[H4CK1T 2016] 1magePr1son- Mozambique Writeup

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Description:

Task: 1magePr1son- Nozambique- Stego- 150

Implementing of the latest encryption system as always brought a set of problems for one of the known FSI services: they have lost the module which is responsible for decoding information. And some information has been already ciphered! Your task for today: to define a cryptoalgorithm and decode the message.
https://ctf.com.ua/data/attachments/planet_982680d78ab9718f5a335ec05ebc4ea2.png.zip
h4ck1t{str(flag).upper()}
https://ctf.com.ua/data/attachments/planet_982680d78ab9718f5a335ec05ebc4ea2.png.zip

For the start we are given with a wallpaper image named planet.png (2560×1850)

h4ck1t_mozambiqu1

Looking carefully at the image we can see a pattern of strange dots, such dots may be connected to the cryptosystem. Those are pixels in different colors that probably belongs to another image. My thought is that the pixels of the flag image was splitted into the wallpaper.

h4ck1t_mozambiqu2

The dots exists every 24 pixels so I wrote a short pythons script in order to combine them into one image:

I ran it and got a big image (the wallpaper size) with this tiny image inside that contains the flag:

h4ck1t_mozambiqu3

Flag: h4ck1t{SPACE_IS_THE_KEY}

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