Text Encryption & Decryption System (GUI)

A powerful, secure, and user-friendly Windows GUI application for text encryption and decryption. Built using pure C and the Win32 API, this tool supports Caesar and Vigenère ciphers, offering both text-based and file-based operations.

🚀 Features

• Clean & Professional Interface: A modern, minimal GUI with clear navigation and visual hints.
• Dual Encryption Algorithms:
  • Caesar Cipher: Classic shift-based encryption.
  • Vigenère Cipher: Stronger polyalphabetic substitution using a keyword.
• Cipher Conversions: unique tool to convert ciphertext directly between Caesar and Vigenère formats.
• File Operations:
  • Directly encrypt or decrypt .txt files.
  • Auto-loads file content.
  • Save results back to new files immediately.
• Robust Input Handling:
  • Validates numeric shifts and alphabetic keys.
  • Auto-clears inputs when switching modes to prevent confusion.
  • Error messages for invalid or missing inputs.

🛠️ Technical Stack

• Language: C (C99 Standard)
• GUI Framework: Windows API (Win32)
• Styles: Custom Owner-Drawn Buttons, color theming, and Segoe UI/Verdana fonts.
• File I/O: Native Windows Common Dialogs (GetOpenFileName, GetSaveFileName).

📦 Installation & Usage

Prerequisites

• A C Compiler (GCC via MinGW is recommended) OR Visual Studio.
• Windows OS (Windows 7/8/10/11).

Compilation

To build the application yourself, run the following command in your terminal:

Using GCC (MinGW):

gcc -o SecureCrypt gui_encryption.c -lgdi32 -luser32 -lcomdlg32 -mwindows

Using Visual Studio (CL):

cl gui_encryption.c user32.lib gdi32.lib comdlg32.lib /Fe:SecureCrypt.exe

Running the App

Double-click SecureCrypt.exe or run it via command line:

.\SecureCrypt.exe

📖 How to Use

1. Select a Mode from the sidebar:

   • Caesar Cipher: Enter text, set a numeric shift (1-25), and click Encrypt/Decrypt.
   • Vigenère Cipher: Enter text, set a secret keyword (letters only), and click Encrypt/Decrypt.
   • Cipher Conversions: Convert text encrypted with one method specifically to the other.
   • File Operations: Browses for a file, select the algorithm, enter key, and process. You can save the output instantly.

2. Input & Output:

   • Type or paste your text in the top "Input Text" box.
   • View the result in the bottom "Process Result" box.
   • Use the Clear button to reset fields.

📂 Project Structure

• gui_encryption.c: Main source code containing the GUI and logic.
• SecureCrypt.exe: The compiled executable application.
• input.txt / output.txt: Example files for testing.

🤝 Contributing

Contributions are always welcome! Please follow these steps:

1. Fork the Project.
2. Create your Feature Branch (git checkout -b feature/AmazingFeature).
3. Commit your Changes (git commit -m 'Add some AmazingFeature').
4. Push to the Branch (git push origin feature/AmazingFeature).
5. Open a Pull Request.

📝 License

This project is licensed under the MIT License - see the LICENSE file for details.