TRIBHUVAN UNIVERSITY
INSTITUTE OF SCIENCE AND TECHNOLOGY
2079 B.S.
Candidates are required to give their answers in their own words as far as practicable.
Group A
Long Answer QuestionsAttempt any Two questions.
- 1Illustrate the concept of security policy and mechanism with an example. Differentiate between block cipher and stream cipher. Explain the process of key expansion in AES.
- 2Describe the properties of hash functions. Discuss how hash value is generated using SHA-1 algorithm.
- 3Show that $Z_5$ is a field. John publishes the ElGamal public key $(q, \alpha, Y_A) = (101, 2, 14)$. Jane desired to send the secret message "CSIT" to John. Using the equivalence A=0, B=1,... , Z = 25, encrypt the message using John's public key. Use a random number $k = 4$.
Group B
Short Answer QuestionsAttempt any Eight questions.
- 4Differentiate between Trojan horse and virus. Describe any two types of intruders.
- 5The message "IMOGUN" was encrypted with a Playfair cipher using keyword "GALOIS". Decrypt the message.
- 6How encryption is done using IDEA algorithm.
- 7Describe the services provided by Pretty Good Privacy protocol to secure email.
- 8What is the condition of for two integers, x and y, to be relatively prime? Find whether 61 is prime or not using Miller-Rabin algorithm.
- 9Define challenge response system. Why do we need Kerberos?
- 10How direct digital signature is different from arbitrated digital signature? How digital signature generation and verification is done using RSA.
- 11Which one is more secure, monoalphabetic cipher or poly alphabetic cipher? Justify. Using Rail fence cipher, encrypt the text "LEARNING AND TEACHING ARE DIFFERENT", using 3 as rails.
- 12Why do we need discrete logarithm over normal logarithm? Find out whether 3 is primitive root of 7 or not.