Stegonography Guide

Hide a text file inside a lossless image (e.g., PNG) using the provided image_lsb.py script.

Definitions

• Steganography is the embedding of a message in another medium.
• Least Significant Bit (LSB) steganography does this by modifying the least significant bits of pixel values to store data.

Prerequisites

• Python 3.9+
• Install dependencies:

pip install pillow numpy

Files

• image_lsb.py – the steganography script
• cover.png – your input (lossless) image
• secret.txt – the text you want to hide
• stego.png – the output image containing hidden data

Step 1: Save Your Text to a File

echo "This is my secret message" > secret.txt

Step 2: Hide the Text in the Image

python image_lsb.py hide cover.png secret.txt stego.png

Arguments

• cover.png → input image (use PNG or another lossless format)
• secret.txt → the file to embed
• stego.png → output image with embedded payload

Step 3: Extract the Hidden Text Later

python image_lsb.py extract stego.png recovered.txt
cat recovered.txt

Arguments

• stego.png → image with embedded payload
• recovered.txt → output file for the extracted text

Notes

• Use lossless formats (PNG). JPEG re-encoding will destroy simple LSB data.
• For better secrecy, encrypt or compress the text before embedding so the bit pattern appears random.
• The cover image must be large enough: it needs 8 bits per payload byte plus a small header.
• The visual appearance of stego.png should be identical to cover.png to the naked eye.