Over the past years, Public Key Infrastructure (PKI) technology has evolved and moved from the research laboratories to the mainstream, in which many organizations are now leveraging it as part of their core infrastructure system for providing and building security in their businesses. Understanding the challenges and requirements of PKI related operations through the sharing of case studies are critical to supporting the continued research and development of PKI technologies and related systems and applications to further progress and innovate for enhancing future development and evolution of PKI in the enterprises. This publication includes topics such as: PKI Operation & Case Study, Non-repudiation, Authorization & Access Control, Authentication & Time-Stamping, Certificate Validation & Revocation, and Cryptographic Applications.