1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter Twelve Network Security

2. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Security threats in a network connected to the Internet Figure 12.1

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Secret key encryption and decryption process Figure 12.2

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Public key encryption and decryption process Figure 12.3

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. DES enciphering algorithm flowchart Figure 12.4

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Data block manipulation of the DES algorithm Figure 12.5

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Various steps in the RSA algorithm Figure 12.6

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A firewall between an enterprise network and the Internet Figure 12.7

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Structure of an X.509 certificate Figure 12.8

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. General format of a PGP message Figure 12.9

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The fields contained in the AU Figure 12.10

12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The AH protocol operates in transport mode or tunnel modes Figure 12.11

13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Position of AH in IPv4 & IPv6 packets ( transport mode) Figure 12.12 I I

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Position of AH in IPv4 & IPv6 packets ( tunnel mode) Figure 12.13

15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The ESP fixed-length and variable-length fields Figure 12.14

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ESP header in IPv4 & IPv6 packets ( transport mode) Figure 12.15

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ESP header format in the tunnel mode Figure 12.16

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A security gateway between the Internet and intranets Figure 12.17

19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The remote-access VPN concept Figure 12.18