Using single SSL certificate for multiple stores
From AbleCommerce Wiki
Question
Is it possible to have multiple AC7 stores with a single SSL certificate?
Answer
There are two scenarios, either you are using sub domains or not. If you are using sub domains then you can get this job done by a Wildcard SSL. Wildcard SSL was meant to work only with subdomains, like http://www.domain1.com, mail.domain1.com, etc.domain1.com and not for full domains, like http://www.store1.com, http://www.store2.com.
If you want to use single certificate with multiple full domains then you can use SANS UCC Certificate, that can be used up to 150 domains with a single certificate/IP from the Digicert(http://www.digicert.com/wildcard-ssl-certificates.htm).