In this work, we propose a joint security approach based on physical layer security (PhySec) and noisy ciphertext to improve the secrecy rate of a relay network with cooperative jamming via two trusted relays. While the secrecy capacity has been considered as the maximum limit for a perfect secrecy at the physical layer, we demonstrate that the consideration of error- prone ciphertext in encryption and its interaction with PhySec allows us to transmit above the PhySec capacity without any leakage. By formulating and solving a non-convex encryption- aided secrecy rate maximization problem, it is shown that beyond PhySec capacity performances can be achieved even in a simple jamming scenario in which the two jammers just send independent jamming signals. The optimal encryption-aware power allocation and the secrecy rate maximization solution are also established in the case of common jamming signals to further increase the secrecy rate. Numerical results are finally provided to demonstrate the superiority of the proposed joint security framework over traditional PhySec.
In this work, we propose a joint security approach based on physical layer security (PhySec) and noisy ciphertext to improve the secrecy rate of a relay network with cooperative jamming via two trusted relays. While the secrecy capacity has been considered as the maximum limit for a perfect secrecy at the physical layer, we demonstrate that the consideration of error- prone ciphertext in encryption and its interaction with PhySec allows us to transmit above the PhySec capacity without any leakage. By formulating and solving a non-convex encryption- aided secrecy rate maximization problem, it is shown that beyond PhySec capacity performances can be achieved even in a simple jamming scenario in which the two jammers just send independent jamming signals. The optimal encryption-aware power allocation and the secrecy rate maximization solution are also established in the case of common jamming signals to further increase the secrecy rate. Numerical results are finally provided to demonstrate the superiority of the proposed joint security framework over traditional PhySec.
Conventional physical layer (PHY) security assumes unencrypted transmissions, requiring zero information leakage to adversaries. By incorporating encryption, this constraint can be relaxed, enabling higher secure transmission rates while tolerating limited leakage. This paper investigates an encryption-aware power allocation strategy and achievable transmission rate of a Gaussian wiretap channel in the presence of multiple cooperative jammers. By analyzing the rate-equivocation region and the corresponding rate maximization problem, optimal cooperative jamming strategy that maximizes the encryption-aware secrecy capacity is first addressed. The encryption-aware rate maximization problem is then shown to be equivalent to a non-convex beamforming vector optimization under a non-linear constraint, which is explicitly solved. Our numerical results illustrate that by utilizing the prior knowledge of encryption, optimizing the power allocation among jamming nodes significantly enhances the achievable secrecy rates.
This paper proposes a new joint cooperative beamforming and jamming (JCBJ) scheme for improving the physical layer security of decode-and-forward wireless networks where a source node transmits to its destination with the aid of multiple intermediate nodes in the presence of an eavesdropper. In the proposed JCBJ scheme, we select the intermediate nodes succeeding in source decoding as the relays to forward the source transmission simultaneously by employing a beamforming weight vector, and meanwhile, use the remaining ones as the friendly jammers to disturb the eavesdropper by sending artificial noise. In order to achieve the secrecy rate maximum, we further study on the power allocation among the source, relays, and jammers under two assumptions of the wiretap link's channel state information. We derive the closed-form optimal solutions by first allocating the transmit power at the source within different ranges to consider all the possible relay selection schemes in which different numbers of relays are employed, and then transforming the multivariable power allocation problem to a set of single-variable optimization subproblems. Our numerical results show the superiority of the proposed JCBJ scheme and the proposed power allocation strategies.
In conventional physical layer security schemes no leakage of private information to adversary nodes is tolerated, and no assumption on the encryption of information is considered. This is a limiting assumption in physical layer security, which compromises the efficiency of such schemes. This paper introduces an approach in which a prior knowledge of encryption can be used to improve the security performance of cooperative jamming in Gaussian wiretap channels as an example of physical layer security approached. The proposed approach, however, is not limited to the considered scenario of cooperative jamming and can be applied to other scenarios. We consider a system composed of a transmitter, a receiver, and eavesdropper and several jamming nodes that work independently, and formulate an optimization problem to maximize the secrecy rate with the knowledge of encryption and attempt to solve it by driving the rate-equivocation region to constrain and determine the feasibility of the solution. We then exploit a linear approximation to solve the resulted nonconvex optimization problem to maximize the secure transmission rate. Our numerical results show that prior knowledge of encryption can be exploited to allocate the available power to the jamming nodes to significantly increase the secure transmission rate.
Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without upper layer data encryption. However, they are hampered by wireless channel conditions: absent feedback, they are typically feasible only when the source-destination channel is better than the source-eavesdropper channel. Node cooperation is a means to overcome this challenge and improve the performance of secure wireless communications. This paper addresses secure communications of one source-destination pair with the help of multiple cooperating relays in the presence of one or more eavesdroppers. Three cooperative schemes are considered: decode-and-forward (DF), amplify-and-forward (AF), and cooperative jamming (CJ). For these schemes, the relays transmit a weighted version of a reencoded noise-free message signal (for DF), a received noisy source signal (for AF), or a common jamming signal (for CJ). Novel system designs are proposed, consisting of the determination of relay weights and the allocation of transmit power, that maximize the achievable secrecy rate subject to a transmit power constraint, or, minimize the transmit power subject to a secrecy rate constraint. For DF in the presence of one eavesdropper, closed-form optimal solutions are derived for the relay weights. For other problems, since the optimal relay weights are difficult to obtain, several criteria are considered leading to suboptimal but simple solutions, i.e., the complete nulling of the message signals at all eavesdroppers (for DF and AF), or the complete nulling of jamming signal at the destination (for CJ). Based on the designed relay weights, for DF in the presence of multiple eavesdroppers, and for CJ in the presence of one eavesdropper, the optimal power allocation is obtained in closed-form; in all other cases the optimal power allocation is obtained via iterative algorithms. Numerical evaluation of the obtained secrecy rate and transmit power results show that the proposed design can significantly improve the performance of secure wireless communications.
In this paper, we consider a two-way relay network where two sources can communicate only through an unauthenticated intermediate relay node. We investigate secure communications of this two-way relay scenario using physical layer security. Specifically, we treat the relay node as an eavesdropper from whom the information transmitted by the sources needs to be kept secret, despite the fact that its cooperation in relaying this information is essential. We first find that a non-zero secrecy rate is indeed achievable in this two-way relay network even without external jammers. Further still, with the help of friendly jammers who can transmit jamming signals to distract the malicious relay, a positive gain of the secrecy rate can be realized. In order to obtain the maximum secrecy rate, we define and then analyze an optimization problem. Finally, an optimal solution of jamming power allocation is provided for the system with friendly jammers.
In this paper, the security of two-phase relaying system with multiple intermediate nodes in the presence of a malicious eavesdropper is investigated. To enhance the secrecy, a joint cooperative beamforming and jamming combined with relay and jammer selection is proposed. First, the source broadcasts its signal to the relays that are located close to source in a cluster, i.e., the source node uses a small amount of power to broadcast its message locally to other nodes of the cluster, while destination and the eavesdropper are located outside this cluster. In the second phase, two relays transmit re-encoded signal with optimal beamforming such that the secrecy rate is maximized. Simultaneously, two other intermediate nodes (which act as friendly jammers) transmit random jamming signals to degrade the eavesdropper’s channel. Our goal in this paper is to maximize the secrecy rate by applying different methods such as cooperative beamforming, cooperative jamming and relay and jammer selection. To avoid operational complexity, we consider the minimum number of intermediate nodes needed for relaying and jamming without losing the performance, i.e., achieving a non-zero secrecy rate. Cooperative beamforming with multiple relays demands high amount of information exchange and therefore increases the operational complexity. Thus, we aim to reduce the number of relays which take part in cooperative beamforming. Limiting the number of relays may have a bad effect on the coding gain which we compensate it with a proposed selection gain scheme. Numerical results demonstrate the advantage of our proposed scheme compared to the scheme with no cooperative jamming. The main contribution of this work is combining cooperative beamforming and jamming with relay and jammer selection to enhance the physical layer security.