BSc CS Sem 5 October 2025 October 2025 Information & Network Security Question Paper - Mumbai University | munotes

Questions asked in this paper

• 2) Figures to the right indicate marks

1. Q3 Illustrations, in-depth answers and diagrams will be appreciated
2. Q4 Mixing of sub-questions is not allowed
3. Q1 Attempt ANY FOUR from the following: (20M)
   • (a) Describe the symmetric cipher model with a neat diagram
   • (b) Define security services and list any four services provided by network security
   • (c) Differentiate between active and passive security attacks
   • (d) Using the Playfair cipher of the 5x5 matrix, encrypt the plaintext “HELLO” using the
   • (e) Explain steps of the RSA algorithm with an example
   • (f) What is steganography? Explain how it is used to protect information
4. Q2 Attempt ANY FOUR from the following: (20M)
   • (a) Explain the working principle of a public-key cryptosystem
   • (b) Describe the steps involved in the Diffie-Hellman key exchange with a simple
   • (c) Explain the concept of HMAC and its advantages over normal hash functions
   • (d) How are digital signatures generated and verified using public-key cryptography? What are the key components of an X.509 certificate?
   • (f) What are the limitations of Kerberos and Public Key Infrastructure in modern
5. Q3 Attempt ANY FOUR from the following: (20M)
   • (a) What is IPSec, and what are its main components?
   • (b) Explain common intrusion techniques used by attackers
   • (c) Explain the working of PGP (Pretty Good Privacy) with a neat diagram
   • (d) Define malicious software and list types of malware
   • (e) Describe the operation of a packet-filtering firewall with an example
   • (f) Explain the working of S/MIME for securing email communication
6. Q4 Attempt ANY FIVE from the following: (15M)
   • (a) Define terms : i) Cryptanalysis ii) Avalanche Effect iii) Encryption
   • (b) Encrypt the message “Secure the documents” using the Rail Fence Cipher with depth
   • (c) Explain the use of ticket-granting tickets (TGT) in Kerberos authentication
   • (d) Discuss any three security requirements of a good hash function
   • (e) State any three advantages of using a firewall
   • (f) Explain virus countermeasures to prevent infection

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