HashKey Chain
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About
HashKey Chain is a regulatory-compliant, institutional-grade OP stack Layer 2 solution bridging traditional finance and Web3. It is powered by Hong Kong's premier virtual asset ecosystem.
Badges
About
HashKey Chain is a regulatory-compliant, institutional-grade OP stack Layer 2 solution bridging traditional finance and Web3. It is powered by Hong Kong's premier virtual asset ecosystem.
Funds can be stolen if
MEV can be extracted if
Sequencer failure
Self sequenceState validation
Fraud proofs (INT)Fraud proofs allow actors watching the chain to prove that the state is incorrect. Interactive proofs (INT) require multiple transactions over time to resolve. Only one entity is currently allowed to propose and submit challenges, as only permissioned games are currently allowed.
Exit window
NoneThere is no window for users to exit in case of an unwanted regular upgrade since contracts are instantly upgradable.
Proposer failure
Cannot withdrawOnly the whitelisted proposers can publish state roots on L1, so in the event of failure the withdrawals are frozen.
HashKey Chain is a 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.
Funds can be stolen if no validator checks the published state. Fraud proofs assume at least one honest and able validator.
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.
Currently, updates to the system state can only be proposed and challenged by the same entity as the proof system is permissioned. If a state root passes the challenge period, it is optimistically considered correct and made actionable for withdrawals.
Proposers submit state roots as children of the latest confirmed state root (called anchor state), by calling the create function in the DisputeGameFactory. A state root can have multiple conflicting children. Each proposal requires a stake, currently set to 0.0 ETH, that can be slashed if the proposal is proven incorrect via a fraud proof. Stakes can be withdrawn only after the proposal has been confirmed. A state root gets confirmed if the challenge period has passed and it is not countered.
Challenges are opened to disprove invalid state roots using bisection games. Each bisection move requires a stake that increases expontentially with the depth of the bisection, with a factor of 1.09493. The maximum depth is 73, and reaching it therefore requires a cumulative stake of 0.00 ETH from depth 0. Actors can participate in any challenge by calling the defend or attack functions, depending whether they agree or disagree with the latest claim and want to move the bisection game forward. Actors that disagree with the top-level claim are called challengers, and actors that agree are called defenders. Each actor might be involved in multiple (sub-)challenges at the same time, meaning that the protocol operates with full concurrency. Challengers and defenders alternate in the bisection game, and they pass each other a clock that starts with 3d 12h. If a clock expires, the claim is considered defeated if it was countered, or it gets confirmed if uncountered. Since honest parties can inherit clocks from malicious parties that play both as challengers and defenders (see freeloader claims), if a clock gets inherited with less than 3h, it generally gets extended by 3h with the exception of 6h right before depth 30, and 1d right before the last depth. The maximum clock extension that a top level claim can get is therefore 10d. Since unconfirmed state roots are independent of one another, users can decide to exit with a subsequent confirmed state root if the previous one is delayed. Winners get the entire losers’ stake, meaning that sybils can potentially play against each other at no cost. The final instruction found via the bisection game is then executed onchain in the MIPS one step prover contract who determines the winner. The protocol does not enforce valid bisections, meaning that actors can propose correct initial claims and then provide incorrect midpoints. The protocol can be subject to resource exhaustion attacks (Spearbit 5.1.3).
The system has a centralized sequencer
While forcing transaction 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.
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.
Regular exits
The user initiates the withdrawal by submitting a regular transaction on this chain. When a state root containing such transaction is settled, the funds become available for withdrawal on L1 after 3d 12h. Withdrawal inclusion can be proven before state root settlement, but a 3d 12h period has to pass before it becomes actionable. The process of state root settlement takes a challenge period of at least 3d 12h to complete. Finally the user submits an L1 transaction to claim the funds. This transaction requires a merkle proof.
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.
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.
The system uses the following set of permissioned addresses:
Guardian is an actor allowed to pause deposits and withdrawals.
- A Gnosis Safe with 3 / 5 threshold.
- Can act on behalf of ProxyAdmin.
- Can change the configuration of AddressManager - set and change address mappings - acting via ProxyAdmin.
- Can upgrade the implementation of OptimismMintableERC20Factory, DisputeGameFactory, SystemConfig, AnchorStateRegistry, DelayedWETH, L1ERC721Bridge, DelayedWETH, OptimismPortal2, SuperchainConfig - acting via ProxyAdmin.
- Can upgrade the implementation of L1StandardBridge - upgrading the bridge implementation can give access to all funds escrowed therein - acting via ProxyAdmin.
- A Gnosis Safe with 3 / 5 threshold.
- A Guardian.
A Sequencer.
The system consists of the following smart contracts on the host chain (Ethereum):
A helper contract that generates OptimismMintableERC20 contracts on the network it’s deployed to. OptimismMintableERC20 is a standard extension of the base ERC20 token contract designed to allow the L1StandardBridge contracts to mint and burn tokens. This makes it possible to use an OptimismMintablERC20 as this chain’s representation of a token on the host chain, or vice-versa.
Upgrade delay: No delay
The dispute game factory allows the creation of dispute games, used to propose state roots and eventually challenge them.
Upgrade delay: No delay
The main entry point to deposit ERC20 tokens from host chain to this chain. This contract can store any token.
Upgrade delay: No delay
Same as FaultDisputeGame, but only two permissioned addresses are designated as proposer and challenger.
Contains the latest confirmed state root that can be used as a starting point in a dispute game.
Upgrade delay: No delay
The PreimageOracle contract is used to load the required data from L1 for a dispute game.
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.
The MIPS contract is used to execute the final step of the dispute game which objectively determines the winner of the dispute.
- Can be used to configure AddressManager - set and change address mappings.
- Can be used to upgrade implementation of OptimismMintableERC20Factory, DisputeGameFactory, SystemConfig, AnchorStateRegistry, DelayedWETH, L1ERC721Bridge, DelayedWETH, OptimismPortal2, SuperchainConfig.
- Can be used to upgrade implementation of L1StandardBridge - upgrading the bridge implementation can give access to all funds escrowed therein.
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.
Contract designed to hold the bonded ETH for each game. It is designed as a wrapper around WETH to allow an owner to function as a backstop if a game would incorrectly distribute funds.
Upgrade delay: No delay
Logic of the dispute game. When a state root is proposed, a dispute game contract is deployed. Challengers can use such contracts to challenge the proposed state root.
Used to bridge ERC-721 tokens from host chain to this chain.
Upgrade delay: No delay
Contract designed to hold the bonded ETH for each game. It is designed as a wrapper around WETH to allow an owner to function as a backstop if a game would incorrectly distribute funds.
Upgrade delay: No delay
The OptimismPortal contract is the main entry point to deposit funds from L1 to L2. It also allows to prove and finalize withdrawals. It specifies which game type can be used for withdrawals, which currently is the PermissionedDisputeGame. This contract stores the following tokens: HSK.
Upgrade delay: No delay
This is NOT the shared SuperchainConfig contract of the OP stack Superchain but rather a local fork. It manages the PAUSED_SLOT, a boolean value indicating whether the local chain is paused, and GUARDIAN_SLOT, the address of the guardian which can pause and unpause the system.
Upgrade delay: No delay
Value Secured is calculated based on these smart contracts and tokens:
The current deployment carries some associated risks:
Funds can be stolen if a contract receives a malicious code upgrade. There is no delay on upgrades.