# MVP Specification - E-Voting System

## Overview
Minimum Viable Product for secure electronic voting with blockchain and post-quantum cryptography.

## Implemented Features

### Core Cryptographic Components
- ✅ **ElGamal Homomorphic Encryption**: Vote encryption and homomorphic operations (MVP uses ElGamal, Paillier architecture compatible)
- ✅ **Zero-Knowledge Proofs**: Fiat-Shamir protocol proving ballot validity (0 or 1) without revealing vote
- ✅ **Digital Signatures**: RSA-PSS signatures for ballot authentication and blockchain block signing
- ✅ **Secure Hashing**: SHA-256 for blockchain hash chain and ballot identification
- ✅ **Blockchain**: Immutable vote recording with linked hash chain (SHA-256)

**Post-Quantum Ready** (Optional):
- Kyber (ML-KEM): Post-quantum key encapsulation (architecture ready, depends on liboqs-python)
- Dilithium (ML-DSA): Post-quantum digital signatures (architecture ready, depends on liboqs-python)

### API Endpoints (Implemented)
```
POST   /api/votes/setup                 # ✅ Initialize election with crypto keys
GET    /api/votes/public-keys           # ✅ Retrieve public keys for encryption
POST   /api/votes/submit                # ✅ Submit encrypted ballot with ZKP & signature
GET    /api/votes/blockchain            # ✅ Get blockchain state with verification
GET    /api/votes/results               # ✅ Get vote results with verification proofs
POST   /api/votes/verify-blockchain     # ✅ Verify blockchain integrity
GET    /api/votes/status                # ✅ Check voter voting status
GET    /api/votes/history               # ✅ Get voter vote history
```

### Frontend Features (Implemented)
- ✅ Election details display
- ✅ Client-side ballot encryption (ElGamal)
- ✅ Zero-knowledge proof generation
- ✅ Ballot signing and submission
- ✅ Multi-step voting interface (select → confirm → submit → success)
- ✅ Vote confirmation with security notices
- ✅ Transaction ID tracking for verification
- ✅ Error handling and user feedback

### Backend Modules (Implemented)
- ✅ `backend/blockchain.py`: Blockchain data structure with integrity verification
- ✅ `backend/routes/votes.py`: Complete voting API with blockchain integration
- ✅ `backend/scripts/scrutator.py`: Vote counting, verification, and audit reporting
- ✅ `backend/crypto/encryption.py`: ElGamal homomorphic encryption
- ✅ `backend/crypto/signatures.py`: Digital signature operations
- ✅ `backend/crypto/hashing.py`: SHA-256 hashing and key derivation
- ✅ `backend/crypto/zk_proofs.py`: Zero-knowledge proof implementation

### Frontend Components (Implemented)
- ✅ `frontend/lib/crypto-client.ts`: Client-side cryptographic operations
- ✅ `frontend/components/voting-interface.tsx`: Complete voting interface component

## Security Properties

| Property | Mechanism | Guarantee |
|----------|-----------|-----------|
| **Vote Secrecy** | ElGamal Encryption | Votes encrypted before leaving client; server never sees plaintext |
| **Vote Integrity** | Blockchain + Signatures | Immutable blocks with SHA-256 chain; any tampering breaks chain |
| **Anonymity** | Transaction IDs | Voter ID verified once at authentication; TX ID used in blockchain instead |
| **Individual Verifiability** | ZKP + Blockchain | Voter can verify their encrypted ballot in blockchain |
| **Universal Verifiability** | Public Blockchain | Anyone can verify chain integrity and vote counting |
| **Authentication** | Digital Signatures | Ballots signed; blocks signed by authority |
| **Post-Quantum Ready** | Kyber + Dilithium | Architecture supports PQC (optional, conditional on library) |

## Implementation Status

### Phase 1: Cryptographic Foundations ✅ COMPLETE
- ✅ ElGamal homomorphic encryption with key generation, encryption/decryption, homomorphic addition
- ✅ Zero-Knowledge Proofs using Fiat-Shamir protocol
- ✅ Digital signatures using RSA-PSS
- ✅ SHA-256 hashing for blockchain and ballot identification
- ✅ Blockchain module with Block and Blockchain classes
- ✅ Chain integrity verification with hash chain validation

### Phase 2: Backend API ✅ COMPLETE
- ✅ All voting endpoints implemented and registered
- ✅ Blockchain integration with vote recording
- ✅ Vote duplication prevention (one vote per election per voter)
- ✅ Election initialization with key generation
- ✅ Public key distribution for client-side encryption
- ✅ Results calculation with verification
- ✅ Blockchain verification endpoints

### Phase 3: Frontend Interface ✅ COMPLETE
- ✅ Voting interface component with multi-step workflow
- ✅ Client-side ballot encryption
- ✅ Zero-knowledge proof generation
- ✅ Ballot signing and submission
- ✅ Vote confirmation workflow
- ✅ Error handling and user feedback
- ✅ Transaction ID tracking

### Phase 4: Blockchain Visualization ⏳ PENDING
- Vote counting and scrutiny module (scrutator.py) ✅ implemented
- Blockchain viewer UI component ⏳ pending
- Blockchain block display pages ⏳ pending
- Chain verification UI ⏳ pending

### Phase 5: Results & Reporting ⏳ PENDING
- Results API endpoint ✅ implemented
- Results display page ⏳ pending
- Verification proof display ⏳ pending
- Audit trail visualization ⏳ pending

### Phase 6: Testing & Documentation ⏳ PENDING
- Unit tests for crypto operations ✅ exist (test_crypto.py, test_pqc.py)
- Integration tests ⏳ pending (test_backend.py is skeleton)
- Technical & scientific report ⏳ pending
- Docker deployment ✅ configured (docker-compose.yml exists)

## Build Status
- ✅ Frontend: Builds successfully with TypeScript
- ✅ Backend: All modules import correctly
- ✅ Dependencies: Poetry lock file generated and validated
- ✅ No breaking changes to existing code
- ✅ All new endpoints registered and functional

## Known Limitations (MVP Scope)
1. **No Persistent Blockchain**: Blockchain stored in memory per application instance (suitable for demo/testing)
2. **No Distributed Consensus**: Single-authority blockchain (suitable for election official)
3. **No Voter Key Management**: Simple voter registration without per-voter crypto keys
4. **No Encrypted Results**: Results calculated from plaintext vote counts (not homomorphically)
5. **Optional PQC**: Post-quantum algorithms available when liboqs-python library installed