Hashing and Message Authentication

This project is a functional implementation of Authenticated Encryption based on the logic from the Cryptography and Network Security curriculum. It demonstrates how to combine Hashing, Secret Salting, and Symmetric Encryption to ensure data Confidentiality, Integrity, and Authenticity.

🚀 Features

• Logic: Implements the $E(K, [M || H(M || S)])$ pipeline.
• Cybersecurity Dashboard: A clean, terminal-style web interface built with Flask.
• Real-time Process Logs: Displays the step-by-step mathematical transformations (Hashing -> Concatenation -> Encryption).
• Tamper Detection: Automatically detects if a single bit of the ciphertext has been altered and triggers a security alert.

🛠 How it Works

1. Authentication: The message ($M$) is concatenated with a shared secret ($S$) and hashed ($H$) using SHA-256.
2. Encapsulation: The resulting hash is appended to the original plaintext message.
3. Confidentiality: The entire package is encrypted using AES-128 (CBC Mode) with a symmetric key ($K$).
4. Verification: The receiver decrypts the package, re-calculates the hash using the shared secret, and compares it to the received hash to verify integrity.

💻 Tech Stack

• Language: Python 3.12
• Web Framework: Flask
• Cryptography: cryptography (Python library)
• Styling: Modern CSS (Neon-Green Terminal Theme)

🔧 Installation & Local Setup

1. Clone the repository:

   git clone [https://github.com/Vickiegatheru/Computer-Network-Security.git](https://github.com/Vickiegatheru/Computer-Network-Security.git)
   cd Computer-Network-Security

2. Create and activate a virtual environment:

   python -m venv venv
   .\venv\bin\Activate.ps1  # Windows PowerShell

3. Install dependencies:

   pip install -r requirements.txt

4. Run the application:

   python app.py

5. Access the app: Open http://127.0.0.1:5000 in your browser.

🧪 Testing Integrity

To test the "Message Authentication" part of the project:

1. Encrypt a message to get the ciphertext.
2. Paste the ciphertext into the Receiver box.
3. Change one character in the ciphertext string.
4. Click "Execute Decrypt." The system will display a "TAMPERED / INVALID" security alert.

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Created as part of the Computer Network Security coursework.