I want to be able to read / write some variables to the current session in my Salesforce site pages.

I have a site built using Salesforce Sites, I need to store/retrieve some values across all the pages (consider that I am building something similar to a shopping cart). However I cant find any good example on how to read and write variables to the session (anonymous user).

I am using Visualforce pages with "several controllers" built in Apex.

I also went through this question:

http://forums.sforce.com/t5/Visualforce-Development/Storing-and-Accessing-of-Session-variables-in-APex-Page-aswell/m-p/153871

The suggested solutions are not valid:

1- Using cookies is not possible, I want more secure place to store the values.

2- Using the same controller also is not possible, I have dozens of pages, i cant use the same controller for them all

3- Using the custom settings seems not valid too, as they are not built for such things

How to store variables in Session and how to access that Session Variable in Apex Page & in Contoller?.
 
Regards,
KK