In this e-book, several advanced security designs and techniques, capable of replacing conventional encryption-based methods, are proposed for future wireless networks. Particularly, the conducted research studies encompass the following main directions: I) Designing cross PHY/MAC layer security techniques using the following approaches: 1) Automatic-repeat-request (ARQ) with adaptive modulation. 2) ARQ with null-space-independent artificial noise. II) Security techniques for OFDM-based waveforms. This includes developing new designs that cover the following topics: 1) OFDM with adaptive interleaving (precoding) and deinterleaving (postcoding). 2) OFDM with subcarrier index selection for enhancing security and reliability of 5G URLLC services. 3) CP-less OFDM with alignment signals for enhancing spectral efficiency, reducing latency, and improving PHY security of 5G and beyond services. III) New inherently secure waveform designs, where a secure channel-based transform waveform, referred to as orthogonal transform division multiplexing (OTDM), is developed for future wireless systems. IV) Security designs for orthogonal space-time block coding (OSTBC)-based MISO systems.