Computer Engineering Department

GTU IMPORTANT QUESTIONS BANK

Subject Name : Information ecurity

Subject Code
Semester

Unit 1:
1 Briefly explain any two active security attacks.
2 Discuss the following terms in brief:
- brute force attack - cryptography
3 Discuss the following terms in brief. - authentication - data integrity
4 Explain playfair cipher substitution technique in detail. Find out cipher
text for the following given key and plaintext. Key =
ENGINEERING Plaintext=COMPUTER
5 Write differences between substitution techniques and transposition
techniques.
6 What is symmetric key cryptography? What are the challenges of
symmetric key cryptography? List out various symmetric key algorithms
and explain Caesar cipher in detail.
7 Explain one time Pad in detail. What are the practical issues of this
algorithm?
8 What is symmetric key cryptography? What are the challenges of
symmetric key cryptography? List out various symmetric key algorithms
and explain Caesar cipher in detail.
9 Write a short note on “Hill Cipher”.
10 Explain data confidentiality, data authentication and data integrity.
11 Describe mono alphabetic cipher.
12 Explain playfair cipher with example.
13 Explain one time pad cipher with example.
Explain one time Pad in detail. What are the practical issues of this
algorithm?
14 Explain columnar transposition Cipher technique
15 Differentiate block cipher and a stream cipher
16 Encrypt the Message “Surgical Strike” with key “GUJAR” using
PLAYFAIR technique.
17 Distinguish between Symmetric encryption and Asymmetric encryption
using suitable example.
18 Describe the term: Authentication, Authorization, Integrity and Non –
 repudiation.
19 Encrypt the message "meet me at the usual place " using the Hill cipher
with the key 9 4
5 7
20 Explain Different type of Attacks on Crypto System.
21 Explain PGP with its Authentication and Confidentiality Operation.
22
Given key K= and plaintext =”ney”. Find out the
ciphertext applying Hill Cipher. Is Hill cipher strong against ciphertext
only attack or known plaintext attack? Justify the answer.
23 How cryptanalyst can exploit the regularities of the language? How
digrams can solve this problem? Use the key “hidden” and encrypt the
message “Message” using playfair cipher
24 Explain the rail fence cipher. Why a pure transposition cipher is easily
recognized?
25 What is the difference between a mono alphabetic cipher
and a polyalphabetic cipher?
26 Encrypt the message “GTU Examination”
using the Hill cipher algorithm with the key matrix

 
Show your
calculations and the result.
27 Perform encryption in Playfair Cipher algorithm with plain text as
“INFORMATION AND NETWORK SECURITY”, Keyword is
“MONARCHY”. (Note: 1.Put j and i both combine as a single field in 5*5
matrix).

Unit 2:
1 Explain single round of DES algorithm. Support your answer with neat
sketches.
2 Elaborate AES encryption & decryption with neat sketches.
3 Explain Byte substitution and Shift row operation of AES in detail.
4 Explain DES key generation process in detail
5 Explain avalanche effect in DES and discuss strength of DES in brief.
6 Describe various steps of AES.
7 Explain counter mode of DES operation.
8 Explain Byte substitution and Shift row operation of AES in detail.
9 Explain the VERNAM Cypher method.
10 Explain the difference between diffusion and confusion.
11 List out the various web security threats
12 What is meant by message digest? Give an example.
13 Explain how DES(Data Encryption standard) algorithm observes Fiestel
structure. Explain key generation and use of S-box in DES algorithm.
14 Briefly describe Mix Columns and Add Round Key in AES algorithm

Unit 3:
1 Explain triple DES with two keys.
2 Discuss Electronic code book and cipher feedback mode with neat
diagrams.
3 Write a short note on DES.
4 Explain double and triple DES.
5 Explain cipher feedback mode of DES operation.
6 Explain DES key generation process in detail.
7 Discuss in detail encryption and decryption process of DES.
8 (i) Explain working of ECB. Why ECB (Electronic code book) is rarely
used to encrypt message?
(ii) Why CFB(Cipher feedback mode) encrypted messages are less
subject to tampering than OFB(Output feedback mode)?
9 Explain the three approaches to attack RSA mathematically.
10 How meet in the middle attack is performed on double DES?
11 Explain CFB algorithm mode with diagram.

12 Explain Counter (CTR) algorithm mode with

diagram
Unit 4:
1 Explain RSA algorithm in detail with suitable example.
2 Discuss Diffie-Hillman key exchange algorithm in detail.
3 What are the principal elements of public-key cryptosystem? Explain in
brief.
4 P and Q are two prime numbers. P=7, and Q=17. Take public key E=5.
If plain text value is 6, then what will be cipher text value according to
RSA algorithm? Explain in detail.
5 What is PKI? What are the components of PKI? Explain Certificate
Authority in detail.
6 Consider the scenario where user A wants to send bulk data (data is in
GBs) to user B using networking. Data exchange has to be done in
confidential manner. The key which is used for encryption can be
intercepted by an attacker. Which is the most efficient and protected
way to achieve secure communication? Justify your answer in detail.
7 Explain key pair generation using RSA algorithm
8 Explain encryption and decryption using RSA.
9 Explain Diffie Hellman key exchange algorithm.
10 Explain man in middle attack in Diffie Hellman key exchange
11 P and Q are two prime numbers. P=7, and Q=17. Take public key E=5.
If plain text value is 6, then what will be cipher text value according to
RSA algorithm? Explain in detail.
12 In a public key cryptosystem using RSA algorithm, user uses two prime
numbers 5 and 7. He chooses 11 as Encryption key , find out decryption
key. What will be the ciphertext , if the plaintext is 2?
13 For Diffie-Hellman algorithm, two publicaly known numbers are prime
number 353 and primitive root of it is 3. A selects the random integer
97 and B selects 233. Compute the public key of A and B. Also
compute common secret key
14 What is the difference between a session key and a master key? List
four general categories of schemes for the distribution of public keys.
Unit 5:
1 Write requirements for hash function and briefly explain simple hash
 function.
2 Give differences between hash function and message authentication
codes.
3 “Only Hashing dose not ensures integrity of message in network
communication” – Justify your answer with suitable example.
4 Differentiate between hashing and encryption. What are the practical
applications of hashing? Compare MD5 and SHA1 hashing algorithms.
5 Explain HMAC algorithm.
6 Explain basic Hash code generation.
7 Explain HTTPS and SSH.
8 Discuss HASH function and its application in Crypto System.
9 Discuss clearly Secure Hash Algorithm with its real time application.
10 What is the difference between weak and strong collision resistance?
Consider the hash functions based on cipher block chaining, What kind
of attack can occur on this?
11 What is the role of a compression function in a hash function?

12 Explain working of Secure Hash Algorithm, with basic arithmetical and

logical functions used in SHA
Unit 6:
1 Write a note on : Message Authentication Codes
2 Explain MAC code generation using block cipher.
3 What is MAC ? How it useful in Crypto System.
4 Is a message authentication code (MAC) function is similar to
encryption. Does MAC provide authentication or confidentiality?
Justify your answer
5 What problem was Kerberos designed to address? What are the three
threats associated with user authentication over a network or Internet?
6 List three approaches to secure user authentication in a distributed
environment.
7 Describe MAC with its security implications

Unit 7:
1 Explain any one approach to Digital Signatures.
2 Write a short note on “Digital Signature Algorithm”.
3 What is digital signature? Explain hash code base digital signature.
4 Explain DSA (Digital Signature Algorithm).
5 Explain digital signature schemes Elgamal and Schnorr
6 Draw Generic Model of Digital Signature
Process
Unit 8:
1 Explain various general categories of schemes for the distribution of
public keys.
2 Write a note on : X.509 Certificate Format.
3 Explain digital public key certificate format.
4 Explain various public key distribution techniques.
5 Write a short note on SSL.
6 Write a short note on public key infrastructure.
7 Described briefly the Authentication process covered by X.509
8 Explain HAND SHAKE protocol in SSL.
Unit 9:
1 Write a detailed note on : Kerberos.
2 What is Kerberos? How Kerberos authenticates the users for authorized
service access?
3 Explain authentication mechanism of Kerberos.
4 What problem was Kerberos designed to address?
4 Unit 10:
5 Discuss SSL architecture in brief.
6 Briefly explain web security threats.
7 What is SSL? Which security services does it offers? How does it
works?
8 Write a short note on:
i. Cipher text only attack
ii. Timing attack
9 What is SSH? How does SSH works?
10 What is KDC? List the duties of a KDC
11 For what purpose Secure Shell (SSH) is useful? Briefly define SSH
protocol.
12 What is the main difference between HTTP and HTTPS protocol. When
HTTPS is used, which elements of the communication are Encrypted?