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I'm looking on a clear schema that would explain how a computer connect to an WiFi access point (WEP or WPA in any version (1,2)).

The basic schema would be :

  • Computer looks which AP are available
  • If one known is found, asks the AP for connecting to it
  • AP answer by asking the password
  • Computer sends the password
  • If the password sent by the Computer is correct, AP grants access and give Computer an IP for this network.

This is a simple workflow, but I'm lacking information regarding :

  1. How the Computer identify the AP. Like if this AP hardware has changed but not the name, will it still be considered by the Computer as the same AP or a new one ?
  2. how the password is sent from the Computer to the AP. I seriously doubt it's sent in clear because that would mean that anyone listening could get the password. Is the AP sending the request for the password with it's public key, and the Computer returning the password encrypted using this public key ? is it something else ?

To be clearer, what I'm looking is an explained tutorial/howto on how the establishing connection between an WiFi hotspot and a user is made, including the type of encryption (if there is) prior the authentication (WEP/WPA) (some kind of HTTPS for WiFi to avoid sniffing?).

Thank you for helping me :)

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WEP and WPA have nothing to do directly with the 802.11 standard. 802.11 could support any sort of authentication in theory. Authentication is actually handled by the access point. –  Ramhound Apr 25 '13 at 15:24
    
Sorry for my mistake, my absence of knowledge in this domain led me to a wrong title question. I updated it, is it better? –  Cyril N. Apr 26 '13 at 7:42
    
I also added a bold text regarding what I expect for the answers, maybe it'll help? –  Cyril N. Apr 26 '13 at 7:52
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1 Answer

up vote 3 down vote accepted

The 802.1x protocol is built on multiple steps.

The supplicant (entity who wants to connect) identify the Access point by its SSID as it would do for any wireless network. Be noted that 802.1x also work on traditional wired networks. For what we know, this can be any hardware that provides this SSID, it can be changed, maybe spoofed.

When you are connected to the LAN/WAN, you can begin to authenticate. You can do this by negotiating with an authenticator (usually the AP itself, or an Ethernet switch). Until you are correctly authenticated, this authenticator will act as a barrier and deny you all traffic to any destination.

There are many mode of authentication available EAP, Radius and many mode for each. All provide many way to exchange keys and way to ensure confidentiality or not. But basically, until you forwarded the required information to the authenticator and it got a positive authentication validation from the authentication server, the switch will remain blocked.

For what I know, you can use a wide range of tools not to send clear text credentials: server certificates (public key encryption), client certificates etc. It kind of share properties with SSL authentication scheme. If you change AP, you will have to do the authentication again. There are possibilities to activate a Fast-roaming protocol by I do not know enough of it to talk about.

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Regarding exclusively the WiFi AP, is there any differences between WEP/WAP (in various versions) regarding the authentication protocol (how password is transmitted) ? –  Cyril N. Apr 24 '13 at 8:56
    
WEP and WAP has nothing to do with the 802.1x protocol AFAIK. It's only a way to crypt the wireless transmission. By the way, they usually require a key prior to connection, that will be incompatible (or will come as an addition) to the 802.1x authentication. In fact, only the authentication server can authenticate you, therefore you can't use any secret to communicate with the authenticator. Not sure if anyone has set up this kind of architecture using WAP/WEP keys, but I think this will just be a burden. –  M'vy Apr 24 '13 at 11:07
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