Multiple Forums, 1 shared login

[csdev]

I need to find a way to allow a number of completely independant VB forums to share a common login so that you log in once and are then logged in to all the forums. Users will have a global login user/pass, but on each individual forum they can have a different username.

I realise that VB was never designed to do this and I have not seen any existing hacks that do this, so I need some advice from you pros about the best way to tackle this problem.

Looking at how VB handles logins, sessions and cookies I think the best way to achieve this is have a central authentication server (with web+mysql) then in embed an invisible image in every page on each forum that will create a cookie on the auth server (system will only support cookie auth).

Then I will need to write a hack so that instead of reading the local session information from the local DB the forums will query the central auth server for session info (either via remote mysql or curl).

Any comments / ideas about the viablity of this project? I would appreciate some experienced opinions.