1<!doctype refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">
2
3<refentry>
4  <refmeta>
5    <refentrytitle>wpa_background</refentrytitle>
6    <manvolnum>8</manvolnum>
7  </refmeta>
8  <refnamediv>
9    <refname>wpa_background</refname>
10    <refpurpose>Background information on Wi-Fi Protected Access and IEEE 802.11i</refpurpose>
11  </refnamediv>
12  <refsect1>
13    <title>WPA</title>
14
15    <para>The original security mechanism of IEEE 802.11 standard was
16    not designed to be strong and has proven to be insufficient for
17    most networks that require some kind of security. Task group I
18    (Security) of IEEE 802.11 working group
19    (http://www.ieee802.org/11/) has worked to address the flaws of
20    the base standard and has in practice completed its work in May
21    2004. The IEEE 802.11i amendment to the IEEE 802.11 standard was
22    approved in June 2004 and published in July 2004.</para>
23
24    <para>Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version
25    of the IEEE 802.11i work (draft 3.0) to define a subset of the
26    security enhancements that can be implemented with existing wlan
27    hardware. This is called Wi-Fi Protected Access&lt;TM&gt; (WPA). This
28    has now become a mandatory component of interoperability testing
29    and certification done by Wi-Fi Alliance. Wi-Fi provides
30    information about WPA at its web site
31    (http://www.wi-fi.org/OpenSection/protected_access.asp).</para>
32
33    <para>IEEE 802.11 standard defined wired equivalent privacy (WEP)
34    algorithm for protecting wireless networks. WEP uses RC4 with
35    40-bit keys, 24-bit initialization vector (IV), and CRC32 to
36    protect against packet forgery. All these choices have proven to
37    be insufficient: key space is too small against current attacks,
38    RC4 key scheduling is insufficient (beginning of the pseudorandom
39    stream should be skipped), IV space is too small and IV reuse
40    makes attacks easier, there is no replay protection, and non-keyed
41    authentication does not protect against bit flipping packet
42    data.</para>
43
44    <para>WPA is an intermediate solution for the security issues. It
45    uses Temporal Key Integrity Protocol (TKIP) to replace WEP. TKIP
46    is a compromise on strong security and possibility to use existing
47    hardware. It still uses RC4 for the encryption like WEP, but with
48    per-packet RC4 keys. In addition, it implements replay protection,
49    keyed packet authentication mechanism (Michael MIC).</para>
50
51    <para>Keys can be managed using two different mechanisms. WPA can
52    either use an external authentication server (e.g., RADIUS) and
53    EAP just like IEEE 802.1X is using or pre-shared keys without need
54    for additional servers. Wi-Fi calls these "WPA-Enterprise" and
55    "WPA-Personal", respectively. Both mechanisms will generate a
56    master session key for the Authenticator (AP) and Supplicant
57    (client station).</para>
58
59    <para>WPA implements a new key handshake (4-Way Handshake and
60    Group Key Handshake) for generating and exchanging data encryption
61    keys between the Authenticator and Supplicant. This handshake is
62    also used to verify that both Authenticator and Supplicant know
63    the master session key. These handshakes are identical regardless
64    of the selected key management mechanism (only the method for
65    generating master session key changes).</para>
66  </refsect1>
67
68  <refsect1>
69    <title>IEEE 802.11i / WPA2</title>
70
71    <para>The design for parts of IEEE 802.11i that were not included
72    in WPA has finished (May 2004) and this amendment to IEEE 802.11
73    was approved in June 2004. Wi-Fi Alliance is using the final IEEE
74    802.11i as a new version of WPA called WPA2. This includes, e.g.,
75    support for more robust encryption algorithm (CCMP: AES in Counter
76    mode with CBC-MAC) to replace TKIP and optimizations for handoff
77    (reduced number of messages in initial key handshake,
78    pre-authentication, and PMKSA caching).</para>
79  </refsect1>
80
81  <refsect1>
82    <title>See Also</title>
83    <para>
84      <citerefentry>
85	<refentrytitle>wpa_supplicant</refentrytitle>
86	<manvolnum>8</manvolnum>
87      </citerefentry>
88    </para>
89  </refsect1>
90
91  <refsect1>
92    <title>Legal</title>
93    <para>wpa_supplicant is copyright (c) 2003-2016,
94    Jouni Malinen <email>j@w1.fi</email> and
95    contributors.
96    All Rights Reserved.</para>
97
98    <para>This program is licensed under the BSD license (the one with
99    advertisement clause removed).</para>
100  </refsect1>
101</refentry>
102