Since some recent version of the Linux kernel, the WEP on WiFi is broken.

I upgraded my notebook to kernel 2.6.21 some months ago and until now, I need some WEP to connect to Internet. It was OK before but I found it shows the following message when I try to set the WEP key using iwconfig:

ieee80211_crypt_wep: could not allocate crypto API arc4
eth1: could not initialize WEP: load module ieee80211_crypt_wep.o


Google can’t tell you the solution, but the source code does: In the previous version of the kernel, the ieee80211_crypt module did all the so-called encryption work, but not it is doing some division of labour. The ieee80211_crypt_wep is handling the WEP part but it does no encryption, however, and it relies on the cryptographic modules to do the data manipulation in general. Because WEP is close to block cipher in structure but some-how using RC4 stream cipher for the data. So it uses the ecb block module with arc4 algorithm module. Nevertheless, the ieee80211_crypt_wep doesn’t know it has to load ecb (for unknown reason), so it don’t work.

Solution: Simply execute the following commands to load the modules before the iwconfig command,

modprobe ecb
modprobe arc4
modprobe ieee80211
modprobe ieee80211_crypt
modprobe ieee80211_crypt_wep
modprobe ipw2200     # because I am using Intel's cards
iwconfig ...