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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
THIRD SEMESTER M.TECH DEGREE EXAMINATION, DECEMBER 2017

ELECTRONICS AND COMMUNICA TION ENGINEERING

I. Microwave and Television Engineering
2. Signal Processing

O1EC7213 - Secure Communication

Answer any two full questions from each part
Limit answers to the required points.

Max. Marks: 60 Duration: 3 hours
PART A
1 a. Discuss different computational complexity classes with examples. (5)
Describe relation among classes.
b. Discuss Fermat's little theorem. Find 3 3! ௦௦7 (4) 2. a. Differentiate
between Ring and Field with examples. (4)

b. What is modular multiplicative inverse? Find multiplicative inverse of 10 (5)
under mod 17.

3. a. Solve the linear congruence 12x mod 7 (4) b Find reminder 16 °° when is
divided with 7.
PART B
4, a. Draw a PN sequence generator with feedback connection governed by (3) I
+X+X2+x9,

b. Discuss Diffe Helman Key Exchange with an example.

c. Use Affine ciphering technique to encrypt the plain text "cryptography" (3)
using function E(x)= 5x+8.

5. a. Use Hill cipher to decipher a cipher "BEST OF LUCK" created with key
(5) matrix

b. Discuss RSA choosing I I and 3 as prime numbers to start with.