This is a solved problem

This is a solved problem

I don't understand why this has to be so complex. If you want to use cookies for authentication, you generate a strong random value and use it as the key into a session cache. The session cache can either be in the database or on some other storage mechanism if you're worried about SQL injection attacks.

The benefit of this method is that you don't need to keep any server-side state for sessions:
all needed information can be kept in the cookie, and the hash ensures the information can't
be forges.