Crypto Tools

A comprehensive cryptography toolkit built with Flask that provides implementations of classical ciphers and steganography techniques.

Features

🔐 Ciphers Currently Implemented

Substitution Ciphers	Description
Shift cipher	Configurable character rotation (Caesar cipher variant)
Mixed-alphabet	Keyword-based alphabet substitution
Atbash	Ancient Hebrew cipher using alphabet reversal
Simple substitution cipher	Custom alphabet substitution with random generation
ROT13	Special case of Caesar cipher with 13-character shift
Baconian	Binary encoding cipher using A/B patterns
Polybius square	Grid-based substitution cipher

🖼️ Steganography

• LSB Steganography - Hide secret messages within image files
• Message Hiding - Embed text into PNG images using least significant bit manipulation
• Message Extraction - Retrieve hidden messages from steganographic images

Technology Stack

• Backend: Flask (Python web framework)
• Frontend: HTML, CSS, JavaScript
• Cryptography: Custom cipher implementations
• Steganography: Stegano library with PIL/Pillow
• Production: Gunicorn WSGI server
• Proxy: Caddy/Nginx reverse proxy support

Setup

Requirements

This project requires Python 3.11 or newer to run.

pip install Flask gunicorn stegano pillow

Initial Run

Development mode:

python app.py

Production with Gunicorn:

gunicorn -w 4 app:app

By default it runs on 127.0.0.1:8000. You can explicitly set your desired port:

gunicorn -w 4 -b 0.0.0.0:5000 app:app

Gunicorn Command Breakdown

Part	Meaning
gunicorn	Starts the Gunicorn server, a production-grade WSGI HTTP server for running Python web apps (Flask, Django, etc.)
-w 4	Runs 4 worker processes to handle requests concurrently. More workers = better performance under load (adjust based on your CPU cores)
app:app	Specifies where to find your Flask app: - First app = Python filename without .py extension (e.g., app.py) - Second app = Flask application object name inside your file (e.g., app = Flask(__name__))

Creating a Systemd Service

Create a systemd service file to run in the background, start on boot, and restart on failure.

Create /etc/systemd/system/crypto-app.service:

[Unit]
Description=Gunicorn instance to serve Crypto Tools Flask app
After=network.target

[Service]
User=root
WorkingDirectory=/usr/share/caddy/crypto-app
ExecStart=/usr/local/bin/gunicorn -w 4 app:app
Restart=always
RestartSec=3

[Install]
WantedBy=multi-user.target

Start and Enable the Service

sudo systemctl start crypto-app
sudo systemctl enable crypto-app
sudo systemctl status crypto-app

Setup Reverse Proxy

You can set up a reverse proxy using nginx or caddy. But I have used caddy

Using Caddy web server:

crypto.sarthak.co.in {
reverse_proxy localhost:8000
}

Usage

Cipher Tools

1. Navigate to the Ciphers section from the home page
2. Select your desired cipher algorithm
3. Enter text to encrypt or decrypt
4. Configure algorithm-specific parameters (shift values, keywords, etc.)
5. Choose encrypt/decrypt action
6. View results instantly

Steganography

1. Go to the Steganography section
2. Upload a cover image (PNG format recommended)
3. Enter your secret message
4. Generate steganographic image with hidden message
5. Extract hidden messages from steganographic images

API Endpoints

• GET / - Home page with tool selection
• GET/POST /cipher - Cipher encryption/decryption interface
• GET/POST /steganography - Steganography tools
• GET /api - API documentation

##Security Notes

⚠️ Educational Purpose: These implementations are for learning and demonstration. Classical ciphers are not suitable for real-world security applications.

⚠️ Steganography Limitations: LSB steganography can be detected by steganalysis tools. Use only for educational purposes.