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ZyAIR G-200 User’s Guide
2-12 Using the ZyAIR Utility
Encryption
WPA improves data encryption by using Temporal Key Integrity Protocol (TKIP), Message
Integrity Check (MIC) and IEEE 802.1x.
Temporal Key Integrity Protocol (TKIP) uses 128-bit keys that are dynamically generated and
distributed by the authentication server. It includes a per-packet key mixing function, a Message
Integrity Check (MIC) named Michael, an extended initialization vector (IV) with sequencing
rules, and a re-keying mechanism.
TKIP regularly changes and rotates the encryption keys so that the same encryption key is never
used twice. The RADIUS server distributes a Pairwise Master Key (PMK) key to the AP that then
sets up a key hierarchy and management system, using the pair-wise key to dynamically generate
unique data encryption keys to encrypt every data packet that is wirelessly communicated
between the AP and the wireless clients. This all happens in the background automatically.
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.
Figure 2-11 WPA Authentication
Follow the instructions in the table to configure WPA security.