This paper identifies security issues posed by ubiquitous computing applications used in university campuses, and propose software architectures to address the issues. Applications in ubiquitous computing environment exploit interactions between personal and public devices, and adapt to user's context. Security issues posed by these applications are privacy, usability, and hybrid scheme. Privacy Profile Negotiation Protocol (PPNP) allows users to change the granularity of their personal profile presented to profileaware services, in order to preserve privacy, and Zero-stop Authentication System (ZSAS) provides real-time automatic authentication of users to leverage usability of user authentication in the physical space. We also present several applications to outline the usage of these systems.