Questions
Syllabus
Qns. By Syllabus

Semester

Subject

Year

Tribhuwan University

Institute of Science and Technology

2081

Bachelor Level / Third Year / Fifth Semester / Science

B.Sc in Computer Science and Information Technology (CSC327)

(Cryptography)

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 Answers Questions

Attempt any TWO questions.
[2*10=20]
1.
Let us consider the 4 bits 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. [10]
2.
What is Message Authentication Code? List the operation of computing digest value in different passes of MD4. Describe about Needhom-Schroeder protocol. [10]
3.
Why do we need discrete logarithm? 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. [10]
Section B

Short Answers Questions

Attempt any Eight questions.
[8*5=40]
4.
Show the encryption of plain text "ALGORITHM" using the key "PSEUDOCODE" using playfair cipher. [5]
5.
Discuss the working mechanism of kerberos protocol. [5]
6.
What is the use of firewall? How circuit level gateway differs from stateful inspection firewall? [5]
7.
What is intrusion? Explain any two types of intrusion detection system. [5]
8.
Find the multiplicative inverse of polynomial (95) using extended euclidean Algorithm. [5]
9.
What is DoS attack? Discuss about PKI trust model. [5]
10.
Using Vigenere cipher with key = “worlds”, encrypt the plain text “hello everyone”. [5]
11.
Describe the different modes of block cipher. [5]
12.
Write short notes on (any two) a. Totient value of any positive integer. b. Properties of hash function. c. Virus or Worms. [5]