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Information Security : Question Paper Jun 2015 - Computer Engineering (Semester 6) | Gujarat Technological University (GTU)
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## Information Security - Jun 2015

### Computer Engineering (Semester 6)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
1 (a) (i) Encrypt the message 'Exam' using the Hill cipher with the key [?egin{bmatrix} 9 &4 \5 &7 end{bmatrix}].
Write the subkey and S-Box generation in Blowfish.
(7 marks)
1 (b) (i) Explain cipher feedback mode of operation.
Given the seed to be 101355, generate first five bits of random number with the help of blum blum shub generator.
(7 marks)
2 (a) (i) Perform encryption using the RSA algorithm.
p=3,q=11(two random numbers).
e(encryption key)=7
M(plaintext message)=5
(ii) Evaluate Euler's totient function Θ (37).
(7 marks)
2 (b) Explain Elliptic curve algorithm.(7 marks) 2 (c) Explain Diffie-Hellman key exchange.(7 marks) 3 (a) Explain the steps involved in International data encryption standard algorithm.(7 marks) 3 (b) How message authentication code can be used to achieve message authentication and confidentiality?(7 marks) 3 (c) Explain scheme for DES encryption.(7 marks) 3 (d) Which techniques are used for the distribution of public keys?(7 marks) 4 (a) (i) Write the benefits of IPSec.(3 marks) 4 (a) (ii) When an encryption scheme is said to be unconditionally secure and computationally secure?(4 marks) 4 (b) Write cast -128 encryption algorithm.(7 marks) 4 (c) (i) Write the properties of hash functions.(3 marks) 4 (c) (ii) Explain the fields included in ESP(Encapsulating security payload) packet.(4 marks) 4 (d) Explain pretty good privacy.(7 marks) 5 (a) (i) Why E-commerce transactions need security?(4 marks) 5 (a) (ii) Explain the use of firewall.(3 marks) 5 (b) Write MD5 algorithm.(7 marks) 5 (c) i) Which type of substitution is called monoalphabetic substitution cipher?
(ii) Which two principal methods are used in substitution ciphers to lessen the extent to which the structure of the plaintext survives in the ciphertext?
(iii) Use playfair algorithm with key 'monarchy' and encrypt the text 'jazz'.
(7 marks)
5 (d) Define SSL session and SSL connection. Which parameters define session state and connection state.(7 marks)