SummaryValue LockedActivityRisk summaryRisk analysisTechnologyOperatorWithdrawalsOther considerationsPermissionsSmart contractsKnowledge nuggets

Stack logoStack

Badges

About

Stack Chain is an Optimium settling on Base. It uses OP stack technology with Celestia for data availability. Stack Chain is a blockchain for bringing points onchain, allowing brands to create and own their loyalty programs.

Value Locked
$2.92 K1.33%
Canonically Bridged
$2.92 K
Externally Bridged
$0.00
Natively Minted
$0.00
View TVL Breakdown
  • Tokens
  • Daily TPS
    0.000.00%
  • 30D tx count
    5.46 K
  • Type
    Optimium
  • Purposes
    Universal, Social
    • Sequencer failureState validationData availabilityExit windowProposer failure

    Badges

    About

    Stack Chain is an Optimium settling on Base. It uses OP stack technology with Celestia for data availability. Stack Chain is a blockchain for bringing points onchain, allowing brands to create and own their loyalty programs.

    Value Locked
    Activity
    Risk summary
    There are 4 additional risks coming from the hostchain Base logoBase
    Fraud proof system is currently under development. Users need to trust the block proposer to submit correct L1 state roots.

    Funds can be stolen if

    1. an invalid state root is submitted to the system (CRITICAL),
    2. a contract receives a malicious code upgrade. There is no delay on code upgrades (CRITICAL).

    Funds can be lost if

    1. the sequencer posts an unavailable transaction root (CRITICAL),
    2. the data is not available on the external provider (CRITICAL).

    Funds can be frozen if

    1. the centralized validator goes down. Users cannot produce blocks themselves and exiting the system requires new block production (CRITICAL).

    MEV can be extracted if

    1. the operator exploits their centralized position and frontruns user transactions.
    Risk analysis
    The L3 risks depend on the individual properties of L3 and those of the host chain combined.
    Fraud proof system is currently under development. Users need to trust the block proposer to submit correct L1 state roots.
    SEQUENCER
    FAILURE    		STATE
    VALIDATION    		DATA
    AVAILABILITY    		EXIT WINDOWPROPOSER
    FAILURE
    Base
    L2
    		Self sequenceNoneOnchainNoneCannot withdraw
    Stack
    L3 • Individual
    		Self sequenceNoneExternalNoneCannot withdraw
    Stack
    L3 • Combined
    		Self sequenceNoneExternalNoneCannot withdraw
    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 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.

    State validation

    None

    Currently the system permits invalid state roots. More details in project overview.

    Data availability

    External

    Proof construction and state derivation fully rely on data that is posted on Celestia. Sequencer tx roots are not checked against the Blobstream bridge data roots onchain, but L2 nodes can verify data availability by running a Celestia light client.

    Exit window

    None

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

    Proposer failure

    Cannot withdraw

    Only the whitelisted proposers can publish state roots on L1, so in the event of failure the withdrawals are frozen.

    Technology
    The section considers only the L3 properties. For more details please refer to Base logoBase

    Fraud proofs are not enabled

    OP Stack projects can use the OP fault proof system, already being deployed on some. This project though is not using fault proofs yet and is relying on the honesty of the permissioned Proposer and Challengers to ensure state correctness. The smart contract system permits invalid state roots.

    • Funds can be stolen if an invalid state root is submitted to the system (CRITICAL).

    1. L2OutputOracle.sol - Etherscan source code, deleteL2Outputs function

    Data is stored on Celestia

    Transactions roots are posted onchain and the full data is posted on Celestia. Since the Blobstream bridge is not used, availability of the data is not verified against Celestia validators, meaning that the Sequencer can single-handedly publish unavailable roots.

    • Funds can be lost if the sequencer posts an unavailable transaction root (CRITICAL).

    • Funds can be lost if the data is not available on the external provider (CRITICAL).

    1. Introducing Blobstream: streaming modular DA to Ethereum
    2. Derivation: Batch submission - OP Mainnet specs
    3. BatchInbox - Etherscan address
    4. OptimismPortal.sol - Etherscan source code, depositTransaction function
    Operator
    The section considers only the L3 properties. For more details please refer to Base logoBase

    The system has a centralized operator

    The operator is the only entity that can propose blocks. A live and trustworthy operator is vital to the health of the system.

    • MEV can be extracted if the operator exploits their centralized position and frontruns user transactions.

    1. L2OutputOracle.sol - Etherscan source code, CHALLENGER address
    2. L2OutputOracle.sol - Etherscan source code, PROPOSER address

    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.

    1. Sequencing Window - OP Mainnet Specs
    2. OptimismPortal.sol - Etherscan source code, depositTransaction function
    Withdrawals
    The section considers only the L3 properties. For more details please refer to Base logoBase

    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 takes a challenge period of 7d to complete. Finally the user submits an L1 transaction to claim the funds. This transaction requires a merkle proof.

    • Funds can be frozen if the centralized validator goes down. Users cannot produce blocks themselves and exiting the system requires new block production (CRITICAL).

    1. OptimismPortal.sol - Etherscan source code, proveWithdrawalTransaction function
    2. OptimismPortal.sol - Etherscan source code, finalizeWithdrawalTransaction function
    3. L2OutputOracle.sol - Etherscan source code, PROPOSER check

    Forced exit

    If the user experiences censorship from the operator with regular exit they can submit their withdrawal requests directly on L1. The system is then obliged to service this request or halt all withdrawals, including forced withdrawals from L1 and regular withdrawals initiated on L2. Once the force operation is submitted and if the request is serviced, the operation follows the flow of a regular exit.

    1. Forced withdrawal from an OP Stack blockchain
    Other considerations

    EVM compatible smart contracts are supported

    OP stack chains are pursuing the EVM Equivalence model. No changes to smart contracts are required regardless of the language they are written in, i.e. anything deployed on L1 can be deployed on L2.

    1. Introducing EVM Equivalence
    Permissions

    The system uses the following set of permissioned addresses:

    Challenger StackMultisig

    Challenger is an actor allowed to delete state roots proposed by a Proposer.

    Used in:

    Guardian StackMultisig

    Guardian is an actor allowed to pause deposits and withdrawals.

    Used in:

    Proposer EOA

    Proposer is an actor allowed to post new state roots of current layer to the host chain.

    Sequencer EOA

    Sequencer is an actor allowed to commit transactions from current layer to the host chain.

    StackMultisig 0x7dCe…c104
    • This is a Gnosis Safe with 3 / 5 threshold.
    • Can act on behalf of ProxyAdmin.
    • Is a Challenger.
    • Can change configuration of AddressManager (acting via ProxyAdmin) - set and change address mappings.
    • Can change configuration of SystemConfig - it can update the preconfer address, the batch submitter (Sequencer) address and the gas configuration of the system.
    • Is a Guardian.
    • Can upgrade implementation of SystemConfig, OptimismPortal, L2OutputOracle (acting via ProxyAdmin).
    • Can upgrade implementation of L1StandardBridge (acting via ProxyAdmin) - upgrading bridge implementation allows to access all funds and change every system component.

    Used in:

    StackMultisig participants (5) 0x4D80…5BAe0x3840…Fd5f0xa0C6…90380xefCf…dD5C0xa400…e6e4

    Those are the participants of the StackMultisig.

    Smart contracts

    The system consists of the following smart contracts on the host chain (Base):

    ProxyAdmin 0x25aB…DC32
    • Can be used to configure AddressManager - set and change address mappings.
    • Can be used to upgrade implementation of SystemConfig, OptimismPortal, L2OutputOracle.
    • Can be used to upgrade implementation of L1StandardBridge - upgrading bridge implementation allows to access all funds and change every system component.
    AddressManager 0x31f0…5668

    Legacy contract used to manage a mapping of string names to addresses. Modern OP stack uses a different standard proxy system instead, but this contract is still necessary for backwards compatibility with several older contracts.

    SystemConfig 0x52c9…9B37Implementation (Upgradable)Admin

    Contains configuration parameters such as the Sequencer address, gas limit on this chain and the unsafe block signer address.

    Can be upgraded by:
    StackMultisig

    Upgrade delay: No delay

    L1CrossDomainMessenger 0x727a…1759Implementation (Upgradable)

    Sends messages from host chain to this chain, and relays messages back onto host chain. In the event that a message sent from host chain to this chain is rejected for exceeding this chain’s epoch gas limit, it can be resubmitted via this contract’s replay function.

    OptimismPortal 0x752B…BD3EImplementation (Upgradable)Admin

    The main entry point to deposit funds from host chain to this chain. It also allows to prove and finalize withdrawals. This contract stores the following tokens: ETH.

    Can be upgraded by:
    StackMultisig

    Upgrade delay: No delay

    L1StandardBridge 0xbA25…515CImplementation (Upgradable)Admin

    The main entry point to deposit ERC20 tokens from host chain to this chain. This contract can store any token. This contract can store any token.

    Can be upgraded by:
    StackMultisig

    Upgrade delay: No delay

    L2OutputOracle 0xCC61…69EFImplementation (Upgradable)Admin

    Contains a list of proposed state roots which Proposers assert to be a result of block execution. Currently only the PROPOSER address can submit new state roots.

    Can be upgraded by:
    StackMultisig

    Upgrade delay: No delay

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

    Generic escrow 0xbA25…515CImplementation (Upgradable)Admin

    Main entry point for users depositing ERC20 token that do not require custom gateway.

    Can be upgraded by:
    ProxyAdmin

    Upgrade delay: No delay

    Escrow for ETH 0x752B…BD3EImplementation (Upgradable)Admin

    Main entry point for users depositing ETH.

    Can be upgraded by:
    ProxyAdmin

    Upgrade delay: No delay

    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
    Thumbnail of How Optimism compresses data

    How Optimism compresses data

    Learn more

    Thumbnail of Superchain Explainer

    Superchain Explainer

    Learn more

    Thumbnail of Modular Rollup Theory

    Modular Rollup Theory

    Learn more