In this study, we investigate information-theoretical security and covert communication. In covert communication, our aim is communication via the source-relay-destination link, without noticing the existence of communication by the multiple antenna warden. For secure transmission, our aim is to prevent possible eavesdropping by multiple antenna untrusted relay. To satisfy these requirements, we proposed a cooperative jamming strategy in two phases of transmission. In the proposed scheme, the source has multiple antenna and the efficiency of the maximum-ratio transmission/maximum-ratio combining (MRT/MRC) method for sending data to the relay has been evaluated. Due to the total transmit power restriction in each phase, a constrained optimization problem is formulated. Then, it is solved by converting to a multi-objective optimization problem. Finally, we employ the non-dominated sorting genetic algorithm II (NSGAII) to solve it.
In this study, we investigate information-theoretical security and covert communication. In covert communication, our aim is communication via the source-relay-destination link, without noticing the existence of communication by the multiple antenna warden. For secure transmission, our aim is to prevent possible eavesdropping by multiple antenna untrusted relay. To satisfy these requirements, we proposed a cooperative jamming strategy in two phases of transmission. In the proposed scheme, the source has multiple antenna and the efficiency of the maximum-ratio transmission/maximum-ratio combining (MRT/MRC) method for sending data to the relay has been evaluated. Due to the total transmit power restriction in each phase, a constrained optimization problem is formulated. Then, it is solved by converting to a multi-objective optimization problem. Finally, we employ the non-dominated sorting genetic algorithm II (NSGAII) to solve it.
In this paper, we investigate the problem of secure communication with covert requirement in untrusted relaying networks. Our considered system model contains one source, one destination, one untrusted relay, and one Willie. The untrusted relay tries to extract the information signal, while the goal of Willie is to detect the presence of the information signal transmitted by the source, in the current time slot. To overcome these two attacks, it is assumed that the destination and the source inject jamming signal to the network in phase I and phase II, respectively. Accordingly, the communication in our proposed system model is accomplished in two phases. In the first phase, when the source transmits its data to the untrusted relay, the destination broadcasts its jamming signal. In the second phase, when the relay retransmits the received signal, the source transmits a jamming signal with one of its antennas. For this system model, we suggest a novel power allocation strategy to maximize the instantaneous secrecy rate subject to satisfying the covert requirements in both of the phases. Since the proposed optimization problem is non-convex, the Successive Convex Approximation (SCA) method is used to change it to a convex optimization problem. Numerical curves are presented to reveal the impact of the untrusted relay's location an number of source antennas on the secrecy performance.
In this paper, we address the problem of joint covert communication and secure transmission in untrusted relaying networks when multiple wardens exist in the network. We first consider a system model consisting of one source, one untrusted amplify-and-forward relay, one destination, and one warden. For covert communications, our aim is to prevent the warden from detecting the presence of communications via the source-relay-destination link. For secure transmission, our aim is to prevent the untrusted relay from decoding the source signal. To satisfy these requirements, we propose that the destination and the source inject jamming signals during the source-to-relay and relay-to-destination transmission phases, respectively. For the considered system model, we propose a power allocation strategy to maximize the secrecy rate and satisfy the covert requirements in both of the phases. Given that the proposed optimization problem is non-convex, we employ the successive convex approximation (SCA) approach to derive a tractable solution. To obtain further insights, we generalize our analytical results to consider multiple untrusted relays and multiple wardens. We focus on two scenarios of non-colluding and colluding wardens. Our results highlight that as the number of relays increases, the achievable secrecy rate increases while the average detection error probability decreases. This is a novel observation of a fundamental trade-off between covert requirement and secrecy performance.
Covert communication can hide confidential signals in environmental noise to avoid being detected and provide comprehensive security for wireless transmission. However, there still exists significant risks in the wireless transmission once being detected. In this paper, we propose a more secure covert scheme, where a multiple antennas transmitter assisted by a multi-antenna UAV jammer maximizes the covert secrecy rate under the scenarios of both correct and incorrect detection by a warden with both error detection probability and eavesdropping rate limitations satisfied. The transmitter and jammer adopt maximum ratio transmission (MRT) and zero-forcing to maximize the transmission rate and minimize the interference at the receiver, respectively. First, we analyze the monotonicity of error detection probability to determine the optimal power detection threshold and the corresponding largest error detection probability. Then, under this worst case, we jointly optimize the transmit and jamming power to maximize the covert secrecy rate while guaranteeing the covert and eavesdropping limits meet their respective requirements. Finally, simulation results are presented to prove the correctness of the theoretical conclusion and evaluate the effectiveness of our proposed scheme.
In this paper, a secured dual-hop confidential communication system is considered. In which, a source transmits secret information to the destination in the presence of an interferer and an eavesdropper. And, multiple relays provide cooperative diversity at the destination. The interferer, source and relays are equipped with single antenna whereas the destination and eavesdropper are equipped with multiple antennas. The maximum ratio combining (MRC) technique is used to get the best output SNR at the receiver. At the receiver, the expression of MRC combiner output SNR is derived using optimal weighting vector to protect the information from eavesdropping, so that the eavesdropper can't decipher the source message. Then, we derive the optimum secrecy capacity expression at the destination. The derived expressions and the numerical results show that there is an enhancement of secrecy capacity due to the strategy of optimization of the output SNR by weighting vector at the destination.
This paper investigates secure communications of energy harvesting untrusted relay networks, where the destination assists jamming signal to prevent the untrusted relay from eavesdropping and to improve the forwarding ability of the energy constrained relay. Firstly, the source and the destination transmit the signals to the relay with maximal ratio transmission (MRT) technique or transmit antenna selection (TAS) technique. Then, the destination utilizes maximal ratio combining (MRC) technique or receive antenna selection (RAS) technique to receive the forwarded information. Therefore, four transmission and reception schemes are considered. For each scheme, the closed-form expressions of the secrecy outage probability (SOP) and the connection outage probability (COP) are derived. Besides, the effective secrecy throughput (EST) metric is analyzed to achieve a good tradeoff between security and reliability. In addition, the asymptotic performance of EST is also considered at the high signal-to-noise ratio (SNR). Finally, simulation results illustrate that: (1) the EST of the system with MRT and MRC scheme are superior to other schemes, however, in the high SNR regime, the EST of the system with MRT scheme is inferior to TAS; and (2) for the source node, there exists an optimal number of antennas to maximize the EST of the proposed schemes.
The two-stage physical layer security transmission scheme based on Simultaneous Wireless Information and Power Transfer and friendly jamming signals aided is proposed to solve the energy-constrained problem of signal processing and secure transmission issues of confidential information upon the multi-antenna relay systems. First, a multi-antenna relay system model based on the amplify-and-forward protocol is established. Then, Considering the scenario of multiple eavesdroppers and non-collusion eavesdropping, Analyzing the transmission process of system energy and information, the optimal transmission antenna selection strategy and the optimal jamming antenna selection strategy are respectively proposed in order to maximize the secrecy performance of the system. Next, the closed-form expressions of the system secrecy outage probability are derived. Finally, the Monte Carlo simulation method is applied to verify the correctness of the theoretical derivation, and the influence of parameters such as the transmit signal-to-noise ratio, power splitting factor and power allocation coefficient on the secrecy performance of the system is analyzed. The simulation results show that the proposed transmission scheme outperforms compared with the existing security transmission scheme.