Quantized bits per sample contributes to the total length of the key generated from samples. Each quantized bit provides security against brute force attack. Ideally, the quantized bits per sample depend on either threshold levels or data range. In this paper, we are proposing a quantization method, which assigns multiple bits to samples using a single threshold and quantized bits per sample are independent of both threshold levels and data range. This quantization technique will be helpful to methods that have low quantized bits per sample. Quantization process is critical in multiple areas of communication. Quantization process highly impacts the number and agreement of quantized bits generated at transmitter and receiver. An efficient quantization method will reduce the effort of consecutive blocks for error correction and a sufficient number of quantized bits will satisfy criteria of minimum quantized bits and limitation of any domain. A well-designed quantization technique will offer more quantized bits per sample and less bit disagreement between transmitter and receiver. Quantization technique will have a high impact on future technology, which uses channel reciprocity and randomness for a dynamic key.
Quantized bits per sample contributes to the total length of the key generated from samples. Each quantized bit provides security against brute force attack. Ideally, the quantized bits per sample depend on either threshold levels or data range. In this paper, we are proposing a quantization method, which assigns multiple bits to samples using a single threshold and quantized bits per sample are independent of both threshold levels and data range. This quantization technique will be helpful to methods that have low quantized bits per sample. Quantization process is critical in multiple areas of communication. Quantization process highly impacts the number and agreement of quantized bits generated at transmitter and receiver. An efficient quantization method will reduce the effort of consecutive blocks for error correction and a sufficient number of quantized bits will satisfy criteria of minimum quantized bits and limitation of any domain. A well-designed quantization technique will offer more quantized bits per sample and less bit disagreement between transmitter and receiver. Quantization technique will have a high impact on future technology, which uses channel reciprocity and randomness for a dynamic key.
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.
Wireless network security is crucial for modern communication systems, requiring robust security mechanisms to safeguard transmitted data. Physical layer security, leveraging channel characteristics for key generation, has emerged as a promising approach. In this paper, we study the process of generating and sharing keys among authorized users without compromising secrecy. However, existing methods face challenges, particularly with a high rate of errors in the generated keys and the risk of using the same key multiple times, which could compromise security. We have explored generating a unique key for each session. Our study examines the bit generation rate and verify the consistency of the secure key. We found the trade-off between the number of symbols and the quantization levels for quadrature amplitude modulation as well as binary phase shift keying. Further, the discussion delves into the impact of channel non-reciprocity on the process of secure key generation. Moreover, we achieved almost zero bit error rate at high signal-to-noise ratio.
Abstract Wireless communications between two devices can be protected by secret keys. However, existing key generation schemes suffer from the high bit disagreement rate and low bit generation rate. In this paper, we propose an efficient physical layer key generation scheme by exploring the Received Signal Strength (RSS) of signals. In order to reduce the high mismatch rate of the measurements and to increase the key generation rate, a pair of transmitter and receiver separately apply adaptive quantization algorithm for quantifying the measurements. Then, we implement a randomness extractor to further increase key generation rate and ensure randomness of generated of keys. Several real-world experiments are implemented to verify the effectiveness of the proposed scheme. The results show that compared with the other related schemes, our scheme performs better in bit generation rate, bit disagreement rate, and randomness.
Providing secure communication links between devices of low computational power has been increasingly investigated during recent years. The need for fast and easy-to-implement security for computationally weak wireless devices has lead to the development of physical layer based key generation approaches. The generation of symmetric cryptographic keys out of wireless channel properties turned out to be a promising approach comprising advantages of symmetric as well as asymmetric cryptography. Numerous quantization schemes have been proposed in previous works to increase the Key Generation Rate (KGR). Also by increasing the sampling rate, the input data can be generated faster. However, due to fast sampling rates, redundancy of subsequent bits will increase. This lowers the quality, that is, the randomness of the generated secret key and makes the system more vulnerable to brute-force attacks. We present and analyze different techniques for transforming a temporally correlated sequence into a compressed sequence of decorrelated bits and, therefore, assure non-redundant key sequences.
Physical layer key generation is an important handshaking step for establishing secure wireless communication in wireless networks. Existing methods based on fine-grained Channel State Information (CSI) have seen significant limitations. Reciprocity, the theoretical basis of physical layer key generation, is sensitive to factors such as noise, interference and hardware level variations. Feedback-based Channel Gain Complement is designed to conquer the imperfect reciprocity between two communication parties in actual environments. In addition, we have found that the adjacent subcarriers are strongly correlated. Quantizing all 30 subcarriers without discrimination will reduce the randomness and strength of the secret key while discarding some carriers will lose important information. We propose a cluster-based quantization method, which balances between the generation speed and consistency in initial key bits. Evaluation results in static and mobile scenarios have shown that under the sampling rate of 5 packet/sec, Bit Generation Rate can reach 20~ 26 bps, and the generated key sequence can pass the NIST standard randomness test.