Cryptography And System Security Question Paper - May 18 - Computer Engineering (Semester 7) - Mumbai University (MU)
1 Answer

Cryptography And System Security - May 18

Computer Engineering (Semester 7)

Total marks: 80
Total time: 3 Hours
(1) Question No. 1 is compulsory.
(2) Attempt any three from remaining five questions.
(3) Assume suitable data if required.
(4) Figures in brackets on the right hand side indicate full marks.

1(a) What is the purpose of S-boxes in DES? Explain the avalanche effect?
(5 marks) 00

1(b) Give examples of replay attacks. List three general approaches for dealing with replay attacks.
(5 marks) 00

1(c) Why is the segmentation and reassembly function in PGP(Pretty Good Privacy) needed?
(5 marks) 00

1(d) List and explain various types of attacks on encrypted message.
(5 marks) 00

2(a) What is the need for message authentication? List various techniques used for message authentication. Explain anyone.
(10 marks) 00

2(b) Explain Kerberos protocol that supports authentication in distributed system.
(10 marks) 00

3(a) What characteristics are needed in secure hash function? Explain the operation of secure hash algorithm on 512 bit block.
(10 marks) 00

3(b) What is a notice in key distribution scenario? Explain the key distribution scenario if A wishes to establish logical connection with B. A and B both have a master key which they share with itself and key distribution center.
(10 marks) 00

4(a) Why E-commerce transactions need security? Which tasks are performed by payment gateway in E-commerce transaction? Explain the SET (Secure Electronic Transaction) protocol.
(10 marks) 00

4(b) In RSA system the public key of a given user e=7 & n=187

  • 1) What is the private key of this user?
  • 2) If the intercepted CT=11 and sent to a user whose public key e=7 & n=187. What is the PT?
  • 3) Elaborate various kinds of attacks on RSA algorithm?
(10 marks) 00

5(a) How can we achieve web security? Explain with example.
(10 marks) 00

5(b) Use Hill cipher to encrypt the text "short". The key to be used is "hill".
(10 marks) 00

6(a) Explain IPSec protocol in detail. Also write applications and advantages of IPSec.
(10 marks) 00

6(b) Differentiate between i) MD-5 and SHA ii) Firewall and IDS.
(10 marks) 00

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