[Internetwache CTF, 2016]
- Category: crypto
- Points: 80
Watching videos is fun! Hint: Stegano skills required. Service: https://procrastination.ctf.internetwache.org
Given was a website including a
song.webm file. Running
mediainfo got us the hint,
that there is a second audio trace inside the file.
ffmpeg to receive the audio file in
ffmpeg -i song.webm -map 0:2 out.wav
After listening to it, we concluded that it must be some dial-up noise. So we ran some DTMF analysis.
multimon-ng -t wav -a DTMF out.wav
This gave us some numbers separated by zeros:
111 127 173 104 122 60 116 63 123 137 127 61 124 110 137 120 110 60 116 63 123
We knew that it must be something like
So we looked in the ASCII Table and saw that this must be some OCT representation.
So the flag was