With the development of wireless communication technology, the application of the physical layer key generation method based on channel characteristics is becoming more and more widespread. In this method, the selection of quantization algorithm in the quantization stage is particularly important. The poor performance of the initial key will affect the efficiency of key reconciliation, and even cause the failure of the whole key generation method. In the existing quantization algorithms, the quantization level and guard interval are fixed, so the performance of the initial key cannot always be optimized in the face of complex and changeable communication environment. Aiming at the above problems, this paper combines the adaptive adjustment of quantization level and guard interval effectively on the basis of existing multi-bit quantization algorithm. This method continues the method of deleting eigenvalues by index value in multi-bit quantization algorithm, which improves the consistency of initial key. Based on information theory, this method selects optimal quantization level on the premise that the initial key is theoretically error-free under different SNR. This method sets the guard interval based on the average error probability of the eigenvalue and the quantization level, which solves the problem of deleting too many eigenvalues when the SNR is high in the method of setting fixed guard interval. Simulation results show that this method is feasible.
With the development of wireless communication technology, the application of the physical layer key generation method based on channel characteristics is becoming more and more widespread. In this method, the selection of quantization algorithm in the quantization stage is particularly important. The poor performance of the initial key will affect the efficiency of key reconciliation, and even cause the failure of the whole key generation method. In the existing quantization algorithms, the quantization level and guard interval are fixed, so the performance of the initial key cannot always be optimized in the face of complex and changeable communication environment. Aiming at the above problems, this paper combines the adaptive adjustment of quantization level and guard interval effectively on the basis of existing multi-bit quantization algorithm. This method continues the method of deleting eigenvalues by index value in multi-bit quantization algorithm, which improves the consistency of initial key. Based on information theory, this method selects optimal quantization level on the premise that the initial key is theoretically error-free under different SNR. This method sets the guard interval based on the average error probability of the eigenvalue and the quantization level, which solves the problem of deleting too many eigenvalues when the SNR is high in the method of setting fixed guard interval. Simulation results show that this method is feasible.
With the continuous progress of communication technology, traditional encryption algorithms cannot meet the demands of modern wireless communication security. Secure communication based on physical layer encryption emerges as a solution. To meet the low Key Disagreement Rate (KDR) and high Key Generation Rate (KGR) requirements for physical layer key generation, this paper proposes two quantization algorithms, Improve-CQG and Interpolate-CQG, based on the Channel Quantization with Guard band (CQG) algorithm. The former divides the characteristic quantization into two phases: threshold filtering and guard band quantization, while the latter adds a step after these two phases: interpolation quantization. Compared to the CQG algorithm, the Improve-CQG algorithm enhances the granularity of filtered quantization values. The core concept of the Interpolate-CQG algorithm is to utilize threshold filtering and the rounded-off quantization values from the guard band quantization phase. The symbol information corresponding to these index values is replaced by a new interpolated symbol and inserted into the key by the agreed quantized coordinates. Simulation proves that the Interpolate-CQG is an effective quantization algorithm for the key generation with lower KDR and higher KGR than the Improve-CQA and Improve-CQG.
Wireless channel has many characteristics such as reciprocity, time variation, spatial uniqueness, etc. This paper extracted secret key from its noisy radio channel measurements at two nodes by exploiting the reciprocity of wireless channel in time division system. Therefore, the secret key could be generated with the channel estimation to overcome the drawback of the key pre-distribution mechanism. Aiming at solving the problem that the multibit adaptive quantization scheme to achieve low key generation consistency probability, the paper proposes m-windows filtering mechanism to preprocess channel eigenvalues. The simulation results show that the improved algorithm achieves higher key agreement rate and key generation rate, especially when the signal to noise ratio is low, reduce the key inconsistency rate particularly noticeable.
The new power system is the national development strategy and development direction of smart grid. Communication is the basis of the development of the new power system. in the distribution automation business, communication is the weakest link. In order to make electric power communication develop more smoothly, we should improve our awareness of security issues. Because of the particularity of electric power communication, it often has very high requirements for the security of communication. In order to effectively ensure the security of electric power communication data, data encryption technology can be applied to the data transmission process, and the security of information transmission can be improved through the application of encryption and decryption keys.Physical layer key generation technology is a security technology that uses wireless channel characteristics as a random source to generate keys. This technology uses the anisotropy, time variation and spatial uniqueness of wireless channels to generate random sequences, which is different from traditional encryption methods. Physical layer key generation technology does not require the key management and distribution of a third party trusted organization. In theory, it can achieve one encryption at a time to achieve the absolute security of Shannon confidential communication[1]. This paper first briefly introduces the wireless channel physical layer key generation model and the general process of key generation scheme based on channel feature quantization, and then studies the improved optimization scheme based on traditional channel detection, preprocessing and quantization algorithm, so as to effectively improve the key generation performance.
Due to non-ideal conditions in the measurements of the wireless channel, high initial bit error rate (BER) in the preliminary key is resulted, which reduces the final secret key generation rate and even causes the secret key generation process fail. Aiming to resolve this problem, we first present and verify an optimal information reconciliation protocol; the validation experiment shows that not only the BER comes down more quickly, but also a higher information rate is achieved. Then, to address the problem of very high initial BER and further improve the efficiency of the secret key generation, we introduce the idea of pre-distillation into the secret key generation system, and present a pre-distillation method, which makes the initial BER comes down quickly, and ensures the subsequent information reconciliation be easily performed; hence the total key generation rate is improved. Experimental results demonstrate that the pre-distillation method has excellent ability of reducing the initial BER, especially in the case of very high initial BER. The combination of our proposed pre-distillation and our optimal information reconciliation is the most efficient one when the initial BER is larger than 0.15, and the information rate is improved by more than forty-nine times when the initial BER is 0.3
Device-to-device communication is increasingly important for emerging wireless applications, including the Internet of Things and industry mobile networks. To establish a secure communication channel between multiple legitimate devices, key agreement is an essential first step. Physical layer channel information is a promising technology for achieving communication security by generating a shared channel key. In this paper, we propose an efficient and random method for generating channel keys based on channel state information (CSI). Firstly, we preprocess the available subcarriers to reduce the correlation of adjacent subcarriers. Secondly, we propose a novel quantization process to generate random and secure channel keys. The part consists of two phases: the quantization phase and the inconsistency removal phase. In the quantization stage, CSI sub carriers are grouped into small blocks, and appropriate thresholds are generated. Then, wireless users quantize the CSI subcarriers into initial bit streams of 0 and 1 with different thresholds. In the inconsistency removal phase, we design an error correction mechanism where wireless users exchange the discarded index sequences in the initial bit streams to achieve key sequence consistency. We implement the proposed scheme using off-the-shelf wireless devices and evaluate its performance. The experimental results show that each CSI packet can produce 30 bits, which have passed the NIST randomness tests.
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.