Physical Layer Security and Authentication with Practical Transmissions

Classic approaches to communications security neglect the physical layer and rely on computational security solutions working at higher layers, like cryptography. However, the physical layer of communications provides for some interesting properties that may be significant for security, like uniqueness, randomness and reciprocity. In this chapter we give an overview of techniques that allow achieving confidentiality and authentication at the physical layer taking into account the typical constraints of practical transmissions, like finite-length coding and discrete modulation formats. We show that, even with these constraints in mind, the physical layer can be a source of security for communications, both in terms of confidentiality and authentication, and provides a basis for hardening security at higher layers.