Bahareh Akhbari

Smart grids combine cyber systems with complex physical networks and present numerous technological challenges. One example is the implementation of communication technology, specifically within the advanced metering infrastructure, which has made it an attractive target for attackers. Cyber attacks, such as impersonation, unauthorised data access, fraud, energy theft, and reduced network reliability, are some of the threats faced by smart grids. Notably, recent proposals by Mahmood et al., Braeken et al., and Chaudhry et al. aimed at establishing secure communication, claiming their methods fulfil the requisite security criteria. This paper, however, reveals that each of these proposals exhibits security vulnerabilities and lacks sufficient features for deployment. In response to these shortcomings, this paper introduces a novel elliptic curve cryptography‐based key establishment scheme, specifically designed to enhance communication security in smart grid cyber‐physical systems. A comprehensive and comparative analysis of the security attributes of the proposed scheme is presented. Furthermore, the security of the scheme is formally validated within the random oracle under the Canetti‐Krawczyk security model. The AVISPA tool is also leveraged to verify the security assertions. The findings demonstrate that the proposed protocol is pioneering in efficiently satisfying the non‐repudiation feature, simultaneously ensuring user anonymity and perfect forward secrecy. It exhibits robustness against various well‐known attacks, including Denial of Service and ephemeral secret leakage attacks, all while effectively managing both computational complexity and communication costs.

In this paper, we use a linear programming (LP) optimization approach to evaluate the equivocation when coding over a wiretap channel model where the main channel is noiseless and the eavesdropper’s channel is a binary symmetric channel (BSC). Using this technique, we present a numerically-derived upper bound for the achievable secrecy rate in the finite blocklength regime that is tighter than traditional infinite blocklength bounds. We also propose a secrecy coding technique that outperforms random binning codes. When there is one overhead bit, this coding technique is optimum and achieves the newly derived bound. For cases with additional bits of overhead, our coding scheme can achieve equivocation rates close to the new bound. Furthermore, we explore the patterns of the generator matrix and the parity-check matrix for linear codes and we present binning techniques for both linear and nonlinear codes using two different approaches: recursive and non-recursive. To our knowledge, this is the first optimization solution for secrecy coding obtained through linear programming. Our new bounds and codes mark a significant breakthrough towards understanding fundamental limits of performance (and how to achieve them in some instances) for the binary symmetric wiretap channel with real finite blocklength coding constructions. Our techniques are especially useful for codes of small to medium blocklength, such as those that may be required by applications with small payloads, such as the Internet of Things.

In this paper, we propose to utilize an intelligent reflecting surface (IRS) as a promising technology to enhance the coverage and physical layer security of non-orthogonal multiple access (NOMA) system. In particular, an IRS-assisted NOMA system is considered with the aid of careful channel ordering of the NOMA users, in which the transmitter sends superposed signals to multiple legitimate users by virtue of the IRS in the presence of multiple eavesdroppers. Meanwhile, the secrecy performance of the IRS-assisted NOMA system is investigated under two wiretapping cases: non-colluding and colluding external eavesdroppers. In the non-colluding case, eavesdroppers operate independently, while in the colluding case, every eavesdroppers can combine their observations to decode the messages. To this end, we derive the approximate closed-form expressions for the secrecy outage probability (SOP) and the asymptotic SOP for each wiretapping case. Also, we assume that the phase of the IRS elements is set by using the ON–OFF control method. Based on analytical results, we show that the secrecy diversity order of the IRS-NOMA at legitimate users is in connection with the number of reflecting elements. From the numerical results, it can be seen that the IRS-NOMA can achieve superior secrecy performance with increasing the number of reflecting elements of the IRS. However, we also find out that using the finite ON state reflective elements can improve the secrecy performance. Actually, increasing the number of ON state reflective elements above five has a negative effect on the system’s secrecy performance.

In this paper, we have combined a game‐theoretic and an information‐theoretic notions to describe the selfish behavior of each user in a two‐user linear deterministic cognitive interference channel (LD‐CIC). The two‐user LD‐CIC is the simple case of the cognitive radio technology in the high SNR regime. This model is a solution to improve the spectral efficiency in software defined network (SDN) concept in 5G. In the two‐user LD‐CIC, the information bits of the primary/licensed transmitter is a‐priori provided at the cognitive/secondary/unlicensed transmitter. So that, the cognitive transmitter can cooperate and utilize the frequency spectrum to send the information bits of the both transmitters. In information‐theoretic approaches, full cooperation is assumed between transmitters for codebook and rate selection in this channel. This may not be a realistic assumption if transmitters are selfish and are willing to maximize their own benefit. In particular, we have defined the Stackelberg equilibrium (SE) region on the capacity region of the two‐user LD‐CIC to capture the behavior of each transmitter when they compete even though one of them is informed of the other transmitter information bits. We have implemented a two‐phase Stackelberg game with the primary and cognitive transmitters acting as the leader in the first phase, and the follower in the second phase, respectively. In this implementation, both transmitters are assumed to be selfish and only interested in optimizing their own pay‐offs. The SE region is characterized as a subset of capacity region in which the transmitters cannot gain more transmission rate by individually deviating from the SE strategy. The achievability of the resultant region has been configured using a randomized Han‐Kobayashi scheme for all the channel gains. Also, we have compared the obtained SE region with the previous equilibrium regions such as Nash equilibrium (NE) region of the linear deterministic interference channel (LD‐IC). The results have shown that the SE points on the sum‐rate of the LD‐CIC capacity region are more than the NE points on the sum rate of the capacity region of LD‐IC, so the SE region of the LD‐CIC is Pareto superior to the NE region of LD‐IC.

In this work, multiple energy‐limited Internet of Things (IoT) users are intended to communicate with their destination (). The scheduled IoT user harvests the energy from a source signal and uses this energy to forward a mixture of its message and the source message to the and the source destination based on non‐orthogonal multiple access (NOMA). Since the messages are transmitted at the same resource block, the far untrusted user (source destination) has the opportunity to access the message destined for the near user () by successive interference cancellation. Therefore, an IoT user scheduling strategy is proposed to achieve the reliability and security of transmission in the network. To indicate the superiority of the proposed scheduling scheme and the impact of different parameters on the network performance under untrusted users, the secrecy outage probability of the system is derived by tracking exact and asymptotic analyses and then it is compared with that of benchmarks through simulations. The results reveal the crucial role of the near user threshold secrecy rate as the system's bottleneck and the negligible impact of the power allocation coefficients and the untrusted far user threshold rate on the secrecy performance with increasing the signal‐to‐noise‐ratio.

With increasing the demand for transmitting secure information in wireless networks, device-to-device (D2D) communication has great potential to improve system performance. As a well-known security risk is eavesdropping in D2D communication, ensuring information security is quite challenging. In this paper, we first obtain the closed-forms of the secrecy outage probability (SOP) and the secrecy ergodic capacity (SEC) for direct and decode- and-forward (DF) relay modes. Numerical results are presented to verify the theoretical results, and these results show the cases that the DF relay mode improves security performance compared to the direct mode at long distances between the transmitter and receiver nodes. Further, we look into the optimization problems of secure resource allocation in D2D communication to maximize the SEC and to minimize the SOP by considering the strictly positive secrecy capacity constraint as a mixed-integer non-linear programming (MINLP) problem. In the continue, we convert the MINLP to convex optimization. Finally, we solve this program with a dual method and obtain an optimal solution in the direct and DF relay modes.

In this paper, the problem of secure communication over an entanglement-assisted classical-quantum multiple access channel is studied under one-shot setting. The main employed approach to this end, is combination of simultaneous decoding and position-based decoding techniques while a recently introduced approach is used to calculate leaked information.

To enhance the performance and the coverage area of the next‐generation heterogeneous wireless networks (HetNets), smaller cells such as femtocells are deployed. A reasonable resource allocation strategy is crucial for the operation of such systems. In this work, the Nash bargaining solution (NBS), Kalai–Smorodinsky bargaining solution (KSBS), and a proposed bargaining solution, which is the combination of NBS and KSBS, are studied to ensure the efficiency and fairness in the transmission rate allocation among femtocells. The mentioned bargaining solutions are optimised subject to the rate constraints due to the Han–Kobayashi (HK) rate splitting scheme, and a maximum tolerable interference caused by femtocell base stations (FBSs) at the macrocell user equipment. Two methods are used to address the bargaining solutions' optimisations. First, the conventional optimisation‐based method is used for the situations where the channel gains are known, then a reinforcement learning‐based algorithm for a real environment is proposed without being aware of the channel gains. To accelerate the speed of the learning process and to initialise the values of quality functions, the hotbooting technique is used. The bargaining solutions are compared by fairness and efficiency criteria in both methods. Numerical simulations show that the proposed reinforcement learning‐based algorithm achieves the same performance derived from the conventional optimisation method. First, this paper studies the two well‐known Nash and Kalai–Smorodinsky bargaining solutions as the good tools to establish fairness in rate allocation problem among femtocells in a HetNet. Then a new bargaining solution is proposed as the combination of the two bargaining solutions. The fairness and the efficiency of the allocated rates to femtocells as the output of optimisation problems of bargaining solutions are compared via Jain index criterion (as the fairness metric) and inverse price of anarchy criterion (as the efficiency metric). Moreover, the femtocell base stations are allowed to use Han–Kobayashi signalling scheme to send their signals in private and common messages which results in the best‐known achievable rate region. Two methods are used to solve the optimisation problems: the conventional optimisation method and the reinforcement learning‐based method (to formulate a real‐world model with the unknown channel gains). It is shown that the proposed bargaining solution (in both methods) results in fairer rates than Nash and Kalai–Smorodinsky bargaining solutions while all of them are efficient.