Subliminal
In this chall, we had to recover the subliminal image. We are given a video where we can see a square that appear on each frame. The video can be found here.
At first I tried to create a program that recover the squares by searching the shape of a square on the video… But this didn’t work and was overcomplicated. I finally chose to just start at the first frame on the top left corner, save it in a folder named squares with its ID (first square ID=1, second ID=2…). I could find the squares because I knew they were 20*20 with the help of my “useless” previous code. It was easy because the squares appeared from the top left corner to the bottom right one and the position of the cube was 20 pixels to the right of the previous one. When the cube reached the end of the image, we went at the beginning of the next line. Then I just had to concatenate all the squares together. The EXIF of the video tells me that it has a frame of 1280*720. I just had to create an image of 1280*720 using all the squares of 20*20.
You can find my code to recover the squares here and the one to generate the final image here
And the we got the flag:
