jc-wepcrack

jc-wepcrack is a distributed WEP cracker. It is entirely cross-platform and architechture neutral. You can use it to retrieve a 40 bit key in approximately 24 hours (if you have a about 10 athlon's laying around.) The tool supports 104 bit keys as well (though that's a largely academic exercise). Try jc-aircrack if you're workin on 104 bit keys.

the example below shows me cracking an included pcap file on my mac.

./jc-wepcrackd -f ..test-data/40bitwep-00-00-00-10-01 -k 40

And now start the client up on another terminal

./jc-wepcrack-client -s localhost

Finally lets go see what the server has to say about the clients submitted key