1. Kerberos
Kerberos is an authentication protocol for trusted hosts on untrusted networks

2. Contents……… What is Kerberos? Aims of Kerberos. Why Kerberos?
How Kerberos work?
Firewall vs. Kerberos?
Applications
Disadvantages

3. What is Kerberos?
Is a name of a computer network authentication protocol
Developed at MIT (Massachusetts Institute of Technology) in the mid 1980s
Available as open source or in supported commercial software
Allows individuals communicating over a non-secure network to prove their identity to one another in a secure manner.
Its designers aimed primarily at a client-server model, and it provides mutual authentication.
Trusted 3rd party authentication scheme.
Assumes that hosts are not trustworthy.
Requires that each client (each request for service) prove it’s identity.
Does not require user to enter password every time a service is requested!

5. Aims of Kerberos
The user's password must never travel over the network.
The user's password must never be stored in any form on the client machine: it must be immediately discarded after being used.
The user's password should never be stored in an unencrypted form even in the authentication server database.
The user is asked to enter a password only once per work session.
Authentication information management is centralized and resides on the authentication server.
Supports Mutual authentication.
provides support for the generation and exchange of an encryption key to be used to encrypt data.

6. Why Kerberos?
Sending usernames and passwords in the clear, endangers the security of the network.
Each time a password is sent in the clear, there is a chance for interception.
In addition to the security concern, password based authentication is inconvenient; users do not want to enter a password each time they access a network service.
Most uses of authentication by assertion require that a connection originate from a ``trusted'' network address, on many networks, addresses are themselves simply assertions.
Stronger authentication methods base on cryptography are required.
Strong authentication technologies are not used as often as they should be, although the situation is gradually improving.

7. How does Kerberos work? Request Ticket from authentication server
Instead of client sending password to application server:
Request Ticket from authentication server
Ticket and encrypted request sent to application server
How to request tickets without repeatedly sending credentials?
Ticket granting ticket (TGT)

8. How does Kerberos work? Ticket Granting Tickets

9. How does Kerberos Work? The Ticket Granting Service

10. How does Kerberos work? The Application Server

11. Firewall vs. Kerberos?
Firewalls make a risky assumption: that attackers are coming from the outside. In reality, attacks frequently come from within.
Kerberos assumes that network connections (rather than servers and work stations) are the weak link in network security.

12. Applications Authentication Authorization Confidentiality
Within networks and small sets of networks

13. Disadvantages
Kerberos makes extensive use of the trusted third party, If the third party simply fails, availability is lost.
If two hosts are on different times, communication may be difficult or impossible.

15. Queries