The image speaks for itself

Aperi'CTF 2019 - Steganography (100 pts).

Aperi’CTF 2019 - The image speaks for itself

Challenge details

Event Challenge Category Points Solves
Aperi’CTF 2019 The image speaks for itself Steganography 100 10

Trouvez le flag. Ici c’est relativement simple: l’image par d’elle même.

Challenge: the_image_speaks_for_itself.bmp - md5sum: 52417e96e7ebadbe0959990f35d28714


Open BMP as raw in Audacity an play the sound to have the flag.


Understand the hints

In this challenge we got two hints:

  • The name of the challenge which says “speaks”
  • The visual content of the BMP file which is a music controller.

The hints converge towards a sound file.


First thing I did was trying to open the BMP file with Audacity (drag and drop). I got the following error:


The error suggests to import the file as raw: “Importer Raw”.

I imported the file as the following: File > Import > Import Raw


The speech is a bit too fast, lets slow it down (Effects > Change speed):



Let’s play it:

Bravo, le flag est APRK{BMP_PCM_POLYGLOT}, le tout en majuscule.

For more information, the challenge has been created using this post.