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🔐 Caesar Cipher Cryptanalysis (Python)

An educational Python implementation of Caesar Cipher brute-force cryptanalysis. This project demonstrates how classical encryption can be broken using exhaustive search and simple English frequency scoring.

It is designed as a learning and academic project to understand why classical ciphers are insecure and how attackers analyze encrypted text — not as a real-world attack tool.

🧱 Project Structure

caesar-cipher-cryptanalysis-python/
│
├── app.py            # Brute-force cryptanalysis tool (CLI based)
├── LICENSE           # Project license
└── README.md         # Project documentation

✨ Features

🔍 Full Brute-Force Search

  • Tests all 25 possible Caesar shifts
  • Supports both:
    • L → Left shift
    • R → Right shift
  • Automatically evaluates all possible plaintext candidates

🧠 English Scoring System

  • Uses frequency-based heuristic scoring
  • Prioritizes common English letters (E, T, A, O, I, N, etc.)
  • Rewards spaces and readable structure
  • Ranks outputs automatically

📊 Auto-Ranked Results

  • Sorts plaintext candidates by likelihood
  • Displays top possible decryptions
  • Removes mirror duplicate results

🧮 Educational Focus

  • Demonstrates cryptanalysis workflow
  • Shows weakness of classical substitution ciphers
  • Reinforces modular arithmetic concepts
  • Clean and modular Python implementation

🛠 Technologies Used

Technology Role
Python 3 Core programming language
ord() / chr() Character-to-ASCII conversion
Modular Arithmetic Circular alphabet shifting (% 26)
Heuristic Scoring English-likeness evaluation

📌 Purpose of This Project

This project is built to:

  • Understand Caesar Cipher weaknesses
  • Learn brute-force cryptanalysis
  • Explore basic frequency analysis concepts
  • Simulate attacker perspective ethically
  • Strengthen Python logic and modular design skills

⚠️ This project is intended strictly for educational and cybersecurity learning purposes.

▶️ How to Run

1️⃣ Clone the repository

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

2️⃣ Navigate to the project folder

cd caesar-cipher-cryptanalysis-python

3️⃣ Run the program

python app.py

4️⃣ Enter Cipher Text

  • Provide any Caesar-encrypted message
  • View automatically ranked possible plaintexts
  • Analyze shift and direction results

🔎 Example

Enter Caesar cipher text: QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD

Top Possible Plaintexts:

Shift  3 | Dir R | Score  72 | THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
Shift 23 | Dir L | Score  72 | THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
...

⚠️ Limitations

  • English scoring is heuristic-based (not statistical-grade)
  • Works only for Caesar Cipher
  • Not designed for real-world encrypted systems
  • CLI-based interaction only

🌟 Future Improvements

  • Implement full frequency distribution comparison
  • Add dictionary-based validation
  • Support file input
  • Add support for other classical ciphers
  • Convert into reusable Python module
  • Build GUI version

⚠️ Disclaimer

This project is created for educational and cybersecurity learning purposes only. It demonstrates the inherent weakness of classical substitution ciphers such as Caesar Cipher. It must not be used for unauthorized access, malicious activity, or real-world security attacks.

🪪 Author

Shakal Bhau

GitHub: ShakalBhau0001