DesigningofReal Time Voice Scrambler / DescramblerBased onMicrocontroller

Abstract

Most of voice channels used in voice terminals such as mobile, telephone exchange are not ciphered. This makes them vulnerable to eavesdropping and hacking. Present day securing voice communication became an urgent need for civil and military applications and especially for real time communication. This work presents a real time microcontroller-based voice scrambling and descrambling (full duplex) using 16KHz sampling frequency. Voice scrambling / descrambling was done in frequency domain and time domain. In frequency domain, a frequency inversion is implemented using sinusoid wave multiplication and 8-order low pass Finite Impulse Response filter. In time domain, a segment permutation technique was implemented. When inputting, voice samples were stored in memory sequentially. However, when playing the voice, samples were read with a random sequence according to a look-uptable. The scrambling / descrambling algorithms were verified using MATLAB and implemented using ARDUINO DUE microcontroller. The system was tested in real time by scrambling the voice input from a microphone and output it through a speaker. Tests show that the scrambled voice was not recognizable at all. Also, the descrambled voice shows acceptable similarity with the original voice.