StackLend: Decentralized Lending Protocol

StackLend is a decentralized lending protocol built on the Stacks blockchain that enables secure, transparent, and efficient lending operations using STX tokens as collateral.

Overview

StackLend allows users to:

• Deposit STX tokens as collateral
• Borrow against their collateral
• Repay loans
• Withdraw collateral
• Participate in liquidations

The protocol implements dynamic interest rates, collateralization ratios, and liquidation mechanisms to maintain system stability and protect users.

Key Features

Collateralization and Borrowing

• Minimum collateralization ratio: 150%
• Maximum collateralization ratio: 500%
• Liquidation threshold: 130%
• Protocol fee: 1% (configurable up to 10%)

Core Functions

For Users

1. Deposit (deposit)

   • Allows users to deposit STX tokens as collateral
   • Updates total deposits and user position
   • Returns the deposited amount

2. Borrow (borrow)

   • Enables borrowing against deposited collateral
   • Requires maintaining minimum collateralization ratio
   • Updates total borrows and user position
   • Returns borrowed amount

3. Repay (repay)

   • Allows users to repay borrowed amounts
   • Updates total borrows and user position
   • Returns repaid amount

4. Withdraw (withdraw)

   • Enables withdrawal of collateral
   • Ensures remaining position maintains minimum collateralization
   • Updates total deposits and user position
   • Returns withdrawn amount

For Liquidators

Liquidate (liquidate)

• Allows liquidation of under-collateralized positions
• Triggers when position falls below liquidation threshold (130%)
• Transfers collateral to liquidator
• Clears user position

Read-Only Functions

1. Get User Position (get-user-position)

   {
     total-collateral: uint,
     total-borrowed: uint,
     loan-count: uint
   }

2. Get Protocol Stats (get-protocol-stats)

   {
     total-deposits: uint,
     total-borrows: uint,
     minimum-collateral-ratio: uint,
     liquidation-threshold: uint,
     protocol-fee: uint
   }

Administrative Controls

Contract owner can adjust key parameters within defined bounds:

1. Set Minimum Collateral Ratio (set-minimum-collateral-ratio)

   • Range: 110% to 500%
   • Must be higher than liquidation threshold

2. Set Liquidation Threshold (set-liquidation-threshold)

   • Must be between minimum collateral ratio (110%) and current minimum collateral ratio
   • Default: 130%

3. Set Protocol Fee (set-protocol-fee)

   • Maximum: 10%
   • Default: 1%

Error Codes

Code	Description
u100	Not authorized
u101	Insufficient collateral
u102	Invalid amount
u103	Loan not found
u104	Loan active
u105	Insufficient balance
u106	Liquidation failed
u107	Invalid parameter

Security Features

1. Access Control

   • Administrative functions restricted to contract owner
   • Self-liquidation prevention
   • Secure parameter bounds

2. Position Management

   • Dynamic collateral ratio tracking
   • Safe position updates
   • Protected withdrawal conditions

3. System Stability

   • Minimum collateralization requirements
   • Liquidation mechanisms
   • Fee structure for sustainability

Interest Calculation

Interest is calculated using the following formula:

interest-per-block = (principal * rate) / 10000
total-interest = interest-per-block * blocks

Usage Examples

Depositing Collateral

;; Deposit STX tokens
(contract-call? .stacklend deposit)

Borrowing Against Collateral

;; Borrow 100 STX
(contract-call? .stacklend borrow u100)

Repaying a Loan

;; Repay 50 STX
(contract-call? .stacklend repay u50)

Withdrawing Collateral

;; Withdraw 75 STX
(contract-call? .stacklend withdraw u75)

Best Practices

1. For Users

   • Maintain healthy collateralization ratios (>150%)
   • Monitor market conditions
   • Repay loans promptly to avoid liquidation

2. For Liquidators

   • Monitor positions near liquidation threshold
   • Ensure sufficient STX balance for liquidation
   • Understand liquidation penalties and rewards

3. For Administrators

   • Regular monitoring of system parameters
   • Gradual parameter adjustments
   • Emergency response planning

Technical Considerations

1. Block Height

   • Used for interest calculations
   • Timestamp approximation
   • Loan duration tracking

2. Position Updates

   • Atomic operations
   • Safe state transitions
   • Balance verification

3. Error Handling

   • Comprehensive error codes
   • Clear error messages
   • Safe state rollback

Contributing

We welcome contributions to StackLend! Please ensure:

1. Comprehensive testing of changes
2. Clear documentation updates
3. Adherence to Clarity best practices
4. Security-first approach