1. Computer Networks Ivan Marsic Rutgers University Chapter 7 – Network Security Chapter 8 – Network Monitoring Chapter 9 – Internet Protocols APPENDIX: Probability Refresher

2. Network Security Chapter 7

3. Topic: Secure Communication  Network Security Problem  Symmetric and Public-Key Cryptosystems  Cryptographic Algorithms  Authentication

4. 4 Network Security Problem Secure/Confidential Communication ?

5. Objectives of Information Security Confidentiality: information not disclosed or revealed to unauthorized persons Integrity: consistency of data—preventing unauthorized creation, modification, or destruction Availability: legitimate users are not unduly denied access to resources, including information resources, computing resources, and communication resources Authorized use: resources are not used by unauthorized persons or in unauthorized ways

6. Message Encoding and Decoding Encoding takes a message M and produces a coded form f(M) Decoding the message requires an inverse function, such that = M.

7. Two Basic Types of Cryptosystems Symmetric systems: both parties use the same (secret) key in encryption and decryption transformations Public-key systems (aka asymmetric systems): the parties use two related keys, one of which is secret and the other can be publicly disclosed

8. Public-Key Cryptosystem 8

9. Public-Key Cryptosystem - mod 9

10. Public-Key Cryptography In RSA, receiver does the following: Randomly select two large prime numbers p and q, which always must be kept secret. Select an integer number E, known as the public exponent, such that (p  1) and E have no common divisors, and (q  1) and E have no common divisors. Determine the product n = p  q, known as public modulus. Determine the private exponent, D, such that (E  D  1) is exactly divisible by both (p  1) and (q  1). In other words, given E, we choose D such that the integer remainder when E  D is divided by (p  1)  (q  1) is 1. Release publicly the public key, which is the pair of numbers n and E, K  = (n, E). Keep secret the private key, K  = (n, D).

11. Example: send the plaintext “hello world” receiver chooses p = 5 and q = 7 receiver chooses E = 5, because 5 and (5  1)  (7  1) have no common factors. Also, n = p  q = 35 receiver chooses D = 29, because i.e., they are exactly divisible. receiver’s public key is K   = (n, E) = (35, 5), which is made public. The private key K   = (n, D) = (35, 29) is kept secret.

12. Example, cont’d Plaintext letter Plaintext numeric representation BEBE Ciphertext B E % n h88 5 = 327688 5 % 35 = 8 e55 5 = 31255 5 % 35 = 10 l1212 5 = 24883212 5 % 35 = 17 l1224883217 o1515 5 = 75937515 5 % 35 = 15 CiphertextCDCD B = C D % nPlaintext letter 88 29 = 1547425049106725343623905288 29 % 35 = 8h 101000000000000000000000000000005e 1748196857210675091509141182522307169712l 1748196857210675091509141182522307169712l 151278340394885893911123275756835937515o Encryption Decryption

13. Example, cont’d While the adversary knows n and E, he or she does not know p and q, so they cannot work out (p  1)  (q  1) and thereby find D.

14. Topic: Authentication  Network Security Problem  Symmetric and Public-Key Cryptosystems  Cryptographic Algorithms  Authentication

15. Authentication Protocol (1) Secure communication is not enough … playback attack: Assumption: Only Sender needs to be authenticated to Receiver, not mutually.

16. Authentication Protocol (2) Solution to playback attack:

17. Impersonation Attack PROBLEM: Public key distribution … Adversary impersonates Bank PROBLEM: Customer unaware that Adversary obtained his account info!

18. Network Monitoring Chapter 8

19. Packet-pair Dispersion

21. Internet Protocols Chapter 9

22. The Internet Reference Model http://en.wikipedia.org/wiki/OSI_model Visit http://en.wikipedia.org/wiki/Internet_reference_model for more details on the Internet reference model

23. IPv6 Header

24. IPv6 Address Prefix Assignments

25. IPv6 Global Unicast Address

26. Example IPv6 Extension Headers

27. Format of IPv6 Extension Headers

28. RIP Header (for IPv4)

29. OSPF Directed Graph of an AS (a) (b)

30. OSPF Header (for IPv4)

31. OSPF - LSA Header

32. eBGP and iBGP Sessions

33. BGP Finite State Machine

34. Detail from Figure 1-49:

35. BGP Header & Message Formats

36. BGP UPDATE Message

37. Example BGP UPDATE Message

38. BGP MULTI_EXIT_DISC ( MED ) Attribute

39. Address Resolution Protocol (ARP) Need for multiple addresses, hierarchical vs. non-hierarchical

40. Address Resolution Protocol (ARP)

41. ARP Packet Format (for IPv4)

42. Mobile IP

43. SNMP

44. Probability Refresher Appendix

45. Jar with Black & White Balls

46. Random Events Possible outcomes of two coin tosses: “Tree diagram” of possible outcomes of two coin tosses:

47. Drawing from Jar/Urn Decided by Rolling a Die

48. Probability Matrix for Ball Drawing

49. Illustration for Bayes Theorem

50. Poisson Process average arrival rate = 5

51. Partitioning of Areas Under Normal Curve

52. How to Read Table A-1