Q.1
14 Marks(a)
Define the following
i)Denial of Service
ii)Masquerade
iii)Non-repudiation
(b)
Differentiate between Brute force and cryptanalysis.
(c)
What are the various types of security attacks? Explain them in detail.
Gujarat Technological UniversitySummer 2025 examination
GTU 3161606 Cryptography and Network security Summer 2025 Question Paper & PDF
B.E. · IT Engineering · Semester 6 · Subject code 3161606
- Total
- 70 marks
- To pass
- 23 marks (33%)
- Duration
- 2.5 Hours 10:30 AM – 1:00 PM
- Questions
- 5 with internal choice
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9 of 25 questions on this paper were also asked in other years. 3 more are types of question GTU sets again with new data. Each is marked below with the years it appeared.See all 17 repeated 3161606 questions, most asked first
Q.2
14 Marks(a)
Use play fair cipher technique to encrypt the message “beauty lies in the eyes of a beholder” with the key “Monarchy”
Also asked in Summer 2026 Q2b, Winter 2025 Q2c
(b)
Hill cipher key is |17 17 5 | |21 8 21 | |2 2 19 | Encrypt “paymoremoney”
(c)
Distinguish between transposition and substitution methods with examples
OR
(c)
List down various modes of operations of block cipher and Explain ECB, OFB and COUNTER modes briefly.
Also asked in Summer 2026 Q3c
Q.3
14 Marks(a)
On what criteria the strength of DES algorithm depends? Explain with reason.
(b)
Compare public key cryptography with private key cryptography in detail.
Also asked in Summer 2026 Q1c
(c)
Explain Key Expansion in AES algorithm.
OR
(a)
Explain meet in the middle attack in DES.
(b)
Explain timing attack in RSA.
(c)
Explain single round function in DES algorithm.
Q.4
14 Marks(a)
What is SHA? Why it is needed in cryptography? Explain.
(b)
In RSA system, the public key of a user is e=7, p=17, q=11. What is the private key of this user? Also decrypt the message 11 using private key.
Also asked in Summer 2026 Q4b
(c)
Explain Diffie Hellman algorithm with example.
Also asked in Summer 2026 Q4c OR, Winter 2025 Q4c OR
OR
(a)
Define unconditionally secure cipher? Why one-time pad cipher is unconditionally secure?
(b)
Write the Euclid’s algorithm and show the steps of Euclid’s algorithm to find gcd(1970,1066).
Also asked in Summer 2026 Q3b, Winter 2025 Q4b
Q.5
14 Marks(a)
Explain X.509 authentication service in brief.
Also asked in Summer 2026 Q4a OR, Winter 2025 Q5c OR
(c)
Explain SHA1 hashing algorithm in detail.
OR
(b)
Explain Digital signature. What requirements should a Digital signature scheme satisfy?
Also asked in Summer 2026 Q3c OR, Winter 2025 Q5c
More Cryptography and Network security papers
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About this paper
Official Gujarat Technological University (GTU) examination paper for Cryptography and Network security (Summer 2025, B.E. · IT Engineering, Sem 6). Features complete 70-mark regular & remedial examination pattern, official marking distribution across all 5 questions, and direct 1-click official PDF download.
Transcribed for student exam preparation from Gujarat Technological University official examination archives. Questions, syllabus guidelines, and curriculum marking schemes remain the intellectual property of Gujarat Technological University.