Analog speech scrambling via the Gabor representation

This paper presents a Gabor-domain scrambling scheme which enables a variety of scrambling options-in time, in frequency, and in the combined time-frequency spaces. The proposed scheme can perform any invertible modification, and not necessarily the commonly permutation operation, rendering the scheme more secure. It is shown that when the oversampled Gabor expansion is used there are modifications which are not legal, and the class of all legal modifications is determined. The synchronization problem usually accompanying the scrambling process is studied. The effect of the Gabor expansion parameters on the synchronization problem and on the security level of the scheme is examined. The performance of the proposed scheme is demonstrated by simulations