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

협력 재밍을 이용한 중계 네트워크의 보안 통신을 위한 최적화 및 할당 기법

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2019. 2. 이재홍.Physical layer security is a promising technology in the upcoming fifth generation (5G) wireless communication because the wireless communication is vulnerable to eavesdrop and it is complex to encrypt a data signal. In physical layer security, secure transmission is satisfied by using the physical characteristics of the wireless channel. Cooperative jamming is one of the efficient techniques to enhance secrecy performance in physical layer security. In cooperative jamming, a cooperating node transmits a jamming signal to interfere the eavesdropper. However, this jamming signal effects not only the eavesdropper but also the destination, which degrades the secrecy performance and causes waste of transmit power. It means the jamming signal transmission needs to be designed properly with optimization and power allocation to enhance security. The dissertation consists of two main results. First, we investigate a two-hop relay network consists of a source, an AF relay, a destination, and an eavesdropper. In this network, cooperative jamming is utilized in which the destination and the source transmit jamming signals in phase 1 and 2, respectively. At the destination, its own jamming signal transmitted in phase 1 is perfectly cancelled, and the jamming signal from the source has negligible strength due to the weak channel condition from the source to destination. We propose an optimal source power allocation for the network to enhance the secrecy performance based on the channel knowledge available at the source. Simulation results show that the proposed source power allocation scheme achieves higher secrecy rate and lower secrecy outage probability than the fixed power allocation schemes. Second, we investigate a two-hop relay network consists of a source, multiple AF relays, a destination, and an eavesdropper. In this network, one relay is selected out of the relays to forwards the data signals. Also, cooperative jamming is utilized in which the destination and the source transmit jamming signals in phase 1 and 2, respectively. We propose power allocation and relay selection scheme to minimize secrecy outage probability with the total power constraint and the power constraints for each phases, respectively. In total power constraint case, power allocation and relay selection problem is formulated and it is divided into a master problem and a subproblem by using the primal decomposition method. Simulation results show that the proposed scheme achieves lower secrecy outage probability than the conventional jamming power allocation scheme as well as without jamming scheme.물리 계층 보안은 무선통신의 보안에 대한 취약점과 암호화의 복잡성이라는 특징으로 인하여, 5세대(5G) 이동통신을 위한 핵심 기술로 간주되고 있다. 물리 계층 보안은 무선 채널의 물리적 특성을 이용하여 보안 통신을 가능하게 한다. 협력 재밍(cooperative jamming)은 물리 계층 보안에서의 보안 성능을 향상시키는 효과적인 기술로, 협력 노드가 재밍 신호를 전송함으로써 도청자를 방해하고, 보안을 달성한다. 그러나, 이러한 재밍 신호는 도청자 뿐 아니라 수신단 역시 방해하게 되므로 과도한 재밍 신호 전송은 보안 성능 향상에 지장을 주고 전력을 낭비하게 된다. 따라서 보안 성능을 향상시키기 위해서는 재밍 신호의 전력 할당 및 최적화를 하는 것이 필수적이다. 본 논문에서의 두 가지 주요한 연구 결과는 다음과 같다. 첫째, 하나의 송신단, 증폭 후 재전송 중계기, 수신단 및 도청자가 존재하는 중계 네트워크를 분석한다. 이 때 수신단 및 송신단이 협력 재밍을 통해 각각 첫 번째 및 두 번째 페이즈에서 재밍 신호를 전송하도록 한다. 수신단이 첫 번째 페이즈에 전송한 재밍 신호는 중계기를 통해 증폭되지만 수신단이 제거할 수 있으며, 송신단의 재밍 신호는 송신단과 수신단 사이의 채널이 약하기 때문에 수신단에 미치지 못한다. 이 때 본 네트워크에서 네트워크의 보안 전송률(secrecy rate) 및 보안 불능 확률(secrecy outage probability)을 향상시키는 송신단의 각 페이즈 별 전송 전력을 송신단이 가진 채널 정보를 통해 최적화한다. 모의 실험을 통해 제안한 전력 할당 기법이 다른 고정 전력 할당 기법에 비해 높은 보안 전송률과 낮은 보안 불능 확률을 달성함을 확인한다. 둘째, 하나의 송신단, 다수의 증폭 후 재전송 중계기들, 하나의 수신단 및 도청자가 존재하는 중계 네트워크를 분석한다. 다수의 중계기 중 하나의 중계기가 선택되어 신호를 전송하게 되며, 협력 재밍을 통해 수신단 및 송신단이 재밍 신호를 전송한다. 이 때 네트워크의 보안 불능 확률을 최소화하기 위한 중계기 선택 및 전력 할당 기법을 다양한 전력 제한에 맞게 분석한다. 네트워크 전체 전력이 제한된 경우에서는 중계기 선택 및 전력 할당 문제를 풀기 위해 두 개의 부문제(subproblem) 로 분할한다. 모의 실험을 통해 제안한 기법이 기존의 기법 및 재밍 신호를 전송하지 않는 기법에 비해 낮은 보안 불능 확률을 달성함을 확인한다.Abstract i 1 Introduction 1 1.1 Background and Related Work 2 1.1.1 Physical Layer Security 2 1.1.2 Cooperative Jamming 3 1.2 Outline of Dissertation 5 1.3 Notations 6 2 Source Power Allocation for Cooperative Jamming in Amplify-and- Forward Relay Network with Eavesdropper 9 2.1 System Model 10 2.2 Source Power Allocation 16 2.2.1 Full CSI for All Links 16 2.2.2 Full CSI for Desired Links only 18 2.3 Simulation Results 23 2.3.1 Identical Channel Condition 23 2.3.2 Non-identical Channel Condition 32 2.3.3 Multiple Antenna Eavesdropper 50 2.4 Summary 50 3 Power Allocation and Relay Selection for Cooperative Jamming in AF Relay Network with Multiple Relays and an Eavesdropper 53 3.1 System Model 55 3.2 Secrecy Outage Probability Analysis 61 3.3 Power Allocation and Relay Selection 66 3.3.1 Total Power Constraint 66 3.3.2 Power Constraints for Each Phases 68 3.4 Numerical Results 70 3.4.1 Multiple Antenna Eavesdropper 86 3.5 Extension to Multiple Relay Selection 86 3.6 Summary 88 4 Conclusion 89 4.1 Summary 89 4.2 Future Works 90 A Obtainment of Optimal Values of alpha in R1 and R2 92 Bibliography 95 Korean Abstract 104Docto