Download DU (University of Delhi) B-Tech 7th Semester Information Security Question Paper

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Name of the Paper
Semester
Time : 3 Hours
cu. m
: 2341702

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: B.Tech. Computer
Science
: CS-702 Information
Security
: VII

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Maximum Marks : 75
Instructions for Candidates :
(a) Write your Roll No. on the top immediately
on receipt of
this question paper.

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(b) Section - A is compulsory.
together.
(c) Attempt any 4 questions from Section - B.
Parts of a question must be answered
Section - A

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1. (a) What is
vulnerability
i
the difference between
and exposure ? 2

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P.T.O.

6132
(b)
(C)

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(d)
(f)
(g)
(h)
(i)

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De?ne linear congruence. Solve the
questions 3x + 4 5 (mod 13). 3
Find the multiplicative inverse of 132 in
Z . 3
l80

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Differentiate between block ciphers and
stream ciphers. 3
Use af?ne cipher to encrypt the message
"Today is our- IS exam" with the key pair
(7.2). 2

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Explain the concept of Fiestal Network. Also
prove that the mixer in Fiestal Cipher is
self-invertible. 5
Why does a round key generator need a
parity dr6p table ? 3

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What is a honeypot ? How is it different
from a honeynet ? 2
Describe the legal issues in Security.
, z/ 2
(j)

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(k)
(1)
(a)
(b)
6132

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What would be the code word corresponding
to the message (1101). The generator
matrix, is given below : 2
g0 l l 0 l 0 0 0
G: g, = 0 l l 0 l 0 O

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g2 1 l l 0 0 1 0
g3 1 0 l 0 0 0 1
Explain Man in the middle attack with a
suitable example. 3
Explain the Public key Infrastructure.

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Section - B
Use the Playfair Cipher t0 encipher the
message "Information need to be secure".
The secret key can be made by filling the
matrix diagonally from top left corner.

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Consider alphabets 'Y' and '2' together in
one cell of the matrix. 5
A Vigenere Cipher is a combination of m
additive ciphers. Justify with an example.
5

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p 3 P.T.O.

6132 *
3.
(a) Consider a symmetric (8,4) code whose

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parity ? check equations are.
6+4=10
V0=ul+u2+u3
Vl=u0+ul+u2
V2=uo+ul+ua

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v3 = uO + u2 + ?3
Where 1.10 111 uz'and 113 are message digits
and Von V2 and V3 are parity-check digits.
Find the generator and parity-check
matrices for this code. Determine the

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minimum distance of this code.
(b) Determine the weight distribution of the
18,4) linear code given In above problem.
Assume the transition probability of a BSC
be p = 102. Compute the probability ef an

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undetected error of this code. I/
6132
If generator g = 2 and p = 11, use Dif?e?Hcllman
algorithm to solve the following for User A and
User B. 1+4+4+l

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(a) Show that 2 is primitive root of 1 1.
(b) If A has public key 9 then what is A's private
key.
(c) If B has public key 3 then what is B's private
key.

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((1) Calculate the shared secret key.
(3) Using the S?box below find out the result
of passing strings.
(i) 1 101 1 1
(ii) 001 100

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?)1111;1
5 P.T.O.

6132 ' ?
S-Box Table i 6 1 32

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0123 456789101112131415
7. Write a short notes on (any five) :
0 10000914 06031505 01 1312 07 11040208 : 2x5=10
1 13 07 00 09 03 04 0610 02 08 05 14 12 11 15 01 i (a) Honeypots
2 13 06 04 09 08 15 03 oo 11 01 02 12 05 1o 14 07 (b) DigitalSignaturc

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3 01 10 13 oo 06 09 08 07 04 15 14 03 11 .05 02 12 (c) E-mailSecurity
(b) Brie?y describe the components of DES (d) Threats
including key generation. 7 (e) Transposition Cipher
. . . . neTime Pad
6. Brlefly explam Rabm Key Generatlon (0 0

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Algorithm. Assume the private key pair is (23,
1]). Calculate the Cipher text if the plain text
is 24.Also calculate all four.possib1e plain text 1
for the corresponding cipher text. 10
f > .t

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