🗳️ Multi-Party Voting System – Hack This Future Winner 🏆

A secure, decentralized, and privacy-preserving voting platform built using Shamir's Secret Sharing, Homomorphic Encryption, and Web3 Blockchain.

Built during Hack This Future 2025, this project aims to modernize and secure electronic voting using cutting-edge cryptography and distributed systems. The ppt file is attached for reference...

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🚀 Architecture Overview

This project consists of 3 frontend applications and a central Python backend:

📱 Frontend Apps

1. User App

   • Cast votes securely using one-time blind signatures
   • Votes are homomorphically encrypted and directly stored on-chain
   • Users remain anonymous — even the backend can't see who voted for whom

2. Admin App

   • Generates cryptographic keypairs (public/private) for each election
   • Splits the private key using Shamir's Secret Sharing
   • Securely distributes shares to 5 Authority instances

3. Authority App (×5 instances)

   • Each runs independently and holds one share of the private key
   • At least 3 out of 5 instances must collaborate to reconstruct the private key
   • The reconstructed key is used only once, to decrypt the homomorphically tallied result

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🧠 Backend

• Built in Python, acts as the main coordinator
• Handles:
  • Verifying and accepting votes
  • Encrypting them using Homomorphic Encryption
  • Storing encrypted votes directly on the blockchain
  • Tallying votes homomorphically without decryption
• At no point does the backend know who voted for whom

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🔐 Key Features

• ✅ End-to-end voter anonymity
• ✅ Blind signatures prevent vote duplication
• ✅ One-hot encoded ballots support secure homomorphic addition
• ✅ Votes are immutable and stored on-chain — no tampering possible
• ✅ Private key reconstruction requires quorum (3 of 5 authorities)
• ✅ Backend tallies encrypted votes, not raw ones

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🛠️ Tech Stack

Layer	Tech
Frontend	Next.js (React), Web3.js
Backend	Python (FastAPI + PyCrypto)
Blockchain	Ethereum, Solidity, Web3.py
Crypto	Shamir’s Secret Sharing, Paillier Homomorphic Encryption, One-Hot Encoding

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⚙️ How It Works

graph TD
A[Admin Frontend] -->|Generate Key| B[Private Key]
B -->|Split with SSS| C1[Authority #1]
B --> C2[Authority #2]
B --> C3[Authority #3]
B --> C4[Authority #4]
B --> C5[Authority #5]
U[User Frontend] -->|Blind Sign & Encrypt| D[Blockchain Smart Contract]
D -->|Encrypted Vote Tally| E[Python Backend]
C1 -->|Share for Decryption| F[Key Reconstruction (3/5 quorum)]
F --> E

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