The standard practice of adding authentication and encryption to the existing protocols at the various communication layers has led to what could be rightly classified as a patchwork of security mechanisms. Given that data security is so critically important, it is reasonable to defend that security measures should be implemented at all layers where it can be done in a cost effective manner. Interestingly, one layer has remained almost oblivious to this shift towards secure communication: the physical layer, which lies at the lowest end of the protocol stack and converts bits of information into modulated signals. The described state of affairs is all the more striking as randomness, generally perceived as a key element of secrecy systems, is abundantly available in the stochastic nature of the noise that is intrinsic to the physical communication channel. This observation has driven a significant amount of research towards the study of security technologies that are embedded at the physical layer of the protocol architecture, a segment of the system where little security exists today. In this talk, we will present the information-theoretic limits of secure communications at the physical layer and discuss the construction of practical coding schemes to highlight the challenges and opportunities related to the design of physical layer security schemes.