Sharing session data between domains

Hi,

Has anyone come up with a clean(ish) way of sending data from a session in one domain to another session in another (SSL) domain. Both domains are on the same application. Scenario is:

- collect data during the shopping process to create an "order". The critical order data can be stored in a hash. - want to pass the order_id over to the new domain but I can only think of somehow serializing the session hash and then passing it as a parameter in the URL when passed to the SSL-protected domain. - I would like to make the URL tamper-proof.

Anyone have any ideas on this? As the domains run on the same Rails application, can I just get away with passing the session_id over to the second domain and somehow "autorestore" the domain directly back from the session store?

O.