Hmmmm.. this time we got a sound file (.mp3). And the description says it’s about something old.

Challenge description

Lets check it out..

If we play the sound file, we will notice instantly that it is Morse code. If you don’t know what that is, check out this explanatory video.

Ok, how to solve this?

If you googled “Morse code online translator”, the first result will be this site:

Lets upload our mp3 file there directly..

Upload our mp3 file

Then if you clicked “Play”, it will start playing the mp3 file, and decoding each letter as soon as its signal/sound is transmitted.

Play the uploaded file

We could notice the word “Flag” there 🤑. After it plays the whole audio file, this is the final result:

the flag

Of course if we submitted the flag like this, it would say “Incorrect flag!!”… because CTFs usually have rules for the format of the flag. In this case, the flag’s format was like this: “flag{xxxx}”.

Morse code doesn’t have an encoding for the curly brackets “{” and “}”. That’s why we’ll have to add them by ourselves.