What has been found to undermine the public key infrastructure system?

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.