Steganography entails disguising sensitive data, by encoding it inside other forms of media. A simple technique is to encode a message one bit at a time into an image, by setting the least significant bit of each pixel to a single bit of the message. To recover the message, one simply strips the LSBs in the same order, until a delimiter is hit.
This tool uses the Python Image Library, or PIL, to read and write image data.
The Python3 fork is called Pillow, which can be installed with pip install Pillow
Image steganography gets tricky with compressed image formats like JPEG. The only image format this tool currently supports is PNG. Using PIL, the input image's data is read as binary. The input message is converted into a binary string, and encoded into the least significant bit of each pixel. Once the message has been fully encoded, a trailing delimiter is written.
To decode, this process is reversed: the least significant bits are read off the image until the delimiter is hit, and the input message is recovered and displayed.
There are two images included to demonstrate the visual differences. The lime
image demonstrates the difficulty the naked eye has in distinguishing between
original and encoded images, while the castle image would have a stronger
resistance to an analytical approach, as it contains a greater color palette.