Wi-Fi


Wi-Fi
is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point (or hotspot) has a range of about 20 meters (65 ft) indoors and a greater range outdoors. Multiple overlapping access points can cover large areas.

“Wi-Fi” is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Wi-Fi is used by over 700 million people. There are over four million hotspots (places with Wi-Fi Internet connectivity) around the world, and about 800 million new Wi-Fi devices are sold every year.[citation needed] Wi-Fi products that complete Wi-Fi Alliance interoperability certification testing successfully may use the “Wi-Fi CERTIFIED” designation and trademark.

Uses

To connect to a Wi-Fi LAN, a computer has to be equipped with a wireless network interface controller. The combination of computer and interface controller is called a station.
All stations share a single radio frequency communication channel.
Transmissions on this channel are received by all stations within range.
The hardware does not signal the user that the transmission was
delivered and is therefore called a best-effort delivery mechanism. A carrier wave is used to transmit the data in packets, referred to as “Ethernet frames“. Each station is constantly tuned in on the radio frequencycommunication channel to pick up available transmissions.

Internet access

A Wi-Fi-enabled device, such as a personal computer, video game console, smartphone or digital audio player, can connect to the Internet when within range of a wireless network connected to the Internet. The coverage of one or more (interconnected) access points—called
hotspots—comprises an area as small as a few rooms or as large as many
square miles. Coverage in the larger area may depend on a group of
access points with overlapping coverage. Wi-Fi technology has been used
successfully in wireless mesh networks in London, UK, for example.[1]

Wi-Fi provides service in private homes and offices as well as in
public spaces at Wi-Fi hotspots set up either free-of-charge or
commercially. Organizations and businesses,
such as airports, hotels, and restaurants, often provide free-use
hotspots to attract or assist clients. Enthusiasts or authorities who
wish to provide services or even to promote business in selected areas
sometimes provide free Wi-Fi access. As of 2008 more than 300 city-wide
Wi-Fi (Muni-Fi) projects had been created.[2] As of 2010 the Czech Republic had 1150 Wi-Fi based wireless Internet service providers.[3][4]

Routers that incorporate a digital subscriber line modem or a cable modem and a Wi-Fi access point, often set up in homes and other buildings, provide Internet access and internetworking to all devices tuned into them, wirelessly or via cable. With the emergence of MiFi and WiBro (a portable Wi-Fi router) people can easily create their own Wi-Fi hotspots that connect to Internet via cellular networks. Now iPhone, Android, Bada and Symbian phones can create wireless connections.[5]

One can also connect Wi-Fi devices in ad-hoc mode
for client-to-client connections without a router. Wi-Fi also connects
places normally without network access, such as kitchens and garden
sheds.

Source: wikipedia.org

WEP Wireless

Wired Equivalent Privacy (WEP) is a weak security algorithm for IEEE 802.11 wireless networks. Introduced as part of the original 802.11 standard ratified in September 1999, its intention was to provide data confidentiality comparable to that of a traditional wired network.[1] WEP, recognizable by the key of 10 or 26 hexadecimal digits, is widely in use and is often the first security choice presented to users by router configuration tools.[2][3]

Although its name implies that it is as secure as a wired connection, WEP has been demonstrated to have numerous flaws and has been deprecated in favor of newer standards such as WPA2. In 2003 the Wi-Fi Alliance announced that WEP had been superseded by Wi-Fi Protected Access (WPA). In 2004, with the ratification of the full 802.11i standard (i.e. WPA2), the IEEE declared that both WEP-40 and WEP-104 “have been deprecated as they fail to meet their security goals”.

WEP was included as the privacy component of the original IEEE 802.11 standard ratified in September 1999.[5] WEP uses the stream cipher RC4 for confidentiality,[6] and the CRC-32 checksum for integrity.[7] It was deprecated in 2004 and is documented in the current standard.[8]

Basic WEP encryption: RC4 keystream XORed with plaintext

Standard 64-bit WEP uses a 40 bit key (also known as WEP-40), which is concatenated with a 24-bit initialization vector (IV) to form the RC4 key. At the time that the original WEP standard was drafted, the U.S. Government’s export restrictions on cryptographic technology limited the key size. Once the restrictions were lifted, manufacturers of access points implemented an extended 128-bit WEP protocol using a 104-bit key size (WEP-104).

A 64-bit WEP key is usually entered as a string of 10 hexadecimal (base 16) characters (0-9 and A-F). Each character represents four bits, 10 digits of four bits each gives 40 bits; adding the 24-bit IV produces the complete 64-bit WEP key. Most devices also allow the user to enter the key as five ASCII characters, each of which is turned into eight bits using the character’s byte value in ASCII; however, this restricts each byte to be a printable ASCII character, which is only a small fraction of possible byte values, greatly reducing the space of possible keys.

A 128-bit WEP key is usually entered as a string of 26 hexadecimal characters. 26 digits of four bits each gives 104 bits; adding the 24-bit IV produces the complete 128-bit WEP key. Most devices also allow the user to enter it as 13 ASCII characters.

A 256-bit WEP system is available from some vendors. As with the other WEP-variants 24 bits of that is for the IV, leaving 232 bits for actual protection. These 232 bits are typically entered as 58 hexadecimal characters. ((58 × 4 bits =) 232 bits) + 24 IV bits = 256-bit WEP key.

Key size is one of the security limitations in WEP.[9] Cracking a longer key requires interception of more packets, but there are active attacks that stimulate the necessary traffic. There are other weaknesses in WEP, including the possibility of IV collisions and altered packets,[6] that are not helped by using a longer key.

Authentication

Two methods of authentication can be used with WEP: Open System authentication and Shared Key authentication.

For the sake of clarity, we discuss WEP authentication in the Infrastructure mode (that is, between a WLAN client and an Access Point). The discussion applies to the ad-Hoc mode as well.

In Open System authentication, the WLAN client need not provide its credentials to the Access Point during authentication. Any client can authenticate with the Access Point and then attempt to associate. In effect, no authentication occurs. Subsequently WEP keys can be used for encrypting data frames. At this point, the client must have the correct keys.

In Shared Key authentication, the WEP key is used for authentication in a four step challenge-response handshake:

  1. The client sends an authentication request to the Access Point.
  2. The Access Point replies with a clear-text challenge.
  3. The client encrypts the challenge-text using the configured WEP key, and sends it back in another authentication request.
  4. The Access Point decrypts the response. If this matches the challenge-text the Access Point sends back a positive reply.

After the authentication and association, the pre-shared WEP key is also used for encrypting the data frames using RC4.

At first glance, it might seem as though Shared Key authentication is more secure than Open System authentication, since the latter offers no real authentication. However, it is quite the reverse. It is possible to derive the keystream used for the handshake by capturing the challenge frames in Shared Key authentication.[10] Hence, it is advisable to use Open System authentication for WEP authentication, rather than Shared Key authentication. (Note that both authentication mechanisms are weak.)

Source: Wikipedia.org