1. Define following terms:
Plain text, cipher text, encryption, decryption, Cryptography (Dec-11), cryptanalysis, cryptology,
symmetric key encryption, Public key encryption, Secure channel, traffic analysis, Masquerade,
Non Repudiation, authentication, availability, access control
2. Differentiate Symmetric and Asymmetric key cryptography. (Dec-11) 3M
3. Considering OSI security architecture define Security attack, security mechanism, security
service (X.800)
4. Explain model for Network Security.
5. Differentiate message confidentiality and message integrity.
Chapter 2
1 Differentiate between block and stream cipher and what are two general approaches to attack to
a conventional encryption scheme.
2 Give classification of cryptography system.
3 Explain conventional (symmetric) encryption model.
4 Compare steganography and encryption.
5 Describe various classical Encryption Techniques (various substitution technique & transposition
technique) and give a Scenario of steganography techniques and show the application area
where it can be used more effectively.
6. Explain the various types of cryptanalytic attack, based on the amount of information known to
the cryptanalyst.(May-11)
OR
Explain various types of attacks on encrypted messages along with known information to
cryptanalysis.
7. What is unconditionally secure and what is computationally secure?
8. Comparison between mono and poly alphabetic encryption.
9.
11. Convert following plaintext into cipher text, “DON’T WORRY MAIN HU NA MUNNABHAI MBBS”
Using Caesar Cipher with k=3
Using Playfair matrix with keyword”SULEMAN”
Using Transposition Methods with keyword”SULEMAN”
Using polyalphabetic method with keyword”ABCD”
12. Construct a playfair matrix with the key “occurrence”. Generate the cipher text for the plaintext
“Tall trees” (May-11) 03M
Construct 5 X 5 playfair matrix for the keyword “OCCURANCE”. (Dec-11)(May-11) 03M
13. Explain vigenere cipher and vernam cipher.
Chapter 4
1 Explain the terms: congruent modulo, residue class
2 Explain properties of modular arithmetic and use it to find 117 mod 13 .
3 What is relative prime number, explain with example. (Dec-11) 1M
4 Using Euclid’s algorithm, find gcd of numbers 380 and 494.
5 Write the Euclid’s algorithm and show the steps of Euclid’s algorithm
to find gcd(1970,1066). (May-11) 04M
6 Write extended Euclidean algorithm. (Dec-11) 03M
Chapter 8
1 What is euler’s totient function?
2 Explain euler’s theorem.
3 What is prime number? What is primitive root of a number?
4 Find Euler’s Totient function for n=13,n=14.
5 Prove Euler’s theorem for a=2,n=11
Chapter 3
1 Explain S-DES scheme.
2 Explain SDES key generation and encryption through diagram.
3 What is motivation for feistel cipher structure?
4 Explain classical feistel network.
Draw and explain Feistel’s structure for encryption and decryption. (Dec-11) (07M)
5 What is the importance of diffusion and confusion? How to achieve it? (May-11)(3M)
6 Explain Avalanche effect (May-11) and also show the desirable property of the Avalanche effect
using example with two plain text that differ by one bit.
7 Explain single round of DES. (Dec-11) 07M
8 What is purpose of S-boxes in DES? (May-11) 03M
9 What is difference between differential and linear cryptanalysis?
10 Explain block cipher modes of operation (Dec-11). OR
Why mode of operation is defined? Explain the simplest mode for
block cipher modes of operation? (May-11) 4M
11 Which parameters and design choices determine the actual algoritm of a feistel cipher?
Chapter 6
1Explain “meet in the middle” attack and how to overcome it using triple DES. and show how it is stronger compared to DES?
2Why the middle portion of 3DES a decryption rather than a encryption?
3Explain Blowfish encryption and decryption. OR
Explain how subkeys are generated in blowfish algorithm and also explain the encr- yption in blowfish algorithm. How does the key-size in blowfish differ from cast-128?(May-11) 07M
4Explain design characteristics of RC5.
5Expalin key expansion and Encryption-Decryption of RC5
OR
Which parameters affect RC5 encryption algorithm. Explain RC5 encryption and decryption process. (May-11) 07M
6Explain RC5 modes of operation
7Explain characteristics (key features) of advanced symmetric block ciphers.
8Explain IDEA in context of conventional encryption technique.
9Explain Cast 128.
10Explain RC2
Chapter 7
1Differentiate link and end to end encryption approach.
2How to achieve traffic confidentiality using link and End-to-End encryption approach?
3What is traffic padding and its significance.
4What is the use of random numbers and give its properties.(criteria used to validate that a sequence of numbers is random) (may-11)
5Draw diagram for symmetric key distribution scenario. OR
Write the key distribution scenario in which each user shares a unique master key with key distribution center (May-11)3M.
6Draw diagram decentralized key distribution scenario.
7What are pseudo number generators.(PRNGs). explain Linear congruential method. (may-11)
8Explain techniques for cryptographically generated random numbers.
9Explain different key distribution techniques.(Dec-11) 07M
10Explain importance of session key lifetime.
Chapter 9
1Explain the principle of public key cryptosystem and show how it differs from conventional encryption techniques. (May-11)
2Describe the application of Public key cryptosystems.
3Give the steps of RSA algorithm. (Dec-11) 04M
Perform encryption-decryption using RSA algorithm for p=7,q=17,e=5, M=10 .
4In a public key system using RSA, the cipher text intercepted is C=10 which is sent to the user whose public key is e=5, n=35. What is the plaintext M? (May-11) 04M
5Perform encryption and decryption using the RSA algorithm for p=3, q=11, e=7, M=5. (May-11)
6Using RSA Algorithm find out the cipher text for integer value 12 as plain text data, take the value of p=5 and q=11.
Chapter 10
1Explain distribution of public keys.
2Briefly expalin Diffie-Hellman key exchage with example. (May-11, Dec-11)
3How key exchange using elliptic curves can be done? (May-11) 04M
Part II
Chapter 11
1Illustrate variety of ways in which hash code can be used to provide message authentication(May-11)-7Marks
2What is cryptographic checksum or message authentication code?Describe the three situation in which message authentication code is used.(May-11)-7Marks
3Explain General structure of secure hash functions.(Dec-11)-3 Marks
3Explain briefly basic uses of MAC.(Dec-11)-4Marks
4Explain Authentication Requirements.
5Explain Authentication Functions.
6Explain Following properties of hash function.(May-11)-7Marks
1)one way property………2Marks
2) Weak collision resistance…..2Marks
3) Compression Function in hash algorithm…..3Marks
7Explain Different characteristic of hash function.
Chapter 12
1Explain Secure Hash algorithm.
2Explain MD5 Hash algorithm(Dec-11)-7Marks
3Explain HMAC algorithm.
Chapter-13
1What is digital Signature? Explain in details.
2Write the digital signature algorithm (May-11, Dec-11)-7 Marks.
Chapter-14
1Explain Kerberos in detail.(Dec-11)-7 Marks
2Explain X.509 authentication service(Dec-11)-7Marks
Chapter-15
1Why is the segmentation and reassembly function in PGP needed?(May-11)-4Marks
2Explain PGP in detail.
3Explain S/MIME in detail.
4Discuss about PGP and S/MIME(Dec-11)-7Marks
Chapter-16
1What parameters characterize the nature of a particular security association in IPSec.
(May-11)-3Marks
2Give the Overview of IP Security.
3Explain Authentication Header.
4Explain Encapsulating Security Payload.
Chapter-17
1List and Define the parameters that define secure socket layer connection state.(May-11)-7Marks
2Explain SSL protocol in detail(Dec-11)-7Marks
3Explain Secure Electronic Transaction Protocol(Dec-11)-7Marks
4What is Dual Signature and Explain construction of Dual Signature.(May-11)-7Marks
Introduction to E-commerce
1Explain Ecommerce in detail.
2Explain Transaction on E-Commerce.
3Explain Requirement of Security on E-commerce.
4What are the security threats to E-commerce transaction(May-11)-3Marks
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