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Among the plenty of studies on physical layer security, multi-antenna signal processing and nodes cooperation are two widely adopted techniques. However, in practical systems there are many single-antenna devices that do not support cooperative transmission either. To guarantee the information security in this scenario, we propose a novel transmission strategy that exploits the temporal characteristics of a multipath fading channel. Specifically, we apply this strategy to a time-reversal-based communication system. We consider a joint design of signal waveform and artificial noise. Based on this approach, specific transmission schemes are designed for the cases with and without eavesdropper's channel state information (CSI), respectively. The numerical results show the superiority of our proposed schemes in terms of security enhancement even when the eavesdropper's CSI is unavailable. [ABSTRACT FROM AUTHOR]

In power-domain nonorthogonal multiple access, passive eavesdropping may appear among the users by successive interference cancellation. Furthermore, the external eavesdropper may do active eavesdropping (i.e., passive eavesdropping plus jamming) by a full-duplex technique. To combat this hybrid eavesdropping, we propose a novel physical layer security scheme. The main contributions in this scheme are as follows: 1) A time constellation is set up by the concept of timing channel, where each point contains several symbols and the intervals between them, exploits these intervals to carry privacy information, and can represent different values (i.e., multiple mapping rules are introduced). Based on this time constellation, different mapping rules are allocated to different users. 2) The beginning symbols of time constellation points are devised to take the information of mapping rule allocation. Moreover, an extra symbol transformation method for each beginning symbol is designed. According to these contributions, the advantages of our scheme are evident: 1) Each user only needs to judge the intervals and extract privacy information from them. It is predicted that the impact of jamming on this operation should be lower than that on directly using the modulated symbols to carry and transfer privacy information. In other words, the mistakes of privacy information acquisition with the time constellation should be less than that with the modulated symbols. 2) The mapping rule allocation and symbol transformation methods generate multiple possible values for one time constellation point. These possibilities bring the difficulty of determining the actual value represented by each point. Therefore, passive eavesdropping can be effectively suppressed. [ABSTRACT FROM AUTHOR]

Security is an issue of paramount importance, yet is it a significant challenge for wireless communications, which becomes more intricate when facing a full duplex (FD) active eavesdropper capable of performing eavesdropping and jamming simultaneously. In this paper, we investigate the physical layer security issue in the presence of an FD active eavesdropper, who launches jamming attacks to further improve the eavesdropping. The jamming, however, also results in self-interference at the eavesdropper itself. This security problem is formulated within a hierarchical game framework where the eavesdropper acts as the leader and the legitimate user is the follower. In particular, we first investigate the follower’s secrecy rate maximization problem and derive the optimal legitimate transmission strategy. Then, the leader’s wiretap rate maximization is expressed as a mathematical program with equilibrium constraints (MPEC). Leveraging the concavity of the follower’s problem, we transform the MPEC problem into a single-level optimization and obtain the jamming power allocation strategy by applying the primal-dual interior-point method. Moreover, we analyze the situations where only partial channel state information is available at the legitimate user and the corresponding impacts on the game. Finally, we present extensive simulation results to validate our theoretical analysis. [ABSTRACT FROM PUBLISHER]

Aiming at allocating more licensed spectrum to wireless sensor nodes (SNs) under the constraint of the information security requirement of the primary system, in this paper, we propose a cooperative relaying and jamming secure transmission (CRJS) scheme in which SNs will relay primary message and jam primary eavesdrop concurrently with SN’s downlink and uplink information transmission in cognitive radio sensor networks (CRSNs). In our proposed CRJS scheme, SNs take advantages of physical layer secure technologies to protect the primary transmission and acquire some interference-free licensed spectrum as a reward. In addition, both decode-and-forward (DF) and amplify-and-forward (AF) relaying protocols are investigated in our proposed CRJS scheme. Our object is to maximize the transmission rate of SNs by optimal allocating of the relaying power, jamming power, and downlink and uplink transmit power under the target secure transmission rate requirement of the primary system. Moreover, two suboptimal algorithms are proposed to deal with these optimization problems. Furthermore, we analyze the transmission rate of SNs and allocate the relaying power, jamming power, and downlink and uplink transmit power for the asymptotic scenarios. Simulation results demonstrate the performance superiority of our developed strategy over conventional jamming scheme in terms of the transmission rate of WSN. [ABSTRACT FROM AUTHOR]