Enhancing wireless security with theory of ill-posed problem: A novel physical-layer encryption mechanism

This paper studies physical-layer security without knowing the eavesdropper's channel state information. The use of ill-posed theory to protect wireless transmissions is proposed. Firstly, the problem of randomized transmission is translated to that of solving ill-posed equation to guarantee wireless transmissions with inherent low-probability-of interception (LPI). Secondly, by exploiting the nonunique or instable solutions of an ill-posed problem, two mechanisms are proposed that satisfy the given security requirement while achieving good throughput performance. Our results show that ill-posed problem is not always nasty. We hope that by identifying ill-posed problem inversely, a theoretical framework of enhancing physical-layer security can be constructed eventually.