Figure 140 Wpa-Psk Authentication - ZyXEL Communications 5 Series User Manual

Chapter 12 Wireless Screens
The Message Integrity Check (MIC) is designed to prevent an attacker from capturing data
packets, altering them and resending them. The MIC provides a strong mathematical function
in which the receiver and the transmitter each compute and then compare the MIC. If they do
not match, it is assumed that the data has been tampered with and the packet is dropped.
By generating unique data encryption keys for every data packet and by creating an integrity
checking mechanism (MIC), TKIP makes it much more difficult to decode data on a Wi-Fi
network than WEP, making it difficult for an intruder to break into the network.
The encryption mechanisms used for WPA and WPA-PSK are the same. The only difference
between the two is that WPA-PSK uses a simple common password, instead of user-specific
credentials. The common-password approach makes WPA-PSK susceptible to brute-force
password-guessing attacks but it's still an improvement over WEP as it employs an easier-to-
use, consistent, single, alphanumeric password.
WPA-PSK Application
A WPA-PSK application looks as follows.
1 First enter identical passwords into the AP and all wireless clients. The Pre-Shared Key
(PSK) must consist of between 8 and 63 ASCII characters (including spaces and
symbols).
2 The AP checks each client's password and (only) allows it to join the network if it
matches its password.
3 The AP derives and distributes keys to the wireless clients.
4 The AP and wireless clients use the TKIP encryption process to encrypt data exchanged
between them.

Figure 140 WPA-PSK Authentication

WPA with RADIUS Application
You need the IP address of the RADIUS server, its port number (default is 1812), and the
RADIUS shared secret. A WPA application example with an external RADIUS server looks
as follows. "A" is the RADIUS server. "DS" is the distribution system.
1 The AP passes the wireless client's authentication request to the RADIUS server.
246
ZyWALL 5/35/70 Series User's Guide