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      1 <!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">
      2 
      3 <refentry>
      4   <refentryinfo>
      5     <date>07 August 2019</date>
      6   </refentryinfo>
      7 
      8   <refmeta>
      9     <refentrytitle>wpa_background</refentrytitle>
     10     <manvolnum>8</manvolnum>
     11   </refmeta>
     12   <refnamediv>
     13     <refname>wpa_background</refname>
     14     <refpurpose>Background information on Wi-Fi Protected Access and IEEE 802.11i</refpurpose>
     15   </refnamediv>
     16   <refsect1>
     17     <title>WPA</title>
     18 
     19     <para>The original security mechanism of IEEE 802.11 standard was
     20     not designed to be strong and has proven to be insufficient for
     21     most networks that require some kind of security. Task group I
     22     (Security) of IEEE 802.11 working group
     23     (http://www.ieee802.org/11/) has worked to address the flaws of
     24     the base standard and has in practice completed its work in May
     25     2004. The IEEE 802.11i amendment to the IEEE 802.11 standard was
     26     approved in June 2004 and published in July 2004.</para>
     27 
     28     <para>Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version
     29     of the IEEE 802.11i work (draft 3.0) to define a subset of the
     30     security enhancements that can be implemented with existing wlan
     31     hardware. This is called Wi-Fi Protected Access&lt;TM&gt; (WPA). This
     32     has now become a mandatory component of interoperability testing
     33     and certification done by Wi-Fi Alliance. Wi-Fi provides
     34     information about WPA at its web site
     35     (http://www.wi-fi.org/OpenSection/protected_access.asp).</para>
     36 
     37     <para>IEEE 802.11 standard defined wired equivalent privacy (WEP)
     38     algorithm for protecting wireless networks. WEP uses RC4 with
     39     40-bit keys, 24-bit initialization vector (IV), and CRC32 to
     40     protect against packet forgery. All these choices have proven to
     41     be insufficient: key space is too small against current attacks,
     42     RC4 key scheduling is insufficient (beginning of the pseudorandom
     43     stream should be skipped), IV space is too small and IV reuse
     44     makes attacks easier, there is no replay protection, and non-keyed
     45     authentication does not protect against bit flipping packet
     46     data.</para>
     47 
     48     <para>WPA is an intermediate solution for the security issues. It
     49     uses Temporal Key Integrity Protocol (TKIP) to replace WEP. TKIP
     50     is a compromise on strong security and possibility to use existing
     51     hardware. It still uses RC4 for the encryption like WEP, but with
     52     per-packet RC4 keys. In addition, it implements replay protection,
     53     keyed packet authentication mechanism (Michael MIC).</para>
     54 
     55     <para>Keys can be managed using two different mechanisms. WPA can
     56     either use an external authentication server (e.g., RADIUS) and
     57     EAP just like IEEE 802.1X is using or pre-shared keys without need
     58     for additional servers. Wi-Fi calls these "WPA-Enterprise" and
     59     "WPA-Personal", respectively. Both mechanisms will generate a
     60     master session key for the Authenticator (AP) and Supplicant
     61     (client station).</para>
     62 
     63     <para>WPA implements a new key handshake (4-Way Handshake and
     64     Group Key Handshake) for generating and exchanging data encryption
     65     keys between the Authenticator and Supplicant. This handshake is
     66     also used to verify that both Authenticator and Supplicant know
     67     the master session key. These handshakes are identical regardless
     68     of the selected key management mechanism (only the method for
     69     generating master session key changes).</para>
     70   </refsect1>
     71 
     72   <refsect1>
     73     <title>IEEE 802.11i / WPA2</title>
     74 
     75     <para>The design for parts of IEEE 802.11i that were not included
     76     in WPA has finished (May 2004) and this amendment to IEEE 802.11
     77     was approved in June 2004. Wi-Fi Alliance is using the final IEEE
     78     802.11i as a new version of WPA called WPA2. This includes, e.g.,
     79     support for more robust encryption algorithm (CCMP: AES in Counter
     80     mode with CBC-MAC) to replace TKIP and optimizations for handoff
     81     (reduced number of messages in initial key handshake,
     82     pre-authentication, and PMKSA caching).</para>
     83   </refsect1>
     84 
     85   <refsect1>
     86     <title>See Also</title>
     87     <para>
     88       <citerefentry>
     89 	<refentrytitle>wpa_supplicant</refentrytitle>
     90 	<manvolnum>8</manvolnum>
     91       </citerefentry>
     92     </para>
     93   </refsect1>
     94 
     95   <refsect1>
     96     <title>Legal</title>
     97     <para>wpa_supplicant is copyright (c) 2003-2022,
     98     Jouni Malinen <email>j (a] w1.fi</email> and
     99     contributors.
    100     All Rights Reserved.</para>
    101 
    102     <para>This program is licensed under the BSD license (the one with
    103     advertisement clause removed).</para>
    104   </refsect1>
    105 </refentry>
    106