[RitSec CTF] 25C, Please

This challenge from RitSec CTF worth 300pts and was solved by only 18 teams.

This challenge is not so different from the concept of the precious challenge that we had already discussed.

The main difference is that by starting a call we can hear that “25C” are required. Again, with the previous DMTF tones generator, we can play the tone of 25C and “insert” them into the machine to start the call. A voice will give us the flag, in reverse.