Recent advances in wireless communication technologies along with a proliferation of mobile devices have enabled a new, and expanded level of ubiquitous access to data and communications. Reliable, secure, and private communications are as essential in these product offerings as network availability, especially as the Internet presents enhanced opportunities for network breaches. Every day new security challenges surface, often a consequence of weak encryption and inherently open access to networks and in some cases lack of a pre-deployed infrastructure. This special issue advances the state-of-the-art research in the area of security, privacy, cryptography, and its applications to future mobile communications. Our special issue emphasizes potential contributions to security and privacy preserving applications and services in the mobile ecosystem. It contains seven papers, in print and online release, covering anonymous RA for trusted computing, cooperative security system for m-Health applications, security solutions for the IMS media plane, a comprehensive survey on Anonymous Voice over IP (VoIP) communication, and an untraceable authentication method for large-scale active-tag RFID systems. These papers will hopefully stimulate further research in this important topic.