Kerbros

Question 1

What are the options for authentications with an external authentication server (AS)?

Answer 1

1. S1 uses the credentials provided by A to run a cryptographic protocol with AS.
2. End-to-end Authentication between A and AS. S1 relays messages and AS informs
   S1 about outcome (ACCEPT / DENY).
3. A runs protocol with AS, interaction results in information A and S1 can use to
   mutually authenticate. (google)

Question 2

What is kerberos?

Answer 2

It is an authentication and an access control service. It acts as a trusted third party key distribution service.