Description
Loopring's zkRollup L2 solution aims to offer the same security guarantees as Ethereum mainnet, with a big scalability boost: throughput increased by 1000x, and cost reduced to just 0.1% of L1.
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Risk summary
Funds can be stolen if
Users can be censored if
MEV can be extracted if
Technology
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. Once the proof is processed on the Ethereum blockchain the L2 block is instantly finalized.
Zero knowledge SNARK cryptography is used
Despite their production use ZK-SNARKs 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 ZK-SNARKs 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.
Operator
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. They can still exit the system.
Withdrawals
Regular exit
The user initiates the withdrawal by submitting a transaction on L2. When the block containing that transaction is proven the funds become available for withdrawal on L1. Finally the user submits an L1 transaction to claim the funds. This transaction does not require 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. Once the force operation is submitted if the request is serviced the operation follows the flow of a regular exit.
Emergency exit
If enough time 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.
Permissioned Addresses
The system uses the following set of permissioned addresses:
This address is the owner of the following contracts: LoopringIOExchangeOwner, ExchangeV3 (proxy owner), BlockVerifier, AgentRegistry, LoopringV3. This allows it to grant access to submitting blocks and upgrade ExchangeV3 implementation potentially gaining access to all funds in DefaultDepositContract.
These addresses are the participants of the 4/6 Loopring MultiSig.
Actors who can submit new blocks, updating the L2 state on L1.
Smart Contracts

The system consists of the following smart contracts:
Main ExchangeV3 contract.
Contract used by the Prover to submit exchange blocks with zkSNARK proofs that are later processed and verified by the BlockVerifier contract.
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).
zkSNARK Verifier based on ethsnarks library.
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).
Milestones
DeFi Port is Live on Loopring
2022 Sep 27th
Dutch auctions, lending, and other DeFi functions can be performed on Loopring.
Learn moreLoopring’s zkRollup AMM is Live
2020 Dec 2nd
Improved implementation, enabling gas-free instant swaps and liquidity changes.
Learn moreLoopring Protocol 3.6 Pre-release
2020 Sep 22nd
Enhancements in transfers, order-book trading and AMM swap.
Learn moreLoopring DEX is online
2020 Feb 27th
zkRollup trading is live, as Loopring launches their order book based exchange.
Learn moreLoopring zkRollup is live
2019 Dec 4th
Loopring Protocol 3.0 is fully operational with support for orderbook trading on WeDex.
Learn more