What does "chain of trust" refer to in PKI?

The concept of "chain of trust" in Public Key Infrastructure (PKI) refers specifically to the hierarchical relationship between Certificate Authorities (CAs) and the certificates they issue. In PKI, the integrity and authenticity of digital certificates are established through a trusted hierarchy.

At the top of the hierarchy, there are Root CAs that are inherently trusted by the system. These Root CAs issue certificates to Intermediate CAs, which in turn may issue certificates to end-entity certificates, such as those for individuals or devices. This hierarchical structure forms a "chain" where each link in the chain is trusted based on the trust established by its parent CA.

When a digital certificate is presented, the system can verify its authenticity by following this chain back to a trusted Root CA. Each certificate in the chain validates the one directly below it, allowing users and systems to establish confidence that the entity presenting the certificate is indeed who it claims to be.

In contrast, other answer choices focus on different aspects of security and management within PKI but do not encapsulate the essential function of establishing trust through a hierarchical relationship among CAs.