Physical layer cryptography and cognitive networks

Recently the huge development of different and heterogeneous wireless communication systems raises the problem of growing spectrum scarcity. Cognitive radio tends to solve this problem by dynamically utilizing the spectrum. Security in cognitive radio network becomes a challenging issue, since more chances are given to attackers by cognitive radio technology compared to conventional wireless network. These weaknesses are introduced by the nature itself of cognitive radio, and they may cause serious impact to the network quality of service. However, to the authors' knowledge, there are no specific secure protocols for cognitive radio networks. This paper will discuss the vulnerabilities inherent to cognitive radio systems, identify novel types of abuse, classify attacks, and analyze their impact. Security solutions to mitigate such threats will be proposed and discussed. In particular, physical payer security will be taken into account. A new modulation technique, able to encrypt the radio signal without any a priori common secret between the two nodes, was previously proposed by the authors (Mucchi et al. 2009, WPC 51, 67-80; Mucchi et al. 2010, WPC 53, 329-347). The information is modulated, at physical layer, by the thermal noise experienced by the link between two terminals. A loop scheme is designed for unique recovering of mutual information. This contribution improves the previous works by proposing the noise loop modulation as physical layer security technique for cognitive radio networks.