Tribhuvan University
Bachelor of Science in Computer Science and Information Technology
Semester 5 · TU Board 2076
Course Title: Cryptography (CSC316)
Full Marks: 60Pass Marks: 24Time: 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.
Group A
Attempt any TWO questions(2 × 10 = 20)
- 1.10
Among monoalphabetic and polyalphabetic cipher, which one is more vulnerable? Justify your statement. Which types of keys are considered weak keys in DES? Explain the round operation in IDEA.
- 2.10
State Fermat's theorem with an example. Given the prime number p=29 and its primitive root g=8, private key sender with X=9 and random integer K=11, encrypt the message m=13 using ElGamal cryptosystem.
- 3.10
Compare the SHA parameters between SHA-1 and SHA-2 families. Decrypt the cipher text DRJI with the key using the Hill cipher.
Group B
Attempt any EIGHT questions(8 × 5 = 40)
- 4.5
Define discrete logarithm. Explain the procedure of sharing the secret key in Diffie Hellman.
- 5.5
Distinguish between stream cipher and block cipher. Encrypt the message WE ARE IN SAME RACE UNTILL OVER LIVE END using Rail fence cipher using 4 as a number of rails.
- 6.5
Define digital signature. Describe the approaches of DSS.
- 7.5
What is the task of a firewall? List the elements of X.509.
- 8.5
How does the nature of worms differ from viruses? Define PKI with its architecture model.
- 9.5
Explain the procedure of mix column transformation in AES with an example.
- 10.5
What is the role of the prime number in the Euler totient Function? Find the GCD of 12 and 16 using the Euclidean algorithm.
- 11.5
Write down any two limitations of MAC. What do policy and mechanism mean in cryptography? Describe with a scenario.
- 12.5
Write short notes on
- Classes of Intruder
- SSL
- DoS Attack
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