Certificate Authentication

Hi, Could someone please tell me whether it is possible to use Certificate Authentication (so only a person with a certain digital certificate download on their computer can access part of my web site) on a virtual web host? Ideally I would like to set-up my own Certificate Authority, but I think I will need root access for that? I have tried asking some web hosts, but they do not seem to have much of a clue! Please Help!!

Thanks,

Marc

if you are running apache you can have a look at this
http://www.apache-ssl.org/docs.html#SSLRequireSSL

I was unable to find a host who supported these functions unless I got a dedicated server with them.