SSL authentication / certificate based common authentication refers to both parties authenticating each other throughout verifying the provided certificate so that the parties are guaranteed of the others' uniqueness.
In technical terms, it refers to a customer's authenticating each other to a server and that server too authenticating itself to the customer all the way through verifying the public key certificate issued by the trusted Certificate Authorities (CAs). Since authentication relies on digital certificates, certification authorities such as VeriSign or Microsoft Certificate Server be an significant division of the common authentication method.
In SSL authentication, the customers is offered through a server's certificate, the client system might try to match the server's CA beside the customer's record of confidential CAs. If the issuing CA is trusted, the customer will confirm that the certificate is authentic plus has not been tampered with.