EFW Support

Hi,
I'm a bit confused.

I need to setup my endian community 2.3 VPN so a handful of clients (mainly WinXpSP3) can connect, possibly simoultaneously.

I found the entry at kb.endian.com/entry/12 and I have it up-and-running, but I'm far from being satisfied.

I would like to avoid user-and-password authentication; I would like to use pre-shared cerificates instead.
Unfortunately the informations on how to do that are a little too terse for me (or I'm just too dumb).

Can someone please tell me:

• is this really possible somehow?
• How to do it (either directly or pointing to some relevent documentation)

Thanks in Advance
Mauro