Satellite internet serves as an indispensable component of the upcoming sixth‐generation networks for providing global broadband internet access service. Due to the open nature of satellite‐ground communication, security issue in satellite internet has always been an important concern for both industry and academia. Although many researchers focus on secure communications in satellite internet, the literature is surprisingly sparse, with no comprehensive overview of the state‐of‐the‐art security techniques. This paper provides an in‐depth survey of secure communications for various satellite internet scenarios. Based on different security mechanisms, we first categorize the existing works of secure communications in satellite internet into two categories: cryptography‐based and physical layer security‐based. The former includes classical encryption‐based and quantum encryption‐based secure communication, and the latter is further divided into precoding‐based, cooperative jamming‐based, relay selection‐based, and physical‐layer authentication‐based secure communication depending on the applied techniques. Finally, we provide some future research directions.

Communication performance relies largely on the availability of channel state information (CSI). This paper investigates the impact of outdated CSI on the achievable covert communication performance in a two-hop wireless relay system under two typical covert transmission schemes of rate-control transmission (RCT) and power-control transmission (PCT). We first apply the typical channel feedback delay model to determine the statistical distribution of outdated CSI, based on which we then develop theoretical models to depict the inherent relationship between outdated CSI and the fundamental covert performance metrics in terms of detection error probability (DEP) and covert rate (CR). With the help of these models, we further explore the optimization of DEP subject to the CR constraint as well as the optimization of CR subject to the DEP constraint to reveal the max-min DEP performance and the maximal CR performance with the outdated CSI. Finally, extensive numerical results are provided to illustrate the impact of outdated CSI on the covert communication performance.

This paper investigates the secure communication in a two-hop cooperative wireless network, where a buffer-aided relay helps forward data from the source to destination, and a passive eavesdropper attempts to intercept data transmission from both the source and relay. To ensure the transmission security and communication quality of service (QoS) of the system, we design novel link selection policies for two cases that the instantaneous channel state information is available or unavailable at the source node. For evaluating the system performance, we then derive the closed-form expressions of end-to-end secrecy outage probability, system throughput and secrecy throughput, respectively. Based on the theoretical performance analysis, we further explore the performance optimization issues, revealing the insightful tradeoffs between the transmission security and QoS. An iterative algorithm is developed to identify the optimal setting of link selection parameters, which is helpful for the practical configuration of link selection policies to satisfy various system performance requirements. Finally, we conduct simulations to validate our theoretical performance analysis, and also provide extensive numerical results to illustrate the efficiency of the proposed link selection policies for ensuring the secure communication in a two-hop cooperative network.

This paper explores the joint secrecy and delay guarantees based on opportunistic jamming and link selection in a wireless relay system consisting of a source, a destination, multiple buffer-aided relays and a passive eavesdropper wiretapping over both hops. Based on the information of link state and buffer status, we design a novel transmission scheme based on link selection and jammer selection, which dynamically grants transmission links different priorities for packet delivery, such that the constraints on both secrecy outage probability and packet delay are jointly satisfied. To understand the performance of the new scheme, we then apply the bitmap technique and Markov chain theory to develop a complete theoretical framework for the modelling of three fundamental metrics, namely reliability outage probability, packet discarding probability and secrecy/delay constrained throughput (SDT). Finally, we provide extensive simulation and numerical results to validate our theoretical modelling, as well as to demonstrate that the proposed scheme is superior to the benchmarks in terms of SDT.

This paper investigates the use of physical (PHY)-layer characteristics of wireless channels for identity authentication in Reconfigurable Intelligent Surface (RIS)-assisted wireless communication systems. We propose a generalized PHY-layer authentication scheme that involves both direct and cascaded channels for RIS-assisted IoT systems. The channels in each coherence block of the authentication phase are estimated using least squares estimation, and the estimation error covariance matrices are determined for performance evaluation. Leveraging the extracted features of the direct and cascaded channels, we establish authentication verification as a problem of differentiating two classes of changes. Auxiliary information in the form of second-order statistics assists the authentication verification procedure. Through statistical derivation using tools from statistical signal processing, matrix analysis, and composite hypothesis testing, we characterize false alarm and detection probabilities of the proposed scheme. Finally, we provide extensive numerical results to evaluate the performance and demonstrate the efficiency of the proposed authentication scheme across various system parameters.

The massive heterogeneous devices and open channels of the Internet of Things (IoT) lead to low efficiency and privacy leakage in the authentication process, which brings great challenges to identity authentication. This paper focuses on the anonymous authentication between the IoT edge device and the cloud server. In this work, we first propose a novel lightweight anonymous authentication protocol (LAAP) to meet security and efficiency requirements. Especially, the proposed protocol uses dynamic pseudonyms to prevent the traceable attacks caused by fixed identity identification and also uses symmetric encryption to optimize the server’s search for anonymous device information, and the time complexity is reduced from to . Then, the formal security analysis and informal security analysis are provided to prove the security of the proposed protocol. Finally, extensive numerical results indicate that the proposed LAAP protocol is superior to the benchmarks in terms of computing overhead and communication overhead, while the storage overhead is consistent with the lowest level among other protocols.