Information
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.
Certificate based authentication is more secure than password based authentication.
Solution
In the Connector element, set the clientAuth parameter to true.
<-- Define a SSL Coyote HTTP/1.1 Connector on port 8443 -->
<Connector port="8443" minProcessors="5" maxProcessors="75" enableLookups="true" disableUploadTimeout="true" acceptCount="100" debug="0" scheme="https" secure="true"; clientAuth="true" sslProtocol="TLS"/>