A) What does the second Law of Identity say? Let's say there is an online shop with search function, shopping cart, registration, ... What does the second Law of Identity mean for this scenario?

B) An attacker manages to intercept a TGT and he comes to the sessionkey of a user: -> Can the attacker now use the Kerberos service on behalf of the user? -> Can the attacker also request the service on behalf of other users?

C) There is a public key authentication service. The service has the public keys of all participants:

Where is the advantage of public key authentication compared to password authentication?

A new participant logs in to the service. How can the service be authenticity of the new subscriber? The communication is carried out via a secure channel.

What needs to be changed in the previous scenario when communicating over an unsecured channel?