hi

the environment is 802.1x access in a wireless networks with EAP-TLS
with MPPE.
now it's clear what you want to know.


Probably now I have understand:
Freeradius after the TLS handshake derive the MPPE keys from the key
material of the handshake and send this keys to the AP.
The client derives this key itself, and the AP and client are
responsable for the rekeying, this rekeying happen every packet that the
AP and the client exchange.
yes, but the mppe keys are not used as WEP keys. that would be a little bit odd since in that way the radius server would have to know how the WEP keys should look like although the server doesn't implement WEP and have no idea of what it is.

so, the MPPE key attributes are only used in order to give the AP the same keying material. client derives this itself from the TLS master. then, either client or the AP generate the session WEP key and the AP takes the broadcast WEP key (which it could already be using with other stations) and all this is exchanged being encrypted and signed with the keying material received from server.



It's all exact?
not quite, see above.


But if it is, when a packet is lost what's appens?
i guess you know now what happens then.


Thanks and I hope this is not too off topic
no but this has been discussed already, just look in the archives for NSSSK or TLS master.


ciao
artur


--
Artur Hecker
D�partement Informatique et R�seaux, ENST Paris
http://www.infres.enst.fr/~hecker


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