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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
          (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 published in July

          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-

          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

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          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) 2003-2019, Jouni Malinen
          <j@w1.fi> and contributors.  All Rights Reserved.

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

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