Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey

This paper provides a comprehensive review of the domain of physical layer security in multiuser wireless networks. The essential premise of physical-layer security is to enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers without relying on higher-layer encryption. This can be achieved primarily in two ways: without the need for a secret key by intelligently designing transmit coding strategies, or by exploiting the wireless communication medium to develop secret keys over public channels. The survey begins with an overview of the foundations dating back to the pioneering work of Shannon and Wyner on information-theoretic security. We then describe the evolution of secure transmission strategies from point-to-point channels to multiple-antenna systems, followed by generalizations to multiuser broadcast, multiple-access, interference, and relay networks. Secret-key generation and establishment protocols based on physical layer mechanisms are subsequently covered. Approaches for secrecy based on channel coding design are then examined, along with a description of inter-disciplinary approaches based on game theory and stochastic geometry. The associated problem of physical-layer message authentication is also introduced briefly. The survey concludes with observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials, 201

Secrecy Enhancement in Cooperative Relaying Systems

Cooperative communications is obviously an evolution in wireless networks due to its noticeable advantages such as increasing the coverage as well as combating fading and shadowing effects. However, the broadcast characteristic of a wireless medium which is exploited in cooperative communications leads to a variety of security vulnerabilities. As cooperative communication networks are globally expanded, they expose to security attacks and threats more than ever. Primarily, researchers have focused on upper layers of network architectures to meet the requirements for secure cooperative transmission while the upper-layer security solutions are incapable of combating a number of security threats, e.g., jamming attacks. To address this issue, physical-layer security has been recommended as a complementary solution in the literature. In this thesis, physical layer attacks of the cooperative communication systems are studied, and corresponding security techniques including cooperative jamming, beamforming and diversity approaches are investigated. In addition, a novel security solution for a two-hop decode-and-forward relaying system is presented where the transmitters insert a random phase shift to the modulated data of each hop. The random phase shift is created based on a shared secret among communicating entities. Thus, the injected phase shift confuses the eavesdropper and secrecy capacity improves. Furthermore, a cooperative jamming strategy for multi-hop decode-and-forward relaying systems is presented where multiple non-colluding illegitimate nodes can overhear the communication. The jamming signal is created by the transmitter of each hop while being sent with the primary signal. The jamming signal is known at the intended receiver as it is according to a secret common knowledge between the communicating entities. Hence, artificial noise misleads the eavesdroppers, and decreases their signal-to-noise-ratio. As a result, secrecy capacity of the system is improved. Finally, power allocation among friendly jamming and main signal is proposed to ensure that suggested scheme enhances secrecy

A Survey of Physical Layer Security Techniques for 5G Wireless Networks and Challenges Ahead

Physical layer security which safeguards data confidentiality based on the information-theoretic approaches has received significant research interest recently. The key idea behind physical layer security is to utilize the intrinsic randomness of the transmission channel to guarantee the security in physical layer. The evolution towards 5G wireless communications poses new challenges for physical layer security research. This paper provides a latest survey of the physical layer security research on various promising 5G technologies, including physical layer security coding, massive multiple-input multiple-output, millimeter wave communications, heterogeneous networks, non-orthogonal multiple access, full duplex technology, etc. Technical challenges which remain unresolved at the time of writing are summarized and the future trends of physical layer security in 5G and beyond are discussed.Comment: To appear in IEEE Journal on Selected Areas in Communication

A Critical Review of Physical Layer Security in Wireless Networking

Wireless networking has kept evolving with additional features and increasing capacity. Meanwhile, inherent characteristics of wireless networking make it more vulnerable than wired networks. In this thesis we present an extensive and comprehensive review of physical layer security in wireless networking. Different from cryptography, physical layer security, emerging from the information theoretic assessment of secrecy, could leverage the properties of wireless channel for security purpose, by either enabling secret communication without the need of keys, or facilitating the key agreement process. Hence we categorize existing literature into two main branches, namely keyless security and key-based security. We elaborate the evolution of this area from the early theoretic works on the wiretap channel, to its generalizations to more complicated scenarios including multiple-user, multiple-access and multiple-antenna systems, and introduce not only theoretical results but practical implementations. We critically and systematically examine the existing knowledge by analyzing the fundamental mechanics for each approach. Hence we are able to highlight advantages and limitations of proposed techniques, as well their interrelations, and bring insights into future developments of this area

Physical layer security solutions against passive and colluding eavesdroppers in large wireless networks and impulsive noise environments

Wireless networks have experienced rapid evolutions toward sustainability, scalability and interoperability. The digital economy is driven by future networked societies to a more holistic community of intelligent infrastructures and connected services for a more sustainable and smarter society. Furthermore, an enormous amount of sensitive and confidential information, e.g., medical records, electronic media, financial data, and customer files, is transmitted via wireless channels. The implementation of higher layer key distribution and management was challenged by the emergence of these new advanced systems. In order to resist various malicious abuses and security attacks, physical layer security (PLS) has become an appealing alternative. The basic concept behind PLS is to exploit the characteristics of wireless channels for the confidentiality. Its target is to blind the eavesdroppers such that they cannot extract any confidential information from the received signals. This thesis presents solutions and analyses to improve the PLS in wireless networks. In the second chapter, we investigate the secrecy capacity performance of an amplify-andforward (AF) dual-hop network for both distributed beamforming (DBF) and opportunistic relaying (OR) techniques. We derive the capacity scaling for two large sets; trustworthy relays and untrustworthy aggressive relays cooperating together with a wire-tapper aiming to intercept the message. We show that the capacity scaling in the DBF is lower bounded by a value which depends on the ratio between the number of the trustworthy and the untrustworthy aggressive relays, whereas the capacity scaling of OR is upper bounded by a value depending on the number of relays as well as the signal to noise ratio (SNR). In the third chapter, we propose a new location-based multicasting technique, for dual phase AF large networks, aiming to improve the security in the presence of non-colluding passive eavesdroppers. We analytically demonstrate that the proposed technique increases the security by decreasing the probability of re-choosing a sector that has eavesdroppers, for each transmission time. Moreover, we also show that the secrecy capacity scaling of our technique is the same as for broadcasting. Hereafter, the lower and upper bounds of the secrecy outage probability are calculated, and it is shown that the security performance is remarkably enhanced, compared to the conventional multicasting technique. In the fourth chapter, we propose a new cooperative protocol, for dual phase amplify-andforward large wireless sensor networks, aiming to improve the transmission security while taking into account the limited capabilities of the sensor nodes. In such a network, a portion of the K relays can be potential passive eavesdroppers. To reduce the impact of these untrustworthy relays on the network security, we propose a new transmission protocol, where the source agrees to share with the destination a given channel state information (CSI) of source-trusted relay-destination link to encode the message. Then, the source will use this CSI again to map the right message to a certain sector while transmitting fake messages to the other sectors. Adopting such a security protocol is promising because of the availability of a high number of cheap electronic sensors with limited computational capabilities. For the proposed scheme, we derived the secrecy outage probability (SOP) and demonstrated that the probability of receiving the right encoded information by an untrustworthy relay is inversely proportional to the number of sectors. We also show that the aggressive behavior of cooperating untrusted relays is not effective compared to the case where each untrusted relay is trying to intercept the transmitted message individually. Fifth and last, we investigate the physical layer security performance over Rayleigh fading channels in the presence of impulsive noise, as encountered, for instance, in smart grid environments. For this scheme, secrecy performance metrics were considered with and without destination assisted jamming at the eavesdropper’s side. From the obtained results, it is verified that the SOP, without destination assisted jamming, is flooring at high signal-to-noise-ratio values and that it can be significantly improved with the use of jamming

Secure Degrees of Freedom Regions of Multiple Access and Interference Channels: The Polytope Structure

The sum secure degrees of freedom (s.d.o.f.) of two fundamental multi-user network structures, the K-user Gaussian multiple access (MAC) wiretap channel and the K-user interference channel (IC) with secrecy constraints, have been determined recently as K(K-1)/(K(K-1)+1) [1,2] and K(K-1)/(2K-1) [3,4], respectively. In this paper, we determine the entire s.d.o.f. regions of these two channel models. The converse for the MAC follows from a middle step in the converse of [1,2]. The converse for the IC includes constraints both due to secrecy as well as due to interference. Although the portion of the region close to the optimum sum s.d.o.f. point is governed by the upper bounds due to secrecy constraints, the other portions of the region are governed by the upper bounds due to interference constraints. Different from the existing literature, in order to fully understand the characterization of the s.d.o.f. region of the IC, one has to study the 4-user case, i.e., the 2 or 3-user cases do not illustrate the generality of the problem. In order to prove the achievability, we use the polytope structure of the converse region. In both MAC and IC cases, we develop explicit schemes that achieve the extreme points of the polytope region given by the converse. Specifically, the extreme points of the MAC region are achieved by an m-user MAC wiretap channel with (K-m) helpers, i.e., by setting (K-m) users' secure rates to zero and utilizing them as pure (structured) cooperative jammers. The extreme points of the IC region are achieved by a (K-m)-user IC with confidential messages, m helpers, and N external eavesdroppers, for m>=1 and a finite N. A byproduct of our results in this paper is that the sum s.d.o.f. is achieved only at one extreme point of the s.d.o.f. region, which is the symmetric-rate extreme point, for both MAC and IC channel models.Comment: Submitted to IEEE Transactions on Information Theory, April 201