1. CSCE 515: Computer Network Programming Chin-Tser Huang huangct@cse.sc.edu University of South Carolina

2. 4/27/2004(C) 2004 Chin-Tser Huang2 What Can Go Wrong… …when your computer y receive or is waiting for a message m? m Internet x y ?

3. 4/27/2004(C) 2004 Chin-Tser Huang3 Message Loss Adversary A can discard m in its transit m x y A

4. 4/27/2004(C) 2004 Chin-Tser Huang4 Message Interception Adversary A can get a copy of m when m passes by m x y m m A

5. 4/27/2004(C) 2004 Chin-Tser Huang5 Message Modification Adversary A can arbitrarily modify the content of m to become m’ m x y m’ A

6. 4/27/2004(C) 2004 Chin-Tser Huang6 Message Insertion Adversary A can arbitrarily fabricate a message m, pretending that m was sent by x x y m src: x dst: y A

7. 4/27/2004(C) 2004 Chin-Tser Huang7 Message Replay Adversary A can replay a message m that has been sent earlier by x and received by y x y m m A

8. 4/27/2004(C) 2004 Chin-Tser Huang8 Denial-of-Service Attack Adversary A can send huge amount of messages to y to block m from arriving at y x y m ……………… ????? A

9. 4/27/2004(C) 2004 Chin-Tser Huang9 Type of Attacks Passive attacks Traffic analysis Message interception Active attacks Message loss Message modification Message insertion Message replay Denial-of-Service attack

10. 4/27/2004(C) 2004 Chin-Tser Huang10 Network Security Services Confidentiality Integrity Authentication Anti-replay … Availability Access control Non-repudiation Anonymity

11. 4/27/2004(C) 2004 Chin-Tser Huang11 Confidentiality Keep message known only to the receiver and secret to anyone else Counter message interception

12. 4/27/2004(C) 2004 Chin-Tser Huang12 Integrity When receiver receives message m, receiver can verify m is intact after sent by sender Counter message modification

13. 4/27/2004(C) 2004 Chin-Tser Huang13 Authentication When receiver receives message m, receiver can verify m is indeed sent by the sender recorded in m Counter message insertion

14. 4/27/2004(C) 2004 Chin-Tser Huang14 Anti-replay When receiver receives message m, receiver can verify m is not a message that was sent and received before Counter message replay

15. 4/27/2004(C) 2004 Chin-Tser Huang15 Availability Property of a system or a resource being accessible and usable upon demand by an authorized entity Counter denial-of-service attack

16. 4/27/2004(C) 2004 Chin-Tser Huang16 Access Control Mechanism to enforce access rights to resources and data Users can access resources and data to which they have access rights Users cannot access resources and data to which they don’t have access rights

17. 4/27/2004(C) 2004 Chin-Tser Huang17 Non-repudiation When receiver receives message m, receiver gets proof that sender of m ever sent m Receiver of m can show proof to third- party so that sender of m cannot repudiate

18. 4/27/2004(C) 2004 Chin-Tser Huang18 Anonymity Identity of sender is hidden from receiver When receiver receives message m, receiver has no clue about sender of m

19. 4/27/2004(C) 2004 Chin-Tser Huang19 Network Security Is Great… Prevent messages from being attacked in their transit Detect and discard messages that are modified, inserted, or replayed Disallow unauthorized access to local system resource and sensitive data

20. 4/27/2004(C) 2004 Chin-Tser Huang20 …But Hard To Achieve Many layers in network architecture Many different media of network connection Adversary’s location hard to determine New attacks keep emerging Cryptographic overhead

21. 4/27/2004(C) 2004 Chin-Tser Huang21 Next … Final exam on Tuesday, May 4, 5:30pm- 7:30pm Take CSCE 715 in Fall 2004 if you are interested in network security Have a good summer!