Eduardo Diaz Dan Fiedler Andres Ramirez

1. AuthenticationAdvanced Software Engineering (CSE870)Instructor: Dr. B. ChengContact info: chengb at cse dot msu dot edu Eduardo Diaz Dan Fiedler Andres Ramirez

2. Road Map • Introduction to Authentication • Needham-Schroeder, Otway-Rees, Kerberos • Commonalities • Additional Requirements • Class Diagrams • State Diagrams • Conclusions

3. Authentication • Meet: • Alice (Staff) • Bob (MISys)

4. Authentication • Purpose • Key exchange. • Allow Alice to secretly communicate with Bob using a shared cryptographic key. • Methods • Private keys, shared keys, public keys… • Potential Problems • Trustworthy? • Safe handling of private keys?

5. Needham-Schroeder • Alice Cathy: {Alice || Bob || rand1} • Cathy Alice: {Alice || Bob || rand1}Ksess || {Alice || Ksess}kbob}kalice 3. Alice Bob: {Alice || ksess}kbob 4. Bob Alice: {rand2}ksess 5. Alice Bob: {rand2 - 1}ksess

6. Needham Schroeder • Motive? • Prevent replay attacks • A valid data transmission is retransmitted maliciously. • Nonces • Randomly generated numbers to identify exchanges. • Key idea: Cathy is trusted by Alice and Bob.

7. Otway-Rees • Alice Bob: num || Alice || Bob || { rand1 || num || Alice|| Bob}kalice 2. Bob Cathy: num || Alice || Bob || {rand1 || num || Alice || Bob}kalice || {rand2 || num || Alice || Bob}kbob 3. Cathy Bob: num || {rand1 || ksess}kalice || {rand2 || ksess}kbob 4. Bob Alice: num || {rand1 || ksess}kalice

8. Otway-Rees • Motivation • Needham-Schroeder assumes all cryptographic keys are secure… in practice generated pseudorandomly… but it can be predicted. • Num • Verify that num agrees through the exchanges. • Key Idea • Cathy is again the trustworthy element.

9. Kerberos • Alice Cerberus: Alice || Barnum • Cerberus Alice: {kalice,barnum}kalice || Talice,barnum • Alice Barnum: Guttenberg || Aalice,barnum || Talice,barnum • Barnum Alice: Alice || {kalice,guttenberg}kalicebarnum || Talice,guttenberg • Alice Guttenberg: Aalice,guttenberg || Talice,guttenberg 6. Guttenberg Alice: {t+1}kalice,guttenberg

10. Kerberos • What is T? • Talice,barnum = Barnum || {Alice || Alice Address || valid time || kalice,barnum}kbarnum • What is A? • {Alice || generation time || kt}kalice,barnum • Kt… not used.

11. Kerberos • Motivation • Separate authentication of the user to ticket granting server and resource being requested. • 2 Servers • Authenticate first • Obtain ticket second • Key Idea: • Time windows • Separation of trusted parties

12. Commonalities • Message Passing • Authentication Requests • Encryption / Decryption • Key Passing • … other than that, not much! • Each protocol has slight variants.

13. Additional Requirements • Same as other groups plus: • Incorporate 2 design patterns • 1 must be a security design pattern • Strategy Design Pattern (encryption algorithms) • Single Access Point (entry and logging) • Instantiate the framework at MISys • At the whitebox level

14. Whitebox Class Diagram

15. N.S. Class Diagram

16. O.R. Class Diagram

17. Kerberos Class Diagram

18. Whitebox Class Diagram-MISys

19. State Diagrams, NS

20. State Diagrams, N.S.

21. State Diagram, O.R.

22. State Diagram, O.R.

23. State Diagram, Kerberos

24. Graybox Class Diagram

25. BlackBox Class Diagram

26. Conclusions • Questions?