CIA/e-voting-system/POA_QUICK_REFERENCE.md

PoA Blockchain - Quick Reference Guide

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

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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

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Running the System

Start Everything

cd /home/sorti/projects/CIA/e-voting-system

# Start all services
docker-compose up -d

# Verify everything is running
docker-compose ps

Check Health

# 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

docker-compose down

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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

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Code Examples

Using BlockchainClient (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)

# 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'

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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)

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)

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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

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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

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Troubleshooting

Validator Not Responding

# Check if running
docker ps | grep validator-1

# Check logs
docker logs validator-1

# Restart
docker-compose restart validator-1

Vote Submission Fails

# 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

# 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

# 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"

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Configuration

Validator URLs (Default)

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:

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
    ]

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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

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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

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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

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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)

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Quick Commands

# 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

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For detailed information, see:

• PHASE_3_INTEGRATION.md - Complete integration guide
• IMPLEMENTATION_COMPLETE.md - PoA implementation details
• POA_ARCHITECTURE_PROPOSAL.md - Architecture decisions