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Appendix E Wireless LANs
NWA1000 Series User’s Guide
186
For added security, certificate-based authentications (EAP-TLS, EAP-TTLS and PEAP) use dynamic
keys for data encryption. They are often deployed in corporate environments, but for public
deployment, a simple user name and password pair is more practical. The following table is a
comparison of the features of authentication types.
WPA2
WPA2 (IEEE 802.11i) is a wireless security standard that defines stronger encryption,
authentication and key management.
Key differences between WPA2 and WEP are improved data encryption and user authentication.
If both an AP and the wireless clients support WPA2 and you have an external RADIUS server, use
WPA2 for stronger data encryption. If you don't have an external RADIUS server, you should use
WPA2-PSK (WPA2-Pre-Shared Key) that only requires a single (identical) password entered into
each access point, wireless gateway and wireless client. As long as the passwords match, a wireless
client will be granted access to a WLAN.
Select WEP only when the AP and/or wireless clients do not support WPA2. WEP is less secure than
WPA2.
Encryption
WPA2 uses TKIP when required for compatibility reasons, but offers stronger encryption than TKIP
with Advanced Encryption Standard (AES) in the Counter mode with Cipher block chaining Message
authentication code Protocol (CCMP).
TKIP uses 128-bit keys that are dynamically generated and distributed by the authentication server.
AES (Advanced Encryption Standard) is a block cipher that uses a 256-bit mathematical algorithm
called Rijndael. They both include 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.
WPA2 regularly change and rotate 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 PMK 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.
Table 57 Comparison of EAP Authentication Types
EAP-MD5 EAP-TLS EAP-TTLS PEAP LEAP
Mutual Authentication No Yes Yes Yes Yes
Certificate – Client No Yes Optional Optional No
Certificate – Server No Yes Yes Yes No
Dynamic Key Exchange No Yes Yes Yes Yes
Credential Integrity None Strong Strong Strong Moderate
Deployment Difficulty Easy Hard Moderate Moderate Moderate
Client Identity Protection No No Yes Yes No