Traditional wireless security schemes neglect the unique properties of the wireless channel. Exploiting physical layer can significantly enhance the conventional security schemes. However, the robustness and bit mismatch rate of current physical-layer-based schemes still need to be improved. Conventional two thresholds quantization is not stable when inserting or removing intermediate objects between legitimate users, and the consistency of the generated secret key is low due to small fluctuations. In this article, we propose a differential secret key generation scheme based on weighted exponential moving average (WEMA) method. Differential quantization is utilized to enhance the robustness of the secret key generation scheme. Furthermore, we prove that WEMA method can effectively smooth out short-term fluctuations and decreasing the bit mismatch rate. Finally, we present a numerical simulation to demonstrate the feasibility of our proposal.
Traditional wireless security schemes neglect the unique properties of the wireless channel. Exploiting physical layer can significantly enhance the conventional security schemes. However, the robustness and bit mismatch rate of current physical-layer-based schemes still need to be improved. Conventional two thresholds quantization is not stable when inserting or removing intermediate objects between legitimate users, and the consistency of the generated secret key is low due to small fluctuations. In this article, we propose a differential secret key generation scheme based on weighted exponential moving average (WEMA) method. Differential quantization is utilized to enhance the robustness of the secret key generation scheme. Furthermore, we prove that WEMA method can effectively smooth out short-term fluctuations and decreasing the bit mismatch rate. Finally, we present a numerical simulation to demonstrate the feasibility of our proposal.
Channel characteristics-based secret key generation is an effective physical-layer security method.The issues of how to remove the effect of random noise and to balance the key generation rate (KGR) and the bit mismatch rate (BMR) are needed to be addressed.In this paper, to reduce the effect of random noise and extract more secret bits, a new quantization scheme with high key generation rate and low bit mismatch rate is proposed.In our proposed scheme, we try to use all measurements and correct the differences caused by noise at the boundary regions instead of simply dropping them.We evaluate and discuss the improvements of our proposed scheme.The results show that our proposed scheme achieves lower bit mismatch rate as well as remaining high key generation rate.
Devices in the Internet of Things (IoT) are usually limited in computing resources and energy capacity, which means that encryption schemes with higher complexity are not suitable for them to ensure secure communication. As a promising solution to this problem, physical layer key generation suggests that shared secret keys can be generated from noisy wireless channel measurements to enhance the security of wireless communications. In this article, we propose a key generation scheme with extremely low implementation complexity, which allows physical layer key generation to be implemented on IoT nodes. First, we preprocess the channel measurements with simple moving average filtering before quantization to improve channel reciprocity. Next, a bidirectional difference quantization scheme is proposed to realize reliable quantization of channel measurements, which is ingenious in that the quantization process does not depend on quantization thresholds, and thus, the mismatched key bits caused by measurements close to quantization thresholds can be effectively avoided. Then, we propose an improved Cascade protocol to achieve lightweight and efficient information reconciliation. The simulation results show that our scheme can well balance the reliability and efficiency of key generation, and has excellent performance in terms of implementation complexity and key randomness.
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.
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.
Secure communication in a wireless environment is very vital, and cryptographic schemes are usually used to ensure it. Secret keys that are unknown to the tappers are needed by cryptographic schemes to secure communication between two legitimate users. In recent years the secret key generation scheme that utilizes a wireless channel as a secret key generation source has become a very interesting and promising topic. The main problem of this scheme is the high wireless channel mismatch between two users due to nonsimultaneous measurements and noise from the device. In this paper, we proposed a secret key generation scheme that uses the Savitzky-Golay filter method to reduce the high mismatch wireless channel. The scheme that was built was also equipped with a multibit quantization method to increase the speed of generation of secret keys. The results of our tests show a decrease in wireless channel mismatch between two users and an increase in the speed of generation of secret keys.
As Beyond 5thGeneration (B5G) networks expand, securing communication links remains a challenge. Physical Layer Security (PLS) is a promising paradigm, and this work explores wireless channel-based Secret Key Generation (SKG) by proposing an Extended Huffman Coding (EHC) framework to enhance quantization stage. While non-uniform coding is common in Analog-to-Digital (A2D) conversion, it remains largely unexplored in SKG due to key mismatch risks. To address this, we propose a Huffman Coding (HC)-inspired framework that generates binary codes using reversed HC principles and extends them by sequentially altering the Least Significant Bit (LSB), ensuring equal-length unique codes for quantization levels while enhancing generation rate, agreement, and randomness. Additionally, histogram/ Probability Density Function (PDF) matching aligns quantization level probabilities at legitimate nodes to minimize mismatches while exchanging minimal statistical information without compromising secrecy. Unlike conventional quantization, which relies on predetermined codes vulnerable to eavesdropping, our scheme dynamically computes quantization codes at runtime, adding an extra layer of security. Moreover, while conventional HC avoids codes of a level to be a subcode of another level, SKG benefits when one code is a subcode of another, making detection harder. Instead of compression, as desired in conventional A2D conversion, SKG requires longer and random keys that reliably match at legitimate nodes, which our scheme ensures. Simulations are conducted under Rice-fading conditions that evaluate the impact of variations in the Rician K-factor on SKG performance. The proposed method is assessed using key SKG metrics named: Key Agreement Rate (KAR), Key Generation Rate (KGR), and Key Randomness Rate (KRR) (employing the NIST test suite). The obtained results demonstrate the potential of our proposed scheme for secure and scalable SKG solutions in future networks.