Appendix D Wireless LANs
NXC Series User’s Guide
498
Note: EAP-MD5 cannot be used with Dynamic WEP Key Exchange
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.
WPA and WPA2
WiFi Protected Access (WPA) is a subset of the IEEE 802.11i standard. WPA2 (IEEE 802.11i) is a wireless
security standard that defines stronger encryption, authentication and key management than WPA.
Key differences between WPA or 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.
If the AP or the wireless clients do not support WPA2, just use WPA or WPA-PSK depending on whether
you have an external RADIUS server or not.
Select WEP only when the AP and/or wireless clients do not support WPA or WPA2. WEP is less secure
than WPA or WPA2.
Encryption
Both WPA and WPA2 improve data encryption by using Temporal Key Integrity Protocol (TKIP), Message
Integrity Check (MIC) and IEEE 802.1x. WPA and WPA2 use Advanced Encryption Standard (AES) in the
Counter mode with Cipher block chaining Message authentication code Protocol (CCMP) to offer
stronger encryption than TKIP.
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.
WPA and WPA2 regularly change and rotate the encryption keys so that the same encryption key is
never used twice.
Table 236 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
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