State Fermat’s theorem with an example. Given the prime number p=29 and its primitive root g=8, private key sender with X=9 and random integer K=11, encrypt the message m=13 using ElGamal cryptosystem. [10]
2.
Define discrete logarithm. Explain the procedure of sharing the secret key in Diffie Hellman. [5]
3.
What is the role of the prime number in the Euler totient Function? Find the GCD of 12 and 16 using the Euclidean algorithm. [5]
Cryptographic Hash Functions and Digital Signatures
1.
Compare the SHA parameters between SHA-1 and SHA-2 families. Decrypt the cipher text DRIJ with the key using the Hill cipher.
$\begin{pmatrix} 7 & 8 \\ 11 & 11 \end{pmatrix}$
[10]
2.
Define digital signature. Describe the approaches of DSS. [5]
3.
Write down any two limitations of MAC. What do policy and mechanism mean in cryptography? Describe with a scenario. [5]
Introduction and Classical Ciphers
1.
Among monoalphabetic and polyalphabetic cipher, which one is more vulnerable? Justify your statement. Which types of keys are considered weak keys in DES? Explain the round operation in IDEA. [10]
Malicious Logic
1.
Write short notes on: a. Classes of Intruder b. SSL c. DoS Attack [5]
Network Security and Public Key Infrastructure
1.
What is the task of a firewall? List the elements of X.509. [5]
2.
How does the nature of worms differ from viruses? Define PKI with its architecture model. [5]
Symmetric Ciphers
1.
Distinguish between stream cipher and block cipher. Encrypt the message WE ARE IN SAME RACE UNTILL OVER LIVE END using Rail fence cipher using 4 as a number of rails. [5]
2.
Explain the procedure of mix column transformation in AES with an example. [5]