A Modulator/Demodulator CMOS IC for Chaotic Encryption of Audio

This paper reports the first experimental verification of chaotic encryption of audio signals using integrated circuits. It is based on a gm-C modulator/demodulator analog CMOS IC that implements a 3rd-order nonlinear differential equation. This has been fabricated in 2.4¿m double-poly technology and includes on-chip tuning circuitry based on amplitude detection. It is capable of generating controllable continuous-time chaotic signals. Also, measurements demonstrate 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 signal-to-noise ratio rises up to +60dB, while retaining similar losses at the receiver.