Literature Overview of Public-Key Infrastructures, with Focus on Quantum-Safe Variants

D4.1 This document provides an overview of the core concepts, usage, applications, and normative frameworks of public-key infrastructures. Moreover, special attention is devoted to the state-of-the-art research on quantum-safe public-key infrastructures, and to hybrid solutions that safeguard compatibility with legacy systems and that remain secure as long as at least one between their classical and their quantum-safe component is secure.