Details
Client-cert authentication requires that each client connecting to the server has a certificate used to authenticate. This is generally regarded as strong authentication than a password as it requires the client to have the cert and not just know a password.
Solution
In the Connector element, set the clientAuth parameter to true.
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: Identification and Authentication.This control applies to the following type of system Unix.