3

If I have two WiFi routers in different locations but with the same SSIDs and I connect a device to one of them, when I bring this device near the location of the other router, it will automatically connect to it as well.

I am wondering how this is not a security issue. In my understanding for a router to connect with a device this device has to send the password to the router and the router then checks if it is correct and connects with the device in case it is. Now what if I have a secured WiFi network A that I don't know the password to and I spin up my own network B with the same SSID near by, couldn't I just wait for one of the devices connected to A to send the password for A to me, because it would like to connect to me, too?

Obviously this is not possible, but I would like to know about the mechanism that prohibits this from happening.

6

Assuming you are talking about a PSK wireless network, then you misunderstand what is actually taking place.

The PSK isn't sent from a client to the AP. Rather it is a common starting point from which the encryption key is built for the session. If the AP and the client have two different PSKs, they will not be able to establish encryption correctly which will cause the communication to fail.

So even if you are near a network with the same SSID, unless it uses the same PSK, you won't be able to connect and your own PSK will be secure. But this answer would also depend on the EAP method in use as well.

If you are talking about WPA2-Enterprise using 802.1X, this is a different process and passwords may be compromised, although even then it is a hash that is sent and not the password itself.

1

Moving from Access point to another is known as Roaming. The client has to authenticate each time it moves from one Access Point to another. It will only work if the client has correct Password for the given SSID. If you bring up rouge Access Point with same SSID, it will never connect, and as YLearn explained, the password is never transmitted from Client to the Access Point for authentication.

The benefit of Roaming if properly designed is that the End user feels as if it is automatically moving from on Access point to the other, but in fact, behind the scenes, the Client goes through the same Authentication process as it did when it connected to the first AP. There is no compromise on Security. The following link gives you more details on how Roaming works.

https://www.hometoys.com/article/2012/04/demystifying-wi-fi-roaming-what-you-need-to-know-to-avoid-costly-mistakes/1812/

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