Using ill-conditioned theory for physical-layer security in time-variant channels

The unstable characteristic of iII-conditioned system is used to guarantee wireless security in this paper. The use of ill-conditioned theory to protect wireless transmissions is proposed as a way to secure wireless networks at physical layer. Firstly, the problem of randomized transmission is converted to that of solving ill-conditioned equation to guarantee wireless transmissions with inherent low-probability-of interception (LPI). Secondly, a conditional ill-conditioned optimization function is constructed. The function of legitimate node is stable because of its matched channel. But the function of eavesdropper is randomized because that she has not the legitimate conditions, which relate to the wireless medium contains domain-specific information. In this context, we propose a security scheme for wireless security in time-variant channels. In this scheme, the variable part of channels is converted to additional conditions, which can be solved by optimizing parameters. In contrast to conventional physical-layer security techniques, the scheme exploits the redundancy of ill-conditioned problem´s solutions instead of array redundancy for deliberate signal randomization, which effectively randomizes the eavesdropper´s received signals but not the authorized receiver´s signals. Extensive simulations and analysis results show that our proposed scheme is useful for securing wireless transmissions.