🚀 Cross-Chain Rebase Token

A protocol that allows users to deposit into a vault and receive rebase tokens that represent their dynamically growing underlying balance.

🌱 How It Works

• Users deposit tokens into a vault.
• In return, they receive rebase tokens — a special ERC20 token whose balanceOf grows linearly over time.
• The growth is calculated based on the interest rate at the time of deposit, which stays fixed for each user.
• Interest is rewarded on every interaction like minting, burning, transferring — or even bridging.

💸 Dynamic Balance (Rebase)

• balanceOf(address) returns a dynamic balance that increases linearly based on:

  • The amount deposited (principal)
  • The user's fixed interest rate
  • Time elapsed since their last interaction

• Rebase logic ensures:

  • Early users benefit from higher interest.
  • Rewards scale with time, incentivizing longer deposits.
  • Interest rate only decreases over time — never increases.

🌉 Cross-Chain Bridging (via Chainlink CCIP)

• This project integrates Chainlink CCIP to bridge rebase tokens cross-chain.
• When bridging:
  • A user’s interest rate travels with them and remains fixed.
  • Accrued interest during bridging is not earned unless bridged back manually.
  • Bridging to L2 preserves rewards but interest doesn't accrue during the bridging period.

Key Bridging Rules:

• 🔄 Only deposit/withdraw on L1.
• ⛓️ Tokens can be bridged to L2, but:
  • Interest does not accrue while on L2.
  • Accrued interest must be bridged manually back to the destination chain.
  • Early bridgers enjoy better rates, rewarding early cross-chain adoption.

✍️ Technical Highlights

• Rebase is handled via a custom ERC20 extension.
• mintAccruedInterest() is called on every user interaction to sync balances.
• Uses per-user interest rate tracking to avoid global recalculations.
• Interest is calculated using: principleBalance * (1 + interestRate * timeElapsed)

🧠 Notes

• 🏦 Assumes rewards are pre-funded into the contract.
• 📉 Interest rate decreases discretely over time.
• 🧊 The interest rate at deposit/bridge time freezes per user.
• 🌐 Users can only deposit/withdraw on L1.
• 💤 No interest is earned while tokens are in transit (bridging).
• 🔁 Bridged users must manually bridge interest accrued back to their destination chain.

📌 Use Cases

• Cross-chain lending protocols
• DeFi vaults with time-based reward mechanics
• Protocols that reward early adopters
• Gamified DeFi products with dynamic interest scaling

🧪 Code Quality

• ✅ 100% test coverage using Foundry’s forge coverage
• 🔒 Covered all edge cases, rebase math, and bridging logic
• 🧬 Built with security-first testing: fuzzing, stateful testing, and custom scenarios

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👨‍💻 Built as part of the Cyfrin Updraft course
🔥 Proud to say this is my most badass project yet
📈 Learning, building & breaking smart contracts one commit at a time
🌍 Big things are coming — ZK, Optimism, and beyond!