PHYSICAL LAYER BASED SECRET KEY EXCHANGE AND AUTHENTICATION TECHNIQUES FOR WIRELESS NETWORKS

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Abstract

Security and power consumption are the first critical concerns in many wireless networks as part of the fast progress in a variety of applications over these networks. While several security algorithms have been implemented in different network layers, hardware complexity issues still exist. These are related to battery consumption of remotely connected devices as well as the power consumption of fixed nodes, which prompt the environmental consideration through the network design and operation to minimize energy consumption. The recent work aims to investigate security issues from the point of view of power-efficiency without compromising performance or adding new vulnerable threats. It was found that the symmetric cipher and secret keys play effective roles in securing confidential data exchange from being intercepted. The process of exchanging private keys (for symmetric ciphers) has been well established in cryptography and many methods have been practically implemented relying on mathematically proven secure algorithms. Nevertheless, those methods require longer key lengths and more sophisticated implementation to satisfy the standard requirements, which may not be appropriate for limited power devices. As an alternative, physical layer based algorithms for establishing security were proposed in the last decade. The contribution of this thesis is described as follows. Summary of some practical security algorithms will be presented by highlighting the main pros and cons of each prototype. Thereafter, the following chapters focus on the complexity aspect of some popular secret key exchange methods. Motivated by the aforementioned reasons and ambition towards the physical layer security, we proposed four approaches based on the conventional physical layer signal processing blocks using multiple antennas, orthogonal multiplexing, spatial modulation, and coding techniques. More specifically, the exchange of the secret key bits is proposed to use MIMO precoding through the detection of the index of the precoding matrix. A private indexing approach is applied to the public precoding codebook based on the channel capacity response. In the second proposed approach, the channel based randomisation vector is used in the orthogonal multiplexing technique. The third proposed approach is based on the spatial modulation where a private antenna order and constellation mapping is proposed to exchange and authenticate secret key bits. Finally, the turbo coding with private interleavers are proposed to exchange secret bits with higher throughput. The latter techniques are manipulated with a channel driven private approach in order to randomly exchange the secret key bits along with authentication. The results show improved performance compared to other existing benchmark techniques in terms of the key error rate, lower vulnerable secret bits, supporting different duplex channels, miss detection, false alarm, generation rate, and computational burden. In addition, a fundamental theoretical analysis shows a high equivocation rate compared to the direct channel based techniques.

Keyword(s)

Physical Layer Security

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