canvas-website/docs/BLOCKCHAIN_IMPLEMENTATION_SUMMARY.md

# Blockchain Integration Implementation Summary

## Completed Components

### 1. Core Blockchain Signing Module ✅
- **File**: `src/lib/auth/cryptoBlockchain.ts`
- EIP-712 structured data signing
- Transaction authorization message creation
- Signature formatting utilities
- Key pair retrieval for signing

### 2. Ethereum Integration ✅
- **File**: `src/lib/blockchain/ethereum.ts`
- Wallet connection (MetaMask, etc.)
- Transaction building and submission
- Chain management (mainnet, sepolia, goerli)
- Proxy contract interaction utilities

### 3. Account Linking Service ✅
- **File**: `src/lib/auth/blockchainLinking.ts`
- Links Web Crypto accounts with Ethereum addresses
- Stores linked account mappings in localStorage
- Account verification utilities

### 4. Wallet Integration ✅
- **File**: `src/lib/blockchain/walletIntegration.ts`
- Proxy contract deployment preparation
- Public key coordinate extraction (P-256)
- Factory contract interaction

### 5. Key Storage ✅
- **File**: `src/lib/auth/keyStorage.ts`
- In-memory key pair storage (session-based)
- Placeholder for persistent storage implementation
- Key pair retrieval utilities

### 6. Smart Contracts ✅
- **File**: `contracts/WebCryptoProxy.sol`
  - Minimal proxy contract for each user
  - Stores P-256 public key
  - Transaction execution with signature verification
  - Replay protection via nonces
  - Deadline enforcement
- **File**: `contracts/WebCryptoProxyFactory.sol`
  - Factory for deploying proxy contracts
  - Deterministic proxy addresses

### 7. React Context ✅
- **File**: `src/context/BlockchainContext.tsx`
- Blockchain state management
- Wallet connection state
- Linked account management
- Event listeners for wallet changes

### 8. UI Components ✅
- **File**: `src/components/auth/BlockchainLink.tsx`
  - Link Web Crypto account with Ethereum wallet
  - Connection status display
- **File**: `src/components/blockchain/WalletStatus.tsx`
  - Display wallet connection status
  - Show linked account information
- **File**: `src/components/blockchain/TransactionBuilder.tsx`
  - Build and authorize transactions
  - Web Crypto API signing integration

### 9. Documentation ✅
- **File**: `docs/BLOCKCHAIN_INTEGRATION.md`
  - Complete integration guide
  - Architecture overview
  - Usage instructions
  - Security considerations

## Dependencies Added

- `viem` - Ethereum interaction library
- `@noble/curves` - Cryptographic utilities (installed but not yet used for P-256 verification)

## Integration Points

### Updated Files
- `src/lib/auth/cryptoAuthService.ts` - Now stores key pairs during registration
- `src/lib/auth/crypto.ts` - Extended with blockchain utilities

## Known Limitations & TODOs

### Critical TODOs

1. **P-256 Signature Verification in Smart Contract**
   - The `verifyP256Signature` function in `WebCryptoProxy.sol` is a placeholder
   - Needs implementation using a P-256 verification library or precompile
   - Options:
     - Use `@noble/curves` compiled to Solidity
     - Import a P-256 verification library
     - Use a precompile (if available on target chain)

2. **Persistent Key Storage**
   - Currently uses in-memory storage (lost on page refresh)
   - Need to implement Web Crypto API's persistent key storage with IndexedDB
   - See `src/lib/auth/keyStorage.ts` for TODO

3. **Nonce Management**
   - Currently uses timestamp-based nonces
   - Should query nonce from contract state
   - Add nonce tracking utilities

4. **Proxy Contract Deployment**
   - Factory address needs to be configured per chain
   - Add deployment utilities
   - Add proxy address lookup

### Nice-to-Have Features

- [ ] Support for multiple chains
- [ ] Transaction history tracking
- [ ] Gas estimation and optimization
- [ ] Error handling and retry logic
- [ ] Gnosis Safe multi-sig wallet support
- [ ] Transaction status monitoring
- [ ] Batch transaction support

## Usage Example

```typescript
// 1. Connect wallet
const { connect, wallet } = useBlockchain();
await connect();

// 2. Link accounts
const { linkWebCryptoAccount } = useBlockchain();
await linkWebCryptoAccount(username);

// 3. Build and sign transaction
const authorization = {
  to: '0x...',
  value: '0',
  data: '0x...',
  nonce: Date.now(),
  deadline: Math.floor(Date.now() / 1000) + 3600,
};

const signed = await signTransactionAuthorization(
  privateKey,
  authorization,
  domain
);
```

## Testing Checklist

- [ ] Wallet connection (MetaMask)
- [ ] Account linking flow
- [ ] Transaction signing with Web Crypto API
- [ ] Proxy contract deployment (once factory is deployed)
- [ ] Transaction execution through proxy
- [ ] Replay protection (nonce checking)
- [ ] Deadline enforcement
- [ ] Error handling

## Next Steps

1. Deploy `WebCryptoProxyFactory.sol` to a testnet
2. Update factory address in `walletIntegration.ts`
3. Implement P-256 signature verification in smart contract
4. Test end-to-end transaction flow
5. Implement persistent key storage
6. Add comprehensive error handling
7. Add transaction monitoring

## Security Notes

- Private keys are stored in memory (session-based) - implement persistent storage for production
- P-256 signature verification must be properly implemented before production use
- Nonce management should use contract state, not timestamps
- Add rate limiting and gas limits to prevent abuse
- Implement proper error handling to prevent information leakage