Full solution of Acronym challenge from ISITDTU Quals 2019.
tl;dr - Steganography

Challenge Points: 826
Challenge Solves: 23
Solved by: stuxn3t & Nihith

Challenge Description:

We got a first blood in this challenge.

Note: As we understood later, the description does have a big role to play in solving the challenge.

We first download the following file Output.png but the file size is 9.2MB which was a little suspicious to me.
So I went through the hex dump of the file and saw the header of another PNG.


After IEND of the 1st PNG, The header of the next PNG starts. You can extract that using “dd”

So I extracted it out and got the following image (Also note that the Image you get after extracting is
corrupted. Change the header from “82” to “89”).


There is a big clue in the image: BLUE STEGO. So I instantly googled for any GitHub repo or tool with the
name bluestego. And I found this link: https://github.com/BinhHuynh2727/BlueStego

This tool was needed to get the flag but it also requires a key. Where do we find a key??

So I tried some more tools on the same image and when using stegsolve(RED plane 0), I found a QR code
hidden in the image.


So after visiting the website, I searched around for a lot of time but I didn’t know what I was looking for.
Finally, the word “DIFF“(Danang International Fireworks Festival) looked like a suitable acronym to be used as
the key for the bluestego tool. Yes, I was right! DIFF is the key.

Yes, then we got the flag.


Yay!! The flag is ISITDTU{D4N4NG_1S_MY_L0V3}