Appendix B Wireless LANs
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The Message Integrity Check (MIC) is designed to prevent an attacker from
capturing data packets, altering them and resending them. The MIC provides a
strong mathematical function in which the receiver and the transmitter each
compute and then compare the MIC. If they do not match, it is assumed that the
data has been tampered with and the packet is dropped.
By generating unique data encryption keys for every data packet and by creating
an integrity checking mechanism (MIC), with TKIP and AES it is more difficult to
decrypt data on a Wi-Fi network than WEP and difficult for an intruder to break
into the network.
The encryption mechanisms used for WPA(2) and WPA(2)-PSK are the same. The
only difference between the two is that WPA(2)-PSK uses a simple common
password, instead of user-specific credentials. The common-password approach
makes WPA(2)-PSK susceptible to brute-force password-guessing attacks but it’s
still an improvement over WEP as it employs a consistent, single, alphanumeric
password to derive a PMK which is used to generate unique temporal encryption
keys. This prevent all wireless devices sharing the same encryption keys. (a
weakness of WEP)
User Authentication
WPA and WPA2 apply IEEE 802.1x and Extensible Authentication Protocol (EAP) to
authenticate wireless clients using an external RADIUS database. WPA2 reduces
the number of key exchange messages from six to four (CCMP 4-way handshake)
and shortens the time required to connect to a network. Other WPA2
authentication features that are different from WPA include key caching and pre-
authentication. These two features are optional and may not be supported in all
wireless devices.
Key caching allows a wireless client to store the PMK it derived through a
successful authentication with an AP. The wireless client uses the PMK when it
tries to connect to the same AP and does not need to go with the authentication
process again.
Pre-authentication enables fast roaming by allowing the wireless client (already
connecting to an AP) to perform IEEE 802.1x authentication with another AP
before connecting to it.
Wireless Client WPA Supplicants
A wireless client supplicant is the software that runs on an operating system
instructing the wireless client how to use WPA. At the time of writing, the most
widely available supplicant is the WPA patch for Windows XP, Funk Software's
Odyssey client.
Содержание NWA-3166
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Страница 15: ...15 PART I Introduction Introduction 17 The Web Configurator 29 Tutorials 33 ...
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Страница 32: ...Chapter 2 The Web Configurator NWA 3166 User s Guide 32 ...
Страница 64: ...Chapter 3 Tutorials NWA 3166 User s Guide 64 ...
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Страница 70: ...Chapter 4 Status Screen NWA 3166 User s Guide 70 ...
Страница 122: ...Chapter 8 Wireless Screen NWA 3166 User s Guide 122 ...
Страница 128: ...Chapter 9 SSID Screen NWA 3166 User s Guide 128 ...
Страница 158: ...Chapter 14 IP Screen NWA 3166 User s Guide 158 ...
Страница 166: ...Chapter 15 Rogue AP Detection NWA 3166 User s Guide 166 ...
Страница 186: ...Chapter 17 Internal RADIUS Server NWA 3166 User s Guide 186 ...
Страница 213: ...Chapter 19 Log Screens NWA 3166 User s Guide 213 ...
Страница 214: ...Chapter 19 Log Screens NWA 3166 User s Guide 214 ...
Страница 235: ...Chapter 20 VLAN NWA 3166 User s Guide 235 ...
Страница 236: ...Chapter 20 VLAN NWA 3166 User s Guide 236 ...
Страница 270: ...Appendix B Wireless LANs NWA 3166 User s Guide 270 ...
Страница 300: ...Appendix D IP Addresses and Subnetting NWA 3166 User s Guide 300 ...
Страница 308: ...Appendix E Text File Based Auto Configuration NWA 3166 User s Guide 308 ...
Страница 314: ...Appendix F How to Access and Use the CLI NWA 3166 User s Guide 314 ...
Страница 326: ...Appendix H Customer Support NWA 3166 User s Guide 326 ...
Страница 332: ...Index NWA 3166 User s Guide 332 ...