CSIT 5th Semester
Cryptography Board Question Paper 2081

CSC 327-2081 ✡
Tribhuvan University
Institute of Science and Technology
2081
✡
Bachelor Level/Third Year/Fifth Semester/Science
Computer Science Information Technology (CSC 327)
(Cryptography)
(New Course)
Full Marks:60 Pass Marks:24 Time:3 hours

Candidates are required to give their answers in their own words as for as practicable.
The figures in the margin indicate full marks

Section A
Long Answer Questions
Attempt any Two question.
[2x10=20]
1.

Let us consider the 4 bit key set as {1100, 1010, 0000, 1111, 0101, 1001} and input text as {1011, 1110, 1011, 1000}. Now trace the first full round operation of IDEA algorithm.

2.

What is message authentication code? List the operations of computing digest value in different passes of MD4. Describe about Needham-Schroeder protocol.

3.

Why do we need discrete logarithms? Illustrate with an example. Consider a Diffie-Hellman scheme with a common prime p=13 between user A and user B. Suppose public key of A is 10 and public key of B is 8. Now determine their private keys and shared secret key. Select any valid primitive root of 13.

Section B

Attempt any Eight questions

[8x5=40]
4.

Show encryption of plaintext "ALGORITHM" using the key "PSEUDOCODE" using playfair cipher.

5.

Discuss the working mechanism of the Kerberos protocol.

6.

What is the use of firewall? How circuit level gateway differs from stateful inspection firewall?

7.

What is intrusion? Explain any two types of intrusion detection system.

8.

Find the multiplicative inverse of polynomial {x^5} using Extended Euclidean Algorithm.

9.

What is DoS attack? Discuss about PKI trust model.

10.

Using Vigenere cipher with key="worlds", encrypt the plain text "hello everyone".

11.

Describe the different modes of block cipher encryption.

12.

Write short notes on (any two)
a) Totient value of a positive integer.
b) Properties of hash function.
c) Virus Vs Worms.