Loopring
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About
Loopring is a ZK Rollup exchange protocol for trading and payments.
Badges
About
Loopring is a ZK Rollup exchange protocol for trading and payments.
DeFi Port is Live on Loopring
2022 Sep 27th
Dutch auctions, lending, and other DeFi functions can be performed on Loopring.
Loopring Supports NFTs
2021 Aug 24th
Loopring supports NFT minting, trading, and transfers.
Funds can be stolen if
Users can be censored if
MEV can be extracted if
Sequencer failure
Force via L1Users can force the sequencer to include a withdrawal transaction by submitting a request through L1 with a 0.02 ETH fee. If the sequencer is down for more than 15d, users can use the exit hatch to withdraw their funds. The sequencer can censor individual deposits, but in such case after 15d users can get their funds back.
State validation
ZK proofs (SN)SNARKs are zero knowledge proofs that ensure state correctness, but require trusted setup.
Exit window
NoneThere is no window for users to exit in case of an unwanted regular upgrade since contracts are instantly upgradable.
Proposer failure
Use escape hatchUsers are able to trustlessly exit by submitting a Merkle proof of funds.
Loopring is a Validity proofs ensure state correctness
Each update to the system state must be accompanied by a ZK proof that ensures that the new state was derived by correctly applying a series of valid user transactions to the previous state. These proofs are then verified on Ethereum by a smart contract.
Zero knowledge SNARK cryptography is used
Despite their production use zkSNARKs are still new and experimental cryptography. Cryptography has made a lot of advancements in the recent years but all cryptographic solutions rely on time to prove their security. In addition zkSNARKs require a trusted setup to operate.
Funds can be stolen if the cryptography is broken or implemented incorrectly.
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 calldata. This ensures that it will always be available when needed.
Each update to the system state must be accompanied by a ZK proof that ensures that the new state was derived by correctly applying a series of valid user transactions to the previous state. These proofs are then verified on Ethereum by a smart contract.
Loopring utilizes Groth16 for their proving system. The source code of the circuits can be found here.
Funds can be lost if the proof system is implemented incorrectly.
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.
Users can force exit the system
Force exit allows the users to escape censorship by withdrawing their funds. The system allows users to force the withdrawal of funds by submitting a request directly to the contract on-chain. The request must be served within a defined time period. If this does not happen, the system will halt regular operation and permit trustless withdrawal of funds.
Users can be censored if the operator refuses to include their transactions. However, there exists a mechanism to independently exit the system.
Regular exit
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. Once the force operation is submitted and if the request is serviced, the operation follows the flow of a regular exit.
Emergency exit
If the 15d deadline passes and the forced exit is still ignored the user can put the system into Withdrawal Mode, disallowing further state updates. In that case everybody can withdraw by submitting a merkle proof of their funds with their L1 transaction.
The system uses the following set of permissioned addresses:
This is a Gnosis Safe with 4 / 6 threshold. This address is the owner of the following contracts: LoopringIOExchangeOwner, ExchangeV3 (proxy), BlockVerifier, AgentRegistry, LoopringV3. This allows it to grant access to submitting blocks, arbitrarily change the forced withdrawal fee, change the Verifier address and upgrade ExchangeV3 implementation potentially gaining access to all funds in DefaultDepositContract.
Those are the participants of the ProxyOwner.
The system consists of the following smart contracts on the host chain (Ethereum):
Main Loopring contract.
Upgrade delay: No delay
ERC 20 token basic deposit contract. Handles user deposits and withdrawals. This contract can store any token.
Contract managing LRC staking for exchanges (one Loopring contract can manage many exchanges). It also allows to change the forced withdrawal fee and the Verifier address.
Auxiliary contract allowing users to process fast withdrawals.
Auxiliary contract able to force withdrawals from L1 on behalf of users.
zkSNARK Verifier based on ethsnarks library.
Upgrade delay: No delay
Agent registry that is used by all other Loopring contracts. Currently used are FastWithdrawalAgent, ForcedWithdrawalAgent, DestroyableWalletAgent and a number of LoopringAmmPool contracts.
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).