An anatomy of trust in public key infrastructure

Public key infrastructure (PKI) is a critical component of information infrastructure, which has strong impacts through cybersecurity to the whole system of interconnected independent critical infrastructures, particularly in the context of fast growth of Internet of Things, where traditional critical infrastructure systems are transforming into smart cyber-physical systems. PKI is a mechanism of trust to support identity authentication, digital certification, secure communication, and privilege authorization. This paper investigates the trust mechanism used in PKIs, and we found that the major PKI specification documents do not precisely define what trust exactly means in PKIs, and there are implicit trust assumptions in the real practice of PKIs. Some assumptions may not be always true. Those implicit trust assumptions may cause different parties particularly relying parties to have different understanding about the meaning of certificates and trust; thus possibly causing misuse of trust. This paper attempts to have an in-depth analysis to PKI trust mechanism.