Two mutually coupled chaotic diode lasers with individual external feedback, are shown to establish chaos synchronization in the low-frequency fluctuations regime. A third laser with identical external feedback but coupled unidirectionally to one of the pair does not synchronize. Both experiments and simulations reveal the existence of a window of parameters for which synchronization by mutual coupling is possible but synchronization by unidirectional coupling is not. This parameter space forms the basis of a proposed public-channel cryptographic scheme and is robust to various possible attacks.
@article{arxiv.cond-mat/0507554,
title = {A framework for public-channel cryptography using chaotic lasers},
author = {Noam Gross and Einat Klein and Michael Rosenbluh and Wolfgang Kinzel and Lev Khaykovich and Ido Kanter},
journal= {arXiv preprint arXiv:cond-mat/0507554},
year = {2007}
}