CIA/e-voting-system/.claude/BLOCKCHAIN_QUICK_START.md

Elections Blockchain - Quick Start

What's New

Elections are now stored immutably on the blockchain with cryptographic security.

Files Added/Modified

New Files:

• backend/blockchain_elections.py - Core blockchain implementation
• backend/init_blockchain.py - Blockchain initialization on startup
• test_blockchain_election.py - Test script to verify integration
• BLOCKCHAIN_ELECTION_INTEGRATION.md - Full technical documentation

Modified Files:

• backend/services.py - Added ElectionService.create_election() with blockchain recording
• backend/main.py - Added blockchain initialization on startup

How It Works

1. Elections Created in Database

# Via API or database init scripts
INSERT INTO elections (name, description, start_date, end_date, ...)
VALUES ('Election Présidentielle 2025', 'Vote pour la présidence', ...)

2. Automatically Recorded to Blockchain

When backend starts or election is created:

• Election data is read from database
• SHA-256 hash of candidates list is computed
• Block is created with previous block's hash (chain integrity)
• Block is signed with RSA-PSS signature
• Block is added to immutable chain

3. Can Be Verified On-Demand

# Check entire blockchain
curl http://localhost:8000/api/elections/blockchain

# Verify specific election
curl http://localhost:8000/api/elections/1/blockchain-verify

Security Features

✓ Hash Chain Integrity

Each block references the hash of the previous block, creating an unbreakable chain. If any block is modified, the chain is broken.

✓ Candidate Verification

Each election includes a SHA-256 hash of all candidates at creation time. Candidates cannot be added/removed/modified without breaking the hash.

✓ RSA-PSS Signatures

Each block is signed for authentication. Signature validation ensures block wasn't created by an attacker.

✓ Tamper Detection

On every verification, the blockchain checks:

• Block hash matches its data
• Hash chain is unbroken
• Signature is valid

If any check fails, tampering is detected.

Testing

Quick Test

# Wait for backend to initialize (~30 seconds after start)
sleep 30

# Run test script
python3 test_blockchain_election.py

# Should output:
# ✓ All tests passed! Elections blockchain integration working correctly.

Manual Testing

# 1. Get all elections in blockchain
curl http://localhost:8000/api/elections/blockchain | jq '.blocks'

# 2. Verify election 1
curl http://localhost:8000/api/elections/1/blockchain-verify | jq '.'

# 3. Check active elections (for comparison)
curl http://localhost:8000/api/elections/active | jq '.'

# 4. Debug all elections with time info
curl http://localhost:8000/api/elections/debug/all | jq '.elections'

How to View Blockchain

Via API

curl http://localhost:8000/api/elections/blockchain

Returns JSON with all blocks:

{
  "blocks": [
    {
      "index": 0,
      "election_id": 1,
      "election_name": "Election Présidentielle 2025",
      "candidates_count": 4,
      "block_hash": "7f3e9c2b...",
      "signature": "8a2e1f3d...",
      ...
    }
  ],
  "verification": {
    "chain_valid": true,
    "total_blocks": 1
  }
}

Via Frontend (Next Phase)

The blockchain visualization component exists at frontend/components/blockchain-visualizer.tsx and can be integrated into a dashboard page showing:

• Block explorer with expandable details
• Hash verification status
• Signature validation
• Chain integrity indicators
• Copy-to-clipboard for hashes

Troubleshooting

No Blocks in Blockchain

# Check database has elections
curl http://localhost:8000/api/elections/debug/all

# If elections exist but blockchain empty:
1. Restart backend: docker compose restart backend
2. Wait 30 seconds for initialization
3. Check logs: docker compose logs backend | grep blockchain

Verification Fails

curl http://localhost:8000/api/elections/1/blockchain-verify

# If "verified": false, check:
# - "hash_valid": false → block data modified
# - "chain_valid": false → previous block modified
# - "signature_valid": false → signature missing or invalid

Backend Won't Start

# Check logs
docker compose logs backend

# Look for:
# - Blockchain initialization errors
# - Database connection issues
# - Import errors (missing blockchain_elections module)

# Restart if needed
docker compose down
docker compose up -d backend

API Endpoints

Method	Endpoint	Purpose
GET	/api/elections/blockchain	Get complete elections blockchain
GET	/api/elections/{id}/blockchain-verify	Verify election integrity
GET	/api/elections/active	Get active elections (comparison)
GET	/api/elections/debug/all	Debug all elections with time info

Files Reference

Core Blockchain

backend/blockchain_elections.py (270 lines)

• ElectionBlock - Immutable block dataclass
• ElectionsBlockchain - Blockchain manager
• record_election_to_blockchain() - Public API to record election
• verify_election_in_blockchain() - Public API to verify election
• get_elections_blockchain_data() - Public API to get blockchain data

Election Service

backend/services.py - ElectionService class

• create_election() - NEW: Creates election and records to blockchain
• get_active_election() - Get currently active election
• get_election() - Get election by ID

Initialization

backend/init_blockchain.py (79 lines)

• initialize_elections_blockchain() - Called on startup
• Syncs existing database elections to blockchain
• Verifies blockchain integrity

backend/main.py - FastAPI app

• Calls initialize_elections_blockchain() on startup

Routes

backend/routes/elections.py - Election endpoints

• GET /api/elections/blockchain - Returns elections blockchain data
• GET /api/elections/{id}/blockchain-verify - Returns verification report

Next Steps

1. Test the integration: Run python3 test_blockchain_election.py
2. View the blockchain: Access /api/elections/blockchain endpoint
3. Integrate with UI: Create a page to display blockchain (component exists at frontend/components/blockchain-visualizer.tsx)
4. Extend blockchain: Add voter registration and vote records to blockchain for full audit trail

Technical Details

See BLOCKCHAIN_ELECTION_INTEGRATION.md for:

• Detailed architecture explanation
• Hash chain security model
• Candidate verification mechanism
• Tamper detection process
• Database initialization flow
• Error handling and logging