We have about 10 sites that we need to use https on and all the names look like this:
- site1.domain.com
- sitename.domain.com
- site2name.domain.com
The domain is always the same but the subdomain is what changes. We don't own the domain but all of our sites are hosted on the same server and DNS is setup to cname our server and whenever we are going to host a new site the institution will cname our server again.
The question is, can we get a wildcard cert that will handle all the sites we have and it not interfere with some other sites that someone else has? Also, can a cert be installed on more than one server? What if we split up some of the sites and put a few on one server and a few on another?
Yes. A wildcard certificate that is installed on your servers and bound to your sites will not interfere with anyone elses subdomains, however anyone else could actually do the same thing (get their own wildcard for that domain) and imitate your site without anyone knowing.
Yes, but you will need to transfer your Private Key to all the other servers as well. How to do this depends on your OS and web server of choice.
That will work fine
The one question you haven't asked that I will answer for you though, is can you even GET this certificate. Sure, if you can get it, it will work, but when you purchase SSL certificates, the most simplest form of validation is them sending an email to a fixed email address on the domain (e.g. [email protected]) - they will give you a selection of email addresses to choose from, but if you don't own the parent domain you will at least require their co-opreating to get your copy of the certificate.
I have a suspicion you might be using a service like freedns.afraid.org. Getting a wildcard certificate when using a service like that could prove logisitcally difficult.
If you want a trusted cert the domain must belong to your organization. It wouldn't "interfere" with some other site, but it's a security issue for everyone else on that domain. I don't think any reputable provider will allow you a wildcard cert for a domain without a valid WHOIS, or at least something on company letterhead that says that you own the domain.