Secure key design approaches using entropy harvesting in wireless sensor network: A survey

Physical layer based security design in wireless sensor networks have gained much importance since the past decade. The various constraints associated with such networks coupled with other factors such as their deployment mainly in remote areas, nature of communication etc. are responsible for development of research works where the focus is secured key generation, extraction, and sharing. Keeping the importance of such works in mind, this survey is undertaken that provides a vivid description of the different mechanisms adopted for securely generating the key as well its randomness extraction and also sharing. This survey work not only concentrates on the more common methods, like received signal strength based but also goes on to describe other uncommon strategies such as accelerometer based. We first discuss the three fundamental steps viz. randomness extraction, key generation and sharing and their importance in physical layer based security design. We then review existing secure key generation, extraction, and sharing mechanisms and also discuss their pros and cons. In addition, we present a comprehensive comparative study of the recent advancements in secure key generation, sharing, and randomness extraction approaches on the basis of adversary, secret bit generation rate, energy efficiency etc. Finally, the survey wraps up with some promising future research directions in this area

Key Generation in Wireless Sensor Networks Based on Frequency-selective Channels - Design, Implementation, and Analysis

Key management in wireless sensor networks faces several new challenges. The scale, resource limitations, and new threats such as node capture necessitate the use of an on-line key generation by the nodes themselves. However, the cost of such schemes is high since their secrecy is based on computational complexity. Recently, several research contributions justified that the wireless channel itself can be used to generate information-theoretic secure keys. By exchanging sampling messages during movement, a bit string can be derived that is only known to the involved entities. Yet, movement is not the only possibility to generate randomness. The channel response is also strongly dependent on the frequency of the transmitted signal. In our work, we introduce a protocol for key generation based on the frequency-selectivity of channel fading. The practical advantage of this approach is that we do not require node movement. Thus, the frequent case of a sensor network with static motes is supported. Furthermore, the error correction property of the protocol mitigates the effects of measurement errors and other temporal effects, giving rise to an agreement rate of over 97%. We show the applicability of our protocol by implementing it on MICAz motes, and evaluate its robustness and secrecy through experiments and analysis.Comment: Submitted to IEEE Transactions on Dependable and Secure Computin

Practical Secrecy at the Physical Layer: Key Extraction Methods with Applications in Cognitive Radio

The broadcast nature of wireless communication imposes the risk of information leakage to adversarial or unauthorized receivers. Therefore, information security between intended users remains a challenging issue. Currently, wireless security relies on cryptographic techniques and protocols that lie at the upper layers of the wireless network. One main drawback of these existing techniques is the necessity of a complex key management scheme in the case of symmetric ciphers and high computational complexity in the case of asymmetric ciphers. On the other hand, physical layer security has attracted significant interest from the research community due to its potential to generate information-theoretic secure keys. In addition, since the vast majority of physical layer security techniques exploit the inherent randomness of the communication channel, key exchange is no longer mandatory. However, additive white Gaussian noise, interference, channel estimation errors and the fact that communicating transceivers employ different radio frequency (RF) chains are among the reasons that limit utilization of secret key generation (SKG) algorithms to high signal to noise ratio levels. The scope of this dissertation is to design novel secret key generation algorithms to overcome this main drawback. In particular, we design a channel based SKG algorithm that increases the dynamic range of the key generation system. In addition, we design an algorithm that exploits angle of arrival (AoA) as a common source of randomness to generate the secret key. Existing AoA estimation systems either have high hardware and computation complexities or low performance, which hinder their incorporation within the context of SKG. To overcome this challenge, we design a novel high performance yet simple and efficient AoA estimation system that fits the objective of collecting sequences of AoAs for SKG. Cognitive radio networks (CRNs) are designed to increase spectrum usage efficiency by allowing secondary users (SUs) to exploit spectrum slots that are unused by the spectrum owners, i.e., primary users (PUs). Hence, spectrum sensing (SS) is essential in any CRN. CRNs can work both in opportunistic (interweaved) as well as overlay and/or underlay (limited interference) fashions. CRNs typically operate at low SNR levels, particularly, to support overlay/underlay operations. Similar to other wireless networks, CRNs are susceptible to various physical layer security attacks including spectrum sensing data falsification and eavesdropping. In addition to the generalized SKG methods provided in this thesis and due to the peculiarity of CRNs, we further provide a specific method of SKG for CRNs. After studying, developing and implementing several SS techniques, we design an SKG algorithm that exploits SS data. Our algorithm does not interrupt the SS operation and does not require additional time to generate the secret key. Therefore, it is suitable for CRNs

Reconfigurable antennas for wireless network security

Large scale proliferation of wireless technology coupled with the increasingly hostile information security landscape is of serious concern as organizations continue to widely adopt wireless networks to access and distribute critical and con dential information. Private users also face more risks than ever as they exchange more and more sensitive information over home and public networks through their ubiquitous wireless-enabled laptops and hand held devices. The fundamental broadcast nature of wireless data transmission aggravates the situation, since unlike wired networks, it introduces multiple avenues for attack and penetration into a network. Though several traditional mechanisms do exist to protect wireless networks against threats, such schemes are a carryover from the traditional wire based systems. Hence vulnerabilities continue to exist, and have been repeatedly demonstrated to be susceptible to failure under di erent circumstances.The resulting uncertainties have led to a signi cant paradigm shift in the design and implementation of wireless security in recent times, among which wireless channel based security schemes have shown the most promise. Channel based security schemes are rooted on the simple fact that a legitimate user and an adversary cannot be physically co-located and hence the underlying multi-path structure corresponding to the two links cannot be the same. However most wireless systems are constrained in terms of bandwidth, power and number of transceivers, which seriously limit the performance of such channel based security implementations. To overcome these limitations, this thesis proposes a new dimension to the channel based security approach by introducing the capabilities of recon gurable antennas. The main objective of this work is to demonstrate that the ability of recon gurable antennas to generate di erent channel realizations that are uncorrelated between di erent modes will lead to signi cant improvements in intrusion detection rates.To this end, two di erent schemes that make use of channels generated by a recon gurable antenna are proposed and evaluated through measurements. The rstscheme is based on associating a channel based ngerprint to the legitimate user to prevent intrusion. The three main components of this scheme are i ) a ngerprint derived from the di erent modes of the antenna, ii ) a metric to compare two ngerprints and iii ) a hypothesis test based on the proposed metric to classify intruders and legitimate transmitters. The second scheme relies on monitoring the statistics of the channels for the legitimate transmitters' links since any intrusion will result in an observable change in the channel's statistics. The problem is posed as a generalized likelihood ratio test (GLRT) which responds to any change in the channel statistics by a large spike in the likelihood ratio's value. The detector's performance is studied as a function of pattern correlation coe cient for both schemes to provide insights on designing appropriate antenna modes for better performance.Moreover this thesis takes a holistic approach to studying the antenna based security schemes. A novel channel modeling approach which combines the cluster channel model and site speci c ray tracer results is proposed and validated to facilitate the analysis of such schemes through simulations without resorting to comprehensive channel measurements. This approach is motivated by the lack of an intuitive and simple channel model to study systems that use recon gurable antennas for any application.Finally the design of a metamaterial based substrate that can help miniaturize antenna arrays and recon gurable antennas is presented. The magnetic permeabilityenhanced metamaterial's capability to miniaturize an antenna's size while maintaining an acceptable level of isolation between elements in an array is experimentallydemonstrated. The bene ts gained in a wireless communication system that uses a patch antenna arrray built on this substrate is quanti ed in terms of mean e ective gain, correlation between the antennas and channel capacity through channel measurements.Despite their capability to signi cantly improve spectral e ciency, the widespread adoption of recon gurable antennas in wireless devices has been hampered by their complexity, cost and size. The work presented in this thesis is therefore intended to serve as a catalyst to the widespread adoption of recon gurable antenna technology by i ) adding value to such antennas by utilizing them for enhancing system security and ii ) providing a mechanism to miniaturize them to facilitate their integration into modern space constrained wireless devices.Ph.D., Electrical Engineering -- Drexel University, 201

Physical Layer Security for Visible Light Communication Systems:A Survey

Due to the dramatic increase in high data rate services and in order to meet the demands of the fifth-generation (5G) networks, researchers from both academia and industry are exploring advanced transmission techniques, new network architectures and new frequency spectrum such as the visible light spectra. Visible light communication (VLC) particularly is an emerging technology that has been introduced as a promising solution for 5G and beyond. Although VLC systems are more immune against interference and less susceptible to security vulnerabilities since light does not penetrate through walls, security issues arise naturally in VLC channels due to their open and broadcasting nature, compared to fiber-optic systems. In addition, since VLC is considered to be an enabling technology for 5G, and security is one of the 5G fundamental requirements, security issues should be carefully addressed and resolved in the VLC context. On the other hand, due to the success of physical layer security (PLS) in improving the security of radio-frequency (RF) wireless networks, extending such PLS techniques to VLC systems has been of great interest. Only two survey papers on security in VLC have been published in the literature. However, a comparative and unified survey on PLS for VLC from information theoretic and signal processing point of views is still missing. This paper covers almost all aspects of PLS for VLC, including different channel models, input distributions, network configurations, precoding/signaling strategies, and secrecy capacity and information rates. Furthermore, we propose a number of timely and open research directions for PLS-VLC systems, including the application of measurement-based indoor and outdoor channel models, incorporating user mobility and device orientation into the channel model, and combining VLC and RF systems to realize the potential of such technologies