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

2. 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