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Aptos (LayerZero)
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Tether USD (USDT)
USD Coin (USDC)
Wrapped Ether (WETH)Description
Aptos Bridge is built on top of LayerZero protocol and is a token bridge for transferring assets from Ethereum to Aptos. It leverages an oracle and relayer for cross-chain security for the protocol.
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Risk summary
Funds can be stolen if
- oracles and relayers collude to submit fraudulent block hash and relay fraudulent transfer (CRITICAL),
- token bridge owner (currently EOA) enables emergency withdrawal and users do not exit with their funds within a week (CRITICAL),
- token bridge owner (currently EOA) sets WETH contract address to a malicious contract that will allow the owner to steal user's ETH (CRITICAL),
- a contract receives a malicious code upgrade. There is no delay on code upgrades (CRITICAL),
- the source code of unverified contracts contains malicious code (CRITICAL).
Users can be censored if
Technology
Principle of operation
Aptos Bridge is a Token Bridge. It locks tokens in Ethereum escrow and mints tokens on Aptos.
Oracles and Relayers
Aptos Bridge is built on top of LayerZero protocol. LayerZero relies on Oracles to periodically submit source chain block hashes to the destination chain. Once block hash is submitted, Relayers can provide the merkle proof for the transfers. Token Bridge owner can withdraw all funds from the bridge escrow after placing the bridge in an emergency withdrawal mode that will allow them to transfer all tokens out after 1 week delay.
Users can be censored if oracles or relayers fail to facilitate the transfer (CRITICAL).
Funds can be stolen if oracles and relayers collude to submit fraudulent block hash and relay fraudulent transfer (CRITICAL).
Funds can be stolen if token bridge owner (currently EOA) enables emergency withdrawal and users do not exit with their funds within a week (CRITICAL).
Funds can be stolen if token bridge owner (currently EOA) sets WETH contract address to a malicious contract that will allow the owner to steal user's ETH (CRITICAL).
Permissions
The system uses the following set of permissioned addresses:
Bridge owner, can setup tokens, fees, WETH token address (potentially malicious). Can withdraw all the funds from the Escrow after unlocking emergency withdrawal with 1 week delay. This is a Gnosis Safe with 3 / 6 threshold.
Those are the participants of the Aptos Multisig.
Contract authorized to relay messages and - as a result - withdraw funds from the bridge.
Can upgrade LayerZero relayer contract with no delay.
Can upgrade LayerZero oracle contract with no delay.
The owner of Endpoint, UltraLightNode and Treasury contracts. Can switch to a new UltraLightNode for an Endpoint. Can switch proof library for an UltraLightNode and change Treasury. This is a Gnosis Safe with 2 / 5 threshold.
Those are the participants of the LayerZero Multisig.
Smart contracts
The system consists of the following smart contracts:
Aptos Token Bridge. This contract stores the following tokens: USDC, USDT, WETH.
The source code of some implementations is not verified on Etherscan.
The source code of some implementations is not verified on Etherscan.
LayerZero Ethereum Endpoint.
LayerZero UltraLight Node V2. Used by oracles to checkpoint source chain block hashes.
LayerZero Treasury.
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).
Funds can be stolen if the source code of unverified contracts contains malicious code (CRITICAL).
