Cross-Chain Interoperability

$USN and $sUSN exist across multiple chains, this page explains how. To move your assets between chains, see Bridging Operations.

How cross-chain bridging works

Ethereum is $USN's canonical home chain. On other chains, $USN is available through Hyperlane and LayerZero, interoperability protocols.

The specific bridge mechansims use lock-and-mint or burn-and-mint model, depending on the origin and destination chain. See specific details below, in the Bridging Mechanism section.

Across all of Noon's briding mechanisms, the goal is to keep total supply consistent across chains. For example, tokens locked on Ethereum back tokens minted elsewhere. The same $USN is never counted twice.

$sUSN follows the same model where it is available cross-chain.

Supported chains

Bridging Mechanisms

1. $USN Bridging Architecture

$USN uses a burn-mint mechanism across all supported chains:

1. Burn Phase: $USN tokens are burned on the origin chain

   • Tokens removed from circulation

   • Supply decreased on origin chain

2. Mint Phase: $USN tokens are minted on the destination chain

   • New tokens created on target chain

   • Total cross-chain supply remains constant

2. $sUSN Bridging Architecture

$sUSN uses a combination of burn lock-mint and burn-mint mechanisms, depending on the origin and destination chain.

2.1. Ethereum → Other Networks: Lock-Mint

When bridging $sUSN from Ethereum to other networks:

1. Lock Phase: $sUSN tokens are locked in the collateral contract on Ethereum

   • Lock Address: 0xE24a3DC889621612422A64E6388927901608B91D

   • Tokens remain in escrow on Ethereum

   • Subtract escrowed tokens when calculating total supply across all chains

2. Mint Phase: Synthetic $sUSN is minted on the destination chain

   • Wrapped/synthetic representation created

   • 1:1 backing by tokens locked on Ethereum

2.2. Other Networks → Ethereum: Burn-Unlock

When bridging $sUSN from other networks back to Ethereum:

1. Burn Phase: Synthetic $sUSN is burned on the origin chain

   • Removes the wrapped representation from circulation

2. Unlock Phase: Original $sUSN is released from the lock contract on Ethereum

   • Tokens return to the user's address

   • Released from 0xE24a3DC889621612422A64E6388927901608B91D

2.3. Other Networks → Other Networks: Burn-Mint

• Burn Phase: $sUSN tokens are burned on the origin chain

  • Tokens removed from circulation

  • Supply decreased on origin chain

• Mint Phase: $sUSN tokens are minted on the destination chain

  • New tokens created on target chain

  • Total cross-chain supply remains constant

A note on bridge risk

Moving tokens across chains depends on bridge infrastructure beyond the core Noon protocol.

Noon uses Hyperlane and LayerZero's lock-and-mint model to keep total supply consistent across chains. However, cross-chain security ultimately depends on that infrastructure performing as designed.

For the full picture of this and every other risk, alongside how Noon manages each, see Risks & Mitigants.