bfBTC Fees

Note: Fees are only taken during requestWithdraw, requestWithdrawNative, and cross-chain actions.

Fee Types

uint8 private constant FEE_TYPE_EVM = 0;      // For EVM chain operations
uint8 private constant FEE_TYPE_NATIVE = 1;   // For native chain [Bitcoin] operations
uint8 private constant FEE_TYPE_CROSSCHAIN = 2; // For cross-chain operations

Fee Parameters

1. Withdraws:

• Percentage Fee

  • Fee rate = 0

  • Fee precision = 100000

  • Actual fee = 0 bfBTC

• Fixed Fee

  • Fee rate = 600

  • Fee precision = 100000000 (1e8)

  • Actual fee = 0.000006 bfBTC

1. WithdrawsNative

• Percentage Fee

  • Fee rate = 0

  • Fee precision = 100000

  • Actual fee = 0 bfBTC

• Fixed Fee

  • Fee rate = 1200

  • Fee precision = 100000000 (1e8)

  • Actual fee = 0.000012 bfBTC

  • Note: The Fixed Fee on the Hemi network is 2,000 (0.00002 bfBTC).

Fee Structure

struct FeeConfig {
    uint128 percentageFee; // Percentage-based fee (precision: 100000)
    uint128 fixedFee;      // Fixed fee amount
}

Fee Calculation

function calculateFee(
    address user,
    uint256 amount,
    uint8 feeType
) public view returns (uint256 percentageFee, uint256 fixedFee)

Description: Calculate fees for a specific operation based on user address and amount.

Parameters:

• user: Address of the user performing the operation

• amount: Amount of the operation

• feeType: Type of fee to calculate (EVM/Native/Crosschain)

Return Values:

• percentageFee: Calculated percentage-based fee

• fixedFee: Fixed fee amount

Calculation Formula:

$$\text{percentageFee} = \text{amount} \times \frac{\text{percentageFeeConfig}}{\text{FEE\_PRECISION}}$$

$$\text{totalFee} = \text{percentageFee} + \text{fixedFee}$$

Notes:

• percentageFee precision is 100000

• Transaction reverts if total fee exceeds operation amount

Fee Events

event FeeUpdated(uint8 indexed feeType, uint256 percentageFee, uint256 fixedFee);
event FeeWhitelistUpdated(address indexed account, bool status);
event FeeCollected(
    address indexed user,
    uint8 indexed feeType,
    uint256 id,
    uint256 amount,
    uint256 percentageFee,
    uint256 fixedFee
);

Additional Information

• Fees are collected in the bfBTC token

• Fee events provide tracking and auditing capabilities

• Whitelist mechanism allows for special cases and promotions

• Fee configuration can be updated based on market conditions