FFTea

Description

The Fourier transform is used to represent a time signal in the frequency domain: with this tool, it is possible to know, for a radio capture, which frequencies are active in the captured frequency band.

This is a perfectly reversible operation: you can perform the reverse operation without losing any information.

Here, there’s no need to perform a Fourier analysis: simply use a Fourier transform of size 64 on the data array contained in the fftea file, and the result will contain the flag. The file generation code is given.

Note: The input file format is a sequence of 64-bit complex numbers (a 32-bit floating-point number for the real and imaginary parts). The contents of the array can be read in Python using the fromfile function in the numpy package: data = numpy.fromfile("fftea", dtype=numpy.complex64).