This was a funny challenge. Below are two pictures provided by the organizer. Just use a picture compare tool and look in to the girl’s boobs. There is nothing to say more.

Picture 1:

ISEC 2009 CTF Prequal Img1

Picture 2:

ISEC 2009 CTF Prequal Img2

Comparing the two pictures using Beyond Compare tool, the secret will be revealed.

Compare 2 Images

The keyword is “OH, WTF” (the text on the pink girl boobs ^^,)

It’s really funny.