Secret Key Exchange and Authentication via Randomized Spatial Modulation and Phase Shifting

Advances in physical layer security techniques have increasingly demonstrated their potential to replace security functionalities that are traditionally included in the upper layers of the Open Systems Interconnection model. This has made it possible for devices with limited layer structures or/and restricted hardware components to offer security measures. In this paper, we consider spatial modulation (SM) systems and propose a unique physical layer technique that uses a random constellation mapping criterion for secret key exchange. The principle idea here is to exploit the inherent symbol-antenna mapping feature of the SM technique to encode the secret key. Specifically, a random phase shift is imposed on each of the modulated symbols using a channel driven approach to uniquely authenticate the transmitted key bits or/and the encrypted confidential data. The results demonstrate that the proposed technique is superior to benchmark techniques in terms of computational complexity and key bit error rate. It will also be shown that the proposed technique offers greater flexibility in terms of the authentication process preference, which is normally unattainable in most of the key exchange proposed techniques.