A comparison of wi-fi and wimax with case studies - Florida State ...

The reason that WEP was safe was because the secret key was not easily broken. However
in some cases, the network designers use the same shared key for all users. That means that
people can read each other’s packets. That is not good for security. If it is a small network, trying
to use the different keys for each user should not be a big problem, but if it is a big network, for
security reasons, if a secret key changes once in a period of time, it is a huge job. How to
distribute a secret key and how to assure it is not repeated are very important issues at this point.
Moreover, IV is another potential risk. The WEP protocol recommends that the IV value should
be different for every packet to avoid the keystream attack. If IV is not a random value, the
encryption will be broken easily. Unfortunately some wireless network cards set the initial IV as
0 and increase the number by one for each packet sent. With this kind of IVs, to break the
encryption is way too easy. Unless the secret key is changed often or assuring the use of random
and different IV for each packet, the risk will remain high. If a hacker collects enough packets
with repeated IV from the same user, the cipher will be broken. [17][55]
3.4. The next generation standard
3.4.1. IEEE 802.11n
IEEE 802.11n is the standard of WLAN for next generation which also called Wi-Fi
(Wireless fidelity). This standard was initiated in 2004 by TGn. The goal of this standard was to
improve the net transmission speed up to 100 Mbps. In the beginning, there were six proposals
that had been posted. After many discussions, there were only two proposals left and they were
from TGnSync and WWiSE. These two groups have their own support from chip makers.
TGnSync has Athero, Agere, Marvell and Intel, while WWiSE has Airgo, Broadcom, Conexant
and Texas Instruments. The first draft was approved in March 2006 and draft 2.0 was approved
in March 2007. Since the demands from the market are becoming higher, Wi-Fi Alliance decided
to start to certifying IEEE 802.11n products based on the draft 2.0 in summer 2007. Now, these
pre-n products are already in stores, such as routers and network cards for desktops or notebooks.
The official approval of IEEE 802.11n standard had been delayed many times because TGnSync
and WWiSE kept fighting for their own proposal to become the official standard. However, they
finally agreed to propose a merged proposal to speed up the birth of official IEEE 802.11n
standard. Therefore, the IEEE 802.11n standard may be finally approved in early 2008. [17] [65]
[66]
Actually, the ideal of these two groups have may be different, but the technologies are the
same. TGnSync emphasizes on improving the peak data rate and WWiSE wants to ameliorate
the MAC-layer. Both of them can reach the goal, or even much better than that. The common
points are they both use MIMO-OFDM as the transmission function and support the bandwidth
for both 20 MHz and 40 MHz. IEEE 802.11n PHY-layer is extended from IEEE 802.11a PHYlayer.
So it is also an OFDM-based PHY-layer and just introduced MIMO technology to increase
the speed. [17] [61]-[66]
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