[OpenID] Doubts about SSL and direct requests between RP and OP

[SitG Admin]

>for example, a simple Java or PHP application/installation would be 
>able to validate a ssl certificate?

Yes. For example, let's assume you're using cURL;
http://unitstep.net/blog/2009/05/05/using-curl-in-php-to-access-https-ssltls-protected-sites/
You might need control of the server (with shared hosting the admins 
might not be willing to risk breaking other features by enabling such 
options), but it's definitely possible through existing libraries.

-Shade