GryphonCTF_2016: Dirty Bird

Category: Misc Points: 20 Description:

You found a dirty ol' square piece of black paper with a QR code on it, naturally, you become curious... Should you scan it? Creator - Shawn Pang (@Optixal)

Hint:

Write-up

Definitely, you should scan it. Till you realize you cannot.

Invert the image, black = white, white = black, scan it. You get an integer 234469727479426972647341726531333337, what the hell? Oh wait, it's a hex-encoded string. Convert it to string using a tool like echo 234469727479426972647341726531333337 | xxd -r -p. You get #DirtyBirdsAre1337 from the previous step. What's this? A pound sign? No stupid, it's a hashtag!

Searching it up in Twitter, gets you

JFWI{7k3_gxps573u_g1y3u}. This looks suspiciously like a flag format, so we run it through the easiest decode algorithm, called ROT. On ROT-23, yuo get GCTF{7h3_dump573r_d1v3r}.

Therefore, the flag is GCTF{7h3_dump573r_d1v3r}.