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.
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.
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.
In traditional physical layer security paradigm, no leakage of confidential information to the eavesdropper is tolerated regardless of whether the message is encrypted or not. This will result in an achievable secure transmission rate that is significantly smaller than the channel capacity. This article presents a novel approach that allows treatment of physical layer security in conjunction with encryption to achieve a flexible trade-off of system resources. We propose a novel framework to model the interplay between secured transmission rate and error probability in error prone ciphertexts. To this end, we use the concept of rate-equivocation region to establish such a connection. To clearly describe the application of our framework, we consider the case of 4-node Gaussian wiretap channel. For such a channel, we characterize the rate-equivocation region in different scenarios, and then use it to study the achievable rate of encryption-aware physical layer security. The obtained results show that, for a fixed transmission power, the prior knowledge of encryption can significantly increase the secured transmission rate. In addition, encryption-aware physical layer security can achieve a target transmission rate at a reduced transmission power compared to the conventional encryption-agnostic physical layer security.
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.
We study strategies for enhanced secrecy using cooperative jamming in secure communication systems with limited rate feedback. A Gaussian multiple-input multiple-output (MIMO) wiretap channel with a jamming helper is considered. The transmitter and helper both require channel state information (CSI), which is quantized at the receiver and fed back through two sum-rate-limited feedback channels. The quantization errors result in reduced beamforming gain from the transmitter, as well as interference leakage from the helper. First, under the assumption that the eavesdropper's CSI is completely unknown, we derive a lower bound on the average main channel rate and find the feedback bit allocation that maximizes the jamming power under a constraint on the bound. For the case where statistical CSI for the eavesdropper's channel is available, we derive a lower bound on the average secrecy rate, and we optimize the bound to find a suitable bit allocation and the transmit powers allocated to the transmitter and helper. For the case where the transmitter and helper have the same number of antennas, we obtain a closed-form solution for the optimal bit allocation. Simulations verify the theoretical analysis and demonstrate the significant performance gain that results with intelligent feedback bit allocation and power control.
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.
Cooperative jamming approach has been commonly used in the field of physical layer security to achieve a good secrecy rate of wireless networks. In this approach, the Gaussian noise signal sent by a friendly jammer can disrupt the reception of the eavesdropper, however, it may also interfere with the legitimate receiver. In this paper, we propose a novel approach, namely, information jamming, to go beyond the secrecy rate achieved by the traditional cooperative jamming approach in a multiple-input single-output (MISO) wiretap channel. We propose that a multi-antenna friendly jammer transmits the source message rather than Gaussian noise signal for simultaneously enhancing the signal strength at the legitimate receiver and canceling the received signal at the eavesdropper. In particular, we aim to maximize the achievable secrecy rate by optimizing the information jammer's beamforming vector. Though the optimization problem is non-convex, we successfully solve it optimally via a two-stage based numerical approach. To gain more useful analytical results, we also propose two suboptimal jamming schemes with low computation, by targeting at improving the legitimate reception and avoiding the eavesdropping, respectively. Finally, numerical results show that the proposed information jamming approach significantly helps go beyond the secrecy rate of the existing cooperative jamming approach, especially when the transmit power of the jammer is large enough.