Implementation of synchronization free speech scrambling module

Abstract

Security of information over communication media is of paramount importance both in civil and military applications. However, implementation of high security digital encryption over noisy and faded analog HF wireless links is quite a challenging problem. The current project aims at developing and implementing a high security digital scrambling scheme over narrow-band analog HF radio set with typical audio baseband of 3 KHz or less. This was possible by using an innovative synchronization-free signal processing and communication technique. The project has resulted in learning to design and develop a complex multi-rate digital signal processing system involving short-time Fourier transform, signal decimation, signal interpolation, digital filters, windowing and signal manipulation (digital scrambling). The complete scheme was first simulated in MATLAB for conceptual testing and then proof-of-concept realized on contemporary Digital Signal Processor TI DSP TMS320C6713 based development board.