IEEE8021X and WEP40

Jouni Malinen j
Sun Sep 6 11:05:03 PDT 2009

On Mon, Aug 03, 2009 at 02:22:10PM +0800, Zhu Yi wrote:

> I tried wpa_supplicant for 802.1X dynamic WEP with iwmc3200wifi driver.
> It worked for WEP104 but not WEP40. After some digging into the code, it
> turns out wpa_supplicant set WEP104 explicitly in file wpa_supplicant
> line 1112 (git version) function wpa_supplicant_associate:

>                         /* Assume that dynamic WEP-104 keys will be used and
>                          * set cipher suites in order for drivers to expect
>                          * encryption. */
>                         cipher_pairwise = cipher_group = CIPHER_WEP104;

> If I comment the "cipher_pairwise = cipher_group = CIPHER_WEP104" line,
> WEP40 works great with 802.1X on my Cisco Aironet 1200 AP. Jouni, Any 
> reason we need to set WEP104 in this case? They should already be set to
> the correct values earlier in the same function.

wpa_supplicant does not know at this point what the WEP key length will
be. This can be determined only after having completed association when
receiving the EAPOL-Key frame from the authenticator. It sounds a bit
odd if a driver were to be unable to association if the key length here
does not match. Or does iwmc3200wifi reject the key configuration for a
different key length later when the key is actually being configured?

Jouni Malinen                                            PGP id EFC895FA

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