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Chapter 4 - System Configuration
4.6.2.3 WiFi Protected Access (WPA)
WPA employs a combination of several technologies to provide an enhanced
security solution for 802.11 wireless networks.
The access point supports the following WPA components and features:
IEEE 802.1X and the Extensible Authentication Protocol
(EAP):
WPA employs
802.1X as its basic framework for user authentication and dynamic key
management. The 802.1X client and RADIUS server should use an appropriate
EAP type—such as EAP-TLS (Transport Layer Security), EAP-TTLS (Tunneled
TLS), or PEAP (Protected EAP)—for strongest authentication. Working together,
these protocols provide “mutual authentication” between a client, the access
point, and a RADIUS server that prevents users from accidentally joining a rogue
network. Only when a RADIUS server has authenticated a user’s credentials will
encryption keys be sent to the access point and client.
Temporal Key Integrity Protocol (TKIP): WPA specifies TKIP as the data
encryption method to replace WEP. TKIP avoids the problems of WEP static keys
by dynamically changing data encryption keys. Basically, TKIP starts with a
master (temporal) key for each user session and then mathematically generates
other keys to encrypt each data packet. TKIP provides further data encryption
enhancements by including a message integrity check for each packet and a
re-keying mechanism, which periodically changes the master key.
WPA Pre-Shared Key Mode (WPA-PSK, WPA2-PSK): For enterprise deployment,
WPA requires a RADIUS authentication server to be configured on the wired
network. However, for small office networks that may not have the resources to
configure and maintain a RADIUS server, WPA provides a simple operating mode
that uses just a pre-shared password for network access. The Pre-Shared Key
mode uses a common password for user authentication that is manually entered
on the access point and all wireless clients. The PSK mode uses the same TKIP
Enterprise AP(if-wireless g)#vap 0
Enterprise AP(if-wireless g: VAP[0])#802.1X required 195
Enterprise AP(if-wireless g: VAP[0])#802.1X session-timeout 300
Enterprise AP(if-wireless g: VAP[0])#auth open-system
235
Enterprise AP(if-wireless g: VAP[0])#encryption 237
Enterprise AP(if-wireless g: VAP[0])#
NOTE
To implement WPA on wireless clients requires a WPA-enabled network card driver and 802.1X
client software that supports the EAP authentication type that you want to use. Windows XP
provides native WPA support, other systems require additional software.