🔐 Image Steganography Tool

A command-line steganography application that hides secret messages within images using the LSB (Least Significant Bit) technique. Developed as part of the Programming in C and C++ Languages (PJC) course at PJATK, Winter 2022/2023.

📋 Overview

This tool allows you to hide and extract secret messages within image files without visibly altering the image. It supports BMP and PPM image formats and uses a robust LSB steganography algorithm that modifies the two least significant bits of each color channel.

🌟 Key Features

• Message Encryption - Hide text messages within images
• Message Decryption - Extract hidden messages from images
• Multi-format Support - Works with BMP (24-bit) and PPM (ASCII) formats
• Capacity Check - Verify if your message fits in the image
• Image Information - Display detailed image metadata
• ASCII Art UI - Beautiful command-line interface with ASCII art
• Error Handling - Comprehensive error messages and validation

🎨 Supported Image Formats

Format	Description	Extension
BMP	24-bit Bitmap images	.bmp
PPM	ASCII-encoded Portable PixMap	.ppm

🏗️ Architecture

The project follows the MVC (Model-View-Controller) pattern:

Core Components

• Models
  • Image - Abstract base class for image handling
  • Bmp - BMP format implementation
  • Ppm - PPM format implementation
  • Message - Steganography algorithm implementation
  • Pixels - Pixel manipulation utilities
• Controllers
  • BaseController - Main application controller
  • FlagController - Command-line flag parsing
  • ArgumentController - Command execution logic
• View
  • CommandLineInterface - User interface with ASCII art

🚀 Getting Started

Prerequisites

• C++14 or higher
• CMake 3.23 or higher
• Command line interface

Building the Project

1. Clone the repository:

git clone https://github.com/yourusername/image-steganography-cpp.git
cd image-steganography-cpp

2. Create build directory and compile:

mkdir build
cd build
cmake ..
make

Or use CMake directly:

cmake -B build
cmake --build build

Installation

After building, the executable will be in the build directory:

./build/steganography

📝 Usage

Command Syntax

steganography [options] <path-to-image>
steganography [options] <path-to-image> "message-to-encrypt"

Available Commands

Flag	Long Form	Description	Example
-h	--help	Display help information	steganography -h
-i	--info	Show image information	steganography -i image.bmp
-e	--encrypt	Hide message in image	steganography -e image.bmp "Secret message"
-d	--decrypt	Extract message from image	steganography -d image.bmp
-c	--check	Check encryption capacity	steganography -c image.bmp "Test message"

Usage Examples

1. Hide a Message

steganography -e beach.bmp "This is my secret message!"

2. Extract a Hidden Message

steganography -d beach.bmp

3. Check Image Information

steganography -i beach.bmp

Output:

.------..------..------..------.
|I.--. ||N.--. ||F.--. ||O.--. |
| (\/) || :(): || :(): || :/\: |
| :\/: || ()() || ()() || :\/: |
| '--'I|| '--'N|| '--'F|| '--'O|
`------'`------'`------'`------'
File path: beach.bmp
File format: .bmp - 24 bit per pixel.
Image resolution: 1920 x 1080
Image size: 6220800 bytes
Last modification time: Tue Dec 20 15:30:00 2022

4. Check Message Capacity

steganography -c image.ppm "Can this message fit?"

🔧 How It Works

LSB Steganography Algorithm

The tool uses the Least Significant Bit (LSB) technique to hide messages:

1. Message Encoding:
   • Prepends a "size" flag (4 bytes) and message length (4 bytes)
   • Converts the message to binary
   • Modifies the 2 least significant bits of each color channel (RGB)
   • Distributes bits across pixels to minimize visual impact
2. Message Decoding:
   • Reads the flag to verify an encoded message exists
   • Extracts the message length
   • Reconstructs the message from the modified bits

Bit Distribution

Each pixel can store 6 bits of data (2 bits per color channel):

• Red channel: bits 0-1
• Blue channel: bits 2-3
• Green channel: bits 4-5

🛡️ Security Considerations

• Messages are not encrypted - only hidden
• No password protection
• Can be detected by steganalysis tools
• Original image is modified (though imperceptibly)

For sensitive data, consider encrypting your message before hiding it.

📊 Technical Details

Maximum Message Capacity

The maximum message length (in bytes) is calculated as:

max_length = ((width × height × 3) - 64) ÷ 8

Where 64 bits are reserved for the header (flag + size).

Performance

• Fast encoding/decoding (O(n) where n = number of pixels)
• Minimal memory footprint
• Supports large images (tested up to 4K resolution)

🧪 Testing

The tool includes comprehensive error handling for:

• Invalid file paths
• Unsupported formats
• Messages too large for the image
• Corrupted image files
• Missing encoded messages

📚 Academic Context

This project was developed as part of the Programming in C and C++ Languages (PJC) course at the Polish-Japanese Academy of Information Technology (PJATK) during the winter semester of 2022/2023.

Learning Objectives

• Advanced C++ programming techniques
• File I/O and binary manipulation
• Image format parsing
• Command-line interface design
• Software architecture patterns (MVC)

🤝 Contributing

This is an academic project. Feel free to use it as a reference for learning, but please write your own implementation if you're working on a similar assignment.

👤 Author

Krzysztof Przybysz
Student ID: s24825
Course: Programming in C and C++ Languages (PJC)
Semester: Winter 2022/2023

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