E 10000CS409122002 Pages: 2

Reg No.: Name:
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Seventh Semester B.Tech Degree Regular and Supplementary Examination December 2021 (2015 Scheme)

Course Code: CS409
Course Name: CRYPTOGRAPHY AND NETWORK SECURITY

Max. Marks: 100 Duration: 3 Hours
PARTA
Answer all questions, each carries 4 marks. Marks

1 7 8 (4)

Encrypt the plain text “short example” using hill cipher with key | |
11 11

2 Differentiate between monoalphabetic substitution and polyalphabetic (4)
substitution with example.

3 Explain the key generation of AES algorithm. (4)

4 Using extended Euclidian algorithm find the gcd of(161,28).Also find two (4)
integers 5,1 such that s >< 161+ £ x 28 = gcd(161,28).

5 State Fermat’s theorem and find the result of 3൩0011 using Fermat’s (4)
theorem.

6 What are the requirements for the practical application of a hash function? (4)

7 List the services included in the operation of PGP. (4)

8 Write down the steps for preparing enveloped data MIME entity. (4)

9 Name the participants included in the secure electronic transaction (SET) (4)
system.

10 What are the protocols used in SSL two layer protocol stack? (4)

PART 1
Answer any two full questions, each carries 9 marks.
11 a) Explain the structure of DES with the help of a neat diagram. How 5 boxes in (6)
DES converts a 6 bit input to a 4 bit output?
b) Encrypt the plain text “instruments” using play fair cipher with key (3)

“monarchy”.

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