Too Fast

Description

Too Fast | 100 points | By Mudasir

I found this QR code, but I can't seem to scan it.

Static resources: ctf.gif

Analysis

As name suggests GIF is too fast to be scanner, so I tried getting each frame.

└─$ ffmpeg -i ctf.gif -vsync 0 frame%d.png

ffmpeg will produce 5 images. None of the images can be scanned to get the flag.

Solution

Since QR code is blocked by colors I used Photoshop to remove them. First I imported all images, selected specific color, masked the selection and inversed the mask (so only color gets hidden). Repeated for all images and result:

too-fast-1.png

Then decoded using online QR scanner

Flag: bcactf{y0U_@lm0$7_m!$s3D_!7_e3idwind}