B.Sc. (Computer Science) Sem 5 Information and Network Security Oct 2025 Question Paper - Mumbai University | munotes

Questions asked in this paper

• N.B. (1) All questions are compulsory. (2) Figures to the right indicate marks. (3) Illustrations, in-depth answers and diagrams will be appreciated. (4) Mixing of sub-questions is not allowed.

SECTION I - Q.1 (Attempt ANY FOUR from the following) 20 Marks

1. (a) Describe the symmetric cipher model with a neat diagram.
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2. (b) Define security services and list any four services provided by network security.
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3. (c) Differentiate between active and passive security attacks.
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4. (d) Using the Playfair cipher of the 5x5 matrix, encrypt the plaintext "HELLO" using the keyword "MONARCHY".
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5. (e) Explain steps of the RSA algorithm with an example.
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6. (f) What is steganography? Explain how it is used to protect information.
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SECTION II - Q.2 (Attempt ANY FOUR from the following) 20 Marks

1. (a) Explain the working principle of a public-key cryptosystem.
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2. (b) Describe the steps involved in the Diffie-Hellman key exchange with a simple numerical example.
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3. (c) Explain the concept of HMAC and its advantages over normal hash functions.
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4. (d) How are digital signatures generated and verified using public-key cryptography?
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5. (e) What are the key components of an X.509 certificate?
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6. (f) What are the limitations of Kerberos and Public Key Infrastructure in modern networks?
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SECTION III - Q.3 (Attempt ANY FOUR from the following) 20 Marks

1. (a) What is IPSec, and what are its main components?
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2. (b) Explain common intrusion techniques used by attackers.
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3. (c) Explain the working of PGP (Pretty Good Privacy) with a neat diagram.
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4. (d) Define malicious software and list types of malware.
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5. (e) Describe the operation of a packet-filtering firewall with an example.
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6. (f) Explain the working of S/MIME for securing email communication.
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SECTION IV - Q.4 (Attempt ANY FIVE from the following) 15 Marks

1. (a) Define terms: i) Cryptanalysis ii) Avalanche Effect iii) Encryption
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2. (b) Encrypt the message "Secure the documents" using the Rail Fence Cipher with depth 3.
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3. (c) Explain the use of ticket-granting tickets (TGT) in Kerberos authentication.
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4. (d) Discuss any three security requirements of a good hash function.
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5. (e) State any three advantages of using a firewall.
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6. (f) Explain virus countermeasures to prevent infection.
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