Stego

A modern, full-stack image steganography application that allows you to hide secret messages inside images using least significant bit (LSB) encoding. Messages can be optionally encrypted with password protection for added security.

What is Steganography?

Steganography is the practice of concealing messages or information within other non-secret data. Unlike encryption (which scrambles data), steganography hides the very existence of the message. This application uses LSB (Least Significant Bit) steganography to embed text messages into image files in a way that's imperceptible to the human eye.

Features

• Hide Messages in Images: Embed secret text messages into any image file (PNG, JPEG, etc.)
• Extract Hidden Messages: Decode and retrieve messages from encoded images
• Optional Encryption: Protect your messages with password-based encryption (Fernet/AES-128)
• Configurable Encoding Density: Adjust bits-per-pixel (1-8) to balance capacity vs. image quality
• Capacity Validation: Automatically checks if your message fits in the selected image
• Modern UI: Clean, responsive interface built with Material-UI
• RESTful API: Well-documented FastAPI backend for programmatic access

How It Works

LSB Steganography

The application modifies the least significant bits of image pixel values to store your message. Since these changes are minimal, they're invisible to the human eye but can be extracted by the decoder.

Example: To hide the letter 'A' (binary: 01000001):

• The 8 bits are distributed across pixel color channels (RGB)
• Each pixel's least significant bit is replaced with one bit from the message
• The image looks identical but now contains hidden data

Optional Encryption

When you provide a password:

1. Your message is encrypted using Fernet (AES-128-CBC) with PBKDF2 key derivation (100,000 iterations)
2. The encrypted data is then embedded into the image
3. Only someone with the correct password can decrypt and read the message

Technology Stack

Backend (API)

• FastAPI - Modern Python web framework
• Pillow - Image processing and manipulation
• cryptography - Fernet encryption for message security
• Pydantic - Data validation and settings management
• Uvicorn - ASGI server

Frontend (Client)

• Next.js 16 - React framework with server-side rendering
• React 19 - UI component library
• TypeScript - Type-safe JavaScript
• Material-UI - Professional UI components
• Axios - HTTP client for API communication

Getting Started

Prerequisites

• Python 3.8+
• Node.js 18+
• Yarn package manager

Backend Setup

1. Navigate to the API directory:

cd API

2. Install Python dependencies:

pip install -r requirements.txt

3. Configure environment variables (optional):

# .env.algorithm - Message boundary markers
PREFIX=~
SUFFIX=^

# .env.cors - CORS configuration
CLIENT_URL=http://localhost:3000
ALLOWED_METHODS=GET,POST

# .env.storage - File storage location
ROOT_DIRECTORY=./_data

4. Start the API server:

uvicorn main:app --reload

The API will be available at http://localhost:8000

Frontend Setup

1. Navigate to the Client directory:

cd Client

2. Install Node dependencies:

yarn install

3. Start the development server:

yarn dev

The application will be available at http://localhost:3000

Usage

Encoding a Message

1. Navigate to the Encode page
2. Upload an image file
3. Enter your secret message
4. (Optional) Set a password for encryption
5. (Optional) Adjust bits-per-pixel for encoding density (1-8)
6. Click Encode
7. Download the encoded image

Decoding a Message

1. Navigate to the Decode page
2. Upload an encoded image
3. (Optional) Enter the password if the message was encrypted
4. (Optional) Adjust bits-per-pixel to match encoding settings
5. Click Decode
6. View the extracted message

Configuration Options

Bits Per Pixel

• Range: 1-8 bits
• Lower values (1-2): Maximum image quality, less capacity
• Higher values (6-8): More capacity, potential visible artifacts

Security Considerations

• Always use encryption (provide a password) for sensitive messages
• The image itself is not encrypted - anyone can attempt to decode it
• Without the password, encrypted messages cannot be decrypted
• Avoid using common or weak passwords

Example Use Cases

• Secure Communication: Send confidential information hidden in innocuous images
• Digital Watermarking: Embed copyright or ownership information in images
• Puzzle Challenges: Create treasure hunts or escape room challenges
• Educational: Learn about steganography and information hiding techniques

License

MIT License - Copyright (c) 2022 Try at Software

Author

Maintained by Tony Troeff

Acknowledgments

• LSB steganography implementation inspired by classical information hiding techniques
• Encryption provided by the Python cryptography library (Fernet)
• UI components from Material-UI