1. cosc 513Presentation, Fall 20001 Network Security Student: Jianping He Student ID: 105592 Instructor: ProfessorAnvari Fall 2000

2. cosc 513Presentation, Fall 20002 Content What is the network security. Encryption Application of Encryption in Network Security Encryption/decryption Digital signature Productivity vs Security Conclusion

3. cosc 513Presentation, Fall 20003 Why network security is important sharing. Because of the resource sharing of networks, more users have the potential to access networked system than single computers. complexity of system. A network combines more operating system, so it more complex than a signal computer. unknown perimeter. In network, a computer on one network can access the resource on the other network many points of attack. In network, the file is stored remote from the computer and may pass through many host computers to get to the user, so the administrator may have no control over other hosts in the network. unknown path. In network, there are more than one path from one host to another. When a user on one host sends a message to a user on another host. It seldom has control over the routing of its message.

4. cosc 513Presentation, Fall 20004 Objectives of Network security Confidentiality Ensure that an unauthorized individual does not gain access to data. Integrity Ensure that data are not altered by unauthorized individuals. Availability Ensure that authorized users are not denied access to the date or resource of the network

5. cosc 513Presentation, Fall 20005 Pattern of Attack to Network Interruption the flow of information is blocked entirely Interception In this attack, the normal flow of information is not affected, but an additional flow, generally to an unauthorized source, is created Modification an unauthorized party not only gains access to but also changes the contents of message before it is received at the destination host Fabrication an unauthorized party inserts counterfeit objects into the network.

6. cosc 513Presentation, Fall 20006 Key Generation ------------------------------------------------------------------- select p, q p and q both prime calculate n = p x q select integer d gcd (  (n),d) =1; 1<d<  (n) calculate e e= d -1 mod  (n) public keyKU ={e, n} private keyKR ={d, n} --------------------------------------------------------------------

7. cosc 513Presentation, Fall 20007 Private Key Encryption Plaintext Encryption Algorithm Plaintext Decryption Algorithm CiphertextEncryption Key

8. cosc 513Presentation, Fall 20008 Private key encryption-contd. A key is used to encrypt a message and the same key is used to decrypt the message. Disadvantage: It is difficult to maintain the security of the key.

9. cosc 513Presentation, Fall 20009 Public Key Encryption Plaintext Encryption Algorithm Plaintext Decryption Algorithm Ciphertext Public Encryption Key Private Decryption Key

10. cosc 513Presentation, Fall 200010 Public key encryption-contd. One key for encryption and another key for decryption. Advantage: Solves the problem of maintaining key security Disadvantage Much more complex than private key encryption Two or three orders of magnitude slow than private key encryption

11. cosc 513Presentation, Fall 200011 Encryption/decryption of message

12. cosc 513Presentation, Fall 200012 Encryption points Link encryption Link layer is encrypted Suite for the transmission line is the point of greatest vulnerability Network encryption IP header is clear Load is encrypted Transport encryption TCP load is encrypted

13. cosc 513Presentation, Fall 200013 Digital Signature

14. cosc 513Presentation, Fall 200014 Security vs Productivity

15. cosc 513Presentation, Fall 200015 Conclusion Identify business-related security issues Analyze security risks, threats, and vulnerabilities Design the security architecture and the associated processes Implement security technology and processes Audit impact of security technology and processes Evaluate effectiveness of current architectures and policies

16. cosc 513Presentation, Fall 200016 Reference Niven,I., and Zuckerman, H.S. An Introduction to the Theory of Numbers. Wiley. New York. 1972 Douglas E. Comer. Computer Networks and Internets. Prentice Hall, 1999, ISBN: 0-13-083617-6. Frederic J. Cooper et al. Implementing Internet Security, New Riders, 1999. ISBN: 1-56205-471-7. Gregory B. White, Computer system and network security. CRC,1996. William Stallings. Network and Internetwork Security. Prentice Hall,1995. ISBN: 0-7803-1107-8