write-ups-challenges-2019-2020/Waldo/README.md
2022-11-24 22:43:03 +01:00

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#Stenography

This challenge uses Stenography to hide an image inside another image. The principle behind is quite simple and the technique used here is known as LSB Stenography or "Least Significant Bit" stenography. when working with images, each pixel holds an RGB or RGBA value. The least significant bit of each R G or B value changes the color to its immediate neighbor out of a range of 255. The image can later be constructed, however with a loss of data since we can only recover the MSB (Most significant bit)

This script has been written rapidely and only works for images that have the same since.

assume the following 2 pictures.

A christmass cards seems innocent enough that no one will expect something to be hidden there

Christmass.png

and were are going to hide Waldo REALLY well this time

WaldoFlag.png

This script will create the flag picture and looks like this

Hidden.png

When we try to recover it again, the flag will have changed slightly because we are only saving and recovering the MSB but it is still readable.

The results after decryption looks as follow

revert.png