How to implement authentication security in WCF?
Means if any user is registered, than only be able to use service.
One way:-
Like, a mobile application at the time of installation update unique key with application Database.
So when client tried to connect with WCF service and if the key match then only be able to connect with service.
I want to know is there some other way to prevent unauthorized access for service?
You can read through this link Programming WCF security.
Read this link to Implement CustomUserNamePassword Authentication
You can configure your bindings to perform CustomUsernamePassowrd Authentication where you validated if the username and password are valid and if so you grant access to the service else deny.