Trakia Journal of Sciences, 7, Suppl. 2, pp 134-137, 2009
Copyright © 2009 Trakia University
Available online at:
ISSN 1313-7050 (print)
ISSN 1313-3551 (online)
Original Contribution
Deniz Mertkan Gezgin1, Ercan Buluş2, Halil Nusret Buluş2
Trakya University Vocational College of Technical Science, Trakya University, 22030,Edirne,
Namik Kemal University, Corlu Engineering Faculty, Computer Eng. Dept, Turkey
The usage area of wireless networks has been increased by the increase on the development of 802.11
wireless networks. As a result of this, the security on wireless networks has become more important.
Various cryptographic algorithms have been developed on the subject of the security and they have
been used in many wireless network applications. IEEE has started to work on security of wireless
networks under the 802.11i standard. As part of these, various cryptographic algorithms have been
developed and stronger algorithms take the place of inadequate ones. So providing a secure
environment on wireless networks has been proposed. In this paper, the security standards used in
access points which are wireless networks devices, the cryptographic algorithms used by these
standards and the superiority of these algorithms are studied.
KeyWords: Security of Wireless Networks, MAC Adress Filtering, Wep, WPA, 802.11i
Recently wireless networks are used widely.
Being rid of cables and developments of the
performances of wireless networks effect it 1 .. The
usage areas has been increased parallel of
development of wireless networks and the
increase on the standards. The places like offices,
amusement places, hotels which have variable
visitors and the places like factories, houses are
places which wireless networks are locally used.
In these places a device like hub in wired
networks is used to access to the wireless
networks, internet share or to set up a local
network. These devices are named “access
points”. They are confused with the wireless
modems which are bought or given by internet
providers. Because some of the wireless modems
have access points properties. In another words
wireless modems used like access points exist.
Access points can be used for many scenarios like
repeater, bridge. These properties will be
discussed. In fact the main idea in this study is the
increase of usage of access points because of the
increase of using wireless networks. In this case,
Vocational Higher school, Trakya University,
22030, Edirne, Turkey;
many clients and users appear. Some of them are
permitted users and some of them are attackers
who want to damage the network, slow down the
speed and destroy the access points. There are
policies in the wireless networks to prevent this.
Most important one of them is locally most used
networks have recently used or developing
security policies. The usage of them changes
according to the security demand. The subject
dealed in this study is security mechanisms and
strategies used in wireless clients.
Access poInt
Access points are known as shortly AP or WAP
(Wireless Access Point). Access point provides a
wireless access to the wired ethernet network.
Access points are connected to hub, key and
wired router and send wireless communication
signals. APs act like cell phone towers: pass from
one location to another so wireless access goes
on. They can be shown as equivalent to hubs on
wired networks. AP devices have their own
memories. They include a software named
Firmware. This firmware can be updated
according to new updates and developments.
Access point devices have security protocols.
Some of them are WEP( Wired Equivalent
Privacy) ,WPA (Wi-Fi Protected Access) and
GEZGIN. et al.
WPA2. APs shouldn’t be confused with wireless
modems and routers. Mostly we use wireless
modems or routers to access internet in our
homes. Beside this, when wireless networks open
for general use are used to access to the internet at
airports, student boardinghouses, restaurants or
hotels, generally access points are used
Figure 1. Wireless Access Point
Wireless access points basically have 3
properties. These are default mode, repeater mode
and bridge mode. Access points carry the data
signals to environment wirelessly by RF signals.
Bridges attaches the devices that are not have
wireless properties. So they help these devices
used commonly. Repeaters strengthen the
wireless RF signals so they increase the range.
is called SSID. Wireless access points can
broadcast in different channels. If you hide access
point, unauthorized users can’t send connection
request to the system since they do not see the
name of the access point in the wireless networks
list. Specialists on this subject can find SSID and
its channel by using 3rd party software. DoS
(Denial Of Service) attacks can be done to the
wireless access points whose SSID is open. So
hiding SSID will be useful. Hiding operation is
done by the device software. After the hiding
operation, users can no more see the SSID in
Windows platform unless they use a 3rd party
software. Authorized users can connect to the
network automatically if they have known the
SSID and its password.
b) Changing Default Password Of Wireless
Access Points
When you buy a wireless access point, eah
company has its own web interface to connect to
the device to manage it. Authorized users or users
the places which have a wireless network without
a password can easily access to the interface by
using gateway adress. One way to prevent this is
changing the password used for connecting the
access point. For example, most known user –
pasword combination is admin – admin. When we
buy an access point device we need to change this
combination. If we don’t, unauthorized users can
change device settings.
Figure 2. Wireless Access Point Modes
Some security problems have appeared since
wireless networks have become more popular.
Since wireless access points or modems
broadcast, all PCs that have wireless Ethernets
and notebooks can see this broadcast. As a result
of this, attackers who have unauthorized access to
the system may cause slowing down the system
speed, or may get a security password in the
system. They can take knowledge about the
system by listening to the RF. Some security
standards and policies have been developed to
prevent these attacks. In this study, security
mechanisms that are included in wireless access
points has been analyzed.
a) SSID (Service set identifiers) Hiding
SSID(Service set identifiers) is called as wireless
network name in order to understand easily.
Access point is the name of it as default but we
can also give a name to it. You can see wireless
networks of different names after scanning. This
MAC Filtering
The word MAC is composed of the first letters of
Media Access Control. It is also known as
physical adress. MAC adress is installed by the
productor company. It can not be changed in
normal ways and the most important is every
network card has a different MAC adress. MAC
adresses are written in 48 bit chiper and each
machine has its own adress, it means that, your
PC or notebook has its own MAC adress. So a
network card uses this MAC adress to send data
to another network card. It seems as two or more
cards can have same number. But in fact the
number produced under 48 bit can have
281.474.976.710.656 possible MAC addresses.
So it is not possible to have same number. Access
points filter the clients requesting the connection
to the network by this number to decide if the
client will connect or not connect. To do this in
security section, MAC filtering should be
activated and allowed MAC addresses should be
entered. So access point gives permission to these
computers. If the one who entered the password
of the access point correctly is not in the list, he
can not connect to the network. A MAC address
can be shown as 01-23-45-67-89-ab.
d) WEP Chiper and Its Usage
WEP is a wireless network standard. In wired
networks its corresponding protocol is named as
Trakia Journal of Sciences, Vol. 7, Suppl. 2, 2009
GEZGIN. et al.
802.1 by its developers. It is exactly named as
Wired Equivalent Privacy. The function of WEP
is to encrypt the data on radio waves. WEP
designed to compete with the traditional network
secrecy is accepted as a part of 802.11 standard in
1999. WEP uses RC4 cryptographic algorithm
designed by Ron Rivest for secrecy and CRC-32
checksum for completeness. The key width used
in WEP is 40 or 104 bits. There are two
verification methods in WEP.
1. Open Key Authentication: Any client
can connect to the network by self
authentication and ignoring WEP keys.
2. Common Key Authentication: WEP is
used for authentication in Shared Key
Authentication. In this communication there
are 4 ways to request and answer.
much more security is provided. 802.1x is used
for key management in WPA. WPA uses a strong
method with 802.1x EAP for authentication. In
WEP data integrity is provided by ICV, beside of
this WPA uses a stronger mechanism called
MIC(Message Integrity Code). WPA gives 2
alternatives for authentication/authorization.
1. WPA-PSK Structure
It has been designed for home users and small
companies. A password in length 8-63 characters
is determined. This is needed to be entered both
in client side and in access point side. This is
called pre-shared key. We choose WPA-PSK
from the authentication method in network
connection properties. It is not suitable in
corporation wireless networks.
2. 802.1X Structure
Figure 3. WEP Authencation
In WEP, RC4 cryptographic algorithm is used
with the common key on clients and access point.
But recently, on Linux or Windows platform,
common key can be taken with some software.
The weakness of RC4 algorithm and no key
management mechanism for common keys cause
this. Encryption does not provide enough secrecy
because of usage of 24-bit Initialization Vector
(IV) causing repeating encryption arrays.
Common key can be got by recording enough
data traffic.
IEEE 802.1x is a port based network access
control mechanism and is used in wired networks
as authentication/authorization method of
units/applications like remote access, VPN, key
production device etc. The components of 802.1x
access control are client (laptop, PDA, cell phone,
PC etc.), access point and RADIUS/TACACS
access control server. Clients notify the access
point about connection request, access point leads
this request towards the RADIUS/TACACS
server, RADIUS/TACACS server makes the
authentication/authorization process and tells the
result to the client and server. According to this
result, access point opens a virtual port to the
client for connection. In addition to this after
these processes the encryption key is produced
for encrypted communication between client and
access point.
e) WPA Chiper and Its Usage
Wi-Fi Alliance has made WPA standard to
overcome the weakness of RC4 algorithm on
WEP standard. WPA supports TKIP and TKIP
(Temporal Key Integrity Protocol) has taken the
place of WEP as a strong cryptographic system.
TKIP uses a new cryptographic algorithm using
computing facilities of wireless devices to carry
out ecriyption process. Also TKIP provides some
configuration after ecryption keys are determined,
changing one point broadcast ecryption key for
every window simultanously, detection of
uniquely start of common key authentication.
WPA uses 128 bits for key length. In WPA, key
is changed for every session and every package so
Figure 4. WPA-Enterprise (RADIUS Server)
f) WPA-2 Encyption (IEEE 802.11i)
It is a security standard produced by IEEE
802.11i work group to overcome the all weakness
of WEP. It is also known as WPA2 or Robust
Security Network (RSN). It is recommended to be
used for authentication/authorization of 802.1x
and for data integrity and encryption in Counter
Mode with Cipher Block Chaining Message
Authentication Code Protocol (CCMP) mode of
Trakia Journal of Sciences, Vol. 7, Suppl. 2, 2009
GEZGIN. et al.
cryptographic algorithm. It uses the same
structure in WPA which is 802.1x. Advanced
Encryption Standard (AES) cryptographic
algorithm is used in Counter Mode. A structure
that prevents repeating encryption key without the
help of per-packet keying mechanism in TKIP
and IV used in WEP and TKIP is produced by
this method. AES is stronger than RC4 and it has
no known weakness. TKIP structure using RC4
cryptographic algorithm for compatibility of
hardware not supporting AES is found in IEEE
802.11i standard.
Security standards and policies in wireless
networks can be change in every situation. The
method used by home user and the method in a
company that need a high security is different.
SSID hiding is not exact security prevention but it
can be useful for some attackers. If WEP and
MAC filtering are used together, networks
become more secure. But although it loads weight
to the system, generally WPA2 is the strongest
structure because it uses AES and AES has no
security holes until now. Weaknesses based on
RC4 in WEP and TKIP supported by WPA based
on RC4 make the key easily taken. RADIUS
server usage in 802.1x authentication method
increases the security. As a result WPA2 and
802.1x are the advised security standards.
Matthew Gast , “802.11 Wireless Networks
The Definitve Guide” ,O’Reilly,April 2005 ,
David Johansson , Alexander Sandström
Krantz , “Practical WLAN Security”,
TDDC03 Projects, Spring 2007
Deniz M. Gezgin, E. Buluş, “Kablosuz
Erişim Noktalarına Yapılan DOS Saldırıları”,
Akademik Bilişim 2008, Çanakkale 30 Ocak1 Şubat 2007
Deniz M. Gezgin, E. Buluş , H. N. Buluş,
“The Technical Analysis of the Comparison
of 802.11n Wireless Network Standard”,
International Scientific Conference ,21 – 22
November 2008, Gabrovo
Borsc, M., Shinde, H., “Personal Wireless
Communications, 2005. ICPWC 2005. 2005
IEEE International Conference on”, 0-78038964-6, 23-25 Jan. 2005
Battal Özdemir (2008), “Kablosuz Yerel
Alan Ağı Güvenliği Klavuzu” ,BGT-6001
IEEE Std 802.11i™-2004, “Wireless LAN
Medium Access Control (MAC) and
Layer (PHY) specifications,
Medium Access Control (MAC) Security
WPA and WPA2 Implementation White
Paper “Deploying Wi-Fi Protected Access
(WPA™) and WPA2™ in the Enterprise”,
March 2005
G.Zeynep Gürkaş, Şafak Durukan, A.Halim
Zaim, Azer Demir, M.Ali Aydın, “
802.11b Kablosuz Ağlarda Güvenliğin Ağ
Trafiği Üzerindeki Etkilerinin Analizi”, II.
Mühendislik Bilimleri Genç Araştırmacılar
Kongresi , MBGAK 2005 ,İstanbul ,Kasım
Figure 5. Wireless Network Security Level
Trakia Journal of Sciences, Vol. 7, Suppl. 2, 2009
Download PDF
Similar pages