Can FFT be useful in encryption of dicom images? I am doing a project on dicom images. I will be encrypting the DICOM image using AES-GCM algorithm. Before encrypting the DICOM image, i thought of taking FFT. Will it provide an advantage during encryption? if so can you explain?
I had a quick look and the images are already encoded with standard image enncoding algorithms, which means DCT and other appropriate transforms have already been used, e.g., as part of jpeg, tiff, mpeg,whatever.

I see no utility to applying an FFT on top of all this effort, neither from a security point of view.