You want to use client certificates to authenticate access to your site.
Add the following mod_ssl directives to your httpd.conf file:
SSLVerifyClient require SSLVerifyDepth 1 SSLCACertificateFile conf/ssl.crt/ca.crt
If you happen to be lucky enough to have a small, closed user community, such as an intranet, or a web site for a group of friends or family, it is possible to distribute client certificates so that each user can identify himself.
Create client certificates, signing them with your CA certificate file, and then specify the location of this CA certificate file using the CACertificateFile directive, as shown above.