EASYCTF - Remember Me

description: I’m such a klutz! I know I hid a flag in this file somewhere, but I can’t remember where I put it! Song is from sukasuka.

hint: Sometimes I can’t tell my left from my right, either.

category: Forensics

In this chall, we have a mp3 file containing an amazing japanese song.

Of course, I tried using file, exiftool and binwalk command, but there were nothing interesting…

I load the file in Audacity, and given the hint, I made the difference between the 2 channels. There are 2 ways to do it:

- split the audio channels into two tracks (Black triangle -> Splitting a Stereo Track), invert the right channel (Select track -> Effect -> invert), set it to be a left channel (Black triangle -> Join Stereo Track) and mix the two tracks together again (Track -> Mix and render).

- The simple way is to use Audacity plugin voice remover (Effect > Vocal Reduction and Isolation)

Using one of those methods, we now have no signal… Or maybe we have a signal ? Let’s try to amplificate the signal (Effect -> Amplification), we can boost the signal to the maximum threshold.

Nice ! we can hear a voice telling us the flag: easyctf{4ud10_st3g}