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🔐 Playfair Cipher Implementation (Python)

A complete and educational Python implementation of the Playfair Cipher encryption algorithm. This project demonstrates matrix generation, digraph processing, and classical substitution encryption & decryption using structured logic.

It is created as a learning and academic project to understand how classical digraph-based cryptography works internally, not as a production-ready security system.

🧱 Project Structure

playfair-cipher-python/
│
├── app.py            # Playfair cipher implementation (CLI based)
├── LICENSE           # Project license
└── README.md         # Project documentation

✨ Features

🔑 Key Matrix Generation

  • Generates a 5×5 Playfair matrix using a keyword
  • Merges J into I (standard academic convention)
  • Fills remaining alphabet in correct order
  • Automatically removes duplicate letters

🔒 Encryption

  • Applies Playfair rules:
    • Same row → shift right
    • Same column → shift down
    • Rectangle rule → swap columns
  • Produces correctly formatted ciphertext

🔓 Decryption

  • Reverses Playfair encryption logic:
    • Same row → shift right
    • Same column → shift down
    • Rectangle rule → swap columns
  • Outputs decrypted plaintext (including padding if present)

🧮 Educational Focus

  • Clean and readable logic
  • Modular and structured functions
  • Ideal for beginners in cryptography
  • No external dependencies

🛠 Technologies Used

Technology Role
Python 3 Core programming language
String Module Alphabet handling
Matrix Logic 5×5 key table implementation

📌 Purpose of This Project

This project is built to:

  • Understand classical Playfair cryptography
  • Learn digraph substitution techniques
  • Explore historical encryption algorithms
  • Study matrix-based encryption systems

⚠️ This project is intended strictly for learning and demonstration purposes.

▶️ How to Run

1️⃣ Clone the repository

git clone https://github.com/ShakalBhau0001/playfair-cipher-python.git

2️⃣ Navigate to the project folder

cd playfair-cipher-python

3️⃣ Run the program

python app.py

4️⃣ Follow the prompts

  • Enter a keyword
  • Choose direction:
    • E → Encrypt
    • D → Decrypt
  • Enter your message
  • View the result

🔎 Example

Encryption :

Enter keyword: MONARCHY

Encrypt or Decrypt (E/D): E
Enter message: INSTRUMENTS

Encrypted: GATLMZCLRQXA

Decryption :

Enter keyword: MONARCHY

Encrypt or Decrypt (E/D): D
Enter message: GATLMZCLRQXA

Decrypted: INSTRUMENTSX

(Note: Final padding letter may appear during decryption.)

⚠️ Limitations

  • Not secure for real-world use
  • Classical cipher (easily breakable)
  • Does not automatically remove padding after decryption
  • CLI-based interaction only

🌟 Future Improvements

  • Add automatic padding removal
  • Add configurable I/J handling
  • Add input validation for shift values
  • Add file encryption support
  • Create GUI version
  • Combine into a classical cryptography toolkit

⚠️ Disclaimer

This implementation is created for educational and learning purposes only. The Playfair Cipher is historically significant but cryptographically insecure and must not be used to protect real-world sensitive data.

🪪 Author

Shakal Bhau

GitHub: ShakalBhau0001