Cross-Chain Rebase Token (CCIP)

A sophisticated DeFi protocol that implements an interest-bearing rebase token system with cross-chain capabilities using Chainlink CCIP. Users can deposit ETH into a vault and receive rebase tokens that automatically accrue interest over time.

Overview

This project consists of three main smart contracts and supporting deployment scripts:

🏦 RebaseToken

An advanced ERC20 token that automatically increases holder balances over time based on individual interest rates:

• Automatic Interest Accrual: Balances grow continuously based on time elapsed
• Individual Interest Rates: Each user can have a custom interest rate set during minting
• Role-Based Access Control: Secure minting and burning operations via AccessControl
• High Precision Calculations: Uses 1e18 precision factor for accurate interest computation
• Owner Controls: Global interest rate management with decrease-only safeguards
• Max Amount Support: Special handling for type(uint256).max transfers and burns

� RebaseTokenPool

A Chainlink CCIP token pool that enables cross-chain transfers while preserving interest rates:

• Burn-and-Mint Mechanism: Secure cross-chain token transfers
• Interest Rate Preservation: Maintains user's individual interest rates across chains
• CCIP Integration: Full compatibility with Chainlink's Cross-Chain Interoperability Protocol
• Security Features: Rate limiting and allowlist support for enhanced protection
• Encoded Transfer Data: Smart encoding of interest rates in cross-chain messages

�🏛️ Vault

A secure vault contract that bridges ETH and RebaseTokens with automatic interest assignment:

• 1:1 Exchange Rate: Deposit ETH to receive equivalent RebaseTokens
• Interest-Bearing Deposits: Your tokens automatically grow while in your wallet
• Flexible Redemption: Redeem tokens back to ETH at any time including full balance
• Automatic Rate Assignment: New deposits inherit current global interest rate
• Secure ETH Handling: Robust error handling for failed ETH transfers

Key Features

• ✅ Interest-Bearing Tokens: Balances automatically increase over time
• ✅ Flexible Interest Rates: Per-user customizable rates
• ✅ Secure Architecture: Role-based access control and ownership patterns
• ✅ Gas Optimized: Efficient interest calculations with precision factors
• ✅ Cross-Chain Ready: Built with Chainlink CCIP integration in mind
• ✅ 100% Test Coverage: Complete test suite with comprehensive edge case coverage

Built With

• Solidity ^0.8.24: Smart contract development
• Foundry: Development framework and testing
• OpenZeppelin: Security-audited contract libraries
• Chainlink CCIP: Cross-chain interoperability protocol

Quick Start

Prerequisites

• Foundry
• Git

Installation

1. Clone the repository

   git clone https://github.com/chauhan-varun/cross-chain-rebase-token.git
   cd cross-chain-rebase-token

2. Install dependencies

   forge install

3. Build the project

   forge build

4. Run tests

   forge test

Usage

Development Commands

Build

forge build

Test

forge test

Test with Verbosity

forge test -vvv

Format Code

forge fmt

Gas Snapshots

forge snapshot

Coverage Report

forge coverage

Generate detailed coverage report:

forge coverage --report lcov

Smart Contract Architecture

RebaseToken.sol

• Inherits: ERC20, Ownable, AccessControl
• Key State Variables:
  • s_interestRate: Global interest rate (default: 5e18 = 5% annually)
  • s_userInterestRate: Mapping of user-specific interest rates
  • s_userLastTimestamp: Mapping of user's last interaction timestamps
• Key Functions:
  • mint(address, uint256, uint256): Mint tokens with custom interest rate
  • burn(address, uint256): Burn tokens from an address (supports max amount)
  • setInterestRate(uint256): Update global interest rate (owner only, decrease-only)
  • balanceOf(address): Returns current balance including accrued interest
  • principleBalanceOf(address): Returns original minted amount without interest
  • transfer(address, uint256): Enhanced transfer with interest accrual and rate inheritance
  • transferFrom(address, address, uint256): Enhanced transferFrom with same features

RebaseTokenPool.sol

• Inherits: TokenPool (Chainlink CCIP)
• Key Features:
  • Cross-chain burn-and-mint mechanism
  • Interest rate preservation across chains
  • Integration with CCIP router and RMN proxy
• Key Functions:
  • lockOrBurn(Pool.LockOrBurnInV1): Burns tokens and encodes interest rate for cross-chain transfer
  • releaseOrMint(Pool.ReleaseOrMintInV1): Mints tokens with preserved interest rate on destination chain

Vault.sol

• Key State Variables:
  • i_rebaseToken: Immutable reference to RebaseToken contract
• Key Functions:
  • deposit(): Deposit ETH, receive RebaseTokens with current global interest rate
  • redeem(uint256): Redeem RebaseTokens for ETH (supports max amount redemption)
  • getRebaseTokenAddress(): Returns RebaseToken contract address
  • getCurrentInterestRate(): Returns current global interest rate
  • receive(): Fallback function for direct ETH deposits

Testing

The project includes comprehensive tests with 100% code coverage for all core contracts:

Coverage Statistics

• RebaseToken.sol: 100% Lines, 100% Statements, 100% Branches, 100% Functions
• Vault.sol: 100% Lines, 100% Statements, 100% Branches, 100% Functions
• RebaseTokenPool.sol: 100% Lines, 100% Statements, 100% Branches, 100% Functions

Test Suites

• ✅ RebaseTokenTest: Core token functionality and interest mechanics (9 tests)
• ✅ AdditionalCoverageTest: Edge cases, max amounts, and error scenarios (11 tests)
• ✅ CrossChainTest: Cross-chain bridging and CCIP functionality (3 tests)
• ✅ Total: 23 tests with comprehensive coverage

What's Tested

• ✅ Token Operations: Minting, burning, transfers with interest rate handling
• ✅ Interest Mechanics: Time-based interest accrual and rate calculations
• ✅ Vault Operations: ETH deposits, token redemptions, and exchange flows
• ✅ Access Control: Role-based permissions and ownership management
• ✅ Edge Cases: Zero balances, max transfers, failed transactions, different interest rates
• ✅ Cross-chain Features: CCIP bridging, interest rate preservation across chains
• ✅ Error Handling: Revert scenarios and comprehensive error condition testing

Run specific test files:

forge test --match-contract RebaseTokenTest
forge test --match-contract AdditionalCoverageTest  
forge test --match-contract CrossChainTest

Security Considerations

• Access Control: Role-based permissions for critical functions
• Integer Overflow: SafeMath patterns and Solidity 0.8+ built-in protection
• Reentrancy: Proper state updates before external calls
• Precision: High-precision arithmetic for accurate interest calculations
• 100% Test Coverage: All code paths tested including edge cases and error conditions
• Failed Transaction Handling: Comprehensive error handling for ETH transfers and edge cases

Local Development

Start Local Blockchain

anvil

Project Structure

src/
├── RebaseToken.sol              # Main rebasing ERC20 token contract
├── RebaseTokenPool.sol          # CCIP token pool for cross-chain transfers
├── Vault.sol                   # ETH ⟷ RebaseToken exchange vault
└── interface/
    └── IRebaseToken.sol         # RebaseToken interface for external integrations

script/
├── Deployer.s.sol              # Deploys RebaseToken and RebaseTokenPool contracts
├── ConfigurePool.s.sol         # Configures token pool settings and permissions
├── BridgeTokens.s.sol          # Handles cross-chain token bridging operations
└── Interactions.s.sol          # Utility script for contract interactions

test/
├── RebaseTokenTest.t.sol       # Core RebaseToken functionality tests
├── AdditionalCoverageTest.t.sol # Edge cases and comprehensive coverage tests
└── CrossChainTest.t.sol        # Cross-chain bridging tests

Script Details

• Deployer.s.sol: Comprehensive deployment script that sets up RebaseToken and RebaseTokenPool contracts with proper CCIP infrastructure including router and RMN proxy configuration
• ConfigurePool.s.sol: Post-deployment configuration script for setting up token pool parameters, allowlists, and admin permissions
• BridgeTokens.s.sol: Cross-chain bridging utility that handles CCIP message construction and token transfers between chains
• Interactions.s.sol: General purpose interaction script for testing and managing deployed contracts

Configuration

The project uses Foundry with the following configuration (foundry.toml):

• Source directory: src/
• Test directory: test/
• Libraries: lib/
• OpenZeppelin remapping for imports

Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Future Enhancements

• 🔮 Cross-Chain Integration: Full Chainlink CCIP implementation
• 🏦 Multi-Asset Support: Support for other ERC20 tokens
• 📊 Yield Farming: Additional DeFi yield strategies
• 🔐 Multi-Sig Support: Enhanced security for vault operations

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Foundry - Ethereum development toolkit
• OpenZeppelin - Secure smart contract library
• Chainlink - Cross-chain infrastructure