Here is our original picture. It is a picture of Emma Watson in an event. We are to extract the flag from this image. I checked for common anomalies in the picture but, couldn’t find any. No extra information in the metadata or the blob content of the image. Then I suspected if it is LSB steganography and checked for it too. But, there could be no meaningful data extracted from the LSB bits.
I could not participate in GiS CTF which was conducted around 10 days back. But, the one good thing about these people is that they always have an archive of all their past events. This is a 150 point Crypto challenge named as Knockers. Here is the question. Dude, here’s a knocker token that will let you access my service on port 80. One day I will let you see my cool stuff on port 7175.