# PoA Blockchain - Quick Reference Guide

**For**: Developers integrating with PoA blockchain
**Last Updated**: November 7, 2025
**Status**: ✅ Production Ready

---

## TL;DR - The Essentials

### What Is PoA?
Proof-of-Authority blockchain with 3 validators. Votes are immutably recorded across all validators.

### Key Facts
- **3 validators** reach consensus on each vote
- **Block created every 5 seconds** with 32 votes per block
- **6.4 votes/second** throughput
- **Can survive 1 validator failure** and still work
- **Fallback** to local blockchain if all validators down

### How Votes Flow
```
Frontend → Backend → BlockchainClient → [Validator-1, Validator-2, Validator-3]
                                                    ↓
                                         All 3 have identical blockchain
```

---

## Running the System

### Start Everything
```bash
cd /home/sorti/projects/CIA/e-voting-system

# Start all services
docker-compose up -d

# Verify everything is running
docker-compose ps
```

### Check Health
```bash
# Backend health
curl http://localhost:8000/health

# Validator health
curl http://localhost:8000/api/admin/validators/health

# Specific validator
curl http://localhost:8001/health
curl http://localhost:8002/health
curl http://localhost:8003/health
```

### Stop Everything
```bash
docker-compose down
```

---

## API Endpoints

### Vote Submission
**POST** `/api/votes/submit`
- Submit encrypted vote to PoA blockchain
- Returns `transaction_id` for tracking

### Check Vote Status
**GET** `/api/votes/transaction-status?transaction_id=tx-xxx&election_id=1`
- Returns: `pending` or `confirmed`
- Includes block info when confirmed

### Get Results
**GET** `/api/votes/results?election_id=1`
- Returns vote counts by candidate
- Includes blockchain verification status

### Verify Blockchain
**POST** `/api/votes/verify-blockchain`
- Checks if blockchain is valid and unmodified
- Returns: `valid` or `invalid`

### Monitor Validators
**GET** `/api/admin/validators/health`
- Shows health of all 3 validators
- Shows which are healthy/degraded/unreachable

---

## Code Examples

### Using BlockchainClient (Python)
```python
from backend.blockchain_client import BlockchainClient

# Create client
async with BlockchainClient() as client:
    # Submit vote
    result = await client.submit_vote(
        voter_id="voter123",
        election_id=1,
        encrypted_vote="base64_encoded_vote",
        transaction_id="tx-abc123"
    )

    # Check status
    status = await client.get_vote_confirmation_status(
        transaction_id="tx-abc123",
        election_id=1
    )

    # Get results
    results = await client.get_election_results(election_id=1)

    # Verify integrity
    is_valid = await client.verify_blockchain_integrity(election_id=1)
```

### API Request (cURL)
```bash
# 1. Get token
TOKEN=$(curl -X POST http://localhost:8000/api/auth/login \
  -H "Content-Type: application/json" \
  -d '{"email":"voter@test.com","password":"pass"}' \
  | jq -r '.access_token')

# 2. Submit vote
curl -X POST http://localhost:8000/api/votes/submit \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "election_id": 1,
    "candidate_id": 42,
    "encrypted_vote": "aGVsbG8gd29ybGQ="
  }' | jq '.transaction_id'

# 3. Check status
TX_ID=$(curl ... | jq -r '.transaction_id')
curl "http://localhost:8000/api/votes/transaction-status?transaction_id=$TX_ID&election_id=1" \
  -H "Authorization: Bearer $TOKEN" | jq '.status'
```

---

## How It Works Internally

### Vote Submission Flow
1. Frontend encrypts vote with ElGamal
2. Backend validates voter and election
3. **BlockchainClient** picks healthy validator
4. **JSON-RPC** sends `eth_sendTransaction` to validator
5. Validator adds vote to transaction pool
6. Every 5 seconds:
   - PoA round-robin picks designated validator
   - Creates block with 32 pending votes
   - Signs block with private key
   - Broadcasts to other 2 validators
7. Other validators verify and accept block
8. All 3 validators add identical block to chain

### Consensus Algorithm (PoA)
```python
next_block_index = len(blockchain)  # 1, 2, 3, ...
authorized_validators = ["validator-1", "validator-2", "validator-3"]
block_creator = authorized_validators[next_block_index % 3]

# Example:
# Block 1: 1 % 3 = 1 → validator-2 creates
# Block 2: 2 % 3 = 2 → validator-3 creates
# Block 3: 3 % 3 = 0 → validator-1 creates
# Block 4: 4 % 3 = 1 → validator-2 creates (repeats)
```

---

## Validator Ports

| Service | Port | Purpose |
|---------|------|---------|
| **Backend** | 8000 | FastAPI server |
| **Bootnode** | 8546 | Peer discovery |
| **Validator-1** | 8001 | RPC (vote submission) |
| **Validator-1 P2P** | 30303 | P2P networking |
| **Validator-2** | 8002 | RPC |
| **Validator-2 P2P** | 30304 | P2P networking |
| **Validator-3** | 8003 | RPC |
| **Validator-3 P2P** | 30305 | P2P networking |

---

## Files Modified in Phase 3

### New
- `backend/blockchain_client.py` - PoA client library
- `PHASE_3_INTEGRATION.md` - Full integration guide
- `POA_QUICK_REFERENCE.md` - This file

### Updated
- `backend/routes/votes.py` - Use PoA for submissions
- `backend/routes/admin.py` - Validator health checks
- `backend/main.py` - Initialize PoA client on startup

---

## Troubleshooting

### Validator Not Responding
```bash
# Check if running
docker ps | grep validator-1

# Check logs
docker logs validator-1

# Restart
docker-compose restart validator-1
```

### Vote Submission Fails
```bash
# Check validator health
curl http://localhost:8000/api/admin/validators/health

# If all down, check Docker
docker-compose ps

# Restart all validators
docker-compose restart validator-1 validator-2 validator-3
```

### Blockchain Out of Sync
```bash
# Check each validator's blockchain
curl http://localhost:8001/blockchain?election_id=1 | jq '.verification'
curl http://localhost:8002/blockchain?election_id=1 | jq '.verification'
curl http://localhost:8003/blockchain?election_id=1 | jq '.verification'

# They should show same block count and last hash
```

### How to View Logs
```bash
# All services
docker-compose logs -f

# Specific service
docker-compose logs -f backend
docker-compose logs -f validator-1
docker-compose logs -f bootnode

# With grep filter
docker logs validator-1 | grep -i "block\|error"
```

---

## Configuration

### Validator URLs (Default)
```python
DEFAULT_VALIDATORS = [
    ("validator-1", "http://localhost:8001"),
    ("validator-2", "http://localhost:8002"),
    ("validator-3", "http://localhost:8003"),
]
```

### Custom Validators
To use custom validator locations, modify `backend/blockchain_client.py`:
```python
class BlockchainClient:
    DEFAULT_VALIDATORS = [
        ValidatorNode(
            node_id="custom-1",
            rpc_url="http://custom-1.example.com:8001",
            p2p_url="http://custom-1.example.com:30303"
        ),
        # ... more validators
    ]
```

---

## Performance Tips

### For High Throughput
- Use 5+ validators (currently 3)
- Increase block size from 32 to 64+ votes
- Batch multiple votes together

### For Lower Latency
- Run validators on same network
- Reduce consensus timeout
- Use dedicated network interface

### For High Availability
- Distribute validators across regions
- Implement cross-region replication
- Add backup validators for failover

---

## Security Checklist

- [ ] Use HTTPS in production
- [ ] Enable authentication on all endpoints
- [ ] Set rate limits per IP/user
- [ ] Monitor validator health continuously
- [ ] Keep validator keys secure
- [ ] Backup database regularly
- [ ] Enable audit logging
- [ ] Verify blockchain integrity periodically

---

## Key Files to Know

```
backend/
├── blockchain_client.py    ← Communication with validators
├── blockchain.py           ← Local blockchain (fallback)
├── routes/
│   ├── votes.py           ← Vote submission endpoints
│   └── admin.py           ← Health monitoring endpoints
└── main.py                ← App initialization

validator/
└── validator.py           ← PoA consensus node

bootnode/
└── bootnode.py            ← Peer discovery service
```

---

## Phase 3 Summary

✅ **BlockchainClient** created for PoA communication
✅ **Vote endpoints** updated to use PoA validators
✅ **Health monitoring** added for operational visibility
✅ **Graceful fallback** to local blockchain if PoA unavailable
✅ **Production-ready** error handling and logging
✅ **Full backward compatibility** maintained

**Status**: Ready for production or Phase 4 (frontend enhancement)

---

## Quick Commands

```bash
# See all running services
docker-compose ps

# View backend logs
docker-compose logs -f backend

# Check validator health (JSON)
curl http://localhost:8000/api/admin/validators/health | jq

# Verify blockchain (specific election)
curl -X POST http://localhost:8000/api/votes/verify-blockchain \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"election_id": 1}' | jq

# Get vote results
curl http://localhost:8000/api/votes/results?election_id=1 \
  -H "Authorization: Bearer $TOKEN" | jq

# Restart validators
docker-compose restart validator-1 validator-2 validator-3

# View a specific validator's logs
docker logs validator-2 | tail -50
```

---

**For detailed information, see**:
- `PHASE_3_INTEGRATION.md` - Complete integration guide
- `IMPLEMENTATION_COMPLETE.md` - PoA implementation details
- `POA_ARCHITECTURE_PROPOSAL.md` - Architecture decisions