Kinto
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About
Kinto is an Orbit stack L2 with account abstraction and KYC enabled for all users, supporting both modern financial institutions and decentralized protocols.
Badges
About
Kinto is an Orbit stack L2 with account abstraction and KYC enabled for all users, supporting both modern financial institutions and decentralized protocols.
2024 Feb 22 — 2025 Feb 21
2024 Feb 22 — 2025 Feb 20
The section shows the operating costs that L2s pay to Ethereum.
2024 Feb 21 — 2025 Feb 20
Security Council Governance
2024 Nov 3rd
Kinto gives the ownership of all L1 system contracts to a Security Council that is properly set up.
First ever Challenge on mainnet
2024 Oct 31st
The first correctly resolved fault proof challenge of a mainnet Orbit stack rollup.
Funds can be stolen if
Users can be censored if
MEV can be extracted if
Sequencer failure
Self sequenceState validation
Fraud proofs (INT)Fraud proofs allow 5 WHITELISTED actors watching the chain to prove that the state is incorrect. At least 5 Challengers are external to the Operator. Interactive proofs (INT) require multiple transactions over time to resolve. There is a 6d 8h challenge period.
Exit window
NoneThere is no window for users to exit in case of an unwanted regular upgrade since contracts are instantly upgradable.
Proposer failure
Self proposeAnyone can become a Proposer after 12d 17h of inactivity from the currently whitelisted Proposers.
Kinto is a Rollup operators cannot compromise the system, but being application-specific might bring additional risk.
Kinto enforces the use of smart wallets and KYC. A valid state transition in Kinto disallows all contract calls by EOAs and new contract creation, unless specifically whitelisted. This setup effectively enforces smart wallet use because the auxiliary contracts of the standard KintoWallet smart wallet (like the EntryPoint and the KintoWalletFactory) are whitelisted. The KYC validation is part of the KintoWallet signature verification. Since all users must use the same implementation of this smart wallet, all user transactions on Kinto check for an up-to-date KYC flag, and are dropped in case the check fails.
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.
- Sequencing followed by deterministic execution - Arbitrum documentation
- SequencerInbox.sol - source code, addSequencerL2BatchFromOrigin function
Ethereum
Updates to the system state can be proposed and challenged by a set of whitelisted validators. If a state root passes the challenge period, it is optimistically considered correct and made actionable for withdrawals.
Whitelisted validators propose state roots as children of a previous state root. A state root can have multiple conflicting children. This structure forms a graph, and therefore, in the contracts, state roots are referred to as nodes. Each proposal requires a stake, currently set to 0.1 ETH, that can be slashed if the proposal is proven incorrect via a fraud proof. Stakes can be moved from one node to one of its children, either by calling stakeOnExistingNode or stakeOnNewNode. New nodes cannot be created faster than the minimum assertion period by the same validator, currently set to 15m. The oldest unconfirmed node can be confirmed if the challenge period has passed and there are no siblings, and rejected if the parent is not a confirmed node or if the challenge period has passed and no one is staked on it.
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).
A challenge can be started between two siblings, i.e. two different state roots that share the same parent, by calling the startChallenge function. Validators cannot be in more than one challenge at the same time, meaning that the protocol operates with partial concurrency. Since each challenge lasts 6d 8h, this implies that the protocol can be subject to delay attacks, where a malicious actor can delay withdrawals as long as they are willing to pay the cost of losing their stakes. If the protocol is delayed attacked, the new stake requirement increases exponentially for each challenge period of delay. Challenges are played via a bisection game, where asserter and challenger play together to find the first instruction of disagreement. Such instruction is then executed onchain in the WASM OneStepProver contract to determine the winner, who then gets half of the stake of the loser. As said before, a state root is rejected only when no one left is staked on it. The protocol does not enforces valid bisections, meaning that actors can propose correct initial claim and then provide incorrect midpoints.
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. After a delay of 1d in which a Sequencer 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.
Regular messaging
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.
Enforced smart wallets and KYC
The Kinto L2 node is a fork of Arbitrum’s geth implementation with notable changes to the state transition function. A valid state transition in Kinto disallows all contract calls by EOAs and new contract creation, unless specifically whitelisted. The current whitelist is sourced directly from the KintoAppRegistry smart contract on Kinto L2, and can be modified by its Owner without delay. This setup effectively enforces smart wallet use because the auxiliary contracts of the standard KintoWallet smart wallet (like the EntryPoint and the KintoWalletFactory) are whitelisted.
The KYC validation is part of the KintoWallet signature verification. Since all users must use the same implementation of this smart wallet, all user transactions on Kinto check for an up-to-date KYC flag, and are dropped in case the check fails.
Users can be censored if a KYC provider changes the users' KYC status.
Ethereum
Roles:
Can submit transaction batches or commitments to the SequencerInbox contract on the host chain.
Can propose new state roots (called nodes) and challenge state roots on the host chain.
Actors:
- A Multisig with 6 / 8 threshold.
- Can act on behalf of UpgradeExecutor.
- Is allowed to interact with RollupProxy - Pause and unpause and set important roles and parameters in the system contracts: Can delegate Sequencer management to a BatchPosterManager address, manage data availability, DACs and the fastConfirmer role, set the Sequencer-only window, introduce an allowList to the bridge and whitelist Inboxes/Outboxes - acting via UpgradeExecutor.
- Can upgrade the implementation of RollupProxy - acting via UpgradeExecutor.
- Can upgrade the implementation of RollupEventInbox, UpgradeExecutor, ChallengeManager, Outbox, L1ERC20Gateway, Bridge, Inbox, L1GatewayRouter, SequencerInbox - acting via ProxyAdmin, UpgradeExecutor.
- A Multisig with 3 / 5 threshold.
- Can upgrade the implementation of Bridger.
- A Multisig with 1 / 5 threshold.
- Member of Kinto SecurityCouncil.
Ethereum
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).
Contract that allows challenging state roots. Can be called through the RollupProxy by Validators or the UpgradeExecutor.
A sequencer (registered in this contract) can submit transaction batches or commitments here.
- Central contract defining the access control permissions for upgrading the system contract implementations.
- Can act on behalf of ProxyAdmin.
- Can be used to interact with RollupProxy - Pause and unpause and set important roles and parameters in the system contracts: Can delegate Sequencer management to a BatchPosterManager address, manage data availability, DACs and the fastConfirmer role, set the Sequencer-only window, introduce an allowList to the bridge and whitelist Inboxes/Outboxes.
- Can be used to upgrade implementation of RollupProxy.
Implementation used in:
Escrows deposited ERC-20 assets for the canonical Bridge. Upon depositing, a generic token representation will be minted at the destination. Withdrawals are initiated by the Outbox contract.
Implementation used in:
This routing contract maps tokens to the correct escrow (gateway) to be then bridged with canonical messaging.
Implementation used in:
This contract implements view only utilities for validators.
Implementation used in:
One of the modular contracts used for the last step of a fraud proof, which is simulated inside a WASM virtual machine.
Helper contract sending configuration data over the bridge during the systems initialization.
Implementation used in:
One of the modular contracts used for the last step of a fraud proof, which is simulated inside a WASM virtual machine.
Can be used to upgrade implementation of RollupEventInbox, UpgradeExecutor, ChallengeManager, Outbox, L1ERC20Gateway, Bridge, Inbox, L1GatewayRouter, SequencerInbox.
One of the modular contracts used for the last step of a fraud proof, which is simulated inside a WASM virtual machine.
One of the modular contracts used for the last step of a fraud proof, which is simulated inside a WASM virtual machine.
One of the modular contracts used for the last step of a fraud proof, which is simulated inside a WASM virtual machine.
Value Secured is calculated based on these smart contracts and tokens:
Contract managing Inboxes and Outboxes. It escrows ETH sent to L2.
Implementation used in:
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).