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       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 ( 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 published in July 2004.

       Wi-Fi Alliance ( 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

       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
       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 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
       Handshake)  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 mechanism (only the method for generating master session key

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 <>  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.

                                12 January 2010