TAMUCTF 2026 - Short Term Fuel Trim

Some stupid numbers or something. Not really sure what they're for, maybe you can figure it out?

NOTE: The flag is fully lowercase!

What we got was a file with complex numbers:

# STFT shape: complex64 (129, 1380)
 (0.000000000000000000e+00+0.000000000000000000e+00j)
 (0.000000000000000000e+00+0.000000000000000000e+00j)
 (-1.484999775886535645e+00+0.000000000000000000e+00j)
 (2.873720169067382812e+00+0.000000000000000000e+00j)
 (9.447572708129882812e+00+0.000000000000000000e+00j)
 (8.104647827148437500e+01+0.000000000000000000e+00j)
 [...]
 (-8.955355644226074219e+00-1.063910579681396484e+01j)
 (2.833513259887695312e+01-1.660429000854492188e+01j)
 (-9.096262931823730469e+00-5.180178642272949219e+00j)
 (2.600643396377563477e+00-3.798989772796630859e+00j)
 [...]

We got STFT (Short-Time Fourier Transform) and a size of the shape. The idea was to parse the data, shape it as stated and create a spectrogram:

What can be read from it?

• a lot of vertical lines (changes in time)
• no letters or numbers (also with different spectrogram parameters)
• energy mostly at the bottom (suggestion for audio signal)
• dark vertical stripe at the end (silence/padding)

Result: possible audio signal (hint saying that flag is in lowercase should also guide to audio and not picture).

After saving as .wav file it was possible to hear the flag already but to be sure to get it correctly I used online tool: https://turboscribe.ai/dashboard
I needed to correct it slightly but it was not hard as a leet speak phrase about FFT was used.

Flag caught by: T0m4sh