Speech encryption based on fast Fourier transform permutation

This paper deals with the permutation of FFT (Fast Fourier Transform) coefficients in a speech encryption system. The scrambling algorithm is based on the permutation of the FFT coefficients and provides a highly secured scrambled signal by permuting a large number of those coefficients. The algorithm for the generation the permutation matrices is explained. This system is useful for a band limited telephone channel and mobile communication. Choice and construction of permutation matrices in the scrambling system are considered. Simulation has been carried out by using the C programming language. The results of simulation and tests show that the proposed scrambling achieves extremely high-level security as well as high speech quality.