Multi Layer Security for MIMO Wiretap System

Mohamed Lassaad Ammari, Paul Fortier

Shiqi Gong, Chengwen Xing, Zesong Fei +1 more

Joseph R. Childress

Mohamed Nafea, Aylin Yener

This chapter considers securing wireless communications at the physical layer using multiple antennas. In particular, the multiple antenna (MIMO) wiretap channel is presented and its secrecy capacity is provided. Further investigation of the high-SNR characterization of the secrecy capacity, i.e., secure degrees of freedom, reveals that the secrecy capacity of the MIMO wiretap channel does not scale with the transmit power when the eavesdropper has an advantage over the legitimate transmitter in the number of antennas. An external multi-antenna cooperative jammer terminal is introduced to the channel model in order to improve its secrecy capacity scaling with power. The secure degrees of freedom for this new multi-terminal multi-antenna channel is characterized. While for these models the eavesdropper channel state information is known at the legitimate terminals, the chapter next removes this assumption and presents results that utilize multiple antennas in order to provide secure communications irrespective of the eavesdropper channel state. An achievable strong secrecy rate and the secure degrees of freedom characterization for the MIMO wiretap channel when the eavesdropper channel is arbitrary, varying, and unknown at the legitimate terminals are presented. Finally, the extension of this model to the two-user multiple access MIMO wiretap channel is considered and its secure degrees of freedom region is characterized. Introduction The wiretap channel and the notion of secrecy capacity, introduced in [1] and generalized by [2], have provided the framework for physical layer design for wireless channels with information theoretic guarantees against eavesdropping. A natural model in wireless communications is one which utilizes multiple antennas for transmission and reception at each node. The improvement in secrecy rate that can be obtained using multiple antennas in a point-to-point channel with an eavesdropper has been studied extensively in several references, including [3, 4]. Specifically, the secrecy capacity of the Gaussian model consisting of a multiple antenna legitimate transmitter, a multiple antenna legitimate receiver, and a multiple antenna eavesdropper, termed the multiple-input multiple-output (MIMO) wiretap channel, has been identified in full generality in [5, 6].

Reem Melki, Hassan Noura, Mohammad M. Mansour +1 more

Ye Fan, Xuewen Liao, Zhenzhen Gao +1 more

In this paper, we study the information-theoretical security of the K-user MIMO Y wiretap Gaaussian channels and deduce the lower bounds of the secure degrees of freedom (SDOF). Due to the different receiving links of the eavesdropper, we propose two MIMO Y wiretap models which are called Broadcast Wiretap Channel (BWC) and Multi-access Broadcast Wiretap Channel (MBWC), respectively. Each legitimate user equipped with M antennas intends to transmit independent signals via an intermediate amplify-and-forward (AF) relay with N antennas. Besides, there exists an eavesdropper with Ne antennas close to the K users (K ≥ 3). Based on the asymptotic real interference alignment and the structured cooperative jamming, the security of the MIMO Y wiretap channels can be guaranteed. From the asymptotic analysis, we can find that a lower bound of the sum SDOF in BWC is K/4. While in the MBWC model, since the relay working in the full duplex mode broadcasts cooperative jamming signals to all the other nodes especially to the eavesdropper, the lower bound of sum SDOF is K2-3K/4(K-1), which is altered along with the number of users.