Unlike conventional anti-eavesdropping methods that always require additional energy or computing resources (e.g., in friendly jamming and cryptography-based solutions), this work proposes a novel anti-eavesdropping solution that comes with mostly no extra power nor computing resource requirement. This is achieved by leveraging the ambient backscatter technology in which secret information can be transmitted by backscattering it over ambient radio signals. Specifically, the original message at the transmitter is first encoded into two parts: (i) active transmit message and (ii) backscatter message. The active transmit message is then transmitted by using the conventional wireless transmission method while the backscatter message is transmitted by backscattering it on the active transmit signals via an ambient backscatter tag. As the backscatter tag does not generate any active RF signals, it is intractable for the eavesdropper to detect the backscatter message. Therefore, secret information, e.g., a secret key for decryption, can be carried by the backscattered message, making the adversary unable to decode the original message. Simulation results demonstrate that our proposed solution can significantly enhance security protection for communication systems.
Unlike conventional anti-eavesdropping methods that always require additional energy or computing resources (e.g., in friendly jamming and cryptography-based solutions), this work proposes a novel anti-eavesdropping solution that comes with mostly no extra power nor computing resource requirement. This is achieved by leveraging the ambient backscatter technology in which secret information can be transmitted by backscattering it over ambient radio signals. Specifically, the original message at the transmitter is first encoded into two parts: (i) active transmit message and (ii) backscatter message. The active transmit message is then transmitted by using the conventional wireless transmission method while the backscatter message is transmitted by backscattering it on the active transmit signals via an ambient backscatter tag. As the backscatter tag does not generate any active RF signals, it is intractable for the eavesdropper to detect the backscatter message. Therefore, secret information, e.g., a secret key for decryption, can be carried by the backscattered message, making the adversary unable to decode the original message. Simulation results demonstrate that our proposed solution can significantly enhance security protection for communication systems.
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.
In this paper, we study on two different strategies - jamming and cooperation - for improving physical layer security in multi-tag ambient backscatter communications, which utilize existing radio frequency source. First of all, we propose a jamming-based multi-tag scheduling method, which selects a tag for data transmission and another tag(s) for artificial noise generation, in order to give a harmful impact to an eavesdropper. Next, we propose a cooperation-based multi-tag scheduling method, which selects a tag for data transmission and another tag(s) for cooperative transmission (the same data) in order to be helpful to a receiver. Through extensive simulations, we evaluate both strategies in terms of bit error rate and secrecy rate. Finally, we provide a guideline which strategy is better to apply for given environments depending on the total number of tags, channel gains between tags and the receiver, and the number of scheduled tags for jamming or cooperation.
Passive radio-frequency identification (RFID) communication raises new transmission secrecy protection challenges, since passive tags stored information lack effective information protection mechanisms. Due to constraints of passive tags, such as limited computation and storage capabilities, security solutions based on the physical-layer security (PLS) are promising candidates compared to those based on conventional lightweight cryptography. Unlike existing endeavors on PLS of RFID wireless communication, we consider an RFID system in the presence of a special proactive eavesdropper, which is able to both enhance the information wiretap and interfere with the information detection at the RFID reader simultaneously by broadcasting its own continuous-wave (CW) signal. To defend against proactive eavesdropping attacks, we propose a wiretap-channel-conscious artificial-noise (AN)-aided secure transmission scheme for the RFID reader, which first estimates both legitimate and wiretap channels and then superimposes an AN signal on the CW signal to confuse the proactive eavesdropper. The transmit power and power allocation between the AN signal and the CW signal are optimized to maximize the secrecy rate. Furthermore, we model the attack and defense process between the proactive eavesdropper and the RFID reader as a hierarchical security game and prove it can achieve the equilibrium. The simulation results show the superiority of our proposed scheme in terms of the secrecy rate and the interactions between the RFID reader and the proactive eavesdropper.
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.
This paper investigates the limit covert rate of the backscatter communication systems based on undecodable ambient radio frequency (RF) signals over additive white Gaussian noise channel. In the considered network, source node Alice expects to transmit information to receiver Bob without being detected by warden Willie, by backscattering undecodable ambient RF signals. In this case, it is challenging for Bob to recover the information from Alice, since the undecodable signals result in both unknown additive and multiplicative interference. A subtle communication strategy is proposed to alleviate the influences of the interference, by which we prove that no matter Willie can or cannot decode the information from the RF source and then eliminate its interference, the limit covert rate is subject to the well-known square root law (i.e.,O(√n) bits pernchannel uses). This interesting result means that even if the RF source is a cooperative node of Willie (e.g., a jammer deployed by Willie to restrict Alice from active transmission), Alice can still covertly and reliably transmit information to Bob by backscattering the ambient RF signals (e.g., the malicious jamming signals).
In this paper, we propose an artificial noise-aided tag scheduling (ANTS) scheme in order to enhance physical layer security in ambient backscatter communications (ABCs), which utilize existing radio frequency (RF) signals such as TV, FM radio, Wi-Fi, and so on. In more detail, we first select the best tag based on the channel gain between a tag and a reader and then select another tag for generating artificial noise affecting an eavesdropper. Consequently, we propose a scheduling criterion to choose both information and artificial noise tags. In addition, we apply a successive interference cancellation (SIC) technique at the reader in order to eliminate the interference from the artificial noise tag. The simulation results show that our proposed ANTS scheme can obtain a better secrecy rate as the channel gain between the tag and the receiver increases and the number of tags increases. Moreover, when the number of tags is sufficiently large, the proposed ANTS scheme significantly outperforms the conventional scheme in terms of average secrecy rate.