Gujarat Technological UniversityWinter 2025 examination

GTU 3161606 Cryptography and Network security Winter 2025 Question Paper & PDF

B.E. · IT Engineering · Semester 6 · Subject code 3161606
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Total
70 marks
To pass
23 marks (33%)
Duration
2.5 Hours 2:30 PM – 5:00 PM
Questions
5 with internal choice
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11 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.1

14 Marks
(a)
3 marksAsked in 2 of 3 papers
List and define any three security services.

Also asked in Summer 2026 Q2a

(b)
4 marks

Define Cryptography and Steganography. Which technique (Cryptography or Steganography) is used in each of the following cases for confidentiality?

1)A student writes the answer to a test on a small piece of paper, rolls up the paper and inserts it in a ball-point pen, and passes the pen to another student.
2)To send a message, a spy replaces each character in the message with a symbol that was agreed upon in advance as the character's replacements.
(c)
7 marks
Discuss following attacks.
1)Brute force attack
2)Frequency analysis attack
3)Man in the middle attack
4)Active attack
5)Passive attack
6)Meet in the middle attack
7)Known plaintext attack

Q.2

14 Marks
(a)
3 marks
Define
i)group
ii)Ring
iii)Field
(b)
4 marks

Let us assign numeric values to the uppercase alphabet (A=0, B=1, …., Z=25). We can now do modular arithmetic on the system using modulo

26
1)What is (A+N) mod 26 in this system?
2)What is (X+6) mod 26 in this system?
3)What is (Y-5) mod 26 in this system?
4)What is (C-10) mod 26 in this system?
(c)
7 marksSame type asked in 3 of 3 papers

Discuss Playfair Cipher. Construct a Playfair matrix with the key “engineering”. And encrypt the message “test this Balloon”.

Also asked in Summer 2026 Q2b, Summer 2025 Q2a

(c)
7 marks

Discuss encryption and decryption process in Vigenere cipher. Using the Vigenere cipher, encrypt the word “Life is full of surprises” using the key “health”.

Q.3

14 Marks
(a)
3 marksAsked in 2 of 3 papers
What is a hash function and what are its primary uses in cryptography?

Also asked in Summer 2026 Q3b OR

(b)
4 marks

Describe the Electronic Codebook (ECB) mode and identify its main advantages and disadvantages.

(c)
7 marksAsked in 2 of 3 papers
Describe the key structure of DES.

Also asked in Summer 2026 Q2c OR

(a)
3 marksAsked in 2 of 3 papers

What is a Message Authentication Code (MAC) and what is its primary use in cryptography?

Also asked in Summer 2025 Q5a OR

(b)
4 marks

Describe the operation of Cipher Feedback (CFB) mode and how it differs from CBC.

(c)
7 marksAsked in 2 of 3 papers
Describe the key structure of AES.

Also asked in Summer 2026 Q2c

Q.4

14 Marks
(a)
3 marks
Describe the consequences of not using HTTPS on a website.
(b)
4 marksSame type asked in 3 of 3 papers

Define the greatest common divisor of two integers. Using Euclidean algorithm find the greatest common divisor of

1)88 and 220
2)2n+1 and n, assume n is non-negative integer.

Also asked in Summer 2026 Q3b, Summer 2025 Q4b OR

(c)
7 marks
Discuss RSA Algorithm in detail.
(a)
3 marks

Explain the differences between TLS and SSL. Why is TLS preferred over SSL today?

(b)
4 marksSame type asked in 2 of 3 papers

Define Multiplicative Inverse. Using Extended Euclidean algorithm find multiplicative inverse of 49 in GF (37).

Also asked in Summer 2026 Q4b OR

(c)
7 marksAsked in 3 of 3 papers

Describe the general process of establishing a shared secret using the Diffie-Hellman method.

Also asked in Summer 2026 Q4c OR, Summer 2025 Q4c

Q.5

14 Marks
(a)
3 marksAsked in 2 of 3 papers
List the duties of a KDC.

Also asked in Summer 2025 Q4c OR

(b)
4 marks

Compare and contrast symmetric and asymmetric encryption methods in the context of remote user authentication.

(c)
7 marksAsked in 3 of 3 papers
Describe the process of creating and verifying a digital signature.

Also asked in Summer 2026 Q3c OR, Summer 2025 Q5b OR

(a)
3 marksAsked in 3 of 3 papers

Describe the role of the Ticket Granting Ticket (TGT) in the Kerberos authentication process.

Also asked in Summer 2026 Q5c, Summer 2025 Q5c OR

(b)
4 marksAsked in 3 of 3 papers
Describe the purpose of following protocols defined in SSL
1)Handshake Protocol
2)ChangeCipherSpec Protocol
3)Alert Protocol
4)Record Protocol

Also asked in Summer 2026 Q4c, Summer 2025 Q5b

(c)
7 marksAsked in 3 of 3 papers

Explain the components of an X.509 certificate and the importance of each component.

Also asked in Summer 2026 Q4a OR, Summer 2025 Q5a

More Cryptography and Network security papers

Questions repeat across sessions. Working through two or three papers shows you which topics GTU asks most.

Summer 202670 marks · 5 questions
Summer 202570 marks · 5 questions

Other Semester 6 subjects

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3161604
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3161605
Software Engineering
3161607
Big Data Analytics
3161608
Artificial Intelligence

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About this paper

Official Gujarat Technological University (GTU) examination paper for Cryptography and Network security (Winter 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.

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