Which of the following is a potential threat that a PKI system must defend against?

Key compromise is a significant threat that a PKI system must defend against because it directly undermines the integrity and security of the cryptographic keys that are foundational to the PKI framework. If a private key is compromised, an unauthorized individual could intercept, decrypt, or forge communications, which could lead to serious breaches of confidentiality and data integrity. The security of a PKI system relies heavily on the confidentiality of private keys, making key compromise a critical concern that must be addressed through robust security measures like key management practices, hardware security modules, and regular audits to identify and mitigate vulnerabilities.

In contrast, while data overload, server efficiency, and application misconfigurations are relevant issues in broader IT security and system management, they do not have the same direct impact on the trust and security mechanisms underpinning PKI as key compromise. Data overload might affect performance but does not typically compromise the cryptographic processes. Server efficiency can enhance performance but does not address security threats. Application misconfiguration could lead to vulnerabilities, but it primarily affects application-level security rather than the cryptographic trust framework established by a PKI.