A user or client, also called an end or mobile station, must authenticate before associating with an Access Point (AP), or broadband Wi-Fi router, and gaining access to the Wi-Fi Local Area Network (LAN). The Institute of Electrical and Electronics Engineers, Inc.* (IEEE) 802.11 standard defines two link-level types of authentication: Open System and Shared Key.
Open System Authentication
Open system authentication simply consists of two communications. The first is an authentication request by the client that contains the station ID (typically the MAC address). This is followed by an authentication response from the AP/router containing a success or failure message. An example of when a failure may occur is if the client's MAC address is explicitly excluded in the AP/router configuration.
Shared Key Authentication
Shared key authentication relies on the fact that both stations taking part in the authentication process have the same "shared" key or passphrase. The shared key is manually set on both the client station and the AP/router. Three types of shared key authentication are available today for home or small office WLAN environments.
Wired Equivalent Privacy (WEP)
WEP is not recommended for a secure WLAN due to its inherent weaknesses. One of the main security risks is a hacker can capture the encrypted form of an authentication response frame, using widely available software applications, and use the information to crack WEP encryption. The process consists of an authentication request from the client, clear challenge text from the AP/router, encrypted challenge text from the client and an authentication response from the AP/router. Two levels for WEP keys/passphrases:
Wi-Fi Protected Access (WPA)*
- 64-bit: 40 bits dedicated to encryption and 24 bits allocated to Initialization Vector (IV). It may also be referred to as 40-bit WEP.
- 128-bit: 104 bits dedicated to encryption and 24 bits allocated to Initialization Vector (IV). It may also be referred to as 104-bit WEP.
WPA was developed by the Wi-Fi Alliance* (WFA) prior to full ratification of IEEE 802.11i, but it complies with the wireless security standard. It is a security enhancement that strongly increases the level of data protection and access control (authentication) to a wireless network. WPA enforces IEEE 802.1X authentication and key-exchange and only works with dynamic encryption keys.
Users might see different naming conventions for WPA in a home or small-office environment. Examples are WPA-Personal, WPA-PSK, WPA-Home, etc. In any event, a common pre-shared key (PSK) must be manually configured on both the client and AP/router.
Wi-Fi Protected Access 2 (WPA2)*
WPA2 is a security enhancement to WPA. The two are not interoperable so a user must ensure the client station and AP/router are configured using the same WPA version and pre-shared key (PSK).
This applies to: