the system., which is simulated inside a WASM virtual machine.

    OneStepProverMath0xE58a…4cc4

    One of the modular contracts used for the last step of a fraud proofAlso referred to as a fault proof, it is the construction of an assertion that fraud was perpetrated on an optimistic rollup. More concretely, that an invalid state transition took place according to the protocol rules. The submitter of a fraud proof would expect a reward from the optimistic rollup protocol for helping maintain the integrity of the system., which is simulated inside a WASM virtual machine.

    OneStepProverMemory0xf8E5…D881

    One of the modular contracts used for the last step of a fraud proofAlso referred to as a fault proof, it is the construction of an assertion that fraud was perpetrated on an optimistic rollup. More concretely, that an invalid state transition took place according to the protocol rules. The submitter of a fraud proof would expect a reward from the optimistic rollup protocol for helping maintain the integrity of the system., which is simulated inside a WASM virtual machine.

    The PoolFactory allows creating and managing staking pools for V2 staking. Users can stake esXAI (and / or Sentry Keys) in pools. This contract’s address is whitelisted in the esXAI token contract, which allows it to initiate arbitrary esXAI token transfers. V2 staking through this contract is currently set to true.

    • Roles:
      • admin: ProxyAdmin; ultimately SafeL2
    Can be upgraded by:

    The referee contract manages the Xai Sentry protocol. Sentry nodes that are tasked to watch the state transitions on Xai receive esXAI rewards for their service. These watchers participate in a game with a central ‘challenger’ by posting their assertions to make sure they are actually watching. In case of a malicious state transition, sentries are supposed to raise an alarm offchain. The referee contract is also a whitelisted address in the esXAI token contract, which allows it to initiate arbitrary esXAI token transfers. New staking through this contract is disabled in favor of the new v2 staking. V1 Stakers can continue to get staking rewards here or withdraw/migrate their assets.

    • Roles:
      • admin: ProxyAdmin; ultimately SafeL2
    Can be upgraded by:
    There are impactful changes to the following contracts, and part of the information might be outdated.

    This is the contract where Xai Sentry Keys for running a sentry nodeA software client that participates in the network. are minted.

    • Roles:
      • admin: ProxyAdmin; ultimately SafeL2
    Can be upgraded by:

    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).

    Program Hashes

    Name
    Hash
    Repository
    Verification
    Used in
    0xdb69...b69a
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