Special issue on physical-layer security.

The unprecedented development of wireless networks and increased concerns for their security have fostered a renewed interest for communication schemes that ensure confidentiality at the physical layer itself. The idea that there is security to be gained by harnessing the randomness of the physical-layer with appropriate coding schemes has now evolved into a flourishing research area, colloquially known as "physical-layer security". Physical-layer security builds upon the pioneering results developed in the seventies by Wyner, Csiszár, and Körner, and in the nineties by Ahlswede, Csiszár, and Maurer, which established the possibility of achieving information-theoretic security by exploiting the noise of the communication channels. While many information-theoretic aspects of physical-layer security are still to be explored, it is fair to say that the area has gained in maturity and the future will see a large number of papers exploring more practical communication-theoretic and signal processing aspects of physical layer security.