bsteno 0.1.0

A python steganography package to insert/extract binary data into/from PNG files

bSteno

bSteno is a python module that allows users to insert and extract binary data (up to 16MB) to/from PNG files. The module doesn't modify the original PNG file and creates a new image instead.

The created PNG file is in RBGA format and the binary data is stored in the two LSBs of each channel. This means that 1 byte is stored in exacly one pixel of the image, with the following format:

• The red channel contains bits 0-1
• The green channel contains bits 2-3
• The blue channel contains bits 4-5
• The alpha channel contains bits 6-7

The presence of the alpha channel makes the image bigger than it could be, but I like the idea of having 1-pixel to 1-byte ratio as this simplifies the code quite a bit. This also makes it easier to extract the data if this scripts gets lost for some reason

The first three bytes/pixel of the image are used to store the size of the binary data. The size is stored in little endian

Installation

$ python3 -m pip install bsteno

Use the CLI

To insert the content of data.bin into source.png and store the output in output.png, run:

$ bsteno_insert --png-in=source.png --data-in=data.bin --png-out=output.png

To extract the binary data contained in output.png and store it in data.bin, run:

$ bsteno_extract --png-in=output.png --data-out=data.bin

Use bSteno as a library

bSteno can also be used as a library. It uses with the Pillow module to handle images.

To insert the content of data.bin into source.png and store the output in output.png, you can run the following code:

import PIL.Image
from bsteno import bsteno

img_in = PIL.Image.open("source.png")
with open("data.bin", "rb") as f:
	data = f.read()
img_out = bsteno.insert(img_in, data)
img_out.save("output.png", optimize=True)

bsteno.insert raises a DataTooBig exception if the data can't fit in the image.

To extract the binary data contained in output.png and store it in data.bin, you can run the following code:

import PIL.Image
from bsteno import bsteno

img_in = PIL.Image.open("output.png")
data = bsteno.extract(img_in)
with open("data.out", "wb") as f:
	f.write(data)

Development

This module uses poetry. After cloning the source code, run

$ poetry install

to prepare the virtual environment and install the cli tools. They can then be run with:

$ poetry run bsteno_insert ...
$ poetry run bsteno_extract ...

Running tests

$ poetry run python -m unittest

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