Loopring logoLoopring

Loopring is a ZK Rollup exchange protocol for trading and payments.
Value Locked

$83.04 M

24.30%

Canonically Bridged
$83.04 M
Externally Bridged
$0.00
Natively Minted
$0.00
  • Tokens
  • Daily TPS
    0.0341.99%
  • 30D tx count
    85.93 K
  • Stage
    Stage 0
  • Type
    ZK Rollup
  • Purposes
    NFT, AMM
  • ...

    Tokens

    Choose token

    Canonically Bridged Tokens (Top 15)

    LoopringCoin V2 (LRC)
    Ether (ETH)
    USD Coin (USDC)
    Wrapped liquid staked Ether 2.0 (wstETH)
    Wrapped BTC (WBTC)
    Immutable X (IMX)
    Rocket Pool ETH (rETH)
    Tether USD (USDT)
    Pepe (PEPE)
    Mask Network (MASK)
    Dai Stablecoin (DAI)
    ChainLink Token (LINK)
    Ethereum Name Service (ENS)
    Uniswap (UNI)
    Decentraland MANA (MANA)

    ...

    ...

    Milestones

    DeFi Port is Live on Loopring

    2022 Sep 27th

    Dutch auctions, lending, and other DeFi functions can be performed on Loopring.

    Learn more

    Loopring Supports NFTs

    2021 Aug 24th

    Loopring supports NFT minting, trading, and transfers.

    Learn more

    Loopring’s ZK Rollup AMM is Live

    2020 Dec 2nd

    Improved implementation, enabling gas-free instant swaps and liquidity changes.

    Learn more

    Loopring Protocol 3.6 Pre-release

    2020 Sep 22nd

    Enhancements in transfers, order-book trading and AMM swap.

    Learn more

    Loopring Supports Payments

    2020 Jun 6th

    Support for ERC20 transfers is live on Loopring.

    Learn more

    Loopring DEX is online

    2020 Feb 27th

    ZK Rollup trading is live, as Loopring launches their order book based exchange.

    Learn more

    Loopring ZK Rollup is live

    2019 Dec 4th

    Loopring Protocol 3.0 is fully operational with support for orderbook trading on WeDex.

    Learn more
    Risk summary
    Risk analysis
    Sequencer failureState validationData availabilityExit windowProposer failure

    State validation

    ZK proofs (SN)

    zkSNARKS are zero knowledge proofs that ensure state correctness, but require trusted setup.

    Data availability

    On chain

    All of the data needed for proof construction is published on Ethereum L1.

    Exit window

    None

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

    Sequencer failure

    Force via L1

    Users 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.

    Proposer failure

    Use escape hatch

    Users are able to trustlessly exit by submitting a Merkle proof of funds.

    Rollup stage
    LoopringLoopring is a
    Stage 0
    ZK Rollup.
    There is no available node software that can reconstruct the state from L1 data, hence there is no way to verify that this system is a rollup.
    Stage 0
    1 issue needs fixing
    Stage 1
    1 issue needs fixing
    Stage 2
    1 issue needs fixing
    Learn more about Rollup stages
    Please keep in mind that these stages do not reflect rollup security, this is an opinionated assessment of rollup maturity based on subjective criteria, created with a goal of incentivizing projects to push toward better decentralization. Each team may have taken different paths to achieve this goal.
    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. These proofs are then verified on Ethereum by a smart contract.

    1. Operators - Loopring design doc

    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.

    1. Operators - Loopring design doc

    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.

    1. Introduction - Loopring design doc
    State validation

    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.


    ZK Circuits

    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.

    Verification Keys Generation

    Groth16 requires a circuit specific trusted setup, so they run their own ceremony. The first phase is run using Powers of Tau ceremony. Some of the instructions on how to regenerate the verification keys can be found here.

    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.

    1. ExchangeV3.sol#L315-L322 - Etherscan source code, submitBlocks function
    2. LoopringIOExchangeOwner.sol#L123-L126 - Etherscan source code, hasAccessTo function call

    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.

    1. Forced Withdrawals - Loopring design doc
    2. Forced Request Handling - Loopring design doc
    Withdrawals

    Regular exit

    The user initiates the withdrawal by submitting a regular transaction on this chain. 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.

    1. Withdraw - Loopring design doc

    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.

    1. Forced Request Handling - Loopring design doc
    2. ExchangeV3.sol#L8118 - Loopring source code, forceWithdraw function

    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.

    1. Forced Request Handling - Loopring design doc
    2. ExchangeV3.sol#L8159 - Loopring source code, withdrawFromMerkleTree function
    Permissions

    The system uses the following set of permissioned addresses:

    ProxyOwner 0xDd2A…9c97

    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. This is a Gnosis Safe with 4 / 6 threshold.

    Those are the participants of the ProxyOwner.

    RollupOwner 0x153C…8512

    The rollup owner can submit blocks, set rollup parameters and shutdown the exchange.

    Smart contracts
    A diagram of the smart contract architecture
    A diagram of the smart contract architecture

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

    Main Loopring contract.

    Can be upgraded by: ProxyOwner

    Upgrade delay: No delay

    LoopringIOExchangeOwner 0x153C…8512

    Contract used by the Prover to submit exchange blocks with zkSNARK proofs that are later processed and verified by the BlockVerifier contract. It allows to give or revoke permissions to submit blocks and to open block submission to everyone.

    DefaultDepositContract 0x674b…Bd3f

    ERC 20 token basic deposit contract. Handles user deposits and withdrawals. This contract can store any token.

    LoopringV3 0xe56D…0C71

    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.

    FastWithdrawalAgent 0xec3C…8a31

    Auxiliary contract allowing users to process fast withdrawals.

    ForcedWithdrawalAgent 0x52ea…4470

    Auxiliary contract able to force withdrawals from L1 on behalf of users.

    BlockVerifier 0x6150…01ef

    zkSNARK Verifier based on ethsnarks library.

    Can be upgraded by: ProxyOwner

    Upgrade delay: No delay

    AgentRegistry 0x39B9…ea14

    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).