Network Security

Network Security Test 1-2010

Part A

1 a) Describe the various attacks on Security in a network                             -5-

   b) Write a playfair matrix with the key word  “WALKING”. Use it to

       encipher the message “SUPPORT NEEDED URGENTLY”. If needed

       use a dummy character.                                                                             -5-

2a) In S-DES the S-Box design is given as

1	0	3	2
3	2	1	0
0	2	1	3
3	1	3	2

0	1	2	3
2	0	1	3
3	0	1	0
2	1	0	3

 S₀  =                                                            S₁=

                                                                         

     Find the output of the S-Box for the combination 1101 and 1000 given

      to S0 and S1 respectively.                                                                              -5-

b) Explain the cipher feedback mode of using DES .                                        -5-

Part B

3a) Give the differences between.

(i)   Differential and Linear Cryptanalysis.

(ii)  Monoalphabetic and Polyalphabetic cipher .                                             -5-

b) In a RSA system the public key of a user is e = 31, n = 3599.

     What is the private key of the user.                                                            -5-

4a) Write down the RSA algorithm.                                                                -5-

b) Perform double transposition technique to decipher the text

        I R I X A T L T N H  Y E I S S T S E V E A T Y  R  S E N X

                The Key is   4 3 1 2 5 6 7                                                                -5-

Part C

5) Explain in detail the S-DES encryption with a block diagram and

      describe all the steps .                                                                             -5-

6) Explain with a block diagram a single round of DES algorithm

    in detail.                                                                                                     -5-

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Network Security Test 2-2010

Part A:

1a) Explain with block diagrams the public-key cryptosystem to provide

            (i) Secrecy

            (ii) Authentication

            (iii) Secrecy and Authentication.                                                                           -5-

b) Perform encryption and decryption using RSA for the following

            p=17, q=31, e=07, M=2.                                                                                    -5-

2a) Consider a Diffie-Hellman scheme with common prime q=11 and a primitive root  α=2    (i) Show that 2 is a primitive root of 11

           (ii) If user A has a public key YA=9. What is A’s private key XA?

           (iii) If user B has a public key YB =3, what is the shared secret key K?            -5-

b) With neat diagrams explain the basic uses of hash function.                                   -5-

Part B:

3a) Explain with neat diagrams SSL Architecture, Session state and Connection state.

                                                                                                                                         -5-                               

b) What are the services offered by SSL Record Protocol. Explain the operation with a diagram. Also show the SSL record Format.                                                                -5-

4a) Explain with a neat diagram the 4 phases of the handshake protocol.                    -5-

b) Write the sequence of events for secure electronic transaction                               -5-

Part C:

5) The given Plain text is PAY MORE MONEY. Find the Cipher text in Hill Cipher -5-

6) Given cipher text is PQCFKU. Find the plain text using Hill Cipher .                      -5-

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Network Security Test 3-2010

Part A

1a) How are passwords stored and verified? Explain the process with a

      neat diagram.                                                                                 -5-

b) What are the uses of audit records? Explain the different types with

      examples.                                                                                      -5-

2a) What are the metrics used for profile based intrusion detection?   

                                                                                                            -5-

b) Write the examples of heuristics which are used to assign degrees of

     suspicious  activities                                                                      -5-

Part B

3a) What is the current state of worm technology                                 -5-

  b) Give the general structure of virus and explain how it works         -5-

4a) Explain the following: (1) Macro Virus

                                            (2) Email Virus                                          -5-

b) How does compression virus infect a program                                 -5-

Part C

5) What are the advanced antivirus techniques  Explain with diagram the

     digital immune system                                                                      -5-

6) What are the strategies for password selection so that password is not    

     easily guessable                                                                                 -5-

                                                                                                                                        

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