Public key infrastructure (PKI) relies heavily on the trustworthiness of certificate authorities (CAs). These CAs are responsible for issuing and verifying digital certificates. If a CA is compromised or disreputable, the entire PKI system's integrity can be undermined because the certificates it issues can no longer be trusted. This can lead to a range of security issues, including the potential for man-in-the-middle attacks, as malicious actors could exploit compromised certificates to impersonate legitimate entities. Thus, maintaining reputable and secure CAs is critical to the PKI system's effectiveness.