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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
Seventh Semester B.Tech Degree Examination (Regular and Supplementary), December 2020

Course Code: CS409
Course Name: CRYPTOGRAPHY AND NETWORKSECURITY

Max. Marks: 100 Duration: 3 Hours
PARTA
Answer all questions, each carries 4 marks. Marks
1 What are the two approaches to attack a cipher? Give example for each. (4)

i)

Use autokey system of Vigenere cipher to encrypt the message “meet me after (4)

the toga party” using the key “largest”.

3 Illustrate the key expansion procedure of IDEA. (4)

4 Define Euler’s Totient Function. Compute 0 (41) and ¢ (115). (4)

5 Distinguish between conventional encryption and public key encryption (4)
system.

6 Explain any two ways in which a hash code can be used to provide message (4)
authentication.

7 Why PGP generate a signature before applying compression (4)

8 List out the security association parameters in IPSec. (4)

9 What is the significance of Alert protocol in SSL and list out any three Alert (4)

messages and their use?
10 What are the key features provided by SET? (4)

PART ‏تا‎
‎Answer any two full questions, each carries 9 marks.
11 a) Encrypt the word “Semester Result” with the keyword “Examination” using (5)

play fair cipher. List the rules used

b) Depict a block cipher mode that can be used to convert block cipher to stream (4)

cipher.
12 a) Explain AES key expansion procedure. (4)
b) Explain the primitive operations of RC4. (5)

13 a) Using double stage columnar transposition technique, encrypt the text (4)
“Cryptography and Network Security” using the key “43125”.
b) Explain the construction of S-box in AES algorithm. (5)

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