Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual page 554

original version of the IEEE 802.11 standard, these are described under the term WEP.
However, because WEP has proven to be insecure (see Section "Security" (page 542)),
the WLAN industry (joined under the name Wi-Fi Alliance) has defined a new extension
called WPA, which is supposed to eliminate the weaknesses of WEP. The later IEEE
802.11i standard (also referred to as WPA2, because WPA is based on a draft version
802.11i) includes WPA and some other authentication and encryption methods.
Authentication
To make sure that only authorized stations can connect, various authentication mecha-
nisms are used in managed networks:
Open
An open system is a system that does not require authentication. Any station can
join the network. Nevertheless, WEP encryption (see Section "Encryption"
(page 537)) can be used.
Shared Key (according to IEEE 802.11)
In this procedure, the WEP key is used for the authentication. However, this proce-
dure is not recommended, because it makes the WEP key more susceptible to at-
tacks. All an attacker needs to do is to listen long enough to the communication
between the station and the access point. During the authentication process, both
sides exchange the same information, once in encrypted form and once in unen-
crypted form. This makes it possible for the key to be reconstructed with suitable
tools. Because this method makes use of the WEP key for the authentication and
for the encryption, it does not enhance the security of the network. A station that
has the correct WEP key can authenticate, encrypt, and decrypt. A station that does
not have the key cannot decrypt received packets. Accordingly, it cannot commu-
nicate, regardless of whether it had to authenticate itself.
WPA-PSK (according to IEEE 802.1x)
WPA-PSK (PSK stands for preshared key) works similarly to the Shared Key
procedure. All participating stations as well as the access point need the same key.
The key is 256 bits in length and is usually entered as a passphrase. This system
does not need a complex key management like WPA-EAP and is more suitable for
private use. Therefore, WPA-PSK is sometimes referred to as WPA "Home".
WPA-EAP (according to IEEE 802.1x)
Actually, WPA-EAP is not an authentication system but a protocol for transporting
authentication information. WPA-EAP is used to protect wireless networks in en-
536 Installation and Administration