In intelligent transportation systems (ITS), communications between vehicles, i.e. vehicle-to-vehicle (V2V) communications are of greatest importance to facilitate autonomous driving. The current state-of-the-art for secure data exchange in V2V communications relies on public-key cryptography (PKC) consuming significant computational and energy resources for the encryption/decryption process and large bandwidth for the key distribution. To overcome these limitations, physical-layer security (PLS) has emerged as a lightweight solution by exploiting the physical characteristics of the V2V communication channel to generate symmetric cryptographic keys. Currently, key-generation algorithms are designed via empirical parameter settings, without resulting in optimum key-generation performance. In this paper, we devise a key-generation algorithm for PLS in V2V communications by introducing a novel channel response quantisation method that results in optimum performance via analytical parameter settings. Contrary to the current state-of-the-art, the channel responses incorporate all V2V channel attributes that contribute to temporal variability, such as three dimensional (3D) scattering and scatterers' mobility. An extra functionality, namely, Perturbe-Observe (PO), is further incorporated that enables the algorithm to adapt to the inherent non-reciprocity of the V2V channel responses at the legitimate entities. Optimum performance is evidenced via maximisation of the key bit generation rate (BGR) and key entropy (H) and minimisation of the key bit mismatch rate (BMR). A new metric is further introduced, the so-called secret-bit generation rate (SBGR), as the ratio of the number of bits which are successfully used to compose keys to the total amount of channel samples. SBGR unifies BGR and BMR and is thus maximised by the proposed algorithmic process.
In intelligent transportation systems (ITS), communications between vehicles, i.e. vehicle-to-vehicle (V2V) communications are of greatest importance to facilitate autonomous driving. The current state-of-the-art for secure data exchange in V2V communications relies on public-key cryptography (PKC) consuming significant computational and energy resources for the encryption/decryption process and large bandwidth for the key distribution. To overcome these limitations, physical-layer security (PLS) has emerged as a lightweight solution by exploiting the physical characteristics of the V2V communication channel to generate symmetric cryptographic keys. Currently, key-generation algorithms are designed via empirical parameter settings, without resulting in optimum key-generation performance. In this paper, we devise a key-generation algorithm for PLS in V2V communications by introducing a novel channel response quantisation method that results in optimum performance via analytical parameter settings. Contrary to the current state-of-the-art, the channel responses incorporate all V2V channel attributes that contribute to temporal variability, such as three dimensional (3D) scattering and scatterers' mobility. An extra functionality, namely, Perturbe-Observe (PO), is further incorporated that enables the algorithm to adapt to the inherent non-reciprocity of the V2V channel responses at the legitimate entities. Optimum performance is evidenced via maximisation of the key bit generation rate (BGR) and key entropy (H) and minimisation of the key bit mismatch rate (BMR). A new metric is further introduced, the so-called secret-bit generation rate (SBGR), as the ratio of the number of bits which are successfully used to compose keys to the total amount of channel samples. SBGR unifies BGR and BMR and is thus maximised by the proposed algorithmic process.
In intelligent transportation systems (ITS), communications
between vehicles, i.e. vehicle-to-vehicle (VV) communications
are of greatest importance to facilitate autonomous
driving. The current state-of-the-art for secure data exchange
in VV communications relies on public-key cryptography (PKC)
consuming significant computational and energy resources for the
encryption/decryption process and large bandwidth for the key
distribution. To overcome these limitations, physical-layer security
(PLS) has emerged as a lightweight solution by exploiting the
physical characteristics of the VV communication channel to generate
symmetric cryptographic keys. Currently, key-generation
algorithms are designed via empirical parameter settings, without
resulting optimum key-generation performance. In this paper,
we devise a key-generation algorithm, namely, Perturbe-Observe
(PO), for PLS in VV communications by introducing a novel
channel response quantisation method that results optimum
performance via analytical parameter settings. Contrary to the
current state-of-the-art, the channel responses incorporate all VV
channel attributes that contribute to temporal variability, such
as three dimensional (3D) scattering and scatterers’ mobility. An
extra add-on is further incorporated that enables the algorithm
to adapt to the inherent non-reciprocity of the VV channel
responses at the legitimate entities. Optimum performance is
evidenced via maximisation of the key bit generation rate (BGR)
and key entropy (H) and minimisation of the key bit mismatch
rate (BMR). A new metric is further introduced, the so-called
secret-bit generation rate (SBGR), as the ratio of the number
of bits which are successfully used to compose keys to the total
amount of channel samples. SBGR unifies BGR and BMR and
is thus maximised by the proposed algorithmic process.
Securing data exchange between intercommunicating terminals, e.g., vehicle-to-everything, constitutes a technological challenge that needs to be addressed. Security solutions must be computationally efficient and flexible enough to be implemented in any wireless propagation environment. Recently, physical layer security has gained popularity, which exploits the randomness of wireless channel responses for extracting high entropy secret cryptographic keys. The current state-of-the-art relies on the independently varying channel sources of randomness, e.g., received signal strength (RSS) and phase. However, the limited capability of RSS-based extraction techniques has motivated researchers to investigate alternative approaches. Although phase-based approaches have emerged in many studies, optimising the extraction performance by adapting the algorithm to the non-reciprocal components of static and dynamic channels remains a challenge. In this paper, we propose an adaptive multilevel quantisation approach that adjusts the size of the quantisation region to the channel responses’ non-reciprocity parameters, thus optimising the trade-off between the bit generation rate (BGR) and the bit mismatch rate (BMR). The probability of error has been theoretically formulated. Accordingly, the order of the quantisation process is adapted for acceptable mismatching probability. Moreover, simulation analysis is conducted to prove the ability of the proposed approach to provide flexible adaptation of the quantisation order at different signal-to-noise ratios (SNRs), achieving fast secret bit generation rates 1. 1$\sim2.85bits/packetatSNRsof10\sim$25 dB for acceptable BMR ≤0.1.
Due to the sensitivity of the information exchanged in Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communication, generating secret keys is critical to secure these communications. As nature is open access, distributed keys are more vulnerable to attacks in the vehicular environment. Physical layer key generation methods using wireless channel characteristics show promise in preventing such attacks, generating keys independently, and removing the need for distribution. In this paper, we present a novel key generation approach in a real vehicular environment based on Channel State Information (CSI), including a new algorithm for key bit extraction. We implemented our algorithm using USRP B210 Software-Defined Radios (SDR) and the industry-standard V2X communication protocol: IEEE 802.11p. The proposed key generation protocol uses the CSI values of each sub-carrier as a source of randomness, from which bits are extracted using a new QAM demodulator quantizer (QAM-Dem-Quan). We compared our technique to state-of-the-art Received Signal Strength (RSS)-based approaches, and show that our method achieves better performance. Moreover, we reached a min-entropy of approximately 70% for the generated keys and a key generation rate of less than150μs/key for key lengths ranging from 16 to 128 bits.
Security is a mandatory requirement in wireless communications since their broadcasting nature make them vulnerable to passive eavesdropping, as well as more advanced active threats, such as jamming or man-in-the-middle attacks. Physical layer security protocols have recently been deployed, derived from the characteristics of the medium for randomness extraction and further key generation. This has a two-fold advantage, as it allows for low computational complexity and high energy efficiency while potentially achieving (unconditionally) secure communications. The core part of physical layer security is channel quantisation, where estimates are harvested and converted into candidate keys. However, existing quantisation approaches do not thoroughly consider the trade-off among relevant metrics, such as the bit generation rate, the bit mismatch rate and key entropy. Furthermore, they fail to consider and exploit the peculiar propagation characteristics of vehicular environments, mainly due to their high mobility. Consequently, the current research aims to design a novel quantisation protocol to strike an optimal balance among the aforementioned metrics, using vehicle-to-vehicle communication as the primary use case. The first step consisted of a deep analysis of existing quantisation schemes through a comprehensive critical narrative of both existing and future developments in the field. This ushered in the novel algorithm’s design with holistically optimised metrics. Quantisation thresholds are analytically derived from the probability density function, stemming from channel modelling, which was meticulously tailored for the chosen propagation environment. Experiments showed that the extracted streams have a superior entropy compared to the state-of-the-art quantisation approach. In another contribution, the algorithm was extended to cope with a continuously changing channel reciprocity, a common phenomenon in vehicle communications. A new feedback block was designed to adapt the thresholds to the varying channel noise, attempting to optimise a newly defined metric. Since the latter includes both quantisation and information reconciliation, experiments confirmed that it is able to reach higher performances than fixed approaches, intrinsically exploiting the capability of existing and future error-correcting techniques. Finally, the algorithm was applied to multi-carrier wireless communication, as depicted by the current standards. In doing so, this study considers the estimation of time-varying coherence regions arising from the non-WSSUS behaviour of vehicle communications for the first time in the literature. Such a novelty was used to adapt the probing rate, avoiding sampling the channel for useless correlated estimates and improving the scheme’s efficiency and statistical robustness.
The rapid technological advancements in wireless networks have resulted in tremendous increase in the number of connected user and machine-type wireless devices. Physical Layer Security (PLS) has a strong potential for providing security to wireless links in massively connected future wireless networks. The key-based PLS methods aim at generating secret key bits for data encryption/decryption at the legitimate communication nodes by exploiting the randomness inherent in wireless channels. This work proposes a novel secret key-bits extraction algorithm named Moving-Window Wrapped-Envelope Secret Key Generation (MWWE-SKG). The proposed algorithm uses first-order statistics from a sliding temporal window of channel samples to select the channel quantization interval for each window from circularly wrapped channel envelope samples. The differences in hardware noise conditions at the legitimate nodes lead to differences in the measurement of ideally reciprocal channels, which further leads to a mismatch in the generated secret key bits, whereas the channel statistics of the same links are more likely to remain unchanged for a reasonably large length of time window over the channel samples. An extensive analysis on the performance of the proposed algorithm is conducted, where the proposed algorithm is observed to provide a promising trade-off between the critical SKG performance metrics namely the Key Generation Rate (KGR), Bit Mismatch Probability (BMP), and the Key Randomness Property (KRP). Furthermore, a comparative performance analysis of the proposed algorithm with other notable techniques is also conducted to demonstrate the superior performance of the proposed algorithm.
With the rise of connected vehicular networks, Vehicle-to-Vehicle (V2V) communication has become a fundamental enabler for intelligent transportation systems. However, the open nature of wireless channels introduces risks such as eavesdropping and key compromise. To address these issues, we propose a secure V2V communication scheme based on Physical Layer Key Generation (PLKG) using LoRa technology. The proposed system utilizes Received Signal Strength Indicator (RSSI) measurements between two moving vehicles as the entropy source. To improve the channel correlation, a Savitzky-Golay filter is applied as a preprocessing step. Adaptive multibit quantization is then used to convert the RSSI into binary sequences, followed by the Cascade algorithm for error reconciliation. To enhance randomness, privacy amplification is applied using universal hashing and SHA-1. Finally, the generated key is used for AES-128 encryption. The system is implemented on Raspberry Pi 4B using AcSiP EK-S76SXB and RAK2245 LoRa modules. Experimental validation was conducted in three movement scenarios firstly both vehicle move from opposite-direction at10km/hfor300meters, secondly both vehicle move at the same-direction at10km/hfor800meters, and lastly same as the second scenario but with different speed at20km/h. Results shown that the system achieves a reliable key generation rate (KGR) of up to 176075.73 bit/s while maintaining low computation time, demonstrating its feasibility for secure real-time V2V communication.