Rating:

We get a sound file on which we can hear someone typing a text on a keyboard.

I have used [this acoustic keylogger from Github](https://github.com/shoyo/acoustic-keylogger) to detect the keystrokes and extract features from them.

This allows me to group similar keystrokes, so I only get 25 different types.
Thus I have a monoaplhabetic substitution of the typed text, which I decrypt with [dcode](https://www.dcode.fr/monoalphabetic-substitution).

See original writeup for detailed instructions.

Original writeup (https://github.com/apoirrier/CTFs-writeups/blob/master/PBCTF2021/Misc/GhostWriter.md).