Secure Sender/Receiver + MITM Proxy

A simple educational project for learning about network security, encryption, and how data can be intercepted.

⚠️ Important: This is for learning only. Only use it on networks you own or have permission to test.

What is This Project?

This project has 3 programs:

1. Sender - A program to encrypt and send files
2. Receiver - A program to receive and decrypt files
3. MITM Proxy - A program that sits between sender and receiver to intercept data

Setup (Easy Steps)

1. Install Python

Download Python 3.8+ from python.org

2. Install Dependencies

Open command line and run:

python -m venv .venv
.venv\Scripts\activate          # Windows
source .venv/bin/activate       # Mac/Linux

pip install -r requirements.txt

3. Run the Programs (3 windows)

Window 1 - Start Receiver:

python receiver.py

Then click "Start Server"

Window 2 - Start MITM Proxy:

python mitm.py 127.0.0.1

Choose option 1 (passive mode)

Window 3 - Start Sender:

python sender.py

• Enter IP: 127.0.0.1
• Click Connect
• Choose encryption (AES is best)
• Send something!

How It Works

Sender → MITM Proxy → Receiver
(encrypt)  (intercept)  (decrypt)

• Sender encrypts your data
• MITM reads it without decryption (passive) or swaps it (active)
• Receiver decrypts and saves it

What You Can Send

• Text - Messages and chat
• Images - PNG, JPG files
• Audio Files - WAV, MP3
• Microphone - Record and send live audio

Encryption Options

Type	Security	Use?
AES	Strong ✅	Yes, it's real encryption
SDES	Weak ⚠️	Only to learn how it works
TEA	Weak ⚠️	Only to learn how it works

Files Created When Running

• received_files/ - Decrypted files from receiver
• mitm_captured/ - Files captured by MITM

Troubleshooting

"Connection refused"

• Make sure receiver starts first
• Make sure MITM starts second
• Make sure sender connects to correct IP

PyAudio won't install (Windows)

• Download wheel from: https://www.lfd.uci.edu/~gohlke/pythonlibs/#pyaudio
• Save it in project folder
• Run: pip install PyAudio‑0.2.14‑cp311‑cp311‑win_amd64.whl
• (Replace 311 with your Python version)

"No module Tkinter"

# Ubuntu/Debian
sudo apt-get install python3-tk

# Fedora
sudo dnf install python3-tkinter

Example: Send a Message

1. Start receiver → click "Start Server"
2. Start MITM → choose 1
3. Start sender → enter 127.0.0.1 → click Connect
4. In sender, click "Send Text"
5. Type your message → click Send
6. Check receiver - you'll see the decrypted message!
7. Check MITM folder - you'll see captured data

Understanding the Code

sender.py

• Creates a GUI window
• Lets you pick encryption type (AES/SDES/TEA)
• Encrypts your data
• Sends it through MITM to receiver

receiver.py

• Creates a GUI window
• Listens for connections
• Receives encrypted data
• Decrypts it
• Saves files to received_files/

mitm.py

• Runs a proxy server
• Listens on port 6000 (sender connects here)
• Connects to receiver on port 5000
• Can read encrypted data (without key)
• Can replace audio (active mode)

Network Ports

• Port 6000 - Where sender connects to MITM
• Port 5000 - Where MITM connects to receiver

Security Notes

⚠️ Important:

• SDES and TEA are NOT secure - only for learning
• AES is real encryption - safe to use
• This project sends keys in plain text (so MITM can intercept)
• Real systems would use better security

What You'll Learn

• How encryption works
• How to intercept network traffic
• How to decrypt data (if you have the key)
• Network programming basics
• Python GUI programming
• Client-server architecture

File Info

• sender.py - ~400 lines
• receiver.py - ~450 lines
• mitm.py - ~500 lines
• Total: ~1,350 lines of Python code

Questions?

Check the code comments - they explain what each part does.

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That's it! Now you can see how network security works.

Remember: Only use this on your own computer or networks you have permission to test.