This document contains a question bank for the subject Cryptography and Network Security. It includes questions grouped under different units of the subject: Introduction and Number Theory, Block Ciphers and Public Key Cryptography, Hash Functions and Digital Signatures. For each question, it provides the question number, question, marks allotted, knowledge level and number of times the question may appear in the assessment. The document also provides details of the subject code, name, class, staff in-charge and course code.

1. DEPARTMENT OF INFORMATION TECHNOLOGY
CS6701
CRYPTOGRAPHY AND NETWORK
SECURITY
Question Bank
IV IT
2019 – 2020 ODD
Prepared by
R. ARTHY, AP/IT

2. DEPARTMENT OF INFORMATION TECHNOLOGY
Academic year 2019 – 2020 ODD Subject Code CS6701
Year / Semester IV IT Course Code (as
per NBA)
C402
Name of the Subject CRYPTOGRAPHY AND NETWORK SECURITY
Name of Staff with
designation/Department
R. ARTHY
Course Outcome
CO
Code
CO Statement Blooms
Taxonomy
Level
C402.1
Make use of classical encryption techniques and number
theory concepts to perform encryption and decryption process
K3
C402.2
Utilize appropriate block cipher, stream cipher algorithms and
public key cryptography algorithms for data security
K3
C402.3
Show how hash functions and digital signature supports
authentication
K2
C402.4
Explain various authentication services and system level
security
K2
C402.5
Outline the threats in Layered Architecture of Networks and
discuss various security approaches.
K2
Prepared by
Name & Signature of Staff member Signature of HOD

3. DEPARTMENT OF INFORMATION TECHNOLOGY
Subject Code : CS6701 Subject Name : Cryptography and Network Security
Class : IV IT / VII Subject In – Charge : R. Arthy, AP/IT
Course Code : C402
QUESTION BANK
UNIT I
INTRODUCTION & NUMBER THEORY
Services, Mechanisms and attacks-the OSI security architecture-Network security model-
Classical Encryption techniques (Symmetric cipher model, substitution techniques,
transposition techniques, steganography). FINITE FIELDS AND NUMBER THEORY:
Groups, Rings, Fields-Modular arithmetic-Euclid‟s algorithm-Finite fields- Polynomial
Arithmetic –Prime numbers-Fermat‟s and Euler‟s theorem-Testing for primality -The
Chinese remainder theorem- Discrete logarithms
Q. No Question
Marks
Allotted
Knowledge
Level
Number
of Times
in AU
PART – A
INTRODUCTION
1. Differentiate between Active attacks and Passive Attacks. 2 K2 2
2. Define Steganography. 2 K1
3. Define cryptanalysis. 2 K1
4. Classify the security threats. 2 K1
5. Define cryptography. 2 K1
6. What is traffic padding? What is its purpose? 2 K1
7. What are the security mechanisms provided through cryptography? 2 K1
8. Why network needs security? 2 K1
NUMBER THEORY
9. State Euler’s theorem. 2 K1 1
10. Find 117
mod 13. 2 K2
11. Define primitive root. 2 K1
12. Why is Modular arithmetic used in cryptography? 2 K1
13. Why are Random numbers used in Network Security? 2 K1

4. 14. Find GCD of 1070 and 1066 using Euclid algorithm. 2 K2 2
15. Sate Fermat’s theorem. 2 K1 2
16. Define order of a group. Find the order of all elements in G =<
Z10*,*>.
2 K1 1
CLASSICAL ENCRYPTION TECHNIQUES
17. Compare Substitution and Transposition techniques. 2 K2
18. Compare Block and Stream cipher mechanisms. 2 K2
19. Illustrate the two basic functions used in encryption algorithms. 2 K2
20.
Decipher the following cipher Text using brute
force attack: CMTMROOEOORW (Hint:
Algorithm-Rail fence).
2 K3
21. Give an example each for substitution and transposition ciphers. 2 K2
22.
Convert the Given Text “kamaraj college of engineering and
technology” into cipher text using Rail fence Technique.
2 K2
23. Identify the list of keys that are required for two people to
communicate via a cipher?
2 K3
24. Why is asymmetric encryption bad for huge data? Specify the
reason.
2 K2 1
PART B
NUMBER THEORY
25. State and Derive Fermat’s theorem & Euler’s
theorem.
13 K2 1
26. State and explain Chinese remainder theorem with example. 13 K2 3
27. Explain the following in detail
(i) Modular Exponentiation
(ii) Finite fields
13
K2 1
28. Explain the following. Groups, Rings and Field. 13 K2 1
INTRODUCTION
29. Explain the different security mechanisms focused by OSI
Security architecture.
13 K2 1
CLASSICAL ENCRYPTION TECHNIQUES
30. Describe the substitution Techniques in detail. 13 K2 4
31. Describe the Transposition Techniques in detail. 13 K2 2
PART C
CLASSICAL ENCRYPTION TECHNIQUES
32. Encrypt the message “PAY” using hill cipher with the
following key matrix and show the decryption to get original
plain text.
| 17 17 5 |
K= | 21 18 21 |
| 2 2 19 |
15 K3

5. 33. Given Cipher text “YMJTYMJWXNIJTKXNQJSHJ”,
knowing the messageis encrypted by Caesar cipher and k=5.
Try to decrypt the message.
15 K2
34. Differentiate between transposition cipher and substitution
cipher. Apply two
stage transpositions Cipher on the “treat diagrams as single
units” using the keyword “sequence”.
15 K2
35. (i) State the rules to perform encryption using playfair cipher
and encrypt
“snowshooos” using „monarchy‟ I and J count as one letter and
x is the filler letter.
(ii) Encrypt the word “Semester Result” with the keyword
“Examination” using playfair cipher.
15 K2 2
36. State and explain Chinese Remainder theorem. Using the same,
find an integer that has a remainder of 3 when divided by 7,4
when divided by 13 but is divisible by 12.
15 K2 3
Subject In – Charge Subject Matter Expert HoD/IT

6. DEPARTMENT OF INFORMATION TECHNOLOGY
Subject Code : CS6701 Subject Name : Cryptography and Network Security
Class : IV IT / VII Subject In – Charge : R. Arthy, AP/IT
Course Code : C402
QUESTION BANK
UNIT II
BLOCK CIPHERS & PUBLIC KEY CRYPTOGRAPHY
Data Encryption Standard-Block cipher principles-block cipher modes of operation-
Advanced Encryption Standard (AES)-Triple DES-Blowfish-RC5 algorithm. Public key
cryptography: Principles of public key cryptosystems-The RSA algorithm-Key management
- Diffie Hellman Key exchange-Elliptic curve arithmetic-Elliptic curve cryptography.
Q. No Question
Marks
Allotted
Knowledge
Level
Number
of Times
in AU
PART – A
BLOCK CIPHERS
1. Define RC5. 2 K1
2. What are the five modes of operation of block cipher? 2 K1
3. State whether symmetric and asymmetric cryptographic algorithm
need key exchange.
2 K1
4. State few application of RC5 algorithm. 2 K1
5. What primitive operations are used in RC5? 2 K1
6. Why is the middle portion of triple DES a decryption rather than
encryption?
2 K1
7. What is avalanche effect? 2 K1 1
8. Is it possible to use the DES algorithm to generate message
authentication code? Justify.
2 K2
9. Differentiate between sub bytes and sub words. 2 K2
10. What is triple encryption? How many keys are used in triple
encryption?
2 K1
11. Give the five modes of operations of block cipher. 2 K1 1
12. If a bit error occurs in plain text block b1, how far does the error
propagate in CBC mode of DES?
2
K2 1
13. Brief the strengths of triple DES. 2 K1 1
14. What is the need of AES? 2 K1 1

7. PUBLIC KEY CRYPTOSYSTEM
15. List the applications of the public key crypto systems. 2 K1
16. Describe any one attack in RSA. 2 K2
17. Differentiate public key and conventional encryptions. 2 K2 1
18. Name the principle elements of a public key crypto system. 2 K1
19. List four general characteristics of schema for the distribution of the
public key.
2 K1
20. What requirements must a public key crypto system provide to fulfill
the secure algorithm?
2 K1
21. Perform encryption and decryption using RSA algorithm for the
following. p=7, q=11; e=17; m=8.
2 K2 1
22. Are strong primes necessary in RSA? State reasons. 2 K1
23. What are the roles of public and private keys? 2 K1
24. Give the significance of hierarchical key control. 2 K1 1
KEY EXCHANGE ALGORITHMS
25. What is the significance of Diffie Hellman key exchange? 2 K1
26. What is an elliptic curve cryptography? 2 K1 1
PART B
BLOCK CIPHERS
27. Describe the following modes of operation in block cipher.
(i) Electronic code book and Cipher block chaining.
(ii) Cipher feedback mode and output feedback mode.
13 K2 2
28. Explain the RC5 method used for encryption and decryption 13 K2 2
29. Draw the general structure of DES and explain how encryption and
decryption are carried out. Mention also the strength of DES
algorithm.
13 K2 3
30. Explain how encryption is done using Advanced Encryption Standard
with necessary diagram.
13 K2 2
31. For each of the following elements of DES, indicate the comparable
element in AES if available.
i. XOR of subkey material with the input to the function
ii. f function
iii. Permutation P
iv. Swapping of halves of the block
13 K2 1
KEY EXCHANGE ALGORITHM
32. Explain Diffie Hellman key exchange algorithm in detail with an
example.
13 K2 2
33. Discuss how discrete logarithm is evaluated for a number? What is
the role of discrete log in the Diffie-Hellman key exchange in
exchanging the secret keyamong two users?
13 K2 2
34. Users A and B use the Diffie- Hellman key exchange technique, a
common prime q=11 and a primitive root alpha=7.
(i) If user A has private key XA=3.What is A‟s public key YA?
13 K2 2

8. (ii)If user B has private key XB=6. What is B‟s public key YB?
(iii) What is the shared secret key? Also write the algorithm.
35. Explain man in the middle attack with respect to Diffie Hellman key
exchange
13 K2 1
PART C
PUBLIC KEY CRYPTOSYSTEM
36. (i) Explain RSA Algorithm.
(ii)Demonstrate the encryption and decryption for the RSA algorithm
parameters.
P=3, Q=11, E=7, d=?, M=5.
15 K2 3
37. Describe the mathematical foundations of RSA algorithm. Perform
encryption decryption for the following:
P=17, q=7, e=5, n=119, message=”6”. Use Extended Euclid‟s
algorithm to find the private key.
15 K2 3
KEY EXCHANGE ALGORITHM
38. User A wants to send some confidential information to user B and
encrypt the confidential information using a shared key. User A does
not want to send the shared key to user B so, User A decides to use
Diffie – Hellman key exchange algorithm to exchange the key. To do
this User A has a private key value as 3 and User B has a private key
value as 6. They also have a common prime as 11 and primitive root
as 7. Help the user A and B to compute public key and shared key
15 K3
39. Explain briefly about Diffie Hellman key exchange algorithm with its
merits and demerits.
15 K2 1
DATA ENCRYPTION SYSTEM
40. Alice wants to send the secret bit information 10110110 to Bob. Alice
had a hope in encrypting the secret bit information using the key
1000100100. She is in need of an expert in cryptography to encrypt
the message using S-DES with following data. Help her is performing
encryption and send the cipher text to Bob.
P10
3 5 2 7 4 10 1 9
P8
6 3 7 4 8 5
IP
2 6 3 1 4 8 5 7
E/P
4 1 2 3 2 3 4 1
15 K3

9. S0 =
c0 c1 c2 c3
r0 1 0 3 2
r1 3 2 1 0
r2 0 2 1 3
r3 3 1 3 2
S1 =
c0 c1 c2 c3
r0 0 1 2 3
r1 2 0 1 3
r2 3 0 1 0
r3 2 1 0 3
P4
2 4 3 1
IP-1
4 1 3 5 7 2 8 6
PUBLIC KEY CRYPTOSYSTEM
41. Why ECC is better than RSA? However, why is it not widely used?
Add justification to the above claim form your point of view.
7 K2 1
42. Explain public key cryptography and when it is preferred. 8 K2 1
Subject In – Charge Subject Matter Expert HoD/IT

10. DEPARTMENT OF INFORMATION TECHNOLOGY
Subject Code : CS6701 Subject Name : Cryptography and Network Security
Class : IV IT / VII Subject In – Charge : R. Arthy, AP/IT
Course Code : C402
QUESTION BANK
UNIT III
HASH FUNCTIONS AND DIGITAL SIGNATURES
Authentication requirement – Authentication function – MAC – Hash function – Security of
hash function and MAC –MD5 - SHA - HMAC – CMAC - Digital signature and
authentication protocols – DSS – EI Gamal – Schnorr
Q. No Question
Marks
Allotted
Knowledge
Level
Number
of
Times
in AU
PART - A
AUTHENTICATION
1. What are the requirements for message authentication? 2 K1
2. What types of attacks are addressed by message authentication? 2 K1
3. Define the classes of message authentication function. K1
4. What is meant by MAC? 2 K1 1
5. How is the security of a MAC function expressed? K1 1
6. What are the requirements / properties of hash function? 2 K1 3
7. Specify the various types of authentication protocols. K1 1
HASH FUNCTIONS
8. What is input block size of MD5? 2 K1
9. Differentiate MAC and hash function. 2 K2 1
10. Differentiate between message authentication code and one way hash
function.
2 K2
11. Why is SHA more secure than MD5? 2 K1
12. List any three hash algorithm. 2 K1
13. Compare MD5 and SHA algorithm. 2 K2
14. What is the role of compression function in hash function? 2 K1 1

11. 15. Define one way property in hash function? 2 K1
DIGITAL SIGNATURE
16. Distinguish between direct and arbitrated digital signature. 2 K2
17. What is digital signature? 2 K1
18. What are the properties a digital signature should have? 2 K1
19. What are the security services provided by digital signature? 2 K1
20. Compare DSA and ElGamal algorithm. 2 K2
21. How is digital signature different from conventional? Give any two. 2 K1
22. List the authentication requirements. 2 K1
23. What are the two approaches of digital signature? 2 K1
24. Mention the significance of signature function in DSS approach. 2 K1 1
25. Compare and contrast the attacks on digital signatures with attacks on
cryptosystems.
2 K2
1
26. If two points p=(x1,y1) and q=(x2,y2) where x1!=x2 and y1!=y2 find
third point r(x3,y3) = p+q on ECC.
2 K2
1
PART B
HASH FUNCTIONS
27. Where are hash functions used? What are the characteristics that are
needed in secure hash function? Write about the security of hash
functions and MACs.
8 K2 1
28. Compare the features of SHA and MD5 algorithm. 7 K2 1
29. Describe MD5 Algorithm to generate message digest in detail. 13 K2 3
30. Describe SHA Algorithm to generate message digest in detail. 13 K2
31. Describe Secure Hash Algorithm to generate message digest in
detail.
13 K2 2
32. Explain the birthday attacks in hash. 7 K2 1
DIGITAL SIGNATURE
33. Examine Digital signature with ElGamal public key cryptosystem. (Or)
Explain in detail ElGamal Public key cryptosystems with an example.
13 K2 3
34. Describe digital signature algorithm and show how signing and
verification is done using DSS.
13 K2 3
35. Explain the steps involved in Schnorr digital signature scheme. 13 K2 1
AUTHENTICATION
36. Write a brief notes on X.509 authentication services. 13 K2
PART C
DIGITAL SIGNAUTURE

12. 37. Using the Elgamal scheme, let q = 3119, alpha = 2 and XA = 127. Choose
K = 307. Find the value of V1 and V2 if m = 320.
15 K3
38. Using Schnorr scheme, let q = 83, p = 997, alpha = 2 and s = 23. Choose r
= 11. If M = 400 and h(400) = 100, Find the value of x, y and x’. Is x = x’
mod p.
15 K3
39. Using the DSS scheme, let q = 101, p = 8081, x = 61 and h = 3. Choose k
= 61. Generate the signature if h(M) = 5000. Verify the signature.
15 K3
Subject In – Charge Subject Matter Expert HoD/IT

13. DEPARTMENT OF INFORMATION TECHNOLOGY
Subject Code : CS6701 Subject Name : Cryptography and Network Security
Class : IV IT / VII Subject In – Charge : R. Arthy, AP/IT
Course Code : C402
QUESTION BANK
UNIT IV
SECURITY PRACTICE & SYSTEM SECURITY
Authentication applications – Kerberos – X.509 Authentication services - Internet Firewalls
for Trusted System: Roles of Firewalls – Firewall related terminology- Types of Firewalls -
Firewall designs - SET for E-Commerce Transactions. Intruder – Intrusion detection system –
Virus and related threats – Countermeasures – Firewalls design principles – Trusted systems
– Practical implementation of cryptography and security.
Q. No Question
Marks
Allotted
Knowledge
Level
Number
of Times
in AU
PART - A
AUTHENTICATION PROTOCOL
1. What are the Classes of message authentication function? 2 K1
2. State the reasons to revoke a certificate before its expiry time. 2 K1 1
3. Assume a client C wants to communicate with a server S using
Kerberos protocol, how can it be achieved?
2 K2
4. What is Kerberos? What are the uses? 2 K1
5. What do you mean by trusted systems? 2 K1
6. List 4 requirements defined by Kerberos. 2 K1
7. What is the role of Ticket Granting Server in inter realm operations of
Kerberos?
2 K1
8. What is the purpose of X.509 standard? 2 K1
9. Write a simple authentication dialogue used in Kerberos. 2 K1 1
10. List any 2 applications of X.509 certificates. 2 K1 1
11. What is X.509 certification and its revocation? 2 K1 1
FIREWALLS
12. List the design goals of firewalls. 2 K1
13. Enlist commonly used firewalls from threats of security. 2 K1

14. 14. Prepare a short note on application level gateway? 2 K1
15. Define firewall. 2 K1
16. Does the firewall ensure 100% security to the system? Comment. 2 K1
17. Define the roles of firewalls. 2 K1 1
18. State the difference between threats and attacks. 2 K2 1
MALICIOUS SOFTWARE
19. Define Worm. 2 K1
20. Differentiate spyware and virus. 2 K2
21. Define virus. Specify the types of viruses? 2 K1
22. Define Zombie. 2 K1 1
INTRUSION DETECTION
23. Who is an intruder? 2 K1
24. What are the advantages of intrusion detection system over firewall? 2 K1
25. List the 3 classes of Intruders. 2 K1 3
SET
26. Define: SET. 2 K1 1
PART B
AUTHENTICATION PROTOCOL
27. Discuss elaborately, how kerberos provides different authentication
services with necessary diagrams.
13 K2 3
28. Compare statistical anomaly detection and rule based intrusion
detection system in detail.
8 K2
29. Explain with the help of an example, how a user’s certificate is
obtained from another certification authority in X.509 scheme.
13 K2
30. Show how is key generated from password in Kerberos? 13 K2
31. Discuss client server mutual authentication with example flow
diagram.
13
K2 1
MALICIOUS SOFTWARE
32. What are viruses? Explain the virus related threats and the counter
measures applied.
13 K2 2
33. Discuss on the significant types of virus categories. 13 K2 2
FIREWALLS
34. Illustrate the three common types of firewalls with diagrams. 13 K2 5
35. How does screened host architecture for firewalls differ from
screened subnet firewall architecture? Which offer more security for
the information assets remain on the trusted network? Explain with
neat sketch?
13 K2

15. 36. Describe the different types of firewalls and its configuration in detail. 13 K2 1
SET
37. Explain in detail about Secure Electronic Transaction with neat
diagram.
13 K2 2
INTRUSION DETECTION SYSTEM
38. Explain Intrusion detection system in detail with suitable diagram. 13 K2 1
PART C
INTRUSION DETECTION SYSTEM
39. Network security is a complex and systematic project. The intrusion
detection system is the first line of defense against network security.
Snort is a famous intrusion detection system in the field of open
source software. It is widely used in the intrusion prevention and
detection domain in the world. Help the researchers to frame a
system that prevents the unauthorized access.
15 K3
40. There are many risk of network attacks in the Internet environment.
Now – a – days, Security on the internet is a vital issue and therefore,
the intrusion detection is one of the major research problems for
business and personal networks which resist external attacks. There
require a system that monitors the network or system activities for
malicious activities and unauthorized access to devices. Identify such
system and give a brief introduction with suitable diagrams.
15 K3
FIREWALL
41. Mapping of the security policy on the procedures and technical
designs is must which has to be followed and implemented while
connecting to the internet. Identify the system that performs this
mapping and describe the relevant architecture.
15 K3
Subject In – Charge Subject Matter Expert HoD/IT

16. DEPARTMENT OF INFORMATION TECHNOLOGY
Subject Code : CS6701 Subject Name : Cryptography and Network Security
Class : IV IT / VII Subject In – Charge : R. Arthy, AP/IT
Course Code : C402
QUESTION BANK
UNIT V
E-MAIL, IP & WEB SECURITY
E-mail Security: Security Services for E-mail-attacks possible through E-mail - establishing
keys privacy-authentication of the source-Message Integrity-Non-repudiation-Pretty Good
Privacy-S/MIME. IPSecurity: Overview of IPSec - IP and IPv6-Authentication Header-
Encapsulation Security Payload (ESP)-Internet Key Exchange (Phases of IKE, ISAKMP/IKE
Encoding). Web Security: SSL/TLS Basic Protocol-computing the keys- client
authentication-PKI as deployed by SSLAttacks fixed in v3-Exportability-Encoding-Secure
Electronic Transaction (SET).
Q. No Question
Marks
Allotted
Knowledge
Level
Number
of Times
in AU
PART - A
E – MAIL SECURITY
1. What are the services provided by PGP? 2 K1
2. Define S/MIME. 2 K1
3. Why is R64 conversion useful for email generation? 2 K1
4. Why is email compatibility function needed in PGP? 2 K1
5. What are the elements of MIME? 2 K1
6. Why does PGP generate a signature before applying compression? 2 K1
7. How can the signed data entity of S/MIME be prepared? Write the
steps.
2 K1
8. Give the reason for using PGP. 2 K1
9. How can the signed data entity of S/MIME be prepared? 2 K1 1
IP SECURITY
10. Draw the header format for an ISAKMP message. 2 K1
11. What are the protocols used to provide IP security? 2 K1
12. Give the applications of IP Security. 2 K1
13. What is tunnel mode in IP security? 2 K1

17. 14. What are the services provided by IPSec? 2 K1
15. Expand and define SPI. 2 K1
16. Differentiate between transport mode and tunnel mode. 2 K2
17. Why does ESP include a padding field? 2 K1
18. Specify the purpose of IP payload in phase I and II inherent in
ISAKMP / IKE encoding.
2 K1 1
19. Justify the following statement:
“With a Network Address Translation (NAT) box, the computers on
your internal network do not need global IPV4 addresses in order to
connect to the Internet”
2 K2 1
WEB SECURITY
20. What is meant by SET? What are the features of SET? 2 K1
21. What is the purpose of SSL alert protocol? 2 K1
22. What are the steps involved in SET Transactions? 2 K1
23. Mention the purpose of handshake SSL protocol. 2 K1 1
24. Define Botnets. 2 K1 1
25. What is the need for trusted OS? 2 K1 1
26. What is dual signature? What is its purpose? 2 K1
PART B
E – MAIL SECURITY
27. Summarize the Operations of PGP? Brief the various services
provided by PGP.
13 K2 3
28. Draw and explain PGP Cryptographic function for
Authentication and confidentiality.
13 K2
29. Explain the key rings and its significance in PGP. Show how the
message generation from sender to receiver and explain with
suitable diagram.
13 K2 2
30. Explain S/MIME certification processing. 8 K2 1
IP SECURITY
31. Summarize the authentication header of IP and Discuss the
encapsulating security payload of IP?
13 K2 2
32. Explain IPSec protocols in detail. Explain the advantages of IPSec. 13 K2 1
33. Briefly explain about Transport Level Security. 7 K2 2
WEB SECURITY
34. List the different protocols of SSL. Explain in detail Handshake
protocol and Tell how does the server get authenticated to client in
SSL?
13 K2
35. What is the importance of web security? Explain secure socket
layer protocol.
13 K2 3

18. 36. What is a dual signature and what is its purpose? With neat
blockdiagram illustrate the Secure Electronic Transaction.
13 K2 1
PART C
E – MAIL SECURITY
37. Evaluate the performance of PGP. Compare it with S/MIME. 15 K3 1
38. Now – a – days, every document is shared through electronic
media. There should be some system or protocol that provides
security to the document either in terms of confidentiality or in
authentication. Identify the protocol that provides the CIA to the
document that is shared electronically.
15 K3
WEB SECURITY
39. Web applications are highly used to transfer currency between
the consumer and vendor. The vendor has to trust the consumer
and consumer should trust the vendor. The E-trust is provided
by a system through which the complete secure transaction is
done. Brief the system with required diagrams such that both
vendor and consumer will trust each other.
15 K3
Subject In – Charge Subject Matter Expert HoD/IT