One Session over multiple joomla sites

[ksduded]

I am planning to have multiple joomla sites which will need a login to get access to. There will be only one username/password to access all the websites, but I want to share the session when the user goes from one joomla site to another. So that once the user has entered through the login area, the different sites do not ask for the user to log in again and again.

 

All the joomla sites will be saved on the same server in different directories.

 

I have not found any joomla module that helps me do this, so I am guessing incorporating a simple log in system through php is the key. But how do i keep the session going on multiple joomla sites. Thanks