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@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