Cryptography
The course introduces the underlying the principles and design of cryptosystems. The course covers the basics concepts of cryptography including: traditional ciphers, block ciphers, stream ciphers, public and private key cryptosystems. The course also includes the theory of hash functions, authentication systems, network security protocols and malicious logic.
Tribhuvan University
Institute of Science and Technology
2082
Bachelor Level / fifth-semester / Science
Computer Science and Information Technology( CSC316 )
Cryptography
Full Marks: 60 + 20 + 20
Pass Marks: 24 + 8 + 8
Time: 3 Hours
Candidates are required to give their answers in their own words as far as practicable.
The figures in the margin indicate full marks.
Section A
Attempt any TWO questions.
Describe the Fiestel Cipher structure. Given the key {2B, 7E, 15, 16, 28, AE, D2, A6, AB, F7, 97, 66, 01, 02, 03, 04}, compute the first 4 byte of next key after first iteration, using the following S-Box in AES.
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 63 | 7C | 77 | 7B | F2 | 6B | 6F | C5 | 30 | 01 | 67 | 2B | FE | D7 | AB | 76 |
Illustrate the man in middle attack in Diffie – Hellman key exchange protocol. Assume the prime number be 19 and 10 as its primitive root. Select 5 as private key and 4 as random integer. Find the cipher text of M = 2 using Elgamal crypto system.
List the properties of hash function. Describe the algorithm for SHA-1.
Section B
Attempt any EIGHT questions.
Describe any three types of malicious logic.
Given the key “HELLOWORLD”, encrypt the plaintext “TURINGTEST” using Play fair cipher.
Explain any two modes of block cipher encryption.
State Fermat’s theorem with example. What is the implication of discrete logarithm?
Describe the working mechanism of digital signature algorithm.
List and explain the types of firewall.
Decrypt the ciphertext “HI” using Hill Cipher where the key is [5/4 3/3].
What is digital certificate? Discuss the certificate life cycle.
Define authentication system. Discuss about challenge response system.