The full-space capability of the reconfigurable intelligent surface (RIS) provides an intelligent radio environment for information transmissions. This paper investigates the RIS-assisted secure transmissions in the presence of multiple eavesdroppers (Eves), where the colluding and the non-colluding behaviors of Eves are considered. We first propose a tractable Gamma distribution to characterize the distributions of the signal-to-noise ratio (SNR) under the Rayleigh, the Rice and the Nakagami-m channels. Then we derive the theoretical expressions of the average security capacity (ASC) for colluding and non-colluding eavesdroppers. Besides, the asymptotic expressions of the ASC are also obtained when the SNRs are large in practical scenarios. The simulation results demonstrate that the RIS is capable of reducing the negative impact of the increase in the number of eavesdroppers on the security performance by deploying more RIS elements in both colluding and non-colluding eavesdroppers.
The full-space capability of the reconfigurable intelligent surface (RIS) provides an intelligent radio environment for information transmissions. This paper investigates the RIS-assisted secure transmissions in the presence of multiple eavesdroppers (Eves), where the colluding and the non-colluding behaviors of Eves are considered. We first propose a tractable Gamma distribution to characterize the distributions of the signal-to-noise ratio (SNR) under the Rayleigh, the Rice and the Nakagami-m channels. Then we derive the theoretical expressions of the average security capacity (ASC) for colluding and non-colluding eavesdroppers. Besides, the asymptotic expressions of the ASC are also obtained when the SNRs are large in practical scenarios. The simulation results demonstrate that the RIS is capable of reducing the negative impact of the increase in the number of eavesdroppers on the security performance by deploying more RIS elements in both colluding and non-colluding eavesdroppers.
In this article, the physical layer security (PLS) is investigated for reconfigurable intelligent surface (RIS)-aided wireless communication systems, where one RIS is deployed to assist the communications between a pair of transmitter (Alice) and receiver (Bob), under a passive eavesdropper (Eve) attack. For the Eve, different from the bounded channel state information uncertainty model, the distribution of the Eve’s location is introduced into the wiretap link. In the proposed system, considering that the Eve can overhear signals transmitted from Alice or reflected by the RIS, two scenarios are studied for RIS-aided secure communication systems: one is that the Eve distributes close to Alice without the RIS orientation, and the other is that the Eve locates close to Bob and in the presence of the RIS. After investigating the probability distribution functions of the Eve’s location and the wiretap link, the novel cumulative density functions (CDFs) of the received signal-to-noise ratios (SNRs) at the Eves are, respectively, derived for the two considered scenarios, taking into account the effects of RIS reflection coefficients, pathloss, and Eve’s location distribution. The closed-form expressions for the probability of the nonzero secrecy capacity and the ergodic secrecy capacity are obtained, providing insights into the impact of the Eve’s location uncertainty and the RIS design on the secrecy performance. Moreover, based on the derived CDFs for received SNRs at Eves, the secrecy outage probabilities are, respectively, analyzed. Specifically, under the constraint of the secrecy outage probability, the closed forms of the minimum required SNRs at Bob and the number of RIS elements are also obtained. Simulation and analytical results corroborate the derived expressions and reveal the tradeoff between the system’s energy efficiency and the number of RIS elements.
This paper investigates the enhancement of security in Rayleigh fading channels using the best reconfigurable intelligent surface (RIS). The study focuses on a scenario involving a single legitimate receiver and a single eavesdropper, both operating over a Rayleigh fading channel. The impact of key parameters such as the eavesdroppers average signal-to-noise ratio (SNR), the number of reflecting elements of a RIS, and the number of RIS is thoroughly examined. Analytical expressions for the ergodic secrecy capacity (ESC) are derived to evaluate the systems secrecy performance. Furthermore, a comparative analysis is carried out between systems with and without RIS integration. The results confirm that deploying RIS significantly improves the ergodic secrecy capacity in wireless systems, thereby providing a foundation for further research and potential realworld implementations.
In this paper, we investigate the secrecy performance of a secure wireless communication system configured with reconfigurable intelligent surfaces (RIS). In particular, a legitimate source sends its private message to a legitimate destination with the aid of an RIS, while a passive eavesdropper intercepts this private information from both source and RIS. Considering this system setup, we first study the statistical analysis of the instantaneous signal-to-noise ratios (SNRs) at the destination and eavesdropper by exploiting the method of moments. Then, we deduce the closed-form expression of the ergodic secrecy capacity (ESC) over independent and identically distributed Rayleigh fading channels. Further, we provide the asymptotic ESC analysis in the high SNR regime to reveal some insightful information. Using the asymptotic ESC analysis, we also analytically present the impact of number of RIS elements on the ESC performance. Lastly, the analytical findings are corroborated via numerical and simulation studies, and show the impact of various involved parameters on the ESC performance.
This letter investigates the ergodic secrecy rate (ESR) of a reconfigurable intelligent surface (RIS)-assisted communication system in the presence multiple eavesdroppers (Eves), and by assuming discrete phase shifts at the RIS. In particular, a closed-form approximation of the ESR is derived for both non-colluding and colluding Eves. The analytical results are shown to be accurate when the number of reflecting elements of the RIS N is large. Asymptotic analysis is provided to investigate the impact of N on the ESR, and it is proved that the ESR scales with log2N for both non-colluding and colluding Eves. Numerical results are provided to verify the analytical results and the obtained scaling laws.
In this letter, we analyze the secrecy performance of a reconfigurable intelligent surface (RIS)-aided communication system with spatially random unmanned aerial vehicles (UAVs) acting as eavesdroppers. We consider the scenarios where the base station (BS) is equipped with single and multiple antennas. The signal-to-noise ratios (SNRs) of the legitimate user and the eavesdroppers are derived analytically and approximated through a computationally effective method. The ergodic secrecy capacity is approximated and derived in closed-form expressions. Simulation results validate the accuracy of the analytical and approximate expressions and show the security-enhanced effect of the deployment of the RIS.
Unlike prior works assuming perfect attack detection, this paper investigates the physical layer security of a simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) aided network under a full-duplex active eavesdropper in the more realistic scenario where its jamming remains undetected by the legitimate transmitter. Assuming Nakagami-m fading channels, we first derive the probability density functions (PDFs) of the signal-to-interference ratios (SIRs) at both the legitimate user and the eavesdropper. Then, using the PDFs, we obtain novel closed-form expressions for key secrecy metrics, including the probability of nonzero secrecy capacity (PNSC), secrecy outage probability (SOP), and average secrecy capacity (ASC). Moreover, the asymptotic PNSC, SOP, and ASC at high signal-to noise ratio (SNR) are also derived. Based on those asymptotic expressions, we present compact expressions for several key performance indicators: 1) the secrecy diversity order and the secrecy array gain of the SOP, and 2) the high SNR slope and the high SNR power offset of the ASC. Results demonstrate that, compared to the passive eavesdropper scheme, the active jamming attack carried out by Eve will not cause any loss in secrecy diversity gain and high SNR slope, but only result in the loss of secrecy array gain and high SNR power offset. Finally, we verify our analytical results via simulations.