A trusted CA is the only entity that can issue trusted digital certificates. This is extremely important because while PKI manages more of the encryption side of these certificates, authentication is vital to understanding which entities own what keys. Without a trusted CA, anyone can issue their own keys, authentication goes out the window and chaos ensues. Reference: https://cheapsslsecurity.com/blog/understanding-the-role-of-certificate-authorities-in-pki/ A trusted CA is the only entity that can issue trusted digital certificates. This is extremely important because while PKI manages more of the encryption side of these certificates, authentication is vital to understanding which entities own what keys. Without a trusted CA, anyone can issue their own keys, authentication goes out the window and chaos ensues. Reference: https://cheapsslsecurity.com/blog/understanding-the-role-of-certificate-authorities-in-pki/