Even though we have configured Site-to-Site VPN and it is working. ( thanks to SDM ) I have a basic doubt about Pre-shared keys.
How does the two devices exchange a pre-shared key or how some kind of mechanism is used to authenticate each other with same key at both ends. How is it possible to share the secret key even before authentication.
Is it done with D-H group, which generates a secret "number or key" with public / private key algorithm. And this key will then be used to encrypt the Pre-shared key.
It is very basic funda but I am still confused.
Please share the explanation.
thanks in advance