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USD₮0 is an . The OFT standard allows tokens to move seamlessly across multiple blockchains using LayerZero's messaging protocol, ensuring a unified supply across all chains. USD₮0 follows this standard, leveraging LayerZero's infrastructure to enable secure and efficient cross-chain transfers while maintaining compatibility with existing USD₮ functionality.
The USD₮0 implementation separates token functionality from cross-chain messaging. This split enables independent upgrades of token and messaging components while maintaining consistent token behavior across chains.
The implementation consists of three main components:
OAdapterUpgradeable (on Ethereum):
Implements LayerZero OFT functionality for Ethereum
Handles both sending and receiving cross-chain messages
Interfaces directly with the TetherToken contract on Ethereum
Locks/Unlocks USD₮ for cross-chain transfers
OUpgradeable (on other chains):
Implements LayerZero OFT functionality for other chains
Handles both sending and receiving cross-chain messages
Interfaces with the TetherTokenOFTExtensoin
Controls minting/burning for cross-chain transfers
TetherTokenOFTExtension (on other chains):
Offers mint/burn interface for the OFT
The graphic illustrates how USD₮ and USD₮0 are transferred across Ethereum, Chain A, and Chain B:
Ethereum → Chain B:
USDT Adapter locks USDT on Ethereum.
A LayerZero message triggers USDT0 OFT on Chain B to mint equivalent USD₮0.
Chain B → Chain A:
USDT0 OFT burns USD₮0 on Chain B.
A message triggers USDT0 OFT on Chain A to mint the equivalent.
Chain A → Ethereum:
USDT0 OFT burns USD₮0 on Chain A.
A message instructs the USDT Adapter to unlock USD₮ on Ethereum.
The flow ensures consistent token supply across chains.
The USD₮0 token implements the following standard interfaces:
ERC20
ERC20Permit (EIP-2612)
EIP-3009 (Gasless transfers)
Key public functions for integration:
The OFT implementation provides cross-chain transfer functionality through LayerZero:
The OFT interface is consistent across all chains, whether using OAdapterUpgradeable on Ethereum or OUpgradeable on other chains. The only difference is that on Ethereum, users need to approve the OFT adapter to spend their USD₮ before calling send
.
The following example shows how to bridge USD₮ from Ethereum to Arbitrum, including necessary approvals and parameter handling.
USD₮0 utilizes a dual-DVN security configuration requiring verification from:
LayerZero DVN
USDT0 DVN
Both DVNs must verify the payloadHash before a cross-chain message can be committed for execution. This setup ensures enhanced security through independent verification of all cross-chain transfers.
OAdapterUpgradeable:
Safe:
ArbitrumExtensionV2:
OUpgradeable:
Safe:
TetherTokenOFTExtension:
OUpgradeable:
Safe:
TetherTokenOFTExtension:
OUpgradeable:
Safe:
TetherTokenOFTExtension:
OUpgradeable:
Safe:
TetherTokenOFTExtension:
OUpgradeable:
Safe:
TetherTokenOFTExtension:
OUpgradeable:
Safe:
TetherTokenOFTExtension:
OUpgradeable:
Safe:
TetherTokenOFTExtension:
OUpgradeable:
Safe:
HyperliquidExtension:
OUpgradeable:
Safe:
For detailed information about LayerZero DVNs and security stacks, refer to: