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Wirless Networks - Dissertation Sample

10 Mar 2017Dissertation Samples

How Wirless networks (802.11) work and what are the disadvantages of

1.0     Wifi  

Wi-Fi (Wireless Fidelity) gets its name from Hi-Fi (High Fidelity) which is based on audio broadcasting. Wi-Fi is a relatively new albeit simple technology that allows computers to connect to one another. These connections can be on the move or can be via a mass hub or clusters of computers utilising the same technology. This said the Wi-Fi transmission can allow any access to various machines across the Internet (both wired and non-wired). Wi-Fi is based on radio wave technology similar to cellular mobile phones or even the less sophisticated ‘walkie talkie’.

Wi-Fi uses radio signals to transmit and receive computer data in the form of 1s and 0s otherwise known as bits (How Wi-Fi works, 2005). These radio signals have a carrier frequency and the data is modulated onto this carrier frequency. Modulation can be anything from pulse modulation to frequency modulation. For Wi-Fi frequency modulation is method of modulating the data onto the high frequency carrier wave. The difference between conventional radio voice communication and data communication is the frequency at which they both transmit and receive the information. Typically voice radio waves are transmitted at 50 MHz whereas Wi-Fi is transmitted between 2.4 to 5 GHz speeds (giving a maximum of 10 and 50 Mbits/second respectively). The higher frequency is based on the exchange rates required by the different information sources, for instance voice operates within the audio range of 20-20,000 Hz and therefore voice does not need to be sent at huge rates as many channels can be sent within 50 KHz windows up to the range of 50 MHz.

For data however, communication speed is one of the most important requirements and huge amounts of 1s and 0s that need to be sent very quickly to get the desired effect in terms of encoding and decoding the computer signal. For Wi-Fi it uses three channels across a very narrow band of the short high frequency range. These 3 channels are used due its switching when interference is found from another Wi-Fi transmitter being in close proximity and in using that particular channel. Wi-Fi has 3 standards which are International Institute for Electrical and Electronic Engineers (IEEE) standards these being; 802.11b, 802.11a and 802.11g. The standards are based on the frequency bands they occupy within the allocated radio frequency spectrum (frequency bands a, b and g).

The standard 802.11b is most commonly used Wi-Fi standard and transmits at 2.4 GHz, whereas 802.11a standard transmits at 5GHz, the 802.11g standard however has a mix of both worlds and transmits across both frequency ranges allowing it to ‘frequency hop’ between many frequencies and therefore give the option of many channels. Wi-Fi uses Complementary code Keying (CCK) to ensure the data is sent correctly in terms of correct information packet lengths (Complementary code keying, 2006). Orthogonal frequency-division multiplexing (OFDM) is at the very heart of Wi-Fi tranmission technology with this technique being the way in which Wi-Fi tranmits many signals very fast over many channels with the recipient picking up the correct channels and the information in the correct order. In addition OFDM allows many people to operate Wi-Fi devices in small promixity with the possiblilities for user bandwidths being very large.  

2.0     Wi-Fi Security 

With the convenience of Wi-Fi technology to be able to connect to hot spots which are Wi-Fi on the move connection points which allow any mobile device to connect to the Internet. Wi-Fi hotspots are usually found in mass public usage areas such as train stations, airports, libraries, hotels and conference centers to name but a few. Security is a very important issue here as the Wi-Fi networks can easily be intercepted if security has not been set up for the device such as key encryption method which asks the user for a password before allowing access.

Currently there are several security standards for Wi-Fi security albeit this is an ever expanding area with a lot of planned improvement for future Wi-Fi standards. Even though the encryption and authentication features of Wired Equivalency Policy (WEP) have been proved to be insecure, it is better to use it than to use no encryption or authentication at all. For more mission critical data, stronger authentication and authentication must be implemented enabling WPA (Wi-Fi Protected Access). This technology requires an 802.1x Radius authentication server which provides the highest security and authentication level (current standards). The negative side of using an 802.1x Radius server is the added complexity, but the key distribution problem is thereby solved Solms B.S., Marais E. (2004).

It is very important for secure environment to utilise the following set of Wi-Fi rules and ensure its Wi-Fi is secure from intrusion and therefore constantly checked for the following using systems that combat against intrusion (Air Defense White Paper, 2004).  

default or improper SSIDs and AP setup

default XP wireless settings
off-hours traffic
rogue and unauthorized access points
unencrypted and unauthenticated traffic
ad hoc peer-to-peer networks

There are drawbacks to using WEP (Loeb, 2001) in that the encryption method can be deciphered by a hacker in relatively easy terms. The very essence of the XOR technique used to check the encrypted message against the key is compromised as most information interchanges send duplicates of information. The XOR logic part of the encryption would not know any different from a compromised to a non compromised information block. Thus the system would let any block of information through thus relaying the encryption key to anyone who can get hold of that particular packet of information. There is a WEP replacement, WEP 2 albeit it has a higher encryption rate of 128 bit instead of the 40 bit key encryption for WEP although it still has problems where the hacker can authenticate him/herself based on the interception of packet information and decoding that message through simplistic computing methods.

For the user, caution needs to be applied to both WEP and WEP2 technologies when using for security purposes. Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access 2 (WPA2) are much more secure methods in that the encryption methods use governmental standards. The WPA standard ranges from password protected for single personal user and server authentication for enterprise or mass user. This is certainly a more secure method to send Wi-Fi information.     Going into WPA and WPA2 in greater depth, WPA2 uses an Advanced Encryption Standard (AES) this is the cipher system used by RSN.

RSN is an equivalent algorithm of the RC4 used in WPA standard. The difference being the encryption algorithm is more complex and does not suffer from the problems associated with WEP. AES is a block cipher, operating on blocks of data 128bits long. CCMP is the security protocol used by AES. It is the equivalent of TKIP in WPA. CCMP however computes a Message Integrity Check (MIC) using the well known, and proven, Cipher Block Chaining Message Authentication Code (CBC-MAC) method. Changing even one bit in a message produces a totally different result. To that end the user or computer knows when a hacker is present trying to get access to the secure information.

The Mangement of the WEP keys was a problem for users in that admistrators found it very difficult to manage large amounts of keys and therefore the keys were not changed very often and this made the life of hackers much easier to get into so called ‘secure networks.’  RSN however establishes a hierarchy of limited life keys, thus being similar to that used for TKIP. AES/CCMP requires 512bits to accommodate all the keys, which is less than that of TKIP and therefore more manageable for the administrator. Similar to TKIP, master keys are not used directly, but are used to derive other keys. For the administrator they only have the responsibility of looking after the Master key (Laverty, 2003).   

3.0     Conclusion  

There are systems and actions for users to take to ensure Wi-Fi is secure against hackers such as monitoring their input output ports with dedicated firewalls or network analyzers. In addition, the user should use the more mature and secure method of securing information from one device and another. These security methods are WPA2, the user should stay away from less developed security technologies such as WEP and WPA early standards.

REFERENCES

  • How Wifi Works, http://computer.howstuffworks.com/wireless-network1.htm, 2005
  • Complementary code keying, http://en.wikipedia.org/wiki/Complementary_code_keying, 2006
  • Solms B.S., Marais E. (2004), From secure wired networks to secure wireless networks e what are the extra risks?, Computer and Security
  • Air Defense White Paper. (2004)., 5 Practical steps to secure your wireless LAN, http://www.airdefense.netO.
  • Loeb L., (2001), What's up with WEP?, http://www-128.ibm.com/developerworks/library/s-wep/, Secure Electronic Transactions It came out of sky
  • WEP 2 (2001), http://www.starkrealities.com/wireless003.html Laverty D,
  • (2003), WPA versus 802.11i (WPA2): How your Choice Affects your Wireless Network Security, http://www.openxtra.co.uk/articles/wpa-vs-80211i.php

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