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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   (http://www.wi-

       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 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) 2003-2015, Jouni Malinen <> and contributors.   All
       Rights Reserved.

       This  program  is  licensed  under  the  BSD  license  (the  one with advertisement clause

                                         19 January 2016                        WPA_BACKGROUND(8)