This repository contains the smart contracts for stEDU, a liquid staking token for EDUCHAIN that uses an index-based reward system with a per-deposit unbonding period.

• Fixed Balance, Index-Accruing: Balances never rebase; instead, the index (share-price) increases when rewards are pushed
• Per-deposit Unbonding Period: Each individual stake is locked for 7 days to prevent front-running and flash loan attacks
• ERC4626 Compliant: Implements the ERC4626 Tokenized Vault Standard for better composability
• Surplus Sync Mechanism: sync() function lets anyone fold accidental WEDU donations into the index

The contracts have been successfully deployed to the opencampus network:

Testnet:

• stEDU: 0x0324da014FC0911502766CAaa740D861634b82b9
• wstEDU: 0xE950c63D61510c2F1867378D0b6D9C3eFA574921

Mainnet:

• stEDU: 0x23642bf3c582B6eEcC0bfa9d8469f43813721b06
• wstEDU: 0x062409E8F205A278858E9ae43C9E3ea59298f968

1. Users stake native EDU and receive stEDU tokens
2. Each deposit is timestamped and tracked individually
3. When rewards are added, the global index increases
4. The value of each stEDU token grows over time as rewards accumulate
5. Users can only unstake after the unbonding period (7 days) has passed for each deposit

• Unbonding Period: Prevents front-running attacks and flash loan exploits
• ReentrancyGuard: Protects against reentrancy attacks during unstaking
• Pausable: Allows emergency pausing of all operations
• FIFO Unstaking: Enforces first-in-first-out unstaking order based on deposit timestamps

sequenceDiagram
    participant User as User
    participant stEDU as stEDU Contract
    participant WEDU as WEDU Token
    participant Owner as Protocol Owner

    User->>stEDU: stake() with EDU
    stEDU->>WEDU: deposit() (wrap EDU to WEDU)
    stEDU-->>User: mint stEDU tokens (EDU * 1e18 / index)
    Note over stEDU: Record deposit timestamp

    Owner->>stEDU: depositRewards() with EDU
    stEDU->>WEDU: deposit() (wrap EDU to WEDU)
    Note over stEDU: index += (rewards * 1e18) / totalSupply()

    Note over User: Wait 7 days (unbonding period)
    User->>stEDU: unstake(shares)
    stEDU->>WEDU: withdraw(eduAmount)
    stEDU-->>User: transfer EDU (shares * index / 1e18)

The index mechanism works as follows:

1. Initially, the index starts at 1e18 (1.0 in decimal)
2. When rewards are added, the index increases by: (rewardAmount * 1e18) / totalSupply
3. To convert stEDU to EDU: stEDUAmount * index / 1e18
4. To convert EDU to stEDU: eduAmount * 1e18 / index

This mechanism ensures that:

• All stakers receive rewards proportional to their stake
• The value of stEDU increases over time without changing balances
• Rewards are automatically compounded

1. Compile:

   npx hardhat compile

2. Run tests:

   # Run all tests
   npm test
   
   # Run specific test suites
   npm run test:basic
   npm run test:staking
   npm run test:rewards
   npm run test:attack
   npm run test:integration

3. Deploy stEDU:

   // Deploy WEDU first (or use existing WEDU contract)
   const WEDU = await ethers.getContractFactory("WEDU");
   const wedu = await WEDU.deploy();
   
   // Deploy stEDU with WEDU address
   const StEDU = await ethers.getContractFactory("stEDU");
   const stEDU = await StEDU.deploy(await wedu.getAddress());

4. Interact with the contract:

   // Stake EDU
   await stEDU.stake({ value: ethers.parseEther("10") });
   
   // Check stEDU balance
   const stEDUBalance = await stEDU.balanceOf(myAddress);
   
   // Check EDU value
   const eduValue = await stEDU.stEDUToEDU(stEDUBalance);
   
   // Deposit rewards (owner only)
   await stEDU.depositRewards({ value: ethers.parseEther("1") });