**JNTU PAPERS**

**JNTU IV B.Tech I Semester Supplimentary Examinations, February 2008**

** Network Security And Cryptography**

**(Computer Science & Engineering)**

**SET-II**

1. (a) What are the various components of symmetric cipher model? Explain.

(b) Write short notes on crypto analysis.

2. Demonstrate that Blow Fish decryption is inverse of Blowfish encryption.

3. (a) Consider the Elliptic curve E11 (1,6) that is , the curve is defined by

y2 =x3 + x + 6 with a modulus of P=11.Determine all of the points in E11(1,6)

(b) For E11(1,6), consider the point G=(2,7) Compute the multiples of G from 2G through 4G.

4. (a) Explain in detail about Extended Euclid’s Algorithm.

(b) Determine Multiplicative inverse of 550 in GF(1759).

5. Explain Secure Hash Algorithm.

6. Explain X.509 Authentication services.

7. (a) What are the basic approaches to building SAs?

(b) What are the roles of the Oakley key determination protocol and ISAKMP in

IPSec?

8. Write notes on

(a) Viruses

(b) Worms

(c) Bacteria.