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| <refentry> |
| <refmeta> |
| <refentrytitle>wpa_background</refentrytitle> |
| <manvolnum>8</manvolnum> |
| </refmeta> |
| <refnamediv> |
| <refname>wpa_background</refname> |
| <refpurpose>Background information on Wi-Fi Protected Access and IEEE 802.11i</refpurpose> |
| </refnamediv> |
| <refsect1> |
| <title>WPA</title> |
| |
| <para>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 2004.</para> |
| |
| <para>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-fi.org/OpenSection/protected_access.asp).</para> |
| |
| <para>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.</para> |
| |
| <para>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).</para> |
| |
| <para>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 mechanisms will generate a |
| master session key for the Authenticator (AP) and Supplicant |
| (client station).</para> |
| |
| <para>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).</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>IEEE 802.11i / WPA2</title> |
| |
| <para>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).</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>See Also</title> |
| <para> |
| <citerefentry> |
| <refentrytitle>wpa_supplicant</refentrytitle> |
| <manvolnum>8</manvolnum> |
| </citerefentry> |
| </para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Legal</title> |
| <para>wpa_supplicant is copyright (c) 2003-2015, |
| Jouni Malinen <email>j@w1.fi</email> and |
| contributors. |
| All Rights Reserved.</para> |
| |
| <para>This program is licensed under the BSD license (the one with |
| advertisement clause removed).</para> |
| </refsect1> |
| </refentry> |