Scribd
Upload
55 views2 pages

Gujarat Technological University: Instructions

This document is an exam for a course on Information Security. It contains 5 questions assessing various topics in cryptography and information security. Question 1 covers cryptanalytic attacks and key distribution scenarios. Question 2 covers block cipher modes of operation, DES S-boxes, and RSA encryption/decryption. Question 3 covers key exchange using elliptic curves, the Playfair cipher, Blowfish algorithm details, and the Hill cipher. Question 4 covers uses of hash codes, PGP segmentation/reassembly, and security threats to e-commerce. Question 5 covers the Digital Signature Algorithm and properties/construction of hash and digital signature techniques.

Uploaded by

Shweta Jha
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
55 views2 pages

Gujarat Technological University: Instructions

This document is an exam for a course on Information Security. It contains 5 questions assessing various topics in cryptography and information security. Question 1 covers cryptanalytic attacks and key distribution scenarios. Question 2 covers block cipher modes of operation, DES S-boxes, and RSA encryption/decryption. Question 3 covers key exchange using elliptic curves, the Playfair cipher, Blowfish algorithm details, and the Hill cipher. Question 4 covers uses of hash codes, PGP segmentation/reassembly, and security threats to e-commerce. Question 5 covers the Digital Signature Algorithm and properties/construction of hash and digital signature techniques.

Uploaded by

Shweta Jha
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
You are on page 1/ 2

Seat No.: _____ Enrolment No.

______

GUJARAT TECHNOLOGICAL UNIVERSITY


B E Sem-VI Examination May 2011

Subject code: 160702


Subject Name: Information Security
Date: 17/05/2011 Time: 10.30 am – 01.00 pm
Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1 (a) (i) Explain the various types of cryptanalytic attack, based on the amount 04
of information known to the cryptanalyst.
(ii) Explain the terms diffusion and confusion. 03

(b) (i) Which two criteria are used to validate that a sequence of numbers is 04
random? Explain the linear congruential method to generate
pseudorandom numbers.
(ii) Write the key distribution scenario in which each user shares a unique 03
master key with key distribution center

Q.2 (a) (i) Why mode of operation is defined? Explain the simplest mode for 04
block cipher modes of operation?
(ii) What is the purpose of S-boxes in DES? Explain the avalanche effect. 03

(b) (i) In a public key system using RSA, the ciphertext intercepted is C=10 04
which is sent to the user whose public key is e=5, n=35. What is the
plaintext M?
(ii) Write the differences between conventional encryption and public key 03
encryption.
OR
(b) (i) Briefly explain the Diffie-Hellman key exchange. 04
(ii) Perform encryption and decryption using the RSA algorithm for p=3, 03
q=11, e=7, M=5.

Q.3 (a) (i) How key exchange using elliptic curves can be done? 04
(ii) Construct a playfair matrix with the key “occurrence”. Generate the 03
cipher text for the plaintext “Tall trees”

(b) Explain how subkeys are generated in blowfish algorithm and also explain 07
the encryption in blowfish algorithm. How does the key-size in blowfish
differ from cast-128?
OR
Q.3 (a) (i) Write the Euclid’s algorithm and show the steps of Euclid’s algorithm 04
to find gcd(1970,1066).
(ii) Encrypt the message “Good morning” using the Hill Cipher with the 03
9 4
key  .
5 7
1
(b) Which parameters affect RC5 encryption algorithm. Explain RC5 07
encryption and decryption process.

Q.4 (a) Illustrate variety of ways in which hash code can be used to provide 07
message authentication.
(b) (i) Why is the segmentation and reassembly function in PGP(Pretty Good 04
Privacy) needed?
(ii)What are the security threats to E-commerce transactions? 03
OR
Q.4 (a) What is cryptographic checksum or message authentication code? 07
Describe the three situations in which message authentication code is
used.
(b) (i) What is the difference between transport mode and tunnel mode? 04

(ii) What parameters characterize the nature of a particular security 03


association in IPSec.

Q.5 (a) Write the Digital Signature Algorithm. 07


(b) Explain the following properties of hash function
(i) One way property 02
(ii) Weak collision resistance 02
(iii) Compression function in hash algorithm. 03
OR
Q.5 (a) List and define the parameters that define secure socket layer connection 07
state.
(b) What is dual signature and explain construction of dual signature. 07

*************

You might also like