GENCASES(1) BSD General Commands Manual GENCASES(1)NAME
gencases — 802.11b weak IV generation tool
SYNOPSIS
gencases (-s pw | -h key) -f file [-n num]
DESCRIPTION
gencases is used to generate test 802.11b packets that are encrypted with
weak initialization vectors as described by Fluhrer, Mantin, and Shamir
(FMS). The packets are saved to a user specified file in libpcap compati‐
ble format for later use with the airsnort(1) program. The intent is to
provide airsnort with the packets required to demonstrate the FMS attack.
Arguments to gencases allow the user to specify the WEP key that will be
used to encrypt the packets as well as the number of packets to be gener‐
ated for each byte of the wep key. The generated packets represent UDP
echo requests from host 192.168.0.2 (on a wired net) to host 192.168.0.10
(on a wireless net) and the corresponding replies. The wireless client
has MAC 00:02:2d:01:23:45, the wired host has MAC 00:04:5A:AB:CD:EF, and
the access point has BSSID 00:02:2D:98:76:54.
The generated packet file can be examined with standard packet analysis
tools such as tcpdump or ethereal. It can also be loaded into
airsnort(1) which, given that a sufficient number of cases were generated
for each key byte, will produce a cracked WEP key. Running the generated
file through the decrypt(1) utility will produce the decrypted versions
of the packets which should reflect the echo request/reply traffic
described above, and which can be verified using tcpdump or ethereal.
OPTIONS-s pw Password as an ASCII string. 5 or 13 characters for 40 and
128 bit WEP cases respectively.
-h key Password as a colon separated list of 2 digit hex values. 5
or 13 hex values for 40 and 128 bit WEP cases respectively.
-f file Output file for generated cases.
-n num Number of sample cases to generate for each key byte
(1-256). Default is 100.
EXAMPLES
Generate 100 cases per key byte with the ASCII password "hello" to file
"test"
gencases -s hello -f test
Generate 200 cases per key byte with the hex key "23:56:89:ab:de" to file
"test"
gencases -h 23:56:89:ab:de -f test -n 200
SEE ALSOairsnort(1)decrypt(1)AUTHORS
Jeremy Bruestle <melvin@melvin.net>
Blake Hegerle <blake@melvin.net>
Snax <snax@shmoo.com>
Linux August 18, 2002 Linux