1GENCASES(1)               BSD General Commands Manual              GENCASES(1)
2

NAME

4     gencases — 802.11b weak IV generation tool
5

SYNOPSIS

7     gencases (-s pw | -h key) -f file [-n num]
8

DESCRIPTION

10     gencases is used to generate test 802.11b packets that are encrypted with
11     weak initialization vectors as described by Fluhrer, Mantin, and Shamir
12     (FMS). The packets are saved to a user specified file in libpcap compati‐
13     ble format for later use with the airsnort(1) program. The intent is to
14     provide airsnort with the packets required to demonstrate the FMS attack.
15
16     Arguments to gencases allow the user to specify the WEP key that will be
17     used to encrypt the packets as well as the number of packets to be gener‐
18     ated for each byte of the wep key.  The generated packets represent UDP
19     echo requests from host 192.168.0.2 (on a wired net) to host 192.168.0.10
20     (on a wireless net) and the corresponding replies. The wireless client
21     has MAC 00:02:2d:01:23:45, the wired host has MAC 00:04:5A:AB:CD:EF, and
22     the access point has BSSID 00:02:2D:98:76:54.
23
24     The generated packet file can be examined with standard packet analysis
25     tools such as tcpdump or ethereal.  It can also be loaded into
26     airsnort(1) which, given that a sufficient number of cases were generated
27     for each key byte, will produce a cracked WEP key. Running the generated
28     file through the decrypt(1) utility will produce the decrypted versions
29     of the packets which should reflect the echo request/reply traffic
30     described above, and which can be verified using tcpdump or ethereal.
31

OPTIONS

33     -s pw         Password as an ASCII string. 5 or 13 characters for 40 and
34                   128 bit WEP cases respectively.
35
36     -h key        Password as a colon separated list of 2 digit hex values. 5
37                   or 13 hex values for 40 and 128 bit WEP cases respectively.
38
39     -f file       Output file for generated cases.
40
41     -n num        Number of sample cases to generate for each key byte
42                   (1-256). Default is 100.
43

EXAMPLES

45     Generate 100 cases per key byte with the ASCII password "hello" to file
46     "test"
47
48           gencases -s hello -f test
49
50     Generate 200 cases per key byte with the hex key "23:56:89:ab:de" to file
51     "test"
52
53           gencases -h 23:56:89:ab:de -f test -n 200
54

SEE ALSO

56     airsnort(1) decrypt(1)
57

AUTHORS

59     Jeremy Bruestle <melvin@melvin.net>
60     Blake Hegerle <blake@melvin.net>
61     Snax <snax@shmoo.com>
62
63Linux                           August 18, 2002                          Linux