Introduction to Cryptography 2072
Attempt all questions.
1. Answer the following questions in short (Any Five). (5 × 2 = 10)
a. What does Euler
Totient function means? What will be the value of PHI (119)?
b. What properties does a good hash function should have?
c. What is the purpose
of S-Box in DES?
d. Define each of the
terms confidentiality, integrity and availability.
e. What do you mean by
primitive root of a prime number p? Is 3 a primitive root of 7?
f. Describe the concept
behind public key infrastructure.
g. What are the possible
phases that a virus can go through, during its life cycle?
2. a) In a RSA system, a user has chosen the primes 5 and 19 to create a key pair. The public key is {e=5, n=?} and the private key is {d=?, n=?}. Decide the private key {d, n}. Show encryption and decryption process for the message “TOGA”
b) Encrypt the message “MEET ME TONIGHT” using the
Hill cipher with the key 
. Show your calculations and the result.
3. a) Differentiate between SSL Session and SSL Connection. How SSL Record protocol provides confidentiality and message integrity.
b) What basic arithmetic and logical functions are
used in SHA-1?
4. a) Briefly describe about MixColumns and AddRoundKey stages in AES. How many bytes in a state are affected by ShiftRows round?
b) List the participants of Secured Electronic
Transaction (SET). Discuss the key features of SET.
5. a) In which situation using Kerberos system seem to be good? Describe what the major components of Kerberos system are.
b) Given the plaintext ”LOST IN PARADISE”, compute the ciphertext
for
i. The Ceaser cipher
with key = 5
ii.
The Railfence cipher with rails = 4
6. a) Differentiate between direct digital signature and arbitrated digital signature. How signing and verifying process is done in Digital Signature Standard.
b) What do you mean by Man-in-Middle attack? Is man in
middle attack possible in Diffie-Hellman algorithm for key exchange? How?