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Wi-Fi Protected Access (WPA/802.11i [WPA2])
Wi-Fi Protected Access (WPA) is a security standard designed by the Wi-Fi Alliance in conjunction with the Institute of
Electrical and Electronics Engineers (IEEE). The AP supports 802.11i (WPA2), based on the IEEE 802.11i security
standard.
WPA is a replacement for Wired Equivalent Privacy (WEP), the encryption technique specified by the original 802.11
standard. WEP has several vulnerabilities that have been widely publicized. WPA addresses these weaknesses and
provides a stronger security system to protect wireless networks.
WPA provides the following new security measures not available with WEP:
• Improved packet encryption using the Temporal Key Integrity Protocol (TKIP) and the Michael Message Integrity
Check (MIC).
• Per-user, per-session dynamic encryption keys:
– Each client uses a different key to encrypt and decrypt unicast packets exchanged with the AP
– A client's key is different for every session; it changes each time the client associates with an AP
– The AP uses a single global key to encrypt broadcast packets that are sent to all clients simultaneously
– Encryption keys change periodically based on the Re-keying Interval parameter
– WPA uses 128-bit encryption keys
• Dynamic Key distribution
– The AP generates and maintains the keys for its clients
– The AP securely delivers the appropriate keys to its clients
• Client/server mutual authentication
–802.1x
– Pre-shared key (for networks that do not have an 802.1x solution implemented)
The AP supports the following WPA security modes:
• WPA: The AP uses 802.1x to authenticate clients and TKIP for encryption. You should only use an EAP that supports
mutual authentication and session key generation, such as EAP-TLS, EAP-TTLS, and PEAP. See 802.1x
Authentication for details.
• WPA-PSK (Pre-Shared Key): For networks that do not have 802.1x implemented, you can configure the AP to
authenticate clients based on a Pre-Shared Key. This is a shared secret that is manually configured on the AP and
each of its clients. The Pre-Shared Key must be 256 bits long, which is either 64 hexadecimal digits or 32
alphanumeric characters. The AP also supports a PSK Pass Phrase option to facilitate the creation of the TKIP
Pre-Shared Key (so a user can enter an easy-to-remember phrase rather than a string of characters).
• 802.11i (also known as WPA2): The AP provides security to clients according to the 802.11i draft standard, using
802.1x authentication, a CCMP cipher based on AES, and re-keying.
• 802.11i-PSK (also known as WPA2 PSK): The AP uses a CCMP cipher based on AES, and encrypts frames to clients
based on a Pre-Shared Key. The Pre-Shared Key must be 256 bits long, which is either 64 hexadecimal digits or 32
alphanumeric characters. The AP also supports a PSK Pass Phrase option to facilitate the creation of the Pre-Shared
Key (so a user can enter an easy-to-remember phrase rather than a string of characters).
NOTE: For more information on WPA, see the Wi-Fi Alliance Web site at http://www.wi-fi.org.
Authentication Protocol Hierarchy
There is a hierarchy of authentication protocols defined for the AP. The hierarchy is as follows, from highest to lowest:
• 802.1x authentication (including 802.1x, WPA, WPA-PSK, 802.11i, 802.11i-PSK)
• MAC Access Control via RADIUS Authentication
• MAC Access Control through individual APs' MAC Access Control Lists
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