Dimensionless Loading

Steganography [250pts]

Description: This PNG looks to be valid, but when we open it up nothing loads. Any ideas?

We are given an image that is unable to open. Running pngcheck, we see that there are invalid dimensions for the image 0x0. When we view this in a hex editor, the byte blocks where the width and height would be is 0x0.

Intuitively we would want to add some dimensions to this, but doing so will ruin the CRC values and mess up the image. An intended solution is to reverse the CRC values with a valid dimension..but I ended up bruteforcing it anyway.

I wrote a small python script to bruteforce the dimensions and write to a new image as well as run pngcheck to see if it is valid:

After letting it run for a while, it turns out the valid dimensions came out as 1378 x 363:

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