📱 Cryptographer: Text, Image & Password Security App (Flutter + Python) 🔐🖼️

A cybersecurity-focused mobile application built with Flutter and a FastAPI backend in Python, designed to perform:

• Text encryption and decryption using Caesar Cipher
• Image encryption and decryption using XOR pixel manipulation
• Password strength evaluation based on entropy and structure

Designed for Cybersecurity Practice, this tool demonstrates a simple yet powerful example of secure message and media exchange.

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🚀 Features

📝 Text Encryption & Decryption

• Caesar Cipher with custom shift key.
• Input any ASCII-compatible message.
• Converts plain text to cipher text and vice versa.
• Buttons for copy, paste, and share.

🖼️ Image Encryption & Decryption

• Select image from gallery or camera.
• Apply XOR encryption/decryption using numeric key.
• Preview of selected image and processed image.
• Share or download the encrypted/decrypted image.
• Saves encrypted images to device gallery.

🔐 Password Strength Checker (NEW in Version 2)

• Enter any password to check how secure it is
• Returns one of: Weak, Medium, Strong, or Very Strong
• Backend evaluates password entropy, character types, and length
• Colored strength indicator: 🔴 Red (Weak), 🟡 Yellow (Medium), 🟢 Green (Strong/Very Strong)

🛠️ Additional

• Fully mobile-friendly layout.
• App bar titles dynamically reflect user-selected operation.
• Clear separation between logic (backend) and UI (Flutter frontend).
• Compatible with Android 15 and MediaStore image saving.

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🧠 How It Works

1. User lands on a Home Screen with four options:

   • Encrypt Text
   • Decrypt Text
   • Encrypt Image
   • Decrypt Image
   • Password checker

2. Based on selection, user is navigated to:

   • process_screen.dart for text
   • image_process_screen.dart for images
   • password_check_screen.dart for password strength checking

3. The Flutter app sends a POST request to the local FastAPI backend:

   • For text: /cipher endpoint
   • For image: /image_cipher endpoint (uses XOR logic on RGB pixels)
   • For password: /check_password endpoint

4. The result is shown on the screen with options to copy, share, or save.

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🧩 Project Structure

cryptographer/ ├── lib/ │ ├── main.dart # Home screen (mode selection) │ ├── process_screen.dart # Text Encryption/Decryption │ ├── image_process_screen.dart # Image Encryption/Decryption screen │ └── password_check_screen.dart # Password Strength Checker ├── backend/ │ ├── requirements.txt # Python dependencies │ ├── render.yaml # render configurations │ └── main.py # FastAPI backend (Python) ├── android/ # Native Android config ├── pubspec.yaml # Dart dependencies └── README.md # You're here!

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🛠 Setup & Installation

1. Install Flutter: https://flutter.dev/docs/get-started/install
2. Clone the repository:

   git clone https://github.com/PulkitGahlot/CODECRAFT_CS_03.git
   cd CODECRAFT_CS_03

3. Install packages:

   flutter pub get

4. Connect your Android phone via USB or use an emulator.
5. Make sure your PC and phone are on the same Wi-Fi network
6. Install dependencies:

   pip install fastapi uvicorn pydantic pillow

7. Run the server:

   uvicorn main:app --host 0.0.0.0 --port 8000 --reload

   or use

   python -m uvicorn main:app --host 0.0.0.0 --port 8000 --reload

8. Replace 10.0.2.2 in Dart code with your PC's local IP (e.g. 192.168.x.x) so the app can reach the server.
9. Run the Application:

   flutter run

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📦 Dependencies

Dart (Flutter)

• http
• flutter/services (clipboard)
• image_picker
• path_provider
• share_plus
• google_fonts

Python

• fastapi
• uvicorn
• pydantic
• pillow

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📱 Screenshots

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📦 Version 2 Enhancements

• Password Strength Checker screen added
• Password entropy logic on backend using FastAPI
• Colored strength text (red/yellow/green)
• Toggle visibility of password text input
• Improved responsiveness & async UX

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Download the application Here

• Cryptographer
• Or Scan the QR Code for Direct Download

NOTE: Encryption and Decryption of Images takes some time (Due to Slow Server response sometime). Please wait for some time to get the Output of the Image Encryption and Decryption. Thank you!

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👨‍💻 Author

Hi, I'm Pulkit Gahlot, a cyber security enthusiast and passionate to be an ethical hacker.

“A good hacker is the one who breaks systems, to build secure ones.”

Feel free to connect!

• Linkedin: Pulkit Gahlot
• X: Pulkit_Gahlot_
• GitHub: PulkitGahlot
• E-Mail: pulkitgahlot85@gmail.com

Thank you for visiting my GitHub page!