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cBridge (Celer) logocBridge (Celer)




Celer cBridge offers cross-chain token bridging in two modes: Token Bridge and Liquidity Network. It also offers AMB facility - ability to pass arbitrary messages across chains. It leverages the "State Guardian Network" aka SGN to perform cross-chain communication. For Liquidity Network, liquidity providers need to rely on SGN to remove their funds from the network.

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Risk summary

Note: This project's overview requires more research and might not present accurate information. If you want to contribute you can edit the information on Github. Alternatively you contact the project team on Twitter and encourage them to contribute a PR.


Principle of operation

Celer cBridge is a hybrid solution able to work in two modes: Token Bridge and Liquidity Network, depending on the token and destination chain. More information is provided in Destination Tokens section.

  • Funds can be frozen if validators (SGN) decide to not process a withdrawal request from liquidity providers (CRITICAL).

  1. Bridging models

Transfers are externally verified

Validation process takes place in an external network called SGN that is operated by validators running on Tendermint consensus protocol. Nodes in the network observe contracts on each supported chain and sign messages when everything is correct. Based on the signature user can withdraw funds from the bridge.

  • Users can be censored if validators (SGN) decide to stop processing certain transactions (CRITICAL).

  • Funds can be stolen if validators (SGN) allow to mint more tokens than there are locked on Ethereum thus preventing some existing holders from being able to bring their funds back to Ethereum (CRITICAL).

  • Funds can be stolen if validators (SGN) sign a fraudulent message allowing themselves to withdraw all locked funds (CRITICAL).

  1. State Guardian Network (SGN)

Destination tokens

Celer cBridge works in two token bridging models: xAsset and xLiquidity. xAsset model, the canonical mapping bridge, is intended for a token that is deployed on Ethereum but is not deployed on the destination chain. In this case cBridge will deploy a mapped version of the token on destination via lock-mint model. xLiquidity model, the pool-based bridge, is intended for token already deployed on Ethereum and destination. When users transfer between these chains they will be depositing their tokens into the pool on Ethereum and withdrawing a matching number of tokens from the pool on the destination chain based on a bridge rate generated by the StableSwap price curve. Additionally, it is worth pointing out that Celer introduced xAsset V2, the standard allowing for seamless cross-chain bridged assets transfers, without the need to return to source chain for liquidity. It is accomplished by changing the lock-mint model from V1 to burn-mint model in V2. What is more, Celer introduced "Open Canonical Token Bridge Standard" aiming to prevent bridge vendor lock-in.

  1. Bridging models
  2. Open Canonical Token Bridge Standard
  3. xAsset V2
  4. StableSwap

Permissioned Addresses

The system uses the following set of permissioned addresses:

Bridge Governance 0xF380…6575

The owner of the Token Bridge, Liquidity Network and Transfer Agent is a governance contract with the permissions to manage: signers responsible for messages relaying, pausers with the ability to pause the bridge as well as governance of the system.

Can vote on proposal which will be executed by the contract. Each voter holds the same voting power.

Can modify bridge operational parameters such as minimal and maximal send amounts, max slippage and transfer delay.

Smart Contracts

A diagram of the smart contract architecture
A diagram of the smart contract architecture

The system consists of the following smart contracts:

Message Bus 0x4066…200C

Contract providing cross-chain AMB facility. It connects with Liquidity Network and Token Bridges to processes certain types of messages.

Liquidity Network 0x5427…1820

Contract providing cross-chain swaps, allows user to deposit funds and withdraw them. Additionally user can add liquidity to this address to generate yield. This contract stores the following tokens: ETH, USDC, WETH, USDT, MASK, BUSD, LYRA.

Token Bridge v1 0xB37D…8595

Contract serving as token bridge, user can deposit funds and later withdraw them from this escrow. This contract stores the following tokens: USDC, WETH, USDT, FRAX, DAI, RLY, WBTC, CELR, FXS, WXT.

Token Bridge v2 0x7510…bAE1

Contract serving as token bridge, user can deposit funds and later withdraw them from this escrow. This contract stores the following tokens: WETH, PSTAKE.

Pegged Token Bridge v1 0x1636…95eB

Contract minting/burning tokens when receiving a message from Token Bridge.

Pegged Token Bridge v2 0x52E4…e084

Contract minting/burning tokens when receiving a message from Token Bridge.

Transfer Agent 0x9b27…1a0b

Routing contract that transfers assets cross-chain using either Liquidity Network or Token Bridge.