The issues of privacy and security in wireless communication networks have taken on an increasingly important role as these networks continue to flourish worldwide. Traditionally, security is viewed as an independent feature addressed above the physical-layer and all widely used cryptographic protocols are designed and implemented assuming the physical-layer has already been established and provides an error free link. However, with the emergence of ad-hoc and decentralized networks, higher-layer techniques, such as encryption, are complex and hard to be implemented. Therefore, there has been a recent attention on studying the fundamental ability of the physical-layer to provide secure wireless communications. In this contribution, we discuss the challenges ahead in implementing wireless physical-layer security.