I thought I would be protected from sniffing if I use a VPN, even in a setting where my traffic is going through a «man-in-the-middle» either by ARP poisoning or an evil twin attack.
Now I was told, that when connecting to the VPN the initial exchange is done in an unprotected environment, and therefore the encryption details could be sniffed as well.
Meaning that my encryption is futile, because the attacker could decrypt the traffic.
I was assuming that encryption keys were exchanged when installing a VPN app, or that the encryption information is somehow protected. If that was true, would that mean, that if I set up a VPN app while already using an evil twin network, that in that case, my traffic would be unprotected?
Or are these assumptions wrong anyway?