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<TM> (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