The code in craft_signal.py applies the inverse Fourier Transform on the bytes it reads from the flag.txt. So we only need to apply the Fourier Transform on the fftea data. This code thus recovers the flag :
import numpy as np
# Load the data from the "fftea" file
data = np.fromfile("challenge", dtype = np.complex64)
data = np.fromfile("fftea", dtype = np.complex64)
I had no idea what this data was. I thus found myself reading a writeup of the year before
Once i had understood how this I2C works i went to writing the program to parse the data and extract the flag : extract.py
import json
import sys
from pyDigitalWaveTools.vcd.parser import VcdParser
To reverse engineer this program I used IDA on one side and gdb on the other side (with pwndbg) so i could see what each input would do.
First of all we see that the program expects one argument Then we realise that the length of the string we pass as argument must be a dividable by two.
From now on we will consider that I am using the program ./strike aabbccddee with aabbccddee a string passed as argument to the program (in gdb)
(gdb) set args aabbccddee