I want to have subdomains with SSL within my domain. The main difference is that each subdomain is hosted by a different person with a different public key/private key pair.

Let me illustrate with an example:

1. User send his public key and requests subdomain from foo.com
2. User is added and assigned subdomain bar (bar.foo.com). Users public key is stored for future validation against bar.foo.com
3. User goes to bar.foo.com and see's a validated SSL connection.

From what I gather, this means that I need to create a CA, which is fine. The problem is that from what I recall, a CA needs a special sort of SSL Cert. How do I go about getting this?