Artificial-noise jamming improves physical-layer security by degrading an eavesdropper's channel, but the injected noise also interferes with the legitimate receiver. We introduce a correlated-jamming protocol based on classical and quantum correlations that suppresses this self-interference while preserving the jamming penalty experienced by the eavesdropper. Bob broadcasts one mode of a correlated two-mode source and retains the second as a local reference. Eve, who has no access to the retained mode, receives the full thermal jamming field, whereas Bob uses an optimized joint measurement to cancel its correlated fluctuations. The residual self-jamming noise is governed by the conditional variance of the transmitted jamming quadrature given the retained reference. Any classically correlated source is bounded by the vacuum-noise floor and therefore restores Bob, at best, to his unjammed receiver noise. An entangled two-mode squeezed source surpasses this limit and produces sub-vacuum residual noise, with the maximum quantum advantage set by the transmissivity of the jamming path back to Bob. In the bright-source regime, this advantage becomes a fixed reduction in Bob's noise floor, independent of the signal and jamming powers. Within a bounded-collection wiretap model, correlated jamming preserves positive secrecy even when Eve has a stronger direct channel than Bob and remains effective against collective measurements on Eve's Gaussian output states. The protocol supports bright classical message transmission and requires no end-to-end quantum channel. Possible applications include shot-noise-limited optical communication, cryogenic microwave networks, and covert or power-constrained secure links.
Artificial-noise jamming improves physical-layer security by degrading an eavesdropper's channel, but the injected noise also interferes with the legitimate receiver. We introduce a correlated-jamming protocol based on classical and quantum correlations that suppresses this self-interference while preserving the jamming penalty experienced by the eavesdropper. Bob broadcasts one mode of a correlated two-mode source and retains the second as a local reference. Eve, who has no access to the retained mode, receives the full thermal jamming field, whereas Bob uses an optimized joint measurement to cancel its correlated fluctuations. The residual self-jamming noise is governed by the conditional variance of the transmitted jamming quadrature given the retained reference. Any classically correlated source is bounded by the vacuum-noise floor and therefore restores Bob, at best, to his unjammed receiver noise. An entangled two-mode squeezed source surpasses this limit and produces sub-vacuum residual noise, with the maximum quantum advantage set by the transmissivity of the jamming path back to Bob. In the bright-source regime, this advantage becomes a fixed reduction in Bob's noise floor, independent of the signal and jamming powers. Within a bounded-collection wiretap model, correlated jamming preserves positive secrecy even when Eve has a stronger direct channel than Bob and remains effective against collective measurements on Eve's Gaussian output states. The protocol supports bright classical message transmission and requires no end-to-end quantum channel. Possible applications include shot-noise-limited optical communication, cryogenic microwave networks, and covert or power-constrained secure links.
This paper investigates cooperative security in wireless networks, where a source (Alice) intends to transmit a confidential message to a legitimate destination (Bob), with the help of a cooperative jammer (Charlie), coexisting with multiple passive eavesdroppers (Eves). In particular, by assuming knowledge of Bob's perfect channel state information (CSI) but only Eves’ statistical CSIs, secrecy beamforming with artificial noise (AN) is utilized for secure transmission, and cooperative jamming (CJ) is explored to further enhance secrecy. We first derive an accurate closed-form expression for the secrecy outage probability (SOP), and establish the condition under which positive secrecy rate is achievable. Then, we provide a secure transmit design for maximizing the SOP constrained secrecy rate. Moreover, based on a strict mathematical analysis, we characterize the impact of the main channel quality and the number of Eves on transmit design and secrecy performance. Specifically, optimal power allocation ratio between the information-bearing signal and the AN signal increases as the main channel quality improves, and decreases with the number of Eves. Numerical results confirm that our design achieves performance improvement in terms of both secrecy rate and secure energy efficiency, as compared to the approach without CJ.
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.
In physical layer security (PHY-security), the frequently observed high correlation between the main and wiretap channels can cause a significant loss of secrecy. This paper investigates a slow fading scenario, where a transmitter (Alice) sends a confidential message to a legitimate receiver (Bob) while a passive eavesdropper (Eve) attempts to decode the message from its received signal. It is assumed that Alice is equipped with multiple antennas while Bob and Eve each have a single antenna (i.e., a MISOSE system). In a MISOSE system, high correlation results in nearly collinear main and wiretap channel vectors, which help Eve to see and intercept confidential information. Unfortunately, the signal processing techniques at Alice, such as beamforming and artificial noise (AN), are helpless, especially in the extreme case of completely collinear main and wiretap channel vectors. On this background, we first investigate the achievable secrecy outage probability via beamforming and AN at Alice with the optimal power allocation between the information-bearing signal and AN. Then, an ingenious model, in which a cooperative jamming relay (Relay) is introduced, is proposed to effectively mitigate the adverse effects of high correlation. Based on the proposed model, the power allocation between the information-bearing signal at Alice and the AN at Relay is also studied to maximize secrecy. Finally, to validate our proposed schemes, numerical simulations are conducted, and the results show that a significant performance gain with respect to secrecy is achieved.
In this paper we propose a two-way protocol of physical layer security using the method of privacy amplification against eavesdroppers. First we justify our proposed protocol by analyzing the physical layer security provided by the classic wiretap channel model (i.e. one-way protocol). In the Gaussian channels, the classic one-way protocol requires Eve's channel to be degraded w.r.t. Bob's channel. However, this channel degradation condition depends on Eve's location and whether Eve's receiving antenna is more powerful than Bob's. To overcome this limitation, we introduce a two-way protocol inspired in IEEE TIT (1993) that eliminates the channel degradation condition. In the proposed two-way protocol, on a first phase, via Gaussian channel, Bob sends randomness to Alice, which is partially leaked to Eve. Then, on a second phase, Alice transmits information to Bob over a public noiseless channel. We derive the secrecy capacity of the two-way protocol when the channel to Eve is also Gaussian. We show that the capacity of the two-way protocol is always positive. We present numerical values of the capacities illustrating the gains obtained by our proposed protocol. We apply our result to simple yet realistic models of satellite communication channels.
This paper considers a Gaussian multi-input multi-output (MIMO) wiretap channel with a legitimate transmitter, a legitimate receiver (Bob), an eavesdropper (Eve), and a cooperative jammer. All nodes may be equipped with multiple antennas. Traditionally, the jammer transmits Gaussian noise (GN) to enhance the security. However, using this approach, the jamming signal interferes not only with Eve but also with Bob. In this paper, besides the GN strategy, we assume that the jammer can also choose to use the encoded jammer (EJ) strategy, i.e., instead of GN, it transmits a codeword from an appropriate codebook. In certain conditions, the EJ scheme enables Bob to decode the jamming codeword and thus cancel the interference, while Eve remains unable to do so even if it knows all the codebooks. We first derive an inner bound on the system’s secrecy rate under the strong secrecy metric, and then consider the maximization this bound through precoder design in a computationally efficient manner. In the single-input multi-output (SIMO) case, we prove that although non-convex, the power control problems can be optimally solved for both GN and EJ schemes. In the MIMO case, we propose to solve the problems using the matrix simultaneous diagonalization (SD) technique, which requires quite a low computational complexity. Simulation results show that by introducing a cooperative jammer with coding capability, and allowing it to switch between the GN and EJ schemes, a dramatic increase in the secrecy rate can be achieved. In addition, the proposed algorithms can significantly outperform the current state of the art benchmarks in terms of both secrecy rate and computation time.
In this paper, we consider physical layer security in wireless communication networks in which a source (Alice) intends to send a confidential message to a legitimate destination (Bob) with the help of a cooperative jammer (CJ), in the presence of a passive eavesdropper (Eve). Assuming that only statistical channel state information (CSI) of Eve is available, artificial-noise (AN) assisted beamforming and cooperative jamming are designed. The goal is to maximize the secrecy rate, subject to a constraint on secrecy outage probability. Numerical results validate the effectiveness of our scheme. Moreover, a higher secure energy efficiency (EE) can be achieved as compared with other schemes without a cooperative jammer.