IT-801 Information Security - May 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aExplain fabrication, interception, Non-Repudiation and Integrity in terms of security.
   How to answer

   • Define fabrication, interception as attacks on authenticity/availability/confidentiality
   • Define non-repudiation and integrity as security services/goals
   • Give example for each
   • Relate to CIA + authentication model
2. 7 Marks
   bEncrypt the following message using Caesar cipher with key = 1. Plaintext is "Laughter is the best medicine".
   How to answer

   • State Caesar cipher shift rule with key = 1
   • Apply shift to each letter of plaintext
   • Write resulting ciphertext preserving spaces
   • Note case handling
3. 7 Marks
   aConsider a plain text alphabet G. Using RSA algorithm and the value as $e=3, d=11$ and $n=15$, find out what this plain text alphabet encrypt to, and verify that upon decryption it transform back to G.
   How to answer

   • Map alphabet G to numeric values
   • Compute ciphertext C = G^e mod n with e=3, n=15
   • Compute decryption M = C^d mod n with d=11
   • Verify result equals original G
4. 7 Marks
   bTo find

   1. i)75 mod 119
   2. ii)89 mod 119
   3. iii)Primitive root of 11
   4. iv)Primitive root of 5
   How to answer

   • Compute 75 mod 119 and 89 mod 119
   • Recall definition of primitive root modulo prime
   • Test candidates for primitive root of 11
   • Test candidates for primitive root of 5
5. 7 Marks
   aExplain in detail the key generation in AES algorithm and its expansion format.
   How to answer

   • State AES key sizes and number of rounds
   • Explain key expansion / Rcon, S-box, RotWord
   • Describe generation of round keys
   • Explain expansion format / key schedule structure
6. 7 Marks
   bGive the five modes of operation of Block cipher. Explain any two.
   How to answer

   • List five modes: ECB, CBC, CFB, OFB, CTR
   • Explain working of any two with diagrams
   • Compare advantages / error propagation
   • Give application example
7. 14 Marks
   Evaluate using Diffie-Hellman key exchange technique. Users A and B use a common prime $q = 11$ and a primitive root $\text{alpha} = 7$.

   1. i)If user A has private key XA = 3. What is A's public key YA?
   2. ii)If user B has private key XB = 6. What is B's public key YB?
   How to answer

   • State Diffie-Hellman public key formula YA = alpha^XA mod q
   • Compute YA = 7^3 mod 11
   • Compute YB = 7^6 mod 11
   • Optionally compute shared secret
8. 7 Marks
   aFormulate what are the requirements of Kerberos? Explain about Kerberos version.
   How to answer

   • List Kerberos requirements: secure, reliable, transparent, scalable
   • Explain AS, TGS, ticket granting process
   • Describe Kerberos version 4 vs version 5 differences
   • Mention realms and limitations
9. 7 Marks
   bHow does PGP provide confidentiality and authentication service for e-mail and file storage applications? Draw the block diagram and explain its components.
   How to answer

   • Explain PGP confidentiality using session key + public key
   • Explain authentication using hash + private key signature
   • Draw PGP block diagram for transmission/reception
   • Explain components: session key, RSA, ZIP, Base64
10. 7 Marks
    aEstimate what is the role of intrusion detection system. What are the three benefits that can be provided by the intrusion detection system?
    How to answer

    • Define IDS and its placement in network
    • Explain detection vs prevention role
    • List three benefits: early warning, forensic evidence, policy compliance
    • Give types: host-based, network-based
11. 7 Marks
    bIllustrate the three common types of firewalls with diagrams.
    How to answer

    • Name three types: packet-filtering, stateful inspection, application proxy / circuit gateway
    • Sketch diagram for each firewall placement
    • Explain filtering logic and limitations
    • Compare security vs performance
12. 7 Marks
    aWhat are Viruses? Explain the virus related threats and the counter measures applied.
    How to answer

    • Define virus as self-replicating malicious code
    • Classify virus threats: file, boot, macro, worm, trojan distinction
    • Explain damage and propagation
    • List countermeasures: antivirus, updates, backup, awareness
13. 7 Marks
    bWhat is secure electronic transaction and how it can be achieved?
    How to answer

    • Define secure electronic transaction (SET)
    • List SET requirements: confidentiality, integrity, authentication
    • Explain dual signature and participants
    • Explain how SSL/SET achieves secure payment
14. 14 Marks
    Write a short notes (any three)

    1. a)DOS and DDOS attack
    2. b)Hash function
    3. c)Secure Socket Layer
    4. d)Steganography
    How to answer

    • Define DOS vs DDOS, hash function, SSL, steganography
    • Explain working principle with example/diagram
    • Mention applications and attacks/countermeasures
    • Conclude with use in information security