NIST hosted the second annual Public Key Infrastructure (PKI) Research Workshop on April 28-29, 2003. The two-day event brought together PKI experts from academia, industry, and government to explore the remaining challenges in deploying public key authentication and authorization technologies, and to develop a research agenda to address those outstanding issues. This proceedings includes the refereed papers, and captures the essence of the panels and interaction at the workshop. The workshop consisted of the presentation of 11 referred papers, three panel discussions, a work-in-progress session and a birds-of-a-feather session. Participants included presenters were from the United States, Canada, Brazil, Japan, Germany, Estonia, and Finland; making the workshop an international event. Based on participant feedback, the workshop provided the most up-to-date information on PKI research and deployment. Due to the success of this event, an expanded workshop is planned for 2004.