# CSVTU QUESTION PAPER

## B. E. VII Sem, ET & T, APR-MAY 2010

## CRYPTOGRAPHY & SECURE COMMUNICATION

**Note**: All units are compulsory. Question 1 is of 2 Marks & question 4 is of 4 marks are compulsory. Sole any one from Question 2 and Question3 each are of 10 marks.

**Unit-I**

**Q.1** What are the two different uses of public Key cryptography related to key distribution? 2

**Q.2** (i) In a public key cryptosystem using RSA,the value of cipher text obtained is C=10 sent to user, whose public key is e=5,n=35.What is the value of plain text M? 5

(ii)Briefly explain Diffie-Hellman key exchange. 5

**Q.3** Explain general categories of scheme for the distribution of public keys, each in detail. 10

**Q.4** Write a short note on: 4

(i)Trap door one way function (ii)Euler’s theorem

(ii)Fermat’s theorem (iv)RSA.

**Unit-II**

**Q.1** What is the role of a compression function in a hash function? 2

**Q.2** What are the approaches of producing message authentication function, explain each in detail? 10

**Q.3** What characteristics are needed in a secure hash function? 10

**Q.4** Explain nature of Brute force attack in hash function and MAC’s? 4

**Unit-III**

**Q.1** What is the difference between direct and arbitrated digital signature? 2

**Q.2** Explain mutual authentication protocol and also comment on its difference with one way authentication protocol? 10

**Q.3** Explain SHA=1 algorithm & also comment on its difference with MD5 algorithm. 10

**Q.4** Explain Digital signature algorithm? 4

**Unit-IV**

**Q.1** What is an SSL protocol stack? 2

**Q.2** Briefly define each type of firewalls, along with its design goal? 10

**Q.3** Explain the application and architecture of IP security? 10

**Q.4** What is the difference between transport mode and tunnel mode in IPv6 security service? 4

**Unit-V**

**Q.1** Explain briefly steganography? 2

**Q.2** Explain the model of in deterministic security model using information theory? 10

**Q.3** Explain the model of deterministic security and comment on it difference with in deterministic model? 10

**Q.4** Comment on the difference between cryptography and steganography along with one example? 4

CSVTU Exam Paper Cryptography & Secure Communication Apr-May 2010