PARISUTHAM INSTITUTE OF TECHNOLOGY & SCIENCE
DEPARTMENT OF COMPUTER SCIENCE & ENGINEERING
PREVIOUS YEAR UNIVERSITY QUESTION PAPERS
CS1353
–
CRYPTOGRAPHY & NETWORK SECURITY
I

B.E Computer Science IT 1352

CRYPTOGRAPHY AND
NETWORK
SECURITY Question paper
PART A

(10*2=20 marks)
:
1. When an encryption algorithm is said to be computationally secure?
2. If a bit error occurs in plain text block P1, how far does the error propagate in CBS
mode of DES and 8

bit CFB mode of DES?
3. In RC
5

CBC

Pad mode, the cipher will be longer than the plaintext at most the size of
a single RC5 block. Why?
4. When an integer a, less than n is said to be the primitive root of n?
5. Define the one way property to be possessed by any hash function.
6. What
is the block size of MD5 and how many bits are produced as the message
digest?
7. What is the role of Ticket Granting Server in inter realm operations of Kerberos?
8. Why the leading two octets of message digest are stored in PGP message along with
the enc
rypted message digest?
9. How the passwords are stored in password file in UNIX operating system?
10. What is the role of bastion host?
PART B

(5*16=80 marks)
:
11. (a) (i) What are the criteria used while designing the DES algorithm?(8 )
(ii) In AES, how
the encryption key is expanded to produce keys for the 10 rounds. (8 )
(OR)
(b) (i)Explain the generation of subkey and S Box from the given 32 bits key by
Blowfish. (8 )
(ii) Describe the block modes of operations of DES with their advantages. (8 )
12.
(a) (i) write the detailed description of RSA algorithm. (8 )
(ii) How discrete logarithm is evaluated for a number? What is the role of discrete
logarithms in the Diffie

Hellman key exchange in exchanging the secret key among two
users? (8 )
(OR)
(b)(i) S
tate the requirements for the design of an Elliptic Curve Crypto system. Using
that, explain how secret keys are exchanged and messaged are encrypted. (8 (ii)
Describe any two applications of public key cryptosystem. (8 )
13. (a) (i) What are Digital Sign
ature Algorithms and show how signing and verification
is done using DSS. (8 )
(ii) Explain how birthday attack is done. (8 )
(OR)
(b) Describe the MD5 message digest algorithm with necessary block diagram. (16)
14. (a)(i) Describe the authentication dial
ogue used by Kerberos for obtaining required
services. (8 )
(ii) Explain the format of the X.509 certificate. (8 )
(OR)
(b) Describe how PGP provides confidentiality and authentication service for e

mail
applications. (8 )
15. (a)(i) Explain any two appro
aches for intrusion detection. (10)
(ii) Suggest any three password selection strategies and identify their advantage and
disadvantages if any. (6)
(OR)
(b) (i) What kind of attacks is possible on packet filtering firewalls and suggest
appropriate counter
measures. (8 )
(ii) Describe the familiar types of firewall configurations. (8 )
II

IT1352

Cryptography and Network Security(2007)
PART

A
(
2*10=20
):
1.What is cryptography?
2.Give any four names of substitution techniques
3.What are the services
defined by x.800?
4.What is the purpose of Diffie

Hellman algorithm?
5.Define man in the middle attack
6.List design objectives for HMAC
7.What is MAC?
8.What are the requirements for digital signature?
9.Give the Kerberos simple dialogue
10.What is firewa
ll?
PART

B
(
5*16=80
):
11 a(i) Briefly explain about OSI security architecture (8 )
(ii) Explain briefly about data encryption standard (8 )
(OR)
b(i) Explain briefly about block cipher principles and modes of operation (12)
(ii) Explain about traffic
confidentiality (4)
12 a(i) Explain briefly about Diffie

Hellman key exchange (16)
(OR)
b(i) Explain briefly about public key cryptography (8 )
(ii) What is the use of RSA algorithm? (8 )
13 a(i) Expalin briefly about MD5 message digest algorithm (12)
(ii) What is the use of authentication protocols? (4)
(OR)
b(i) Explain briefly about RIPEMD (16)
14 a(i) Explain about Kerberos (16)
(OR)
b(i) Explain briefly about web security (16)
15 a(i) Discuss the design principles of firewall (8 )
(ii) What is me
ant by password management? (8 )
(OR)
b(i) What is meant by virus and explain briefly about threats? (16)
III

IT1352

CRYPTOGRAPHY
AND NETWORK SECURITY
PART

A
(
2*10=20
)
:
1. What is encryption?
2. What is product cipher?
3. Difference between
conventional encryption and public key encryption
4. What is trap door?
5. Define Hash function
6. Define PEM
7. What is MIME?
8. What is Bastion host?
9. What are the types of firewall?
10. What is honeypot?
PART

B
(
5*16=80
):
11 a(i) Explain briefly abo
ut classical encryption techniques (16)
(OR)
b(i) What is the evaluation criteria for AES? (16)
12 a(i) Briefly explain about elliptic curve architecture and cryptography (16)
(OR)
b(i) Explain briefly about RSA algorithm (8)
(ii) Explain briefly about ke
y management (8)
13 a(i) What is the need of secure hash algorithm (10)
(ii) What is digital signature standard? (6)
(OR)
b(i) Explain briefly about HMAC digital signature (16)
14 a(i) What is PGP and Explain briefly about its working principles (16)
(OR
)
b(i) Explain In detail IP security (16)
15 a(i) What is the need of virus counter measures? (8)
(ii) What are the types of firewall? (8)
(OR)
b(i) Explain in detail Intrusion detection (8)
(ii) Explain in detail trusted systems (8)
IV

B.E/B.Tech
DEGREE EXAMINATION, May/june 2009 (Regulation 2004)
Computer Science and Engineering
IT 1352
–
CRYPTOGRAPHY AND NETWORK SECURITY
PART

A
:
1. What are the key principles of security?
2. How does simple columnar transposition work?
3. Show that 3 is
a primitive root of 7
4. Find the GCD of 2740 and 1760 using Euclidian algorithm.
5. Why is SHA more secure than MD5?
6. Mention the fundamental idea of HMAC.
7. What are the security options PGP allows when sending an email message?
8. How IPSec does offers the authentication and confidentiality services?
9. What is IP address spoofing?
10. What are the common technique used to protect a password file?
PART
–
B
:
11. (a) (i
) Draw the general structure of DES and explain the encryption decryption
process.(10)
(ii) Mention the strengths and weakness of DES algorithm. (6)
Or
(b) Describe the block cipher modes of operation in detail. (16)
12. (a)(i) Explain how encryption
and decryption are done using RSA crypto system (8)
(ii) How do elliptic curves take part in Encryption and Decryption process (8)
Or
(b) Users A and B use the Diffie Hellman key exchange technique a common prime
q=11 and a primitive root alpha=7.
(i) I
f user A has private key XA =3 what is A’s public key YA?
(ii) If user B has private key XB =6 what is B’s public key YB?
(ii
i
) What is the shared secret key? Also write the algorithm.(4)
(iv) How man in middle attack can be performed in Diffie Hellman
algorithm
13. (a) (i) how does SHA

1 logic produce message digest? (10)
(ii) Explain the challenges/ response approach in mutual authentication.(6)
Or
(b) (i) Explain Digest signature algorithm(DSA) in detail. (10)
(ii) What is Message Authentication
? Explain. (6)
14. (a) How does PGP provide confidentiality and authentication service for e

mail and
file storage applications? Draw the block diagram and explain its components. (16)
Or
(b) (i
) Bring out the importance of security associations in IP. (6)
(ii) Describe the SSL Specific protocol
–
Handshake action in detail. (10)
15. (a) Explain the types of Host based intrusion detection. List any 2 IDS software
available. (16)
Or
(b)(i) Wh
at are the positive and negative effects of firewall? (8)
(ii) Describe packet filtering router in detail. (8)
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