Let us consider the 4 bits key set as {1100, 1010, 0000, 1111, 0101, 1001} and input text as {1011, 1110, 1011, 1000}. Now trace the first full round operation of IDEA algorithm.

What is Message Authentication Code? List the operation of computing digest value in different passes of MD4. Describe about Needhom-Schroeder protocol.

Why do we need discrete logarithm? Illustrate with an example. Consider a Diffie-Hellman scheme with a common prime p = 13 between user A and user B. Suppose public key of A is 10 and public key of B is 8. Now determine their private keys and shared secret key. Select any valid primitive root of 13.

Show the encryption of plain text “ALGORITHM” using the key “PSEUDOCODE” using playfair cipher.

Discuss the working mechanism of kerberos protocol.

What is the use of firewall? How circuit level gateway differs from stateful inspection firewall?

What is intrusion ? Explain any two types of intrusion detection system.

Find the multiplicative inverse of polynomial {95} using extended euclidean Algorithm.

What is DoS attack ? Discuss about PKI trust model.

Using Vignere cipher with key = “worlds”, encrypt the plain text “hello everyone”.

Describe the different modes of block cipher.

Write short notes on (any two)

1. Totient value of any positive integer.
2. Properties of hash function.
3. Virus or Worms.