A modulator/demodulator CMOS IC for chaotic encryption of audio

Abstract

This paper reports the first experimental verification of chaotic encryption of audio signals using integrated circuits. It is based on a gm-Cmodu¬ lator/demodulator analog CMOS IC that implements a 3rd-order nonlinear differ¬ ential equation. This has been fabricated in 2.4|j,m double-poly technology and includes on-chip tuning circuitry based on amplitude detection. It is capable of gen¬ erating controllable continuous-time chaotic signals. Also, measurements demon¬ strate how to exploit the synchronization between two of them for encrypted transmission. In these experiments, the worst-case signal to noise ratio of the recovered signal is greater than +40dB (at the low corner of the audio spectrum) with less than -0.2dB loss of the input signal power. At higher frequencies, the sig¬ nal-to-noise ratio rises up to +60dB, while retaining similar losses at the receiver.