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Reg No.:_ Name:

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
EIGHTH SEMESTER B.TECH DEGREE EXAMINATION, MAY 2019

Course Code: EC468
Course Name: SECURE COMMUNICATION
Max. Marks: 100 Duration: 3 Hours
PARTA

Answer any two full questions, each carries 15 marks. Marks

1 a) Differentiate between active and passive attacks. (5)

b) Solve the equation 3x+4 = 6(mod 13). (5)

c) Give different types of attacks in a cryptosystem. (5)

2 8) Itis told in arithmetic that the remainder of an integer divided by 4 is the same as (5)
the remainder of division of the two rightmost digits by 4. Use the properties of
mod operator to prove this claim.
b) Differentiate between group, ring, abelian group and field with examples. (10)

3 9) Find whether the set of whole numbers is an Abelian Group under addition. (5)

Justify.
b) Define the inverse and identity elements for any operation in a group. (5)
c) Discuss attacks on integrity. How it can be prevented? (5)
PART ‏تا‎
‎Answer any two full questions, each carries 15 marks.
4 a) Discuss the properties of an ideal cryptographic system. (5)
b) Using the Key: PAY, do OTP for LAY. (5)
c) Give the basic permutations and substitution in DES. (5)
5 a) Discuss four transformations used in Advanced Encryption Standard. (10)
b) Give the advantages of Poly Alphabetic Cipher. (5)
6 a) Explain Diffie- Hellman public key cryptosystem with an example. (10)
b) Encrypt the word SECURE using Key as 3 using Ceaser Cipher. (5)

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