Optical countermeasures and security of free-space optical communication links

Sidorovich, V. G.

doi:10.1117/12.565348

Cited by 13 publications

(4 citation statements)

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“…This technology is already being deployed in the form of infrared communications [11]-[12], and ultraviolet (UV) systems are currently under development [13]- [14]. However, despite the numerous benefits that this technology offers, coding is still needed for those scenarios in which the channel itself does not provide absolute secrecy, such as when the beam of light is reflected or scattered by solid objects, dust or water droplets [15]. Although in this case the signal has been degraded, an eavesdropper could still gain valuable information.We examine the fundamental limits of coding for secure communication over optical channels by studying the secrecy capacity of the Poisson channel, a common model for direct detection optical communications systems.…”

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confidence: 99%

The Degraded Poisson Wiretap Channel

Laourine

Wagner

2012

IEEE Trans. Inform. Theory

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Providing security guarantees for wireless communication is critically important for today's applications. While previous work in this area has concentrated on radio frequency (RF) channels, providing security guarantees for RF channels is inherently difficult because they are prone to rapid variations due small scale fading. Wireless optical communication, on the other hand, is inherently more secure than RF communication due to the intrinsic aspects of the signal propagation in the optical and near-optical frequency range. In this paper, secure communication over wireless optical links is examined by studying the secrecy capacity of a direct detection system. For the degraded Poisson wiretap channel, a closed-form expression of the secrecy capacity is given. A complete characterization of the general rate-equivocation region is also presented. For achievability, an optimal code is explicitly constructed by using the structured code designed by Wyner for the Poisson channel. The converse is proved in two different ways:the first method relies only on simple properties of the conditional expectation and basic information theoretical inequalities, whereas the second method hinges on the recent link established between minimum mean square estimation and mutual information in Poisson channels. .). Part of this paper will be presented in the 2010 IEEE International Symposium on Information Theory (ISIT 2010). than the eavesdropper's. For RF channels, however, this is difficult to guarantee in practice due to the possibility of multipath fading. Indeed, even if the legitimate receiver is closer to the transmitter than the eavesdropper is, the legitimate receiver may still have a weaker channel due to fading. Moreover, since the fading state is a sensitive function of the position of the receivers, it is difficult to predict the degree of fading experienced by the legitimate receiver and the eavesdropper given imperfect information about their locations.One possible solution to this problem is to use optical or near-optical frequencies instead of RF. For optical wireless systems, the detector is usually multiple orders of magnitude larger than the wavelength of the transmitted beam, which provides natural immunity against multipath fading via spatial diversity [10]. This immunity makes predictions about the quality of the legitimate receiver's and the eavesdropper's signal based on their position more accurate. In fact, with the multipath problem gone, the only major channel impairment remaining is the pathloss which can be safely assumed to be higher for the eavesdropper if the legitimate receiver can guarantee that he is closer to the transmitter.Another advantage of optical communications over RF is that the transmitted signal is highly directional, making interception by a malevolent third party more difficult. This should be contrasted with the relatively-omnidirectional nature of RF transmissions, for which the signal is broadcasted over a wide angle. Yet another advantage of wireless optical communication is the...

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confidence: 99%

The Degraded Poisson Wiretap Channel

Laourine

Wagner

2012

IEEE Trans. Inform. Theory

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“…However, despite the numerous benefits that this technology offers, coding is still needed for those scenarios in which the channel itself does not provide absolute secrecy, such as when the beam of light is reflected or scattered by solid objects, dust or water droplets [6]. Although in this case the signal has been degraded, an eavesdropper could still gain valuable information.…”

Section: Introductionmentioning

confidence: 97%

Secrecy capacity of the degraded Poisson wiretap channel

Laourine

Wagner

2010

2010 IEEE International Symposium on Information Theory

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Providing security guarantees for the information "traveling" through the air is of critical importance for today's applications. Previous research concentrated on studying this problem when the medium used for communication is radio frequency (RF) channels. However, providing security guarantees on RF channels is a complicated task as RF channels' conditions are prone to rapid variations due small scale fading and at a given moment it is difficult to predict which of the main or wiretapper's channel has a better quality. Wireless optical communication is inherently more secure than regular RF communication. Despite this fact, optical communication is not completely immune against wiretapping and signal interception. The purpose of this paper is to study the secrecy capacity of a direct detection optical communication system. For the degraded Poisson wiretap channel, we give a complete characterization of the secrecy capacity in terms of the system parameters.

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“…Because of the high directionality of optical beams compared to the almost broadcast nature of RF signals, this makes them much harder, yet not impossible, to intercept. For this reason, the literature related to physical layer security in wireless optical communications is much scarcer, both for visible light [17] and free-space [18]- [20] optical (FSO) communications.…”

Section: Introductionmentioning

confidence: 99%

Physical-Layer Security in Free-Space Optical Communications

2015

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The communication between two legitimate peers in the presence of an external eavesdropper is studied from a physical-layer security perspective in the context of free-space optical (FSO) communications. We discuss viable mechanisms to eavesdrop the communication and study the effect of random optical irradiance fluctuations inherent to FSO communications on the probability of achieving a secure transmission. We observe that the joint effect of laser-beam divergence and turbulence-induced fading on the received irradiance, under certain conditions, allows an external eavesdropper close to the legitimate receiver to compromise the communication. Interestingly, we also observe that an eavesdropper placed close to the legitimate transmitter can easily compromise the communication by taking advantage of the larger attenuation suffered by the signal when propagating through the FSO link.

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Optical countermeasures and security of free-space optical communication links

Cited by 13 publications

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The Degraded Poisson Wiretap Channel

The Degraded Poisson Wiretap Channel

Secrecy capacity of the degraded Poisson wiretap channel

Physical-Layer Security in Free-Space Optical Communications

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