|
Before it can communicate with a wireless device, an access point
must authenticate that device. An access point uses any of three
authentication mechanisms or types, and can use more than one. The
authentication mechanisms are as follows:
Open
Allows any device to authenticate and then attempt to communicate
with the access point. If the access point is using WEP and the
other device is not, the other device does not attempt to authenticate
to the access point. If the other device is using WEP but its WEP
keys do not match the keys on the access point, the other device
authenticates to the access point but cannot pass data. If the device's
WEP key does not match the access point's key, it can authenticate
but not pass data.
Shared Key
The access point sends an unencrypted challenge text string to
any device attempting to communicate with the access point. The
device requesting authentication encrypts the challenge text and
sends it back to the access point. If the challenge text is encrypted
correctly, the access point allows the requesting device to authenticate.
Both the unencrypted challenge and the encrypted challenge can be
monitored, however, which leaves the access point open to attack
from an intruder who guesses the WEP key by comparing the unencrypted
and encrypted text strings. Because of this weakness, Shared Key
authentication can be less secure than Open authentication. If the
device's WEP key matches the access point's key, it can authenticate
and communicate.
Network-EAP
By using the Extensible Authentication Protocol (EAP) to interact
with an EAP-compatible RADIUS server on your network, the access
point helps a wireless client device and the RADIUS server to perform
mutual authentication and derive a dynamic unicast WEP key. The
RADIUS server sends the WEP key to the access point, which uses
it for all unicast data signals that it sends to or receives from
the client. In addition, the access point encrypts its broadcast
WEP key with the client's unicast key and sends it to the client.
See the Authentication
Server Setup page for instructions on setting up EAP on the
access point.
|
