CSIT 5th Semester
Cryptography Board Question Paper 2080

CSC 327-2080 ✡
Tribhuvan University
Institute of Science and Technology
2080
✡
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.

Define discrete logarithms. How key generation, encryption and decryption is done in RSA. In a RSA cryptosystem, given p=13 and q=7, determine private key, public key, and perform encryption and decryption for the text M= "hi" using 0 to 25 for letters from a to z.

2.

Write down the encryption and decryption process at 2-DES and 3-DES. Explain the Fiestel cipher structure. Divide 5x^2 + 4x + 6 by 2x + 1 over GF (7).

3.

What are the applications of hash functions? Discuss how SHA-1 algorithm generates hash value from a given message.

Section B

Attempt any Eight questions

[8x5=40]
4.

Show encryption and decryption of "csit" using hill cipher having key K =

32
57

5.

Give the formal definition of Authentication system. Describe about one way and mutual Authentication system.

6.

List the stage of certificate life cycle. What are the types of firewalls?

7.

What is malicious logic? How Zombies are different from Trojan horses?

8.

How Miller Rabin test is used for primality testing? Show whether the number 561 passes the test.

9.

Show that the set of integers is Ring under addition and multiplication.

10.

How substitution ciphers are different from transposition ciphers? Given a message M="CSIT PROGRAM IS A HOT CAKE", encrypt M using Rail Fence cipher with rail size=3.

11.

Describe about IPSec. List the five services of PGP.

12.

How does meet in middle attack work in Diffie Hellman key Exchange protocol? Explain.