> For the complete documentation index, see [llms.txt](https://docs.noon.capital/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.noon.capital/2.-usdusn-and-usdsusn/cross-chain-interoperability.md).

# Cross-Chain Interoperability

<mark style="color:violet;">**$USN**</mark> and <mark style="color:violet;">**$sUSN**</mark> exist across multiple chains, this page explains how. To move your assets between chains, see [**Bridging Operations**.](/2.-usdusn-and-usdsusn/cross-chain-interoperability/bridging-operations.md)

## <mark style="color:$primary;">How cross-chain bridging works</mark>

Ethereum is <mark style="color:violet;">**$USN**</mark>'s **canonical home chain**. On other chains, <mark style="color:violet;">**$USN**</mark> 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 <mark style="color:purple;">**Noon**</mark>'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 <mark style="color:violet;">**$USN**</mark> is never counted twice.

<mark style="color:violet;">**$sUSN**</mark> follows the **same model** where it is available cross-chain.

## <mark style="color:$primary;">Supported chains</mark>

<figure><img src="https://3816918787-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FL26rQzcNmiUZrCXkxkjS%2Fuploads%2FbMMjzouMW0RTLbDW2EtQ%2Fimage.png?alt=media&amp;token=a11561f6-492f-4c42-862c-f1940d89f32c" alt=""><figcaption></figcaption></figure>

## <mark style="color:$primary;">Bridging Mechanisms</mark>

### 1. <mark style="color:violet;">$USN</mark> Bridging Architecture

<mark style="color:violet;">**$USN**</mark> uses a **burn-mint** mechanism across all supported chains:

1. **Burn Phase**: <mark style="color:violet;">**$USN**</mark> tokens are burned on the origin chain
   * Tokens removed from circulation
   * Supply decreased on origin chain
2. **Mint Phase**: <mark style="color:violet;">**$USN**</mark> tokens are minted on the destination chain
   * New tokens created on target chain
   * **Total cross-chain supply remains constant**

<figure><img src="https://t9012456302.p.clickup-attachments.com/t9012456302/eae4ba04-0806-458a-9d44-0410b36f69e5/image.png" alt=""><figcaption></figcaption></figure>

### **2.&#x20;**<mark style="color:violet;">**$sUSN**</mark> Bridging Architecture

<mark style="color:violet;">**$sUSN**</mark> uses a combination of burn lock-mint and burn-mint mechanisms, depending on the origin and destination chain.&#x20;

**2.1. Ethereum → Other Networks: Lock-Mint**

When bridging <mark style="color:violet;">**$sUSN**</mark> from Ethereum to other networks:

1. **Lock Phase**: <mark style="color:violet;">**$sUSN**</mark> tokens are locked in the collateral contract on Ethereum
   * Lock Address: `0xE24a3DC889621612422A64E6388927901608B91D`
   * Tokens remain in escrow on Ethereum
   * Subtract escrowed tokens when calculating total supply across all chains
2. **Mint Phase**: Synthetic <mark style="color:violet;">**$sUSN**</mark> 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 <mark style="color:violet;">**$sUSN**</mark> from other networks back to Ethereum:

1. **Burn Phase**: Synthetic <mark style="color:violet;">**$sUSN**</mark> is burned on the origin chain
   * Removes the **wrapped representation** from circulation
2. **Unlock Phase**: Original <mark style="color:violet;">**$sUSN**</mark> 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**: <mark style="color:violet;">**$sUSN**</mark> tokens are burned on the origin chain
  * Tokens removed from circulation
  * Supply decreased on origin chain
* **Mint Phase**: <mark style="color:violet;">**$sUSN**</mark> tokens are minted on the destination chain
  * New tokens created on target chain
  * **Total cross-chain supply remains constant**

<figure><img src="https://t9012456302.p.clickup-attachments.com/t9012456302/17c007bc-e1b1-4a45-897a-fe166e93a160/image.png" alt=""><figcaption></figcaption></figure>

## <mark style="color:$primary;">A note on bridge risk</mark>

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**.](/1.-noon-the-basics/risks-and-mitigants.md)