Speech encryption based on Fast Fourier Transform permutation

This report deals with describing permutation of FFT (Fast Fourier Transform) coefficients in speech encryption system. The scrambling algorithm is based on the permutation of the FFT coefficients and provides highly secured scrambled signal by permuting a large number of those coefficients. The algorithm for 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 scrambling system are considered. Simulation have been done by using C programming language. The results of simulation and tests shows that proposed scrambling achieves extremely high-level security as well as high speech quality.