This paper introduces a revolutionary physical layer security paradigm: Artificial Signal Injection and Superposition (ASIS), a novel framework that actively injects carefully designed artificial signals into the communication channel, creating a superposition with legitimate user data to achieve unprecedented security guarantees. Unlike traditional physical layer security methods that rely on passive channel characteristics, ASIS actively engineers the signal space to create controlled interference that benefits legitimate receivers while confounding eavesdroppers. Our approach leverages multi-dimensional signal processing, game-theoretic optimization, and information-theoretic principles to design injection signals that are: (1) decodable by intended receivers using advanced signal separation techniques, (2) indistinguishable from noise or interference to unauthorized listeners, and (3) adaptive to channel conditions and eavesdropper capabilities. The ASIS framework provides provable security against both passive and active attacks, achieves informationtheoretic secrecy rates, and can be implemented using existing wireless hardware with firmware upgrades. Experimental results from our software-defined radio testbed demonstrate 40 dB SNR advantage for legitimate receivers over eavesdroppers, bit error rates below 10 −6 for legitimate users versus > 0.4 for eavesdroppers, and throughput improvements of 15-30% compared to conventional cryptographic approaches due to reduced overhead. The proposed system represents a paradigm shift in secure communications, moving from passive protection to active signal-space engineering for security.
This paper introduces a revolutionary physical layer security paradigm: Artificial Signal Injection and Superposition (ASIS), a novel framework that actively injects carefully designed artificial signals into the communication channel, creating a superposition with legitimate user data to achieve unprecedented security guarantees. Unlike traditional physical layer security methods that rely on passive channel characteristics, ASIS actively engineers the signal space to create controlled interference that benefits legitimate receivers while confounding eavesdroppers. Our approach leverages multi-dimensional signal processing, game-theoretic optimization, and information-theoretic principles to design injection signals that are: (1) decodable by intended receivers using advanced signal separation techniques, (2) indistinguishable from noise or interference to unauthorized listeners, and (3) adaptive to channel conditions and eavesdropper capabilities. The ASIS framework provides provable security against both passive and active attacks, achieves informationtheoretic secrecy rates, and can be implemented using existing wireless hardware with firmware upgrades. Experimental results from our software-defined radio testbed demonstrate 40 dB SNR advantage for legitimate receivers over eavesdroppers, bit error rates below 10 −6 for legitimate users versus > 0.4 for eavesdroppers, and throughput improvements of 15-30% compared to conventional cryptographic approaches due to reduced overhead. The proposed system represents a paradigm shift in secure communications, moving from passive protection to active signal-space engineering for security.
Passive eavesdropping compromises confidentiality in wireless networks, especially in resource-constrained environments where heavyweight cryptography is impractical. Physical layer security (PLS) exploits channel randomness and spatial selectivity to confine information to an intended receiver with modest overhead. However, typical PLS techniques, such as using beamforming, artificial noise, and reconfigurable intelligent surfaces, often involve added active power or specialized deployment, and, in many designs, rely on precise time synchronization and perfect CSI estimation, which limits their practicality. To this end, we propose AmbShield, an AmBD-assisted PLS scheme that leverages naturally distributed AmBDs to simultaneously strengthen the legitimate channel and degrade eavesdroppers' without requiring extra transmit power and with minimal deployment overhead. In AmbShield, AmBDs are exploited as friendly jammers that randomly backscatter to create interference at eavesdroppers, and as passive relays that backscatter the desired signal to enhance the capacity of legitimate devices. We further develop a unified analytical framework that analyzes the exact probability density function (PDF) and cumulative distribution function (CDF) of legitimate and eavesdropper signal-to-interference-noise ratio (SINR), and a closed-form secrecy outage probability (SOP). The analysis provides clear design guidelines on various practical system parameters to minimize SOP. Extensive experiments that include Monte Carlo simulations, theoretical derivations, and high-SNR asymptotic analysis demonstrate the security gains of AmbShield across diverse system parameters under imperfect synchronization and CSI estimation.
Passive eavesdropping compromises confidentiality in wireless networks, especially in resource-constrained environments where heavyweight cryptography is impractical. Physical layer security (PLS) exploits channel randomness and spatial selectivity to confine information to an intended receiver with modest overhead. However, typical PLS techniques, such as beamforming, artificial noise, and reconfigurable intelligent surfaces, often require additional active power or specialized deployment and rely on precise time synchronization and perfect CSI estimation, which limits their practicality. Meanwhile, the role of ambient backscatter devices (AmBDs) in potentially strengthening the legitimate channel while limiting eavesdroppers in generalized wireless network settings has not been fully investigated. To this end, we propose AmbShield, an AmBD-assisted PLS scheme that leverages naturally distributed AmBDs to simultaneously strengthen the legitimate channel and degrade eavesdroppers' reception without requiring extra transmit power and with minimal deployment overhead. In AmbShield, AmBDs are exploited as friendly jammers that randomly backscatter to create interference at eavesdroppers, and as passive relays that backscatter the desired signal to enhance the capacity of legitimate devices. We further develop a unified analytical framework that analyzes the exact probability density function (PDF) and cumulative distribution function (CDF) of legitimate and eavesdropper signal-to-interference-noise ratio (SINR), a closed-form secrecy outage probability (SOP), its high-SNR asymptote, and a secrecy diversity order (SDO). The analysis provides clear design guidelines on various practical system parameters to minimize SOP. Extensive experiments that include Monte Carlo simulations, theoretical derivations, and high-SNR asymptotic analysis demonstrate the security gains of AmbShield across diverse system parameters under imperfect synchronization and CSI estimation.
Owing to the openness of wireless channels, ensuring the security of communication for massive multiple-input multiple-output (MIMO) systems faces severe challenges. For the massive MIMO system in the presence of a full-duplex (FD) multi-antenna eavesdropper, a dual artificial-noise (AN) injection scheme is proposed to enhance communication security in this paper. Specifically, AN is superimposed onto the transmitted pilot signals to interfere with the eavesdropper from estimating the legitimate user channel in pilot training phases. In the phase of data transmission, the AN generated in the null space of the legitimate user is introduced to prevent the eavesdropper from receiving the confidential messages. Meanwhile, an iterative optimization algorithm is presented to obtain the optimal power allocation between the information-bearing signals and the AN for the potential countermeasures taken by the eavesdropper. Numerical results are presented to validate the superior performance of the proposed scheme in security ensurance compared to the conventional ones with AN injection schemes.
Abstract The broadcast nature of radio propagation in wireless communication has been suspected as the loopholes of passive or active attacks by unauthorized users (eavesdroppers). The physical layer security techniques operate at the lowest stack of OSI layer against conventional cryptographic approaches, operating at the upper layer. However, techniques such as channel coding, power (directional antenna and artificial noise), and spread spectrum have been (and continuously) deployed to safeguard against sophisticated attacks. Most of these deployments are theoretical, and a few are enhanced for efficient security against an intruder. In this article, a boundary technique approach is proposed and applied to the physical layer to improve its secrecy‐capacity and subdue adversary effects at the legitimate receiver. Hybrid performance metrics were adopted, and a Monte Carlo simulation was performed. The result obtained using secrecy outage probability, secrecy‐capacity, and intercept‐probability show that our proposed techniques enhance the secret transmission between the main transmitter and legitimate receiver. The simulation results were compared with the analytical methods. It was found that the channel between the transmitter and the main receiver has a better signal‐to‐noise ratio than the corresponding eavesdropper's channel. Conclusively, performance of the proposed technique is validated for applications in emerging wireless communication systems.
Backscatter wireless communication lies at the heart of many practical low-cost, low-power, distributed passive sensing systems. The inherent cost restrictions coupled with the modest computational and storage capabilities of passive sensors, such as RFID tags, render the adoption of classical security techniques challenging; which motivates the introduction of physical layer security approaches. Despite their promising potential, little has been done to study the prospective benefits of such physical layer techniques in backscatter systems. In this paper, the physical layer security of wireless backscatter systems is studied and analyzed. First, the secrecy rate of a basic single-reader, single-tag model is studied. Then, the unique features of the backscatter channel are exploited to maximize this secrecy rate. In particular, the proposed approach allows a backscatter system's reader to inject a noise-like signal, added to the conventional continuous wave signal, in order to interfere with an eavesdropper's reception of the tag's information signal. The benefits of this approach are studied for a variety of scenarios while assessing the impact of key factors, such as antenna gains and location of the eavesdropper, on the overall secrecy of the backscatter transmission. Numerical results corroborate our analytical insights and show that, if properly deployed, the injection of artificial noise yields significant performance gains in terms of improving the secrecy of backscatter wireless transmission.
Physical layer security (PLS) has emerged as a new concept and powerful alternative that can complement and may even replace encryption-based approaches, which entail many hurdles and practical problems for future wireless systems. The basic idea of PLS is to exploit the characteristics of the wireless channel and its impairments including noise, fading, interference, dispersion, diversity, etc. in order to ensure the ability of the intended user to successfully perform data decoding while preventing eavesdroppers from doing so. Thus, the main design goal of PLS is to increase the performance difference between the link of the legitimate receiver and that of the eavesdropper by using well-designed transmission schemes. In this survey, we propose a conceptual, generic, and expandable framework for classifying the existing PLS techniques against wireless passive eavesdropping. In this flexible framework, the security techniques that we comprehensively review in this treatise are divided into two primary approaches: signal-to-interference-plus-noise ratio-based approach and complexity-based approach. The first approach is classified into three major categories: first, secrecy channel codes-based schemes; second, security techniques based on channel adaptation; third, schemes based on injecting interfering artificial (noise/jamming) signals along with the transmitted information signals. The second approach (complexity-based), which is associated with the mechanisms of extracting secret sequences from the shared channel, is classified into two main categories based on which layer the secret sequence obtained by channel quantization is applied on. The techniques belonging to each one of these categories are divided and classified into three main signal domains: time, frequency and space. For each one of these domains, several examples are given and illustrated along with the review of the state-of-the-art security advances in each domain. Moreover, the advantages and disadvantages of each approach alongside the lessons learned from existing research works are stated and discussed. The recent applications of PLS techniques to different emerging communication systems such as visible light communication, body area network, power line communication, Internet of Things, smart grid, mm-Wave, cognitive radio, vehicular ad-hoc network, unmanned aerial vehicle, ultra-wideband, device-to-device, radio-frequency identification, index modulation, and 5G non-orthogonal multiple access based-systems, are also reviewed and discussed. The paper is concluded with recommendations and future research directions for designing robust, efficient and strong security methods for current and future wireless systems.