Ensuring secure optical wireless communication in underwater environments is a critical challenge, but still largely unexplored. In this work, we propose a novel physical-layer jamming scheme based on multi-mirror reflection and cooperative interference. Specifically, we consider concave mirrors with low curvature paired with an optical concentrator as integrated at both the transmitter and the legitimate receiver. his architecture collects the incident jamming signal over a wide acceptance angle, focuses it onto the mirror surface, and re-radiates it over an enlarged apparent source area, yielding a significant intensity gain on the jamming path toward the eavesdropper. The resulting jamming reflections significantly impair the capability of a potential passive eavesdropper to intercept the communication. On the other hand, the integrity and quality of the legitimate link is guaranteed. Such a security framework is presented for the typical optical signaling based on intensity modulation and direct detection, and its passive, zero-overhead architecture requires no knowledge of the eavesdropper's position or channel, making it particularly suited to dynamic underwater deployments. The effectiveness of the proposed strategy is validated through simulations, including a detailed model of optical propagation in different channel scenarios and water types affected by turbulenceinduced fading. At the eavesdropper side, successive interference cancellation based detection is assumed, since it results as the most favorable strategy for the eavesdropper and yielding a conservative lower bound on the system secrecy performance. Numerical results confirm that even when the eavesdropper has perfect knowledge of the illegitimate link, the proposed scheme achieves robust physical-layer security across a wide range of underwater conditions, preserving the legitimate link reliability.
Ensuring secure optical wireless communication in underwater environments is a critical challenge, but still largely unexplored. In this work, we propose a novel physical-layer jamming scheme based on multi-mirror reflection and cooperative interference. Specifically, we consider concave mirrors with low curvature paired with an optical concentrator as integrated at both the transmitter and the legitimate receiver. his architecture collects the incident jamming signal over a wide acceptance angle, focuses it onto the mirror surface, and re-radiates it over an enlarged apparent source area, yielding a significant intensity gain on the jamming path toward the eavesdropper. The resulting jamming reflections significantly impair the capability of a potential passive eavesdropper to intercept the communication. On the other hand, the integrity and quality of the legitimate link is guaranteed. Such a security framework is presented for the typical optical signaling based on intensity modulation and direct detection, and its passive, zero-overhead architecture requires no knowledge of the eavesdropper's position or channel, making it particularly suited to dynamic underwater deployments. The effectiveness of the proposed strategy is validated through simulations, including a detailed model of optical propagation in different channel scenarios and water types affected by turbulenceinduced fading. At the eavesdropper side, successive interference cancellation based detection is assumed, since it results as the most favorable strategy for the eavesdropper and yielding a conservative lower bound on the system secrecy performance. Numerical results confirm that even when the eavesdropper has perfect knowledge of the illegitimate link, the proposed scheme achieves robust physical-layer security across a wide range of underwater conditions, preserving the legitimate link reliability.
Providing secure optical wireless communication is a crucial challenge also in underwater scenarios, even though it has not been extensively investigated in the literature yet. In this paper, we propose a novel physical layer optical jamming scheme for underwater communications that, by leveraging signal reflection by mirror surfaces integrated with the reference transmitter (Alice), allows a reliable signal detection for a legitimate node while denying the transmission interception to potential eavesdroppers. Preliminary results demonstrate the proposed solution to effectively deny a reliable signal detection for an eavesdropper, while preserving the legitimate link integrity.
Underwater wireless optical communication (UWOC) possesses significant advantages, such as high bandwidth, low latency, and low power consumption, making it a key technology for building information networks in marine environments. However, due to the scattering effect of seawater, some photons carrying information inevitably scatter out of their predetermined paths, leading to the possibility for information leakage. Therefore, we propose a physical-layer security analysis model for UWOC systems based on the wiretap channel model. The model evaluates the security of the communication system by calculating the capacity difference between the legitimate channel and the eavesdropping channel in the UWOC system. Specifically, the model first constructs the three-dimensional intensity distribution of scattered photons in the underwater channel via Monte Carlo simulations and experimental measurements. Then, it calculates the capacities of both the legitimate and eavesdropping channels based on the decoding results. Finally, the three-dimensional distribution of secrecy capacity is derived to assess the security of the communication system. In this work this model is used to analyze the security of the UWOC system in clear seawater environments. The results show that the secrecy capacity of the system is zero within a certain range near the transmission path, demonstrating that scattered photons can cause information leakage. We recommend that, in practical applications, monitoring the non-signal transmission area near the transmitter is essential to ensure communication security. This research provides a solution for analyzing the quantitative security of UWOC, which can strongly support the design of UWOC systems and encoding/decoding schemes.
Although underwater wireless optical communication (UWOC) receives much interest lately, security issues associated with it get little attention. In this work, it is the first attempt to investigate the physical layer security (PLS) performance of the vertical UWOC system with perfect and imperfect channel state information (CSI). Specifically speaking, the communication between two legitimate peers in the presence of an external eavesdropper is studied from the information-theoretic security perspective. Assuming that turbulence-induced fading over the vertical UWOC links is respectively subject to cascaded lognormal (LN) and Gamma-Gamma (GG) distributions for weak and moderate/strong turbulence conditions, and the angular pointing error is randomized by the Beckmann distribution, the composite cascaded statistical fading models are derived with the comprehensive effects of path loss, underwater turbulence, angular pointing errors, and channel estimation error. On the basis of these models, analysis frameworks of the probability of strictly positive secrecy capacity (SPSC), secrecy outage probability (SOP), and average secrecy capacity (ASC) are further obtained for this UWOC system, which are confirmed by Monte Carlo (MC) simulations. Furthermore, the effects including the number of layers, the level of channel estimation error, the link distance, the location of the eavesdropper, the quality of the main and eavesdropping channels on this system are analyzed for different water conditions. The presented results give valuable insights into the practical aspects of deployment of UWOC networks.
In this study, physical layer security (PLS) in a dual-hop underwater optical wireless communication (UOWC)-radio frequency (RF) network under the intruding attempts of multiple eavesdroppers via RF links is considered. An intermediate decode-and-forward (DF) relay node between an underwater source and a destination transforms the optical signal into an electrical form and forwards it to the destination node with the help of harvested energy by the relay from an integrated power beacon within the system. The source-to-relay link, i.e., a UOWC link, is assumed to follow a mixture of exponential generalized Gamma turbulence with pointing error impairments whereas all the remaining links, i.e., RF links, are assumed to undergo κ-μ shadowed fading. Here, two eavesdropping scenarios are considered depending on the types of intruders, i.e., colluding (Scenario-I) and non-colluding (Scenario-II) eavesdropping operations. The analytical expressions of secrecy outage probability (SOP), probability of strictly positive secrecy capacity (SPSC), and effective secrecy throughput (EST) are derived for each scenario. Furthermore, the impacts of UOWC and RF channel parameters as well as detection techniques on secrecy capacity are demonstrated. A comparative study between two scenarios demonstrates that the collusion between the eavesdroppers imposes the most harmful threat on secrecy throughput but a better secrecy level can be attained by adopting diversity at the destination and power beacon nodes along with heterodyne detection rather than intensity modulation and direct detection technique. Finally, all the derived expressions are verified with the numerical results.
As Internet of Things (IoT) has boomed in recent years, many security issues have also been exposed. Focusing on physical layer security in wireless Internet of Things network communication, a series of security methods have been widely studied. Nevertheless, cooperative jamming methods in physical layer security to fight against collusive eavesdroppers have not been thoroughly studied yet. In this article, we study a cooperative-jamming-based physical layer secure transmission scheme for Internet of Things wireless networks in the presence of collusive eavesdroppers. We design a cooperative jamming strategy without knowing the channel state information of eavesdroppers. Considering the cooperation of multiple nodes with multiple antennas, this strategy can maximize the signal-to-interference-plus-noise ratio at an actuator (legitimate receiver). Meanwhile, the generated cooperative jamming signals can reduce the signal-to-interference-plus-noise ratio at eavesdroppers. To explore the theoretical security performance of our strategy, we perform a secrecy outage probability analysis and an asymptotic analysis. In the cases of cooperative jamming and without cooperative jamming, the closed-form expressions of the secrecy outage probability are deduced, and the influence of system parameters on the secrecy outage probability becomes more intuitive through a strict mathematical asymptotic behavior analysis. In addition, considering the energy limitation of Internet of Things devices, we propose a power allocation algorithm to minimize the total transmission power given the security requirements. The numerical results show the effectiveness of our schemes and are consistent with the theoretical analysis.
The environment of wireless sensor networks (WSNs) makes the communication not only have the broadcast nature of wireless transmission, but also be limited to the low power and communication capability of sensor equipment. Both of them make it hard to ensure the confidentiality of communication. In this paper, we propose a cluster-based cooperative jamming scheme based on physical layer security for WSNs. The mathematical principle of the scheme is based on the design principle of code division multiple access. By using the orthogonality of orthogonal vectors, the legitimate receiver can effectively eliminate the noise, which is generated by the cooperative jamming nodes to disturb the eavesdropper. This scheme enables the legitimate receiver to ensure a strong communication confidentiality even if there is no location or channel advantage comparing with eavesdroppers. Through extensive simulations, the security performance of the proposed scheme is investigated in terms of secrecy rate.