5G communications bring revolutionary services beyond 4G, namely enhanced Mobile Broadband (eMBB), massive Machine Type Communications (mMTC), and Ultra-Reliable Low-Latency Communications (URLLC), opening up a plethora of new applications and capabilities in defense and commercial spaces. However, the complexity and heterogeneity of 5G networks and applications also bring unprecedented security challenges that demand innovative solutions. We propose to leverage unique 5G physical-layer technologies to bring an extra layer of security protection that is orthogonal to conventional cryptography-based wireless security. More specifically, we create and demonstrate low-overhead and 5G-compliant hardware to prevent eavesdropping attacks against eMBB links with antenna subset modulation scheme and to achieve lightweight identification for mMTC devices utilizing RF fingerprinting from spectral regrowth.