Single Sign-On (SSO) is a practical requirement for software applications, which rely on distributed, networked services requiring authentication. SSO is as much a convenient feature for users as it is a security concern for application designers. The security requirement becomes critical in institutions that adhere to HIPPA regulations. In this chapter, we discuss SSO as it applies to a grid portal using remote computational resources and grid storage, which contain Personal Health Information (PHI). We cover the implementation of Public Key Infrastructure(PKI) to meet HIPPA security requirements such as authentication, confidentiality, nonrepudiation, and dataintegrity. Furthermore, we discuss the different technologies in PKI that solves these security concerns with respect to protecting research data and make SSO possible in the grid environment at the Biomedical Informatics Research Network (BIRN).