Table of Contents

## B.Tech

### (SEM VII) THEORY EXAMINATION 2020-21

### CRYPTOGRAPHY AND NETWORK SECURITY

**[Time: 3:00 Hours] Total Marks: 70**

Note: Attempt all Sections. If require any missing data: then choose suitably.

**SECTION-A**

**Attempt all questions in brief. 2 x 7 = 14**- What do you mean Brute Force Attack?
- Define CIA?
- Define the concept of confusion and Diffusion?
- Find all the primitive roots of 11.
- Find gcd(24140, 16762) using Euclid’s algorithm?
- List out the services provided by the Digital Signature.
- What are the five principal services provided by PGP?

**SECTION-**B

**2 . Attempt any three questions in brief. 7 x 3 = 21**

- Explain the Security Attack with Example.
- Explain the Structure of DES Algorithm and define the role of fiestal cipher in DES in detail.
- Explain symmetric and Asymmetric Cryptography with the help of diagrammatic representation. And how-to symmetric cryptography is different from asymmetric Cryptography.
- State Chinese remainder theorem and find X for the given set of congruent equations using CRT: X=2(mod3), X=3(mod5), X=2(mod7).
- Describe RSA algorithm, Suppose alice and bob uses a public key cryptosystem using RSA, the two prime no is P=13 and q=17 and e=7 the find out the decryption key d and Perform the encryption and decryption of the message “CRYPTOGRAPHY” Using 00 to 25 for letters A to Z.

**SECTION-**B

**3. Attempt any one part of the following: 7 x 1 = 7**

- Explain Block modes of operation and also explain the Electronic Code Book (ECB) mode is not a secured mode of encryption and highlight the problems with this mode.
- Give a real-life example where both confidentiality and integrity are needed. Explain why encryption alone does not provide integrity of information.

**4. Attempt any one part of the following: 7 x 1 = 7**

- Compare Substitution and Transposition techniques.
- Encrypt the following using play fair cipher using the keyword:

MONARCHY. “SWARAJ IS MY BIRT RIGHT”. Use X as blank space.

**5. Attempt any one part of the following: 7 x 1 = 7**

- Define Primality Test and also explain Miller Rabin Algorithm using base 2 to test whether the number 341 is composite or not?
- Explain AES algorithm What is the difference between the AES decryption algorithm and the DES algorithm.

**6. Attempt any one part of the following: 7 x 1 = 7**

- Explain the Kerberos protocol for key distribution? Explain the functionality of each step.
- How does worms and viruses compare? Describe the component of the virus and how does it protect from anti-virus software’s?

**7. Attempt any one part of the following: 7 x 1 = 7**

- What do you mean by SHA 1 algorithm What basic arithmetical and logical functions are used in SHA?
- Explain in detail about S/MIME and what difference between S/MIME and PGP.

## Download Cryptography and Network Security Question paper 2020-21

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