Evaluating entropy rate of laser chaos and shot noise

TL;DR

This paper presents an experimental method to accurately evaluate the entropy rate of laser chaos and shot noise, discriminating their contributions and optimizing randomness extraction for secure applications.

Contribution

It introduces a novel approach using permutation entropy growth rate to distinguish chaos from shot noise and demonstrates suppression of time delay signatures in laser chaos.

Findings

Quantified entropy generation in laser chaos and shot noise.

Discriminated chaos and shot noise using permutation entropy growth.

Achieved up to 95% suppression of time delay signature.

Abstract

Evaluating entropy rate of high-dimensional chaos and shot noise from analog raw signals remains elusive and important in information security. We experimentally present an accurate assessment of entropy rate for physical process randomness. The entropy generation of optical-feedback laser chaos and physical randomness limit from shot noise are quantified and unambiguously discriminated using the growth rate of average permutation entropy value in memory time. The permutation entropy difference of filtered laser chaos with varying embedding delay time is investigated experimentally and theoretically. High resolution maps of the entropy difference is observed over the range of the injection-feedback parameter space. We also clarify an inverse relationship between the entropy rate and time delay signature of laser chaos over a wide range of parameters. Compared to the original chaos, the time delay signature is suppressed up to 95% with the minimum of 0.015 via frequency-band extractor, and the experiment agrees well with the theory. Our system provides a commendable entropy evaluation and source for physical random number generation.