extiop / yet-another-shade-of-lsb

Yet another shade of LSB (YASLSB) technique bridges the well-knowns LSB and PVD steganography approaches together. It can be applied to PNG images.

Yet another shade of LSB

Yet another shade of LSB (YASLSB) technique bridges the well-knowns LSB and PVD steganography approaches together. It can be applied to PNG images.

How it works

This proof of concept is only working for the green channel at the moment, it hides data using a variant of the LSB steganography. Input data is converted to base2, then for each "0" or "1" to encode, a trick is used. The latter is to alter the image a tiny bit to get the right delta between two following pixels.

For a green pixel g and its previous one pg, delta_green = g - pg can be computed. To encode "0", delta_green < 0 is set, to encode "1", delta_green > 0 is set. Hence, for decryption, delta_green is evaluated: - if it is less than 0, a "0" is encoded. - if it is greater than 0, a "1" is encoded.

Proof of concept with the green channel

I encrypt my data 4n0th3r_cust0m_pr0duct10n:

python3 encrypt.py -i images/pepo.png -d 4n0th3r_cust0m_pr0duct10n -o images/encrypted.png
[+] Base2 length data: 200
[+] Successfully encoded plaintext in ./images/encrypted.png

Keep in mind that I need that length and it is encoded in the decryption process, I might figure out how automate that in the future. Anyway, I decrypt it:

python3 decrypt.py -i images/encrypted.png                                                  
[+] Retrieved plaintext from ./images/encrypted.png: 4n6th3r_cust0m_pr0duct10n

Voilà! Give it a try yourself by cloning my repository!

Limitations

Only green channel is supported for encoding at the moment, as a proof of concept.

Dependency

sudo pip install pillow

Roadmap

• Add support for encoding into red, blue and alpha channels.
• Improve accuracy of threshold to encode data to minimize image modification
• Implement a way to unhide a secret without knowing its size
• Add support for other kind of images (JPG, GIF...)

Contributing

Please if you want to bring your stone to the building, read and follow CONTRIBUTING.md.