单一标志的概念视图

I'd like to create a single sign on for multiple websites (sitea.com, siteb.com, sitec.com). All sites are with the same company. Any database is also with the same company/location. Some are asp.net web apps and some are forums. I'd like to try and abstract away the SSO so it is not tangled up with any one site. I've outlined my approach below:I'd like to create a single sign on for multipl