Session and Cookies

[eluser]Ajaxian64[/eluser]
Hi,
I have a general question/remark.
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I need session for authentification. And I would like to filter access (to some controller actions) thanks to session.
I also need flash data for quick messages
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I do not understand why we need to use Session for flash message.
Due to this I have to set up Session for msg purpose and then when I test whether a session exist it saids me yes, and for sure it exists, but for message purposes not really for Auth purpose...
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Am I wrong when I said that It would have been better to use 2 different mechanisms.
My feeling would be to use cookies for messages and Session for Auth (and only for this)