1. ©Brooks/Cole, 2003 Chapter 16 Security

2. ©Brooks/Cole, 2003 Define four aspects of security in a network: privacy, authentication, integrity, and nonrepudiation. Understand how these aspects can be achieved using encryption and decryption. Understand the difference between secret-key and public-key encryption. After reading this chapter, the reader should be able to: O BJECTIVES Realize how a digital signature can provide privacy, integrity, and nonrepudiation.

3. ©Brooks/Cole, 2003 Figure 16-1 Aspects of security

4. ©Brooks/Cole, 2003 PRIVACYPRIVACY 16.1

5. Figure 16-2 Secret key encryption

6. ©Brooks/Cole, 2003 In secret key encryption, the same key is used in encryption and decryption. However, the encryption and decryption algorithms are the inverse of each other. Note:

7. ©Brooks/Cole, 2003 Figure 16-3 DES

8. ©Brooks/Cole, 2003 Figure 16-4 Public key encryption

9. ©Brooks/Cole, 2003 Figure 16-5 RSA

10. ©Brooks/Cole, 2003 Figure 16-6 Combination

11. ©Brooks/Cole, 2003 DIGITALSIGNATUREDIGITALSIGNATURE 16.2

12. Figure 16-7 Signing the whole document

13. ©Brooks/Cole, 2003 Figure 16-8 Signing the digest

14. ©Brooks/Cole, 2003 Figure 16-9 Sender site

15. ©Brooks/Cole, 2003 Figure 16-10 Receiver site