Technology is making rapid progress and is making many things easier.As the
innovative thinking of persons is increasing day-by-day,new methods for wireless
networking has been evolved of which our present topic Wi-Fi is the most accepted
Wi-Fi, an acronym for Wireless-Fidelity which is the wireless way to handle
networking. It is also known as 802.11 networking. The big advantage of WiFi is its
simplicity. You can connect computers anywhere in your home or office without the need
for wires. The computers connect to the network using radio signals, and computers can be
up to 100 feet or so apart.
This is the Electromagnatic spectrum. Range of Radio Wave is 3 kHz to 300 GHz.
Radio waves are mainly use for communication. Wifi uses radio technology.
FLAVOURS OF WIFI
IEEE 802.11, is a set of standards to allow different devices to communicate
wirelessly. It is created by the IEEE (pronounced eye-triple-e) LAN/MAN Standards
IEEE 802.11 b
Appear in late 1999
Operates at 2.4GHz radio spectrum
11 Mbps (theoretical speed) - within 30 m Range
4-6 Mbps (actual speed)
100 -150 feet range
Most popular, Least Expensive
Interference from mobile phones and Bluetooth devices which can reduce the
IEEE 802.11 a
Introduced in 2001
Operates at 5 GHz (less popular)
54 Mbps (theoretical speed
15-20 Mbps (Actual speed)
50-75 feet range
Not compatible with 802.11b
IEEE 802.11 g
Introduced in 2003
Combine the feature of both standards (a,b)
100-150 feet range
54 Mbps Speed
2.4 GHz radio frequencies
Compatible with ‘b’
Use OFDM Technology
(OFDM is a orthogonal frequency division multiplexing. It is basically a method of
encoding digital data on multiple carrier frequencies)
IEEE 802.11 n
Introduced in 2009
Uses multiple antennas that function in a "MIMO" mode ( multiple-input multipleoutput)
2.5 GHz and 5 GHz radio frequency
150 Mbps speed
Range up to 230 feet indoor
APPLICATIONS OF WIFI
These are the placese where wifi is used
o Small Businesses or SOHO
o Large Corporations & Campuses
o Health Care
o Wireless ISP (WISP)
Many devices can use wi-fi e.g. personal computers, video-game consoles,
smartphones, some digital cameras, tablet computers and digital audio players. These can
connect to a network resource such as the Internet via a wireless network access point.
ADVANTAGES OF WI-FI
1. Wi-Fi is a core technology in GPS Industries Applications.
2. Wi-Fi technology available in hotels, airports, etc., will be more inclined to bring
laptop with us when traveling for personal reasons.
3. Frees network devices from cables, allows for a more dynamic network to be grown.
1. Changes the way people live, communicate, work and play.
4. Many reliable and bug-free Wi-Fi products on the market
2. 5.It helps to become more productive at home, like online shopping and banking;
5. Wi-Fi technology allows getting out of home office and working in other rooms.
DISADVANTAGES OF WI-FI
1. 1.The 802.11b and 802.11g flavors of Wi-Fi use the 2.4 GHz spectrum, which is
crowded with other devices such as Bluetooth, microwave ovens, cordless phones,
or video sender devices, among many others.
2. 2.Power consumption is fairly high compared to other standards, making battery life
and heat a concern.
3. 3.It is not always configured properly by users.
As Wi-Fi is now shipped in millions of products and deployed in millions of homes,
business and hotspots worldwide, the technology has moved beyond the realm of a
computer feature. Wi-Fi has fast become a cultural phenomenon.
Elements of WIFI
Walkie Talkie Network
WIFI's Radio Technology
Working of WIFI
Communication in WIFI
Adding WIFI to a computer
WIFI's network topologies
Elements of a WI-FI Network
Access Point (AP) - The AP is a wireless LAN transceiver or “base station” that can
connect one or many wireless devices simultaneously to the Internet.
Wi-Fi cards - They accept the wireless signal and relay information. They can be
internal and external. (e.g PCMCIA Card for Laptop and PCI Card for Desktop PC)
Safeguards - Firewalls and anti-virus software protect networks from uninvited users
and keep information secure.
Wi-Fi’s Walkie-Talkie Network
To understand the wire less technology let us consider a pair of Walkie-Talkies.These
are small radios that can transmit and receive radio signals.When we talk into a WalkieTalkie, our voice is picked up by a microphone, encoded onto a radio frequency and
transmitted with the antenna. Another Walkie-Talkie can receive the transmission with its
antenna, decode our voice from the radio signal and drive a speaker.
Simple Walkie-Talkies like this transmit at a signal strength of about 0.25 watts, and
they can transmit about 500 to 1,000 feet.
If we want to connect two computers together in a network using Walkie-Talkie
technology. Equip each computer with a Walkie-Talkie. Give each computer a way to set
whether it wants to transmit or receive. Give the computer a way to turn its binary 1s and
0s into two different beeps that the walkie-talkie could transmit and receive and convert
back and forth between beeps and 1s/0s. This would actually work. The only problem would
be that the data rate would be very slow. Walkie-talkie is designed to handle the human
voice.So it is not being able to send very much data in this way(may be 1,000 bits per
Wi-Fi's Radio Technology
WiFi radios that work with the 802.11b and 802.11g standards transmit at 2.4 GHz,
while those that work with the 802.11a standard transmit at 5 GHz. Normal walkietalkies normally operate at 49 MHz. The higher frequency allows higher data rates.
WiFi radios use much more efficient coding techniques that also contribute to the
much higher data rates. For 802.11a and 802.11g, the technique is known as
orthogonal frequency-division multiplexing (OFDM). For 802.11b, it is called
Complementary Code Keying (CCK).
The radios used for WiFi have the ability to change frequencies. 802.11b cards can
transmit directly on any of three bands, or they can split the available radio
bandwidth into dozens of channels and frequency hop rapidly between them. The
advantage of frequency hopping is that it is much more immune to interference and
can allow dozens of WiFi cards to talk simultaneously without interfering with each
WORKING OF WIFI
The most important items which makes Wi-Fi working in the laptop or desktop are
Wi-Fi Card which fits in your laptop or computer.
Hotspots which create Wi-Fi Network.
o A Wi-Fi hotspot is created by installing an access point to an internet
o An access point acts as a base station.
o When Wi-Fi enabled device encounters a hotspot the device can then
connect to that network wirelessly.
o A single access point can support up to 30 users and can function within a
range of 100 – 150 feet indoors and up to 300 feet outdoors.
o Many access points can be connected to each other via Ethernet cables to
create a single large network.
Radio Signals are the keys which make WiFi networking possible. These radio signals
transmitted from Wi-Fi antennas are picked up by WiFi receivers such as computers
and cell phones that are equipped with WiFi cards. Whenever a computer receives
any of the signals within the range of a WiFi network which is usually 300 - 500 feet
for antennas, the WiFi card will read the signals and thus create an internet
connection between the user and the network without the use of a cord.
Access points which consist of antennas and routers are the main source which
transmit and receive radio waves.
Antennas work stronger and have a longer radio transmission with a radius of 300500 feet which are used in public areas while the weaker yet effective router is more
suitable for homes with a radio transmission of 100-150 feet.
You can think WiFi card as being an invisible cord that connects your computer to the
antenna for a direct connection to the internet.
WiFi cards can be external or internal, meaning that if a WiFi card is not installed in
your computer, you may purchase a USB antenna attachment and have it externally
connect to your USB port, or have an antenna-equipped expansion card installed
directly to the computer. For laptops, this card will be a PCMCIA card in which you
insert to the PCMCIA slot on the laptop.
A Wi-Fi hotspot is created by installing an access point to an internet connection. The
access point transmits a wireless signal over a short distance . typically covering
around 300 feet. When a Wi-Fi enabled device, such as a Pocket PC, encounters a
hotspot, the device can then connect to that network wirelessly.
Most hotspots are located in places that are readily accessible to the public, like
airports, coffee shops, hotels, book stores and campus environments. 802.11b is the
most common specification for hotspots worldwide. The 802.11g standard is
backwards compatible with .11b but .11a uses a different frequency range and
requires separate hardware such as an a, a/g, or a/b/g adapter. The largest public
Wi-Fi networks are provided by private internet service providers (ISPs) that charge a
fee for users to connect to the internet.
COMMUNICATION IN WI-FI
Data exchange in Wi-Fi can be summarized into three phases:
Phase I: Where data is prepared for transmission; it is encoded; changed into frames (digital
signals are sent in frames for better QoS). The frequency for data transmission is also chosen
depending upon the technique used to send the signals wirelessly.
Phase II: Where data is transmitted with air as the medium of wave transmission
Phase III: Where data is received, decoded, acknowledged and then used.
All of these phases apply some of the popular digital communications spread spectrum
techniques for signal multiplexing (FHSS, Infrared, OFDM etc.), make use of security
methods (WEP, WPA).
Adding WiFi to a Computer
Many new laptops come with a Wi-Fi card built in. It is also easy to add a Wi-Fi card to an
older laptop or a desktop PC. The process is
Take a 802.11a, 802.11b or 802.11g network card. 802.11g has the advantage of
higher speeds and good interoperability on 802.11b equipment.
For a laptop, this card will normally be a PCMCIA card that slide into a
PCMCIA slot on laptop. Or take a small external adapter and plug it into a USB
For a desktop machine, take a PCI card & install inside the machine, or a small
external adapter and connect to the computer with a USB cable.
Install the card
Install the drivers for the card
Find an 802.11 hotspot
Access the hotspot.
WI-FI NETWORK TOPOLOGIES
1. AP-based topology (Infrastructure Mode)
2. Peer-to-peer topology (Ad-hoc Mode)
3. Point-to-multipoint bridge topology
AP-based topology (Infrastructure mode)
The client communicate through Access Point.
BSA-RF coverage provided by an AP.
ESA-It consists of 2 or more BSA.
ESA cell includes 10-15% overlap to allow roaming.
AP is not required.
Client devices within a cell can communicate directly with each other.
It is useful for setting up of a wireless network quickly and easily.
Point-to-multipoint bridge TOPOLOGY
This is used to connect a LAN in one building to a LANs in other buildings even if the
buildings are miles apart. These conditions receive a clear line of sight between
buildings. The line-of-sight range varies based on the type of wireless bridge and
antenna used as well as the environmental conditions.
Wi-fi is a simple, cost-effective way to connect to the Internet , Without the need to
physically connecting wires.
Hotspot s a geographic area setup in any public location, and has a readily accessible
Security is a huge challenge for Wi-Fi Networks, many Security Techniques are used
to improve it.
The Future of Wi-Fi
This is the graph of Hotels offering Wi-Fi.
The future of Wi-Fi is very bright. Its growing in popularity because of decreasing cost and
the freedom it gives to users.
Security is essential part of Wifi Technology. Wi-Fi can be less secure than wired
connections (such as Ethernet) because an intruder does not need a physical connection.
Why security is more of a concern in wireless?
no inherent physical protection
physical connections between devices are replaced by logical associations
sending and receiving messages do not need physical access to the network
infrastructure (cables, hubs, routers, etc.
ƒ broadcast communications
wireless usually means radio, which has a broadcast nature
transmissions can be overheard by anyone in range – anyone can generate
• which will be received by other devices in range
• which will interfere with other nearby transmissions and may
prevent their correct reception (jamming).
Wi-Fi Security Threats
Wireless technology doesn’t remove any old security issue, but introduces new ones
o Man-in-the-middle attacks
o Denial of Service
Eavesdropping is the act of secretly listening to the private conversation of others without
Easy to perform, most impossible to detect
By default , everything is transmitted in clear text
-No secuirty offered by the transmission medium
Different tools available on the internet
-Network sniffers, protocol analysers
With the right equipment, it’s possible to eavesdrop traffic from few kilometres
Man In The Middle Attack
An attack where a user gets between the sender and receiver of information and sniffs any
information being sent.
Attacker spoofs a disassociate message from the victim
The victim starts to look for a new access point, and the attacker advertises his own
AP on a different channel, using he real Aps MAC address
The attacker connects to the real
AP using victim’s MAC address
Denial of Service
Denial-of-service attack (DoS attack) is an attempt to make a machine or network resource
unavailable to its intended users.
Attack on transmission regency used
Not very technical, but works
Attack on MAC layer
Spoofed deauthentication / disassociatin messages
Can target on specific user
Attacks on higher layer protocol(TCP/IP protocol)
Wireless communication security requirements
Confidentiality – messages sent must be encrypted
Authenticity – origin of messages received must be verified
Replay detection – freshness of messages received must be checked
Integrity – modifying messages on-the-fly (during radio transmission) is not
so easy, but possible, Integrity of messages received must be verified
ƒ Access control – access to the network services should be provided only to
Open/free/Unsecured (No Password)
WEP (Wired Equivalent privacy)
WPA (Wifi Protected access)
Leaving your Wi-Fi unsecured is synonymous with leaving your front door wide open,
so anyone could simply walk in. Leaving your Wi-Fi unsecured also transmits data packets
between users and the router in unencrypted format, which makes these data packets easy
to intercept and read.
WEP (Wired Equivalent Privacy)
WEP (Wired Equivalent Privacy) was the default encryption protocol introduced in
the first IEEE 802.11 standard back in 1999. It is based on the RC4 encryption algorithm,
with a secret key of 40 bits or 104 bits being combined with a 24-bit Initialisation Vector (IV)
to encrypt the plaintext message M and its checksum – the ICV (Integrity Check Value). The
encrypted message C was therefore determined using the following formula:
C = [ M || ICV(M) ] + [ RC4(K || IV) ]
where || is a concatenation operator and + is a XOR operator
Figure : WEP encryption protocol
What’s wrong with WEP?
IV values can be reused
In fact the standard does not specify that the value needs to change at all. Reusing keys is a
major cryptographic weakness in any security system.
IV length is too short
24 bit keys allow for around 16.7 million possibilities. Sounds a lot, but on a busy network
this number can be achieved in a few hours.
Weak keys are susceptible to attack
Certain keys value combinations, ’Weak IVs’, do not produce sufficiently random data for
the first few bytes. This is the basis of the highly publicized attacks on WEP and the reason
that keys can be discovered.
Manufacturers often deliberately disallow Weak IV values. This is good in that it reduces the
chances of a hacker capturing weak keys, but also has the effect of reducing the already
limited key possibilities further, increasing the chance of reuse of keys.
Master keys are used directly
From a cryptographic point of view using master keys directly is not at all recommended.
Master keys should only be used to generate other temporary keys. WEP is seriously flawed
in this respect.
Key Management and updating is poorly provided for
Administration of WEP keys is not well designed and difficult to do on large networks. Users
tend to change keys very infrequently which gives a potential hacker lots of time to collect
enough packets to launch an attack.
Message integrity checking is ineffective
WEP does have a message integrity check but hackers can change messages and recompute
a new value to match. This makes the checking ineffective against tampering.
Although WEP is far from an ideal security solution you should still use it. Some security is
better than none. A determined attacker may be able to discover your keys given time and
enough weak IVs, but that’s no reason to leave all of your doors open.
WPA (Wifi Protected access)
Wi-Fi Protected Access, or WPA, was introduced to correct the inherent weaknesses
of WEP. Although it does improve security, it has its own problems. The encryption key used
by WPA relies on a passphrase, the service set identification name (SSID), SSID length and a
random value. The majority of the information used to create this 256-bit key is readily
known, so a would-be hacker needs only guess the passphrase to have access to the
network. Dictionary attacks systematically attempt numerous combinations of words,
characters and phrases to guess this passphrase. It was determined that a passphrase
comprised of less than 20 characters could be defeated.
TKIP packet is comprised of three parts:
1. A 128-bit temporal key that is shared by both clients and access points.
2. An MAC address of a client device.
3. A 48-bit initialization vector describes a packet sequence number.
This combination guarantees various wireless clients use different keys.
In order to be compatible with existing hardware, TKIP uses the same encryption
algorithm (RC4) as WEP. As such, only software or firmware upgrade is required to
implement TKIP. Compared with WEP, TKIP changes the temporal keys every10000
packets. This dynamic distribution leaves potential hackers little room to crack TKIP
In general, most security experts believe that TKIP is a stronger encryption than
WEP. However, they also agree that TKIP should be an interim solution because of its
use of RC4 algorithm.
A summary of WPA benefits
In general, the security advantages of WPA over WEP are:
Apply stronger network access control through mutual authentication
Support better security technologies like 802.1X, EAP, RADIUS and preshared keys
Adopt dynamic keys in TKIP to establish better key management
Enforce data integrity through Michael Message Integrity Check
Provide forward compatibility to ultimate wireless security solution, 802.11i
WPA potential security issues:
There are still potential encryption weaknesses in TKIP. Fortunately, the successful
crack is expected to be heavy and expensive.
Performance may be sacrificed potentially due to a more complex and computation
intensive authentication and encryption protocols.
WPA2 Wi-Fi Protected Access 2
Was ratified in 2004 as a solution to the key encryption problems contained in WEP
A couple of small flaws appeared in WPA2, which require a quality of service attack
or physical positioning between the user and router, but neither of these flaws are
considered a severe threat that exposes user data.
WPA2 offers two encryption algorithms: AES and TKIP. TKIP is essentially WPA
encryption, so for the benefits of WPA2 encryption, you should choose AES.
Another option on most routers is to choose both, which allows the stronger
security of AES when applicable, but uses the weaker TKIP when compatibility issues
WIFI Security Tips
Wireless networking can be kind of scary from a security standpoint. It opens up whole new
attack vectors that were not present with wired network infrastructures. That doesn't mean
you can't do it securely, however, and I aim to give you some ideas that can help you in that
Don't broadcast your SSID. -
Use good wireless encryption. -WEP is not exactly "good" encryption. With a freely
available tool like aircrack, you can sniff wireless traffic protected by WEP and crack
security on that network in a matter of minutes. WPA is the current, common
encryption standard you should probably be using -- though, of course, you should
use something stronger as soon as it becomes available to you. Technology is
advancing every day, on both sides of the encryption arms race, after all.
Restrict access by MAC address. -restricting the MAC addresses allowed to connect
to the network helps ensure you are not one of the "low hanging fruits" that people
prefer to attack.
Shut down the network when it's not being used-If you have the sort of network
that does not need to be running twenty-four hours a day, seven days a week, you
can reduce the availability of it to security crackers by turning it off when it isn't in
Monitor your network for intruders. You should always make sure you have an eye
on what's going on, that you are tracking attack trends. The more you know about
what malicious security crackers are trying to do to your network, the better the job
of defending against them you can do. Collect logs on scans and access attempts, use
any of the hundreds of statistics generating tools that exist to turn those logs into
more useful information, and set up your logging server to email you when
something really anomalous happens.
Cover the bases. Make sure you have some kind of good firewall running, whether
on a wireless router or on a laptop you use to connect to wireless networks away
Is Wi-Fi Safe for Human?
Wifi health effects on the human body are commonly dismissed because we love the
convenience. Wi-Fi dangers are ignored. After all we can walk around our house with our
laptop and not lose connection. No messy inconvenient cords. We can keep up with mails
and conduct our work at coffee shops, airports, hotels, even hospitals. Who wants to give
up ths kind of convenience?
And yet, have we stopped to think about the fact that there was no safety testing conducted
before it went into used.
Here are some of the most common symptoms people report when exposed to microwave
radiation from cell phones and towers
Wireless security has undergone major evolutions in last 7 years. WEP, the original
security standard, is widely considered as broken. The IEEE 802.11 Group, the Wi-Fi
Alliance and major network equipment vendors like Cisco are all working together to
develop a new level of security standards.
SANS Institute InfoSec Reading Room
802.11ac: The Fifth Generation of Wi-Fi Technical White Paper