Numerical Study on Secrecy Capacity and Code Length Dependence of the Performances in Optical Wiretap Channels

TL;DR

This paper numerically analyzes the secrecy capacity of optical wiretap channels using on-off keying modulation, demonstrating the potential for secure satellite-ground optical links over wider distances than quantum key distribution, and estimating necessary code lengths.

Contribution

It provides a numerical study of secrecy rates in optical wiretap channels and establishes bounds on code length for secure communications in satellite links.

Findings

Secure optical links possible over wider distances than quantum key distribution.

Upper bounds on decoding error and leaked information are provided.

Reasonable code lengths for secure communication schemes are shown to exist.

Abstract

Secrecy issues of free-space optical links realizing information theoretically secure communications as well as high transmission rates are discussed. We numerically study secrecy communication rates of optical wiretap channel based on on-off keying modulation under typical conditions met in satellite-ground links. It is shown that under reasonable degraded conditions on a wiretapper, information theoretically secure communications should be possible in a much wider distance range than a range limit of quantum key distribution, enabling secure optical links between geostationary earth orbit satellites and ground stations with currently available technologies. We also provide the upper bounds on the decoding error probability and the leaked information to estimate a necessary code length for given required levels of performances. This result ensures that a reasonable length wiretap channel code for our proposed scheme must exist.