1. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Chapter 29 Internet Security

2. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 CONTENTS INTRODUCTION PRIVACY DIGITAL SIGNATURE SECURITY IN THE INTERNET APPLICATION LAYER SECURITY TRANSPORT LAYER SECURITY: TLS SECURITY AT THE IP LAYER: IPSEC FIREWALLS

3. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 INTRODUCTION 29.1

4. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-1 Aspects of security

5. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 PRIVACY 29.2

6. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-2 Secret-key encryption

7. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 In secret-key encryption, the same key is used by the sender (for encryption) and the receiver (for decryption). The key is shared.

8. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Secret-key encryption is often called symmetric encryption because the same key can be used in both directions.

9. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Secret-key encryption is often used for long messages.

10. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 We discuss one secret-key algorithm in Appendix E.

11. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 KDC can solve the problem of secret-key distribution.

12. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-3 Public-key encryption

13. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Public-key algorithms are more efficient for short messages.

14. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 A CA can certify the binding between a public key and the owner.

15. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-4 Combination

16. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 To have the advantages of both secret-key and public-key encryption, we can encrypt the secret key using the public key and encrypt the message using the secret key.

17. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 DIGITAL SIGNATURE 29.3

18. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-5 Signing the whole document

19. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Digital signature cannot be achieved using only secret keys.

20. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Digital signature does not provide privacy. If there is a need for privacy, another layer of encryption/decryption must be applied.

21. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-6 Signing the digest

22. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-7 Sender site

23. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-8 Receiver site

24. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 SECURITY IN THE INTERNET 29.4

25. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 APPLICTION LAYER SECURITY 29.5

26. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-9 PGP at the sender site

27. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-10 PGP at the receiver site

28. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 TRANSPORT LAYER SECURITY (TLS) 29.6

29. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-11 Position of TLS

30. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-12 Handshake protocol

31. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 SECURITY AT THE IP LAYER (IPSec) 29.7

32. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-13 Authentication

33. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-14 Header format

34. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-15 ESP

35. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-16 ESP format

36. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 FIREWALLS 29.8

37. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-17 Firewall

38. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-18 Packet-filter firewall

39. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 A packet-filter firewall filters at the network or transport layer.

40. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 29-19 Proxy firewall

41. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 A proxy firewall filters at the application layer.