Puzzle [STEG]

QR Code segments hidden in an image file.

📁 Challenge Description

Is the original always better? Maybe, should we check? (I’m just a poor boy, I need no sympathy,)

ZIP Password: wgmy2022

👀 Analysis

From initial observation, we are not really sure what information is hiding in this image since it is a stego challenge. Hence, I launch stegsolve again to look for clues.

NOTE: The puzzle.jpg is utterly big causing stegsolve out of the screen range after rendered the file.

Luckily, we can barely observe some QR code fractions scattered around on the top of puzzle.jpg.

Based on this observation, the FLAG most likely is hiding in the QR Code. Additionally, the organizers’ hint might come in handy.

We checked the original image and found that the image size is exactly identical compared to puzzle.jpg.

🚩 Solution

Stegsolve has an Image Combiner feature which can overlap two image files and perform various operations such as XOR, ADD, SUB, .... In this situation, SUB gives the best output.

Combine each QR Code fraction together manually with GIMP. (Can’t find a way to automate the process -.-)

To install GIMP in Debian OS: sudo apt install gimp

• Upload the Combined image.
• Select Free Select Tool.
• Trace every segment and combine the pieces.
• Scan QR Code to get the FLAG.

FLAG: wgmy{3b68891a1ba20a27b9efd93f8d8c2fb0}