One known problem with WPA2 is that anybody who knows the preshared key can snoop on the handshake and decrypt all subsequent traffic between any parties on the network. In the typical coffee shop scenario, where anybody who is willing to pay $2 for a coffee can get the PSK, this is a big problem.
Could Diffie-Hellman be used to mitigate this problem? In my understanding, what DH boils down to is a way for two parties to share a key without ever having to send it over the wire. Or as Wikipedia puts it:
Diffie–Hellman Key Exchange establishes a shared secret between two parties that can be used for secret communication for exchanging data over a public network.
So my questions are:
- Could DH be used to stop people who knows the PSK from snooping on your WiFi?
- Are there any downsides to this that explains why it is not used in WPA2-PSK?
- Are there any WiFi protocols that uses a solution like this?