With the rapid development of wireless communication, the traditional communication encryption method is not adequate for our needs of high-speed and low latency. As a consequence, Physical Layer-Key Generation (PKG) and Reconfigurable Intelligent Surface (RIS) emerged. The existing researches on the combination of PKG and RIS mainly focus on the randomness increase of the communication environment and the key generation rate under a quasi-static environment. On the other hand, there is little research on the active attack of RIS by eavesdroppers. In this paper, the attack and defense method based on the combination of RIS and PKG is discussed. We propose a random phase attack method derived from the multiple-input single-output (MISO) model and analyze the effectiveness of the attack. To resist the random phase attack under a hypothetical scenario in which RIS is under the control of the attacker, we propose a path separation and path detection defense method according to the Multiple Signal Classification (MUSIC) algorithm. Simulation results show that the Bit Disagreement Rate (BDR) achieves a significant reduction, which proves the effectiveness of the proposed defense method based on path detection and path separation.
With the rapid development of wireless communication, the traditional communication encryption method is not adequate for our needs of high-speed and low latency. As a consequence, Physical Layer-Key Generation (PKG) and Reconfigurable Intelligent Surface (RIS) emerged. The existing researches on the combination of PKG and RIS mainly focus on the randomness increase of the communication environment and the key generation rate under a quasi-static environment. On the other hand, there is little research on the active attack of RIS by eavesdroppers. In this paper, the attack and defense method based on the combination of RIS and PKG is discussed. We propose a random phase attack method derived from the multiple-input single-output (MISO) model and analyze the effectiveness of the attack. To resist the random phase attack under a hypothetical scenario in which RIS is under the control of the attacker, we propose a path separation and path detection defense method according to the Multiple Signal Classification (MUSIC) algorithm. Simulation results show that the Bit Disagreement Rate (BDR) achieves a significant reduction, which proves the effectiveness of the proposed defense method based on path detection and path separation.
Physical layer key generation (PKG) is a promising means to provide on-the-fly shared secret keys by exploiting the intrinsic randomness of the radio channel. However, the performance of PKG is highly dependent on the propagation environments. Due to its feature of controlling the wireless environment, reconfigurable intelligent surface (RIS) is appealing to be applied in PKG. In this article, in contrast to the existing literature, we investigate both the constructive and destructive effects of RIS on the PKG scheme. For the constructive aspect, we have identified static and wave-blockage environments as two RIS-empowered-PKG applications in future wireless systems. In particular, our experimental results in a static environment showed that RIS can enhance the entropy of the secret key, achieving a key generation rate (KGR) of 97.39 bit/s with a bit disagreement rate (BDR) of 0.083. In multi-user systems where some remote users are in worse channel conditions, the proposed RIS-assisted PKG algorithm improves the sum secret key rate by more than 2 dB, compared to the literature. Furthermore, we point out that RIS could be utilized by an attacker to perform new jamming and leakage attacks and give countermeasures, respectively. Finally, we outline future research directions for PKG systems in light of the RIS.
Reconfigurable Intelligent Surface (RIS) is a new paradigm that enables the reconfiguration of the wireless environment. Based on this feature, RIS can be employed to facilitate Physical-layer Key Generation (PKG). However, this technique could also be exploited by the attacker to destroy the key generation process via manipulating the channel features at the legitimate user side. Specifically, this paper proposes a new RIS-assisted Manipulating attack (RISM) that reduces the wireless channel reciprocity by rapidly changing the RIS reflection coefficient in the uplink and downlink channel probing step in orthogonal frequency division multiplexing (OFDM) systems. The vulnerability of traditional key generation technology based on channel frequency response (CFR) under this attack is analyzed. Then, we propose a slewing rate detection method based on path separation. The attacked path is removed from the time domain and a flexible quantization method is employed to maximize the Key Generation Rate (KGR). The simulation results show that under RISM attack, when the ratio of the attack path variance to the total path variance is 0.17, the Bit Disagreement Rate (BDR) of the CFR-based method is greater than 0.25, and the KGR is close to zero. In addition, the proposed detection method can successfully detect the attacked path for SNR above 0 dB in the case of 16 rounds of probing and the KGR is 35 bits/channel use at 23.04MHz bandwidth.
The attacker can manipulate a reconfigurable intelligent surface (RIS) to jamming attack to break the channel reciprocity, resulting in an increasing key disagreement rate (KDR) to interrupt the physical layer key generation (PKG). In this letter, a countermeasure for PKG is proposed to resist the RIS jamming attack. The proposed countermeasure includes the atomic norm minimization (ANM)-based multipath separation algorithm and statistic feature-based path detection algorithm, which can reconstruct the reciprocal channel without needing a wide frequency band. Simulation results show that the proposed countermeasure can significantly reduce KDR from 0.33 to 0.03 when SNR is 10 dB and achieve an excellent key generation rate (KGR) compared with existing schemes.
Recently, there is a growing interest in employing reconfigurable intelligent surface (RIS) to assist physical layer key generation in wireless networks. However, current works only studied the RIS-aided key generation schemes in SISO (single-input-single-output) communications, which have relatively low key generation rate (KGR). Therefore, here, in order to fill this gap, we propose the new and really novel RIS-aided MIMO (multiple-input-multiple-output) key generation scheme. By fully exploring the reflection signals from the RIS to the legitimate communication partners as the introduced, controllable and artificial randomness, combined with the spatial degree-of-freedom of RIS and MIMO incident and reflected signals, the KGR performance can be significantly improved. The information theoretical security is fully investigated, and the upper bound value of KGR is derived to comprehensively evaluate the system performance. The simulations fully validate the effectiveness and robustness of the proposed new and really novel, and interesting scheme.
Reconfigurable intelligent surface (RIS), which can manipulate the wireless environment, has recently been integrated into physical-layer key generation (PKG) systems to establish randomness symmetric keys in static environments. However, few studies have jointly considered the optimization and randomization of the RIS elements to simultaneously achieve a high key generation rate (KGR) and communication performance. This study proposes a RIS-assisted communication and security-integrated protocol for dual-function integration of communication enhancement and PKG in static environments. The protocol partitions RIS elements for beamforming and random beams for parallel execution, utilizing a sparsity adaptive matching pursuit-based channel estimation algorithm to obtain individual channel state information. Subsequently, an optimization problem is formulated for KGR maximization while satisfying quality of service (QoS) requirements. The non-convex optimization problem is addressed through monotonicity analysis and triangle inequality. We validate the efficacy of the proposed protocol by developing a 4.9 GHz RIS-assisted PKG prototype system, comprising modular hardware and flexible software. The field trials demonstrate a 30.81 bit/s KGR for static environments with an average received power increase of 10.6 dB, achieving effective simultaneous integration of communication and security.
In this paper, we explore the physical layer security (PLS) of an active reconfigurable intelligent surface (RIS) assisted multi-input single-output (MISO) system in the presence of a passive eavesdropper (Eve), whose channel is unknown to the legitimate transmitter. In this practical scenario, we first propose an artificial noise (AN) based PLS approach, which can effectively deteriorate the eavesdropping by jointly designing the disturbance signal and the active RIS. However, the AN scheme requires a vast amount of energy to emit the noise signal, which can be potentially suppressed by Eve using more antennas. To tackle this issue, we then introduce another novel reconfigurable intelligent fading (RIF) approach, which utilizes the active RIS to rapidly manipulate the propagation environment, so that Eve suffers a fast fading channel, while the legitimate user (LU) still experiences a slow fading channel. Since Eve encounters difficulties in effectively estimating her fast fading channel, she cannot perform reliable legitimate information detection in a coherent manner, thereby significantly reducing the risk of information leakage and enabling secure communications. Simulation results demonstrate the effectiveness of both proposed approaches. Moreover, the RIF scheme achieves a substantial improvement in security performance compared to the AN scheme, particularly for the cases with limited transmit power.