🔐 A Two-Party Secure Computation Protocol using Homomorphic Encryption

✨ Overview

This project implements a two-party secure computation protocol using Homomorphic Encryption (HE), enabling privacy-preserving arithmetic operations on encrypted data. The protocol follows the client-server model where:

• The Client encrypts input data and selects an operation.

• The Server performs the desired operation without decrypting the data.

• The encrypted result is sent back to the client.

Built with TenSEAL, the protocol supports multiple HE schemes (BFV, Paillier, CKKS) for integer and floating-point operations, featuring a user-friendly Tkinter GUI.

🎯 Key Features

Schemes	Supported Operations
CKKS	Addition, Subtraction, Multiplication, Division, Square, Cube, Percentage, Dot product, Matrix Multiplication
BFV	Addition, Subtraction, Multiplication, Square, Cube, Dot product, Matrix Multiplication
Paillier	Addition, Subtraction, Private set membership

🎯 Technical Highlights:

• 🚀 Multi-scheme Support:

  BFV: Used only for integer arithmetic.
  
  Paillier: Used for additive homomorphic encryption.
  
  CKKS: Used for  real or floating-point arithmetic.
  

• 🔒 Secure Socket Communication:

  Encrypted data transmission via socket programming.
  
  The server performs the computation on the encrypted data.
  

• 🎨 Graphical User Interface:

  Intuitive Tkinter-based client interface.
  
  Real-time encrypted result display.
  

• ⚙️ Cross-platform Compatibility:

  Tested on Windows and Linux environments.
  

⚙️ Installation Guide

🪟 Windows Setup

Prerequisites

Install Python latest version

-> https://www.python.org/downloads/

Install pip

• If pip is missing, do this:

• Download get-pip.py from:

  https://bootstrap.pypa.io/get-pip.py
  
  (Right-click → Save )
  

• Open the Command Prompt where the file is saved.

  Run this:
  
  python get-pip.py
  
  Upgrade pip:
  
  python -m pip install --upgrade pip
  

Install Dependencies

• Install numpy

  pip install numpy
  

• Install TenSEAL

  pip install tenseal
  

ℹ️ Note: socket, pickle, and tkinter are built-in with Python on Windows, so no need for separate installation.

🐧 Linux Environment

Prerequisites

Install Python latest version:

sudo apt update
sudo apt install python3

Install pip

sudo apt update 
sudo apt install python3-pip

Install Dependencies

Install Numpy and TenSEAL

sudo apt update
pip3 install numpy
pip3 install tenseal

Install Tkinter (if not pre-installed)

sudo apt update
sudo apt-get install python3-tk

Technologies Used 🚀

• Python 3
• TenSEAL✅ (Homomorphic Encryption Library)
• Socket Programming✅
• Tkinter✅ (GUI for Client)
• Pickle✅ (Serialization)

🚀 Usage

• 1. Start the Server

     python3 server.py
     

  Server runs on 127.0.0.1:12345 by default

• 2. Launch the Client GUI

     python3 client.py
     

• 3. Perform Operations:

     • Enter the required data

     • Select the encryption scheme

     • Select the arithmatic operation (buttons auto-adjust based on scheme)

     • The final result is decrypted and it is shown in the output box of the GUI

🧠 Supported Operations

Operation	BFV	Paillier	CKKS
Addition	✅	✅	✅
Subtraction	✅	✅	✅
Multiplication	✅	❌	✅
Division	❌	❌	✅
Square / Cube	✅	❌	✅
Percentage	❌	❌	✅
Dot Product	✅	❌	✅
Private Set Membership	✅	✅	❌
Matrix multiplication	✅	❌	✅

📁 File Structure

homomorphic-calculator/
├── client.py            # GUI client application
├── server.py            # HE computation server
├── README.md            # This documentation
└── requirements.txt     # Dependencies

🛠️ Troubleshooting

Issue	Solution
ImportError: No module named 'tenseal'	Run pip install tenseal
Socket connection errors	Verify the server is running before starting the client
Paillier division attempts	Use the CKKS scheme for division operations

🧪 Research Applications

Ideal for:

• Privacy-preserving cloud computations

• Secure medical data analysis

• Confidential financial modelling