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Linux 2.6 - man page for wpa_background (linux section 8)


       wpa_background - Background information on Wi-Fi Protected Access and IEEE 802.11i

       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 approved in June 2004 and pub-
       lished 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/Open-

       IEEE 802.11 standard defined wired equivalent privacy (WEP) algorithm for protecting wire-
       less 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  pro-
       tect against bit flipping packet data.

       WPA  is	an  intermediate solution for the security issues. It uses Temporal 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 mecha-
       nism (Michael MIC).

       Keys can be managed using two different mechanisms. WPA can either use an external authen-
       tication 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-Per-
       sonal", respectively. Both mechanisms will generate a master session key for the Authenti-
       cator (AP) and Supplicant (client station).

       WPA  implements a new key handshake (4-Way Handshake and Group Key Handshake) for generat-
       ing 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
       mechanism (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 version 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 initial key handshake, pre-
       authentication, and PMKSA caching).


       wpa_supplicant is copyright (c) 2003-2007, Jouni Malinen <j@w1.fi> and contributors.   All
       Rights Reserved.

       This program is dual-licensed under both the GPL version 2 and BSD license. Either license
       may be used at your option.

					07 September 2010			WPA_BACKGROUND(8)

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