WPA_BACKGROUND(8) WPA_BACKGROUND(8)
NAME
wpa_background - Background information on Wi-Fi Protected Access and
IEEE 802.11i
WPA
The original security mechanism of IEEE 802.11 standard was not designed
to be strong and has proven to be insufficient for most networks that
require some kind of security. Task group I (Security) of IEEE 802.11
working group (http://www.ieee802.org/11/) has worked to address the
flaws of the base standard and has in practice completed its work in May
2004. The IEEE 802.11i amendment to the IEEE 802.11 standard was ap-
proved in June 2004 and published in July 2004.
Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version of the IEEE
802.11i work (draft 3.0) to define a subset of the security enhancements
that can be implemented with existing wlan hardware. This is called Wi-
Fi Protected Access<TM> (WPA). This has now become a mandatory component
of interoperability testing and certification done by Wi-Fi Alliance.
Wi-Fi provides information about WPA at its web site (http://www.wi-
fi.org/OpenSection/protected_access.asp).
IEEE 802.11 standard defined wired equivalent privacy (WEP) algorithm
for protecting wireless networks. WEP uses RC4 with 40-bit keys, 24-bit
initialization vector (IV), and CRC32 to protect against packet forgery.
All these choices have proven to be insufficient: key space is too small
against current attacks, RC4 key scheduling is insufficient (beginning
of the pseudorandom stream should be skipped), IV space is too small and
IV reuse makes attacks easier, there is no replay protection, and non-
keyed authentication does not protect against bit flipping packet data.
WPA is an intermediate solution for the security issues. It uses Tempo-
ral Key Integrity Protocol (TKIP) to replace WEP. TKIP is a compromise
on strong security and possibility to use existing hardware. It still
uses RC4 for the encryption like WEP, but with per-packet RC4 keys. In
addition, it implements replay protection, keyed packet authentication
mechanism (Michael MIC).
Keys can be managed using two different mechanisms. WPA can either use
an external authentication server (e.g., RADIUS) and EAP just like IEEE
802.1X is using or pre-shared keys without need for additional servers.
Wi-Fi calls these "WPA-Enterprise" and "WPA-Personal", respectively.
Both mechanisms will generate a master session key for the Authenticator
(AP) and Supplicant (client station).
WPA implements a new key handshake (4-Way Handshake and Group Key Hand-
shake) for generating and exchanging data encryption keys between the
Authenticator and Supplicant. This handshake is also used to verify that
both Authenticator and Supplicant know the master session key. These
handshakes are identical regardless of the selected key management mech-
anism (only the method for generating master session key changes).
IEEE 802.11I / WPA2
The design for parts of IEEE 802.11i that were not included in WPA has
finished (May 2004) and this amendment to IEEE 802.11 was approved in
June 2004. Wi-Fi Alliance is using the final IEEE 802.11i as a new ver-
sion of WPA called WPA2. This includes, e.g., support for more robust
encryption algorithm (CCMP: AES in Counter mode with CBC-MAC) to replace
TKIP and optimizations for handoff (reduced number of messages in ini-
tial key handshake, pre-authentication, and PMKSA caching).
SEE ALSO
wpa_supplicant(8)
LEGAL
wpa_supplicant is copyright (c) 2003-2022, Jouni Malinen <j@w1.fi> and
contributors. All Rights Reserved.
This program is licensed under the BSD license (the one with advertise-
ment clause removed).
07 August 2019 WPA_BACKGROUND(8)
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