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GITS Teaser 2015 CTF - Don't Panic! Shift Keying! Writeup14 December 2014 by mf
We are given two hints to start with - an image and a pice of text:
In a far away land, shaped like the head of a pwnie, dem natives found a way to communicate in secret (sorta) bearly advanced esoteric RF technol0gies... I once befriended a bear in a bar on pwnie island. He kept rambling on about Richard Stallman, and some treasure... He handed me this napkin, and said we could speak through the ether I captured this message data to a GNU Radio complex data file... Maybe its a secret to the treasure!?!? Demodulate the key
So as the hint says, we just have to fire up GNU radio and construct the inverse operations from the ones performed.
Running the design gives out flag.jpg: