Redmine

Hi, i'm looking for an explanation about how is forge the big string in session table (or in cookie string)

I need that to verify, in another application (in php), if the user is logged in on redmine.

I found that:
When i'm not logged

session_id: a302d66cafc61fdbe1c07dae3b3aaa6a
session_data: BAh7BiIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNo
SGFzaHsABjoKQHVzZWR7AA==

And after login

session_id: a302d66cafc61fdbe1c07dae3b3aaa6a
session_data: BAh7BzoMdXNlcl9pZGkGIgpmbGFzaElDOidBY3Rpb25Db250cm9sbGVyOjpG
bGFzaDo6Rmxhc2hIYXNoewAGOgpAdXNlZHsA

Even if i logout and relog, i get same data. So, anyone know how is forge this huge string ?

Thanks