Seccon 2015 / Seccon Wars 2015

Description

We are given a link to a video : https://youtu.be/8SFsln4VyEk

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The Challenge

This challenge was probably one of the simplest ones in this CTF.

Going through the video, we can notice some shadows of a QR code on the screen being formed by the scrolling yellow text.

Obviously the QR code isn’t scannable as some parts of the barcode is blending with the black background.

At this point, we need to extract the frames of the video, either through software like VLC or by taking a couple of screenshots.

I took about 85 screenshots in rapid succession.

With these frames, we can use a graphics editor like Photoshop to overlay the images, therefore filling the background to reveal a cleaner version of the QR code.

I used an equivalent called Acorn to do the blending.

Scan it and we obtain the flag!

Flag : SECCON{TH3F0RC3AVVAK3N53P7}