In the US, insults are not something for which you can be prosecuted. Calling someone a son of a bitch is not defamatory. No one believes you are really the child of a dog. So that is an opinion. Defamation requires a false factual statement. Truth is a complete defense.
What is Public Key Infrastructure (PKI)? Public Key Infrastructure (PKI) is a set of hardware, software, people, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates. In cryptography, a PKI is an arrangement that binds public keys with respective user identities by means of a certificate authority (CA). Wikipedia.org
First, let's be clear about what a PKI is not. A PKI is not an authentication method; rather it is an infrastructure that uses digital certificates as an authentication mechanism and is built to better manage certificates and their associated keys. A digital certificate is itself a way to reliably identify the user or computer claiming to be the owner of a specific public key.