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data to communicate with other client. We can use
Message Integrity Check (MIC)[6] to compute the
checksum. The MIC is based on destination MAC,
source MAC, and payload. Any changes to these will
affect the MIC value that will be checked out. This
method can solve the replay attack.
C. 802.1X/EAP
IEEE 802.1X is a standard of controlling port access.
Extensible Authentication Protocol (EAP), the extension
of Remote Access Dial-In User (RADIUS), allows
wireless client adapters to communicate with different
back-end servers such as RADIUS.
The main function of 802.1X/EAP is that a client and
an AP should be authenticated each other before
communication. The process of authentication as follow:
(1) Wireless client associates with AP.
(2) AP rejects all user requests to WLAN and sends
ask-for password message.
(3) Client inputs user and password.
(4) RADIUS server and client perform mutual
authorization through AP.
(5) RADIUS server delivers the given key to AP.
(6) Client derives a unique WEP key from AP through
radio transmission.
But the WEP key is transmitted with plaintext in this
case. So we can use Lightweight Extensible
Authentication Protocol (LEAP) to solve it. The biggest
difference between EAP and LEAP is that we use a
session key to encrypt the WEP key. This can solve the
insecurity problem of transmitting the WEP key with
plaintext.
LEAP provides two benefits: The first benefit is the
mutual authentication between AP and client before
communication. The second benefit it centralized the
encryption WEP key management to enhance the
security.
Ⅵ. CONCLUSIONS
Because of the characteristic of widely used WLAN
its security problem also becomes more important.
802.11b protocol provides some security mechanisms
such as: SSID association, MAC filtering and WEP
authentication. But we know they are insecure by
analyzing them.
The data, which are encrypted with WEP, are also
insecure. WEP algorithm is based on the RC4, but we
have proved that RC4 has weaknesses. And WEP
algorithm’s weakness is repeat-used IVs. Hackers can
crack the WEP key with these two weaknesses.
To enhance the security of WLAN there are three
mechanisms: WEP improvement, Message Integrity
Check and 802.1X/EAP.
REFERENCES
[1] IEEE Standands Board. 802 part 11: Wireless LAN
Medium Access Control (MAC) and Physical Layer
(PHY). specification. IEEE Standand 802.11, 1999 Edition
[2] WANG S M, TAO R, WANG Y. WLAN and Its Security
Problems[R]. Proceeding of the Fourth International
Conference on Parallel and Distributed Computing,
2003:241-244
[3] Christian Barnes, Tony Bautts. Hack Sproofing Your
Wireless Network[M]. Syngress Press, 2002
[4] Scott Fluhrer, Itsik Mantin, and Adi Shamir. Weakness in
the Key Scheduling Algorithm of RC4. Eight Annual
Workshop on Selected Areas in Cryptography, August
2001
[5] Adam Stubblefield, John Ioannidis, Aviel D, Rubin,
“Using the Fluhrer, Mantin, and, hamir Attack to Break
WEP”, 2001, AT&T Labs Technical Report TD-4ZCPZZ,
pp.1-12
[6] Niels Ferugson, Macfergus Micheal. An Improved MIC
for 802.11 WEP[C]. Document submitted to IEEE 802.11
WG, January 2000
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