Stablecoin Bridges

Simple contracts that allow swapping other Dollar stablecoins into JuiceDollar and back.

Overview

The swap page allows you to swap other recognized Dollar stablecoins against JuiceDollars and back. Moving back into other stablecoins is only possible as long as there is some of the other stablecoin left in the bridge contract. Essentially, this pegs JuiceDollar 1:1 to other stablecoins and helps stabilizing its value. In order to protect JuiceDollar from a crash of the connected stablecoins, the bridge contract is limited in time and volume. After a year the latest, it needs to be replaced with a new contract.

System participants should closely watch the amount of other stablecoins flowing in and out. Having a lot of outflow could be an indication that it is too cheap to mint JuiceDollars, i.e. implied interest rates being too low. Having large inflows could be an indication that going into JuiceDollars is too attractive and interest rates too high.

How Bridges Work

Stablecoin bridges enable 1:1 conversion between trusted external stablecoins and JUSD:

Source Stablecoin (e.g., USDC) ←→ JuiceDollar (JUSD)
         1:1 exchange rate

Minting JUSD

When you deposit a source stablecoin:

1. Your stablecoin is transferred to the bridge contract
2. An equal amount of JUSD is minted to your address
3. The bridge's minted counter increases

// Mint to yourself
function mint(uint256 amount) external

// Mint to another address
function mintTo(address target, uint256 amount) external

Burning JUSD

When you want your stablecoin back:

1. Your JUSD is burned
2. An equal amount of source stablecoin is sent to you
3. The bridge's minted counter decreases

// Burn and receive to yourself
function burn(uint256 amount) external

// Burn and send to another address
function burnAndSend(address target, uint256 amount) external

Bridge Limitations

Each bridge has built-in limitations to protect the JuiceDollar system:

Volume Limit

uint256 public immutable limit;
uint256 public minted;

The limit caps the maximum amount of JUSD that can be minted through this bridge. This prevents over-reliance on any single external stablecoin.

Example: A bridge with a 10M JUSD limit can never have more than 10M JUSD outstanding.

Time Horizon

uint256 public immutable horizon;

Every bridge has an expiration date (horizon). After this time:

• No new minting is allowed
• Users can still burn JUSD to retrieve their stablecoins
• A new bridge must be deployed to continue operations

Typical duration: 52 weeks (1 year)

Why expire bridges?

• Forces periodic review of connected stablecoins
• Allows governance to adjust limits based on market conditions
• Provides opportunity to switch to better alternatives

Decimal Handling

Bridges automatically handle different decimal places between tokens:

function _convertAmount(
    uint256 amount,
    uint8 fromDecimals,
    uint8 toDecimals
) internal pure returns (uint256)

Example: USDC (6 decimals) ↔ JUSD (18 decimals)

• Deposit 1,000,000 USDC (1 USDC) → Receive 1,000,000,000,000,000,000 JUSD (1 JUSD)

Emergency Stop

Bridges include an emergency mechanism that allows qualified JUICE holders to permanently stop a bridge if the underlying stablecoin is compromised.

How Emergency Stop Works

function emergencyStop(
    address[] calldata _helpers,
    string calldata _message
) external

Requirements:

• Caller needs 10% of total voting power (higher than normal 2% quorum)
• Helpers array must be sorted and valid
• Once stopped, the bridge cannot be reactivated

When to Use Emergency Stop

• The source stablecoin loses its peg
• Security vulnerability discovered in source stablecoin
• Regulatory action against source stablecoin issuer
• Evidence of fractional reserve or fraud

After Emergency Stop

bool public stopped;

When stopped = true:

• mint() and mintTo() are permanently disabled
• burn() and burnAndSend() still work
• Users can always retrieve their deposited stablecoins

Emergency Stop Quorum

Parameter	Value
Required voting power	10% of total votes
Effect	Permanent - cannot be reversed
Burn functionality	Still available

The higher quorum (10% vs 2%) prevents abuse while still allowing rapid response to genuine emergencies.

Bridge Monitoring

Checking Bridge Status

// Source stablecoin address
function usd() external view returns (IERC20)

// JUSD contract
function JUSD() external view returns (IJuiceDollar)

// Expiration timestamp
function horizon() external view returns (uint256)

// Maximum mintable amount
function limit() external view returns (uint256)

// Currently minted amount
function minted() external view returns (uint256)

// Whether bridge is stopped
function stopped() external view returns (bool)

Health Indicators

Metric	Healthy	Warning
minted / limit	< 80%	> 90%
Time to horizon	> 30 days	< 7 days
stopped	false	true

Monitoring Flows

Watch the balance changes to understand market dynamics:

Flow Direction	Interpretation
Inflow (minting)	JUSD is attractive, possibly interest rates too high
Outflow (burning)	JUSD is less attractive, possibly rates too low
Balanced	Market in equilibrium

StartUSD Bridge (Historical)

During the initial launch of JuiceDollar, a bootstrap token called StartUSD (SUSD) was used to initialize the system. StartUSD was a simple ERC-20 token with no intrinsic value, created solely to enable the first JUSD minting and governance setup during a time-limited 6-week bootstrap phase.

The StartUSD bridge has since expired. SUSD is no longer part of the system and all JUSD in circulation is now backed by real collateral and audited stablecoins.

Bridge Contracts (Expired)

Network	Address
Mainnet	0x51ff8141D731676Fb21aE1E5D5A88c04511994dD (opens new window)
Testnet	0x9ba2264bE7695044f59B9ca863E69aC38B3c913d (opens new window)

Property	Value
Source Token	StartUSD
Limit	Configured at deployment
Horizon	6 weeks (bootstrap period)

Adding New Bridges

New stablecoin bridges can be added through the governance process:

Requirements for New Bridges

1. Trusted stablecoin: The source must be a reputable, audited stablecoin
2. Sufficient liquidity: Enough market depth for meaningful volume
3. Governance approval: Pass the 14-day minter application period without veto

Deployment Process

1. Deploy StablecoinBridge contract with parameters:

   • Source stablecoin address
   • JUSD address
   • Volume limit
   • Duration in weeks

2. Propose as new minter via suggestMinter()

3. Wait for application period (minimum 14 days)

4. If no veto, bridge becomes active

Example Bridge Deployment

// Deploy new USDC bridge
StablecoinBridge usdcBridge = new StablecoinBridge(
    USDC_ADDRESS,           // Source stablecoin
    JUSD_ADDRESS,           // JUSD contract
    10_000_000 * 10**18,    // 10M JUSD limit
    52                       // 52 weeks duration
);

// Propose to governance
jusd.suggestMinter(
    address(usdcBridge),
    14 days,                 // Application period
    1000 * 10**18,          // 1000 JUSD fee
    "USDC Bridge - https://docs.example.com/usdc-bridge"
);

Security Considerations

Bridge Risks

Risk	Mitigation
Source stablecoin failure	Volume limits, emergency stop
Bridge contract exploit	Immutable code, audits
Governance attack	10% quorum for emergency
Expiration oversight	Time limits force review

Best Practices for Users

1. Check bridge status before large transactions
2. Monitor horizon - don't deposit near expiration
3. Verify addresses - use only official bridge contracts
4. Diversify - don't rely on a single bridge for large amounts

Events

// Emitted when bridge is permanently stopped
event EmergencyStopped(address indexed caller, string message)

Current Bridges

Mainnet (Chain ID: 4114)

Bridge	Source	Address	Status
USDC	USDC	0x920D...20F (opens new window)	Active
USDT	USDT	0x5CC0...614 (opens new window)	Active
CTUSD	CTUSD	0x8D11...0bd (opens new window)	Active
StartUSD	SUSD	0x51ff...4dD (opens new window)	Expired

Testnet (Chain ID: 5115)

Bridge	Source	Address	Status
StartUSD	SUSD	0x9ba2...3d (opens new window)	Expired

Additional bridges may be added through governance.