# Interoperability

## <mark style="color:orange;">Token Information</mark>

#### <mark style="color:purple;">USN</mark>

* **Bridge Mechanism**: Burn-Mint

#### <mark style="color:purple;">sUSN</mark> (Staked <mark style="color:purple;">USN</mark>)

* **Bridge Mechanism**: Lock-Mint / Mint-Unlock
* **Ethereum Lock Address**: `0xE24a3DC889621612422A64E6388927901608B91D`\ <br>

| Token                                       | Mechanism               | Ethereum Direction | Other Networks Direction |
| ------------------------------------------- | ----------------------- | ------------------ | ------------------------ |
| <mark style="color:purple;">**sUSN**</mark> | Lock-Mint / Mint-Unlock | Lock on ETH        | Mint synthetic           |
| <mark style="color:purple;">**sUSN**</mark> | Lock-Mint / Mint-Unlock | Unlock from ETH    | Burn synthetic           |
| <mark style="color:purple;">**USN**</mark>  | Burn-Mint               | Burn               | Mint                     |
| <mark style="color:purple;">**USN**</mark>  | Burn-Mint               | Mint               | Burn                     |

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

### <mark style="color:purple;">**sUSN**</mark> Bridging Architecture

**Ethereum → Other Networks (Lock-Mint)**

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

1. **Lock Phase**: <mark style="color:purple;">**sUSN**</mark> tokens are locked in the collateral contract on Ethereum
   * Lock Address: `0xE24a3DC889621612422A64E6388927901608B91D`
   * Tokens remain in escrow on Ethereum \
     \* This should be subtracted to not get double counted if following all chains supply
2. **Mint Phase**: Synthetic <mark style="color:purple;">**sUSN**</mark> is minted on the destination chain
   * Wrapped/synthetic representation created
   * 1:1 backing by locked tokens on Ethereum

**Other Networks → Ethereum (Mint-Unlock)**

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

1. **Burn Phase**: Synthetic <mark style="color:purple;">**sUSN**</mark> is burned on the source chain
   * Removes the wrapped representation from circulation
2. **Unlock Phase**: Original <mark style="color:purple;">**sUSN**</mark> is released from the lock contract on Ethereum
   * Tokens returned to user's address
   * Released from `0xE24a3DC889621612422A64E6388927901608B91D`

```
┌─────────────────────────────────────────────────────────────┐
│                    sUSN Bridge Flow                          
├─────────────────────────────────────────────────────────────┤
│                                                              
│  Ethereum → Other Networks (Lock-Mint)                   
│  ┌──────────┐         ┌──────────┐         ┌──────────┐
│  │ User sUSN│  Lock   │Collateral│  Mint   │Synthetic │
│  │          │────────>│ Contract │────────>│   sUSN   │
│  │          │         │0xE24a... │         │          │
│  └──────────┘         └──────────┘         └──────────┘
│                                                          
│  Other Networks → Ethereum (Mint-Unlock)                 
│  ┌──────────┐         ┌──────────┐         ┌──────────┐    
│  │Synthetic │  Burn   │Collateral│ Unlock  │ User sUSN│    
│  │   sUSN   │────────>│ Contract │────────>│          │    
│  │          │         │0xE24a... │         │          │    
│  └──────────┘         └──────────┘         └──────────┘    
│                                                              
│  Other Networks → Other Networks (non Ethereum) (Burn-Mint)                              
│  ┌──────────┐         ┌──────────┐         ┌──────────┐    
│  │ User sUSN│  Burn   │ Hyperlane│  Mint   │ User USN │    
│  │ Chain A  │────────>│ Protocol │────────>│ Chain B  │    
│  │          │         │          │         │          │    
│  └──────────┘         └──────────┘         └──────────┘    
│                                                             
└─────────────────────────────────────────────────────────────┘
```

### <mark style="color:purple;">USN</mark> Bridging Architecture

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

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

```
┌─────────────────────────────────────────────────────────────┐
│                     USN Bridge Flow                          
├─────────────────────────────────────────────────────────────┤
│                                                              
│  Chain A → Chain B (Burn-Mint)                              
│  ┌──────────┐         ┌──────────┐         ┌──────────┐    
│  │ User USN │  Burn   │ Hyperlane│  Mint   │ User USN │    
│  │ Chain A  │────────>│ Protocol │────────>│ Chain B  │    
│  │          │         │          │         │          │    
│  └──────────┘         └──────────┘         └──────────┘    
│                                                              
└─────────────────────────────────────────────────────────────┘
```