Voice Scrambler

Abstract

Threats to communication systems which have existed since men started sending messages are eavesdropping, modification, replay, masquerading, penetration and repudiation. Implementation of speech secrecy mechanism has always been a challenge in these systems. The term scrambling has been and still is used on occasions to describe the encryption process to protect voice communication. The aim of scrambling is to corrupt as much as possible a speech signal in such a way that it cannot be recovered to an intangible speech signal, after it has been transmitted over a channel. While digital scrambling provides very high security, it is usually difficult to implement due to its fundamental requirement of much wider bandwidth as compared to analog signals. This project is about the design and implementation of a real time voice scrambling technique on wired communication systems. We have selected Linear Feedback Shift Register technique as our scrambling algorithm which is implemented on an audio signal in digital domain and provides more security than analog domain implemented algorithms. Moreover, selected technique does not require extra bandwidth. We have designed and developed an electronic circuit for practical implementation of project. The scheme is also being realized on contemporary digital signal processor DSP TMS 320C6713 based development board. Implemented technique has produced satisfactory results and its strength can be increased further by including more delayed output values in the algorithm.