Secure Communications over Wireless Networks

1 Introduction

This chapter is concerned with the study of secrecy capacity and secure outage performance for the wireless channels, focusing on the recent research of secure communications where a legitimate user communicates with a legitimate receiver in the presence of an eavesdropper. Perfect secrecy is achieved when the transmitter and the legitimate receiver can communicate at some positive rate, while insuring that eavesdropper gets zero bits of information. Specifically, two different channels, such as fading and additive white Gaussian noise (AWGN) channels are considered for the study. The open nature of wireless communication network makes it susceptible to eavesdropping and fraud. As a result, the privacy and security in wireless communication networks have taken on an increasingly important role, as these networks are used to transmit personal information. Moreover, the problems of cryptography and secrecy systems furnish an interesting application of communication theory. Traditionally, channel fading has been viewed as a source of unreliability of communication. Therefore, the natural problem of great interest is, how we can achieve high data rates with reliability in spite of the harsh wireless channel subject to the fading, limited power and bandwidth resources. Since the goal of this work is to achieve reliable communication at the maximum possible data rate, the relevant information-theoretic measure is secrecy capacity (i.e. the maximum transmission rate at which the eavesdropper is unable to decode any information) of the channel. The probability of non-zero secrecy capacity and secure outage probability are the measures of secure outage performance for the relevant channel model. Moreover, security issues arising in wireless communication networks include confidentiality, integrity, authentication and nonrepudiation. Confidentiality is the measure of reliability which guarantees that legitimate receiver successfully receives the intended information from the source node, while eavesdroppers are unable to decode any information from the intended information. Integrity guarantees that original information sent by the source node is not modified by the eavesdroppers during its transmission. Authentication ensures that a recipient of information i.e. legitimate receiver is able to identify the sender of received information i.e. the source of original information from which the information has been sent. Nonrepudiation ensures that a sender of information is not able to deny having transmitted that information and the recipient is not able to deny having received the information.