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What is Kerberos? Network authentication protocol Developed at MIT in the mid 1980s Kerberos is a three-headed dog Available as open source or in supported.

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Presentation on theme: "What is Kerberos? Network authentication protocol Developed at MIT in the mid 1980s Kerberos is a three-headed dog Available as open source or in supported."— Presentation transcript:

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2 What is Kerberos? Network authentication protocol Developed at MIT in the mid 1980s Kerberos is a three-headed dog Available as open source or in supported commercial software Uses private-key cryptography for providing authentication across open networks

3 What's with the 3 heads?  Authentication – The confirmation that a user who is requesting services is a valid user of the network services requested  Authorization – The granting of specific types of service to a user, based on their authentication, what services they are requesting, and the current system state  Accounting – The tracking of the consumption of network resources by users

4 what can it do? Kerberos is mostly used in application-level protocols such as TELNET or FTP, to provide user to host security. It is also used, though less frequently, as the implicit authentication system of data stream (such as SOCK_STREAM) or RPC mechanisms. It could also be used at a lower level for host to host security, in protocols like IP, UDP, or TCP (ISO model levels 3 and 4), although such implementations are currently rare, if they exist at all.

5 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.

6 Design Requirements Interactions between hosts and clients should be encrypted. Must be convenient for users Protect against intercepted credentials.

7 Cryptography Approach Private Key: Each party uses the same secret key to encode and decode messages. Uses a trusted third party which can vouch for the identity of both parties in a transaction. Security of third party is imperative.

8 How does Kerberos work? Consists of three phases: 1. Getting the initial ticket. //user obtains a ticket from Kerberos.// 2. Getting the server ticket. //user obtains a ticket for a server from TGS.// 3. Requesting the service. //user presents the ticket to server for service.//

9 the ticket system Has a Key Distribution Center (KDC), containing a database of: –principles (customers and services) – encryption keys

10 How does Kerberos work?: Ticket Granting Tickets

11 How does Kerberos Work?: The Ticket Granting Service

12 How does Kerberos work?: The Application Server

13 Applications Authentication Authorization Confidentiality Within networks and small sets of networks

14 Weaknesses and Solutions If TGT stolen, can be used to access network services. Only a problem until ticket expires in a few hours. Subject to dictionary attack.Timestamps require hacker to guess in 5 minutes. Very bad if Authentication Server compromised. Physical protection for the server.

15 Benefits of Kerberos Standards-based strong authentication Broad operating-system support Provides for single sign-on (SSO) capability Passwords never traverse the network Password guessing more difficult Stolen authentication tickets are hard to reuse

16 Limitation: Scalability Recent modifications attempt to address this problem Public key cryptography for Client Authentication and cross realm authentication Issues are not resolved

17 Implementations of Kerberos  Kerberos 5 protocol is described in RFC 1510 – http://www.ietf.org/rfc/rfc1510.txt  Major implementations – MIT Kerberos http://web.mit.edu/kerberos/www/ – Heimdal Kerberos http://www.pdc.kth.se/heimdal/ – Sun's SEAM Kerberos  All implementations have similar commands and interfaces – They are compatible for authentication – Administrative interfaces are not always compatible

18 Common user commands kinit – Obtain and cache Kerberos ticket-granting ticket – Used to authenticate with the KDC klist – List cached Kerberos tickets kdestroy – Destroy Kerberos tickets – Used to clear out the ticket cache kadmin – Kerberos database administration program ktutil – Kerberos keytab file maintenance utility

19 Step by step process for intallation of kerbros http://www.ncsa.illinois.edu/Use rInfo/Resources/Software/kerbe ros/windows_install_kfw.html

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