Questions
Syllabus
Qns. By Syllabus

Semester

Subject

Year

Tribhuwan University

Institute of Science and Technology

2078

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.
Define CIA triad. State the encryption process of double and triple DES. What is the task of S-Box in DES? Discuss with an example. [10]
2.
Explain the generic model of digital signature process. Consider the two prime numbers 7 and 19. Select 29 as public key and 41 as private key. Encrypt the plaintext 4 and decrypt the cipher text 3 using RSA. [10]
3.
Define Galois field with an example. Explain any two modes of block cipher encryption. Determine the quadratic residues of 7. [10]
Section B

Short Answers Questions

Attempt any Eight questions.
[8*5=40]
4.
What does intrusion mean? How the system detect intrusion? List any four types of firewall. [5]
5.
Decrypt the message 'GVPJ' using Hill cipher taking the key as {Row1 = 3 7, Row2= 5 12}. [5]
6.
Describe the PKI trust model. [5]
7.
Define authentication system. Illustrate the need of mutual authentication over one way authentication with an example. [5]
8.
Find the value of 72019mod  137^{2019} \mod 13 using Fermat’s Little theorem. Define Euler totient function with an example. [5]
9.
List the properties of hash function. Discuss the first pass of MD4. [5]
10.
Differentiate between Symmetric and Asymmetric cipher. Encrypt the message 'HELL' using the key 'FAIL' using Vernam cipher. [5]
11.
Divide 3x2+4x+33x^2 + 4x + 3 by 5x+65x + 6 over GF(7). [5]
12.
Define SSL protocol. Mention the services provided by PGP. [5]