With the convergence of embedded computers and wireless communication, pervasive computing has become the inevitable future of computing. Every year, billions of computing devices are built. They are ubiquitously deployed and are gracefully integrated with people and their environments. Service discovery is an essential step for the devices to properly discover, configure, and communicate with each other. Authentication for pervasive service discovery is difficult. In this chapter, we introduce a user-centric service discovery model, called PrudentExposure, which automates authentication processes. It encodes hundreds of authentication messages in a novel code word form. Perhaps the most serious challenge for pervasive service discovery is the integration of computing devices with people. A critical privacy challenge can be expressed as a “chicken-andegg problem”: both users and service providers want the other parties to expose sensitive information first. We discuss how a progressive and probabilistic model can protect both users’ and service providers’ privacy.