Category: Misc Points: 325 Solved By: Apicius
Challenge
Well, it’s just too usual to hide a flag in stegano, database, cipher, or server. What if we decide to sing it out instead?
Author: pamLELcu
Files: flag.mp3, vocaloid_heardle.py
Solution
Before looking at the python script, I thought I'd first give flag.mp3 a listen. Upon listening to it, it seems that it's spliced together vocaloid songs of about 3 seconds in length each, with the whole file being 33 seconds long.
Next up was to check out the script. I went through the script and added comments detailing what it was doing in order to properly understand it.
The function of this script is to take a file flag.txt and encode it into unicode characters, fetch a song with an ID that matches the unicode character, and then add the first three seconds of it to the flag.mp3 file.
Rather than coming up with a fancy way to do this, I solved it using a rather simple method. I created a file named flag.txt, supplied unicode characters 33 through 126, and then ran the program. This gave me a folder full of tracks with the title being a number that corresponds with a unicode character. From here I split flag.mp3 into 11 parts, and then listened to each song and matched it with a unicode character. The resulting characters being:
[118, 48, 67, 97, 108, 111, 73, 100, 60, 51, 117]
When I took these numbers and converted them to ASCII I was given the flag:
Flag: SEKAI{v0CaloId<3u}