Wi-Fi Protected Access
Wi-Fi Protected Access (WPA) is a system to secure wireless (WiFi) networks, created to patch the security of the previous system, WEP (Wired Equivalent Privacy); researchers have found a number of weaknesses in WEP. As a replacement, WPA implements part of the IEEE 802.11i standard, and was intended as an intermediate measure to take the place of WEP while the new security standard (802.11i) was prepared. Certifications for implementations of WPA started in April 2003, while the full 802.11i was ratified in June 2004.
WPA is designed for use with an 802.1X authentication server, which distributes different keys to each user; however, it can also be used in a less secure pre-shared key (PSK) mode. Data is encrypted using the RC4 stream cipher, with a 128-bit key and a 48-bit initialization vector (IV).
One major improvement over WEP is given by the Temporal Key Integrity Protocol (TKIP), which dynamically changes keys as the system is used. When combined with the much larger IV, this defeats the well-known key recovery attacks on WEP.
In addition to authentication and encryption, WPA also provides vastly improved payload integrity. The cyclic redundancy check (CRC) used in WEP is inherently insecure; it is possible to alter the payload and update the message CRC without knowing the WEP key. A far more secure message authentication code (here termed a Message Integrity Check (MIC)) called "Michael" is used in WPA. Further, the MIC used in WPA includes a frame counter, which prevents replay attacks being executed.
In summary, by increasing the size of the keys, the number of keys in use, and adding a secure message verification system, WPA makes breaking into a Wireless LAN far more difficult. The Wi-Fi Alliance have announced that they will use the term WPA2 to refer to the full IEEE 802.11i standard.
The Wi-Fi Alliance has introduced the terms WPA(2)-Personal and WPA(2)-Enterprise for use in their Wi-Fi Interoperability Certificate. WPA(2)-Personal refers to WPA operating in pre-shared key mode while WPA(2)-Enterprise refers to WPA operating with an authentication server. The terms serve to indicate what features and capabilities the certified product has in terms of security.
References
- Wi-Fi Alliance. (2003). Wi-Fi Protected Access: Strong, standards-based, interoperable security for today’s Wi-Fi networks. Retrieved March 1, 2004 from http://www.wifialliance.com/OpenSection/pdf/Whitepaper_Wi-Fi_Security4-29-03.pdf
- Wi-Fi Alliance. (2004). Wi-Fi Protected Access? security sees strong adoption: Wi-Fi Alliance takes strong position by requiring WPA security for product certification. Retrieved January 5, 2004 from http://www.wi-fi.org/opensection/ReleaseDisplay.asp?TID=4&ItemID=165&StrYear=2004&strmonth=2