EHAX RecCTF 2026 — Frequency ka khel

Right off the bat when I noticed the hint saying: You know "BALL"? i believe its 1500 1000 6500 6500. These numbers seem to be quite important as I was running out of time so close to the end of the recCTF I downloaded the file which seemed to be a .wav audio file I immediately recognized this file format I once played a similar file on windows, opening it heard weird noises or beeps thinking what kind of alien language they're using remembered Koi mil gaya for a solid 2 seconds, what are they trying to say? is it morse code?? as the problem was worth more than 300+ points I grew anxious…..

by the way at the end of this post you'll find how overthinking could potentially ruin your preparation and turn even a simple ctf problem into the hardest problem you've ever seen…

First Approach:

So, I got down on business to check the file metadata and to figure out if I would need to convert the file into some other format or not. No luck at all I couldn't find anything in the metadata using exiftool I rushed to my linux terminal and tried to read the file using cat wrong choice again.

2. Second Approach: I used gemini and it recommended audacity to inspect the file I downloaded audacity to get a better look at the audio file try to filter out anything odd in the file as the hint said something about frequencies this was the first app that was recommended because audacity uses a logarithmic scale for its spectrogram, which squishes higher frequencies together and gives a good visual image learnt a bit about logarithmic and linear scales, gemini tried to give the answer straight but was wrong 2 times eventually I got down with a pen and paper to decipher the actual hidden characters and it was so fun, soon as I saw the squished frequencies they were like concentrated horizontal lines I knew there's a pattern that's happening at some particular frequency and the first one was 3000 Hz, looked at the hint again and that was it I saw two LL's and ahead there were two repeating 6500 6500 immediately I thought they're relating the frequencies with letters then rest was simple enough: B->1500, A->1000 and the rest is history like a problem of waves and frequencies I matched those frequencies with every alphabet in English with pen and paper and the frequencies said something like: EHAXIHOPEYOUGUYSHADFUN format of FLAG- EHAX{IHOPEYOUGUYSHADFUN} and that was the answer can't believe it was so simple!!!!

Lakshit Kumar Jangid