🔐 Encryption System

A Python encryption toolkit demonstrating classical ciphers, clean architecture, and test-driven development.

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✨ Overview

This project is a Python encryption toolkit that implements several classical encryption algorithms while demonstrating good software engineering practices.

The system separates encryption logic from the command-line interface, includes automated tests with pytest, and is designed to be easily extended with additional cipher methods.

This repository focuses on demonstrating:

• Modular Python architecture
• Algorithm implementation
• CLI application design
• Unit testing with pytest
• Clean and maintainable code structure

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🚀 Features

Feature	Description
Multiple Cipher Methods	Caesar, Vigenère, Substitution, Base64, and a custom cipher
CLI Interface	Interactive command-line tool for encryption and decryption
Input Validation	Key validation specific to each cipher
Unit Tests	Automated testing with pytest
Modular Architecture	Encryption logic separated from the user interface
Extensible Design	New ciphers can be added with minimal changes

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🔐 Supported Encryption Methods

Caesar Cipher

A classical substitution cipher that shifts each letter by a fixed number of positions.

Key Format: Integer (1–25)

Example:

Input:  HELLO
Key:    3
Output: KHOOR

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Vigenère Cipher

A polyalphabetic substitution cipher that uses a keyword to determine shifting values.

Key Format: Alphabetic string (example: SECRET)

Example:

Input:  HELLO
Key:    KEY
Output: RIJVS

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Substitution Cipher

A cipher that replaces each letter with a custom alphabet mapping.

Key Format: 26 unique letters representing a full alphabet permutation.

Example:

Plain alphabet:  abcdefghijklmnopqrstuvwxyz
Cipher alphabet: qwertyuiopasdfghjklzxcvbnm

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Base64 Encoding

Encodes text using the Base64 encoding scheme.

Commonly used for safe transmission of binary data as text.

Example:

Input:  HELLO
Output: SEVMTE8=

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Custom Cipher

A custom encryption method combining several transformations.

Process:

1. ASCII shift (±4)
2. Convert characters to hexadecimal
3. Reverse the resulting string

This demonstrates how multiple transformations can be chained to form a custom cipher pipeline.

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📦 Installation

Requirements

• Python 3.8 or higher
• pip

Setup

git clone https://github.com/Lautarocuello98/Encryption-System.git
cd Encryption-System
pip install -r requirements.txt

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🎯 Quick Start

Run the CLI application:

python cli.py

Example interaction:

Select encryption method:

1. Caesar Cipher
2. Vigenère Cipher
3. Substitution Cipher
4. Base64 Encoding
5. Custom Cipher

Enter choice (1-5): 1
Enter text: Hello World
Enter shift value (1-25): 3
Encrypt (e) or Decrypt (d)? e

Result: Khoor Zruog

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💻 Using the Project as a Python Library

Example:

from encryption import Encryption

enc = Encryption()

# Caesar Cipher
encrypted = enc.encrypt("hello", "caesar", "3")
print(encrypted)

# Vigenère Cipher
encrypted = enc.encrypt("hello", "vigenere", "secret")
print(encrypted)

# Base64
encrypted = enc.encrypt("hello", "base64", None)
print(encrypted)

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📁 Project Structure

Encryption-System/
│
├── encryption.py
├── cli.py
├── test_project.py
├── requirements.txt
├── README.md
├── LICENSE
└── __init__.py

• encryption.py → Core encryption logic and cipher implementations
• cli.py → Command-line interface
• test_project.py → Automated tests using pytest

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🧪 Running Tests

Install dependencies:

pip install -r requirements.txt

Run tests:

pytest

Verbose output:

pytest -v

Run a specific test:

pytest test_project.py::test_caesar_cipher -v

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🏗 Architecture & Design

The project follows several clean code principles.

Separation of Concerns

Encryption logic is completely independent from the CLI interface.

Testability

Core logic functions can be tested without user interaction.

Extensibility

Adding a new cipher requires minimal changes.

Example:

def rot13(self, text):
    return self.caesar(text, 13)

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💡 Use Cases

• Educational projects for understanding classical cryptography
• Demonstrating Python architecture and testing practices
• Integration as a module in larger Python applications
• Portfolio project showing algorithm implementation

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📊 Code Quality

This project includes:

• Clean modular architecture
• Automated tests with pytest
• Clear function structure
• Error handling and input validation
• Readable and maintainable code

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🔒 Security Note

⚠️ Educational Purpose

This project implements classical encryption algorithms and is intended for learning and experimentation.

It should not be used to protect sensitive data.

For real-world security applications, use industry-standard libraries such as:

• cryptography
• TLS / SSL protocols
• AES / RSA encryption standards

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🚀 Possible Future Improvements

• GUI interface with tkinter
• File encryption support
• Additional classical ciphers (Playfair, Transposition, etc.)
• Web API interface
• Batch encryption processing

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📄 License

This project is licensed under the MIT License.

See the LICENSE file for details.

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👨‍💻 Author

Lautaro Cuello

GitHub: https://github.com/Lautarocuello98
LinkedIn: lautaro-cuello-7ba4063a3

Python developer focused on automation, scripting, and practical tools.

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