one authentification for different applications

I'm building four websites. They all should have the same login-datas开发者_运维问答 (user can registrate on website 1 and also can use website 2 and 3 by using the same Login-Name).

My idea was to use the MS SQL Membershipprovider (good idea?). Now I don't know where to place the SQL-Mebershipprovider (in an extra databse? or together with the websites? -> sound like getting chaos^^)

A other idea I've read was to create a webservice to the authentification?

But I think I'm getting problems with the data consitency, because I think there is no way to point from one database to an other (linking for example the usertable in database one to the texttable in databse 2).

I want to use MVC3 and a MS SQL-database.

Any experiences or ideas? Thanks a lot!

You can use a separate membership database to do this and just point the providers of each site at this database.

If you wanted to use the role provider you would have to have the same roles in all four websites which may not be what you want. You could use a central database to just handle authentication and then create a local user record in each website that links back to your central user database (you will have to do this linking manually i.e. no relationship). This will then let you role your own role provider for each site.