Trying to implement to the dft in finite fields (GF(m = 337) with 8th_unit_root = 85 since my data is of size 8) - in the inverted dft defined here: https://en.wikipedia.org/wiki/Discrete_Fourier_transform_over_a_ring i need to calculate a^(-jk). I don't know how exactly to do that. Do I run modinverse( powmod(a, jk), m ) or am I wrong ? There were parts of me who understood it as: powmod ( modinverse( a, m), j*k).
powmod is the exponentiation in modular space. modinverse is a function to calculate the inverse of a number in modular space. dft is the discrete fourier transform
thx for any help