Physical layer security (PLS) of wireless communications is becoming increasingly significant with the advent of 6G. The reconciliation of channel-based secret key generation (SKG) methods is necessary to avoid inconsistencies after key generation, resulting in increased communication overhead, leakage of key information, and reduced security performance. This paper proposes a fuzzy secret key generation (FSKG) method that does not require the legitimate user to perform a consistency check after fuzzy extraction of the phase, which is used directly to encrypt the constellation rotation of the key. The proposed scheme allows users to code-decode the key bits to reduce the transmission error probability and improve the key consistency, and the simulation results prove that the proposed FSKG scheme outperforms traditional SKG schemes like CQA and CQG. The simulation results also indicate that the best secure key rate can be achieved by applying PSK modulation.
Physical layer security (PLS) of wireless communications is becoming increasingly significant with the advent of 6G. The reconciliation of channel-based secret key generation (SKG) methods is necessary to avoid inconsistencies after key generation, resulting in increased communication overhead, leakage of key information, and reduced security performance. This paper proposes a fuzzy secret key generation (FSKG) method that does not require the legitimate user to perform a consistency check after fuzzy extraction of the phase, which is used directly to encrypt the constellation rotation of the key. The proposed scheme allows users to code-decode the key bits to reduce the transmission error probability and improve the key consistency, and the simulation results prove that the proposed FSKG scheme outperforms traditional SKG schemes like CQA and CQG. The simulation results also indicate that the best secure key rate can be achieved by applying PSK modulation.
Secret key generation based on a wireless channel (WC-SKG) is a promising solution to address the security issues in wireless communication. However, the consistency of channel estimation between two legal communication nodes in WC-SKG is often poor due to the receiver noise, signal power, etc., leading to a low secret key generation rate (SKGR). Although there are several denoising algorithms such as orthogonal transformation to address this issue, existing schemes overlook the fact that data symbols are also affected by the channel. This results in existing schemes only using the pilot symbols for channel estimation and not fully utilizing the received signal power of the WC-SKG. To address this issue, we propose a consistency enhancement algorithm based on constellation decision information (CEA-CDI), which utilizes both pilot symbols and soft decision information of data symbols to improve SKGR. Monte Carlo simulation and numerical results demonstrate that our proposed scheme can improve performance by approximately 16 dB compared to initial channel estimation.
The diverse application scenarios envisioned for sixth generation (6G) are characterized by the deep integration of sensing and ubiquitous connectivity, which imposes unprecedentedly stringent security requirements. However, due to the open nature of wireless channels, mobile communications systems always face severe information security threats such as falsification, spoofing, interception, and repudiation. Cryptography-based symmetric and asymmetric encryption techniques remain mainstream solutions for information protection. Symmetric encryption is efficient and secure for legitimate users but suffers from key-distribution difficulties over open wireless channels, whereas asymmetric encryption resolves this problem but faces increasing risks from quantum computing due to its reliance on structured mathematical hardness assumptions. In response to these limitations, physical layer security (PLS) has gained a great deal of research attention as a powerful security component that leverages the features of varying wireless channels. Existing PLS schemes can be broadly classified into two categories. The first one takes advantage of the legitimate link’s opportunistic channel-quality superiority over or different spatial-domain directions from the attacking link, which still faces many practical implementation difficulties. The second category is termed physical-layer key generation (PLKG). It extracts the unique features of the legitimate link’s channel variation, which is often reciprocal, as the source of secret key generation and therefore can naturally implement secure key distribution tasks. This advantage no doubt injects new vigor to symmetric encryption as a stronger protection approach. Following this trend, we in this paper concentrate on the PLKG techniques. Specifically, we present a comprehensive overview on existing PLKG schemes, discussing diverse secret key generation and reconciliation methods. We further investigate the model-driven and deep-learning-based approaches tailored for the scenario with imperfect channel reciprocity between the sender and receiver. After comprehensively reviewing major existing schemes, we further discuss a recently proposed PLKG design based on codeword reconstruction, which makes use of the strong error-correcting capability of the forward-error-correction (FEC) codes to effectively implement secure and consistent secret key generation between the legitimate sender and receiver. Finally, we share our opinions on the unsolved challenges and potential research directions dedicated to PLKG toward meeting the security requirements of 6G.
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 advancement of automation and intelligence in rail transit systems, rail transit sensor networks (RTSN) play a crucial role in detection and maintenance, operation status monitoring, and safety protection. However, the open nature of RTSN makes them susceptible to eavesdropping. This paper proposes a novel key generation algorithm that leverages both fuzzy and precise phase. Contrary to conventional secret key generation (SKG) methods that rely on channel characteristics, our approach eliminates the quantization step. Instead, it utilizes the phase of the channel estimation sequence as the fuzzy phase and maps successfully decoded data as the precise phase. By combining these two types of phases, we rotate the constellation points to achieve encrypted transmission of key information. Numerical results demonstrate that our proposed scheme surpasses traditional methods in terms of reliability and security, significantly enhancing the key generation rate, which provides an effective solution for secure communication on RSTN.
Physical-layer secret key generation (SKG) provides high-level security for data encryption in wireless communications, using the shared unique channel state information between legal partners. Most of SKG schemes focused on only SKG itself, while the combination of SKG and encrypted data transmission using the generated secret keys needs to be explored. Here, we propose and demonstrate a secure wireless communication scheme, where SKG and encrypted data communication are integrated together. For SKG, the randomness originated from the input data is utilized to increase the effective key generation rate (KGR) up to 20.8Kb/s when the input data rate is 250Kb/s. Afterwards, the data is encrypted using the generated secret keys and advanced encryption standard (AES). The feasibility and robustness of the integrated system have been verified by the experimental results. Compared with the system where SKG and encrypted data communication are separated, the time required to transfer the same amount of data will be reduced by 48.04%.
As an alternative and appealing approach to providing information security in wireless communication systems, secret key generation at physical layer has demonstrated its potential in terms of efficiency and reliability over traditional cryptographic methods. Without the necessity of a management centre for key distribution or reliance on computational complexity, physical layer key generation protocols enable two wireless entities to extract identical and dynamic keys from the randomness of the wireless channels associated with them.\nIn this thesis, the reliability of secret key generation at the physical layer is examined in practical wireless channels with imperfect channel state information (CSI). Theoretical analyses are provided to relate key match rate with channel's signal-to-noise ratio (SNR), degrees of channel reciprocity, and iterations of information reconciliation.\nIn order to increase key match rate of physical layer secret key generation, improved schemes in the steps of channel estimation and sample quantization are proposed respectively. In the channel estimation step, multiple observations of the wireless channels are integrated with a linear processor to provide a synthesized and more accurate estimation of the wireless channel. In the sample quantization step, a magnitude based quantization method with two thresholds is proposed to quantize partial samples, where specific quantization areas are selected to reduce cross-over errors. Significant improvements in key match rate are proven for both schemes in theoretical analysis and numerical simulations. Key match rate can even achieve 100% in both schemes with the assistance of information reconciliation process.\nIn the end, a practical application of physical layer secret key generation is presented, where dynamic keys extracted from the wireless channels are utilized for securing secret data transmission and providing efficient access control.