# Cryptography And Network Security Assignment 2 Answers 2022

NPTEL Cryptography And Network Security Assignment 2 Answers 2022:- In this post, We have provided answers of NPTEL Cryptography And Network Security Assignment 2. We provided answers here only for reference. Plz, do your assignment at your own knowledge.

## NPTEL Cryptography And Network Security Assignment 2 Answers 2022 [July-Dec]

Q1. What is the size of plaintext in Data Encryption Standard(DES)?

(a) 28
(b) 54
(c) 64
(d) 92

`Answer:- c`

Q2. DES is a rOund Feistel cipher having block length ..

(a) 16,64
(b) 8,56
(c) 16,16
(d) 16,32

`Answer:- a`

3. What kind of cipher DES is ?

(a) block cipher
(b) stream cipher
(c) bit cipher
(d) permutation cipher

`Answer:- a`

4. A cryptosystem has perfect secrecy if Pr[xly]= Pr[x] for all X E P, y E C, where P and C are the plaintext space and ciphertext space respectively. The above statement is ..

(a) True
(b) False

`Answer:- a `

5. For a stream cipher, the plaintext and the key are given by 1000 and 0100, respectively. Then the ciphertext is .

(a) 1111
(b) 0000
(c) 1100
(d) 0011

`Answer:- c`

6. What is the size of output produced by each S-box in DES algorithm?

(a) 8
(b) 4
(c) 2
(d) 16

`Answer:- b`

7. Consider one bit encryption C = P®K and Pr(K = 0) = Pr(K = 1) = 0.5, Pr(P = 0) = 0.6, Pr(P = 1) = 0.4. Then Pr(P= 0|C = 1) 1S ….

(a) 0.5
(b) 0.4
(c) 0.6
(d) None of these

`Answer:- c`

8. How many rounds a Data Encryption Standard (DES) system has with an initial and final permutation block?

(a) 16
(b) 8
(c) 32
(d) None of these

`Answer:- a`

9. One-time pad possesses perfect secrecy. The above statement is…

(a) True
(b) False

`Answer:- a`

10. The key size of DES is ..

(a) 48
(b) 32
(c) 64
(d) 56

`Answer:- d`

## About Cryptography And Network Security

The aim of this course is to introduce the student to the areas of cryptography and cryptanalysis. This course develops a basic understanding of the algorithms used to protect users online and to understand some of the design choices behind these algorithms. Our aim is to develop a workable knowledge of the mathematics used in cryptology in this course. The course emphasizes to give a basic understanding of previous attacks on cryptosystems with the aim of preventing future attacks. A wide variety of basic cryptographic primitives will be discussed along with recent developments in some advanced topics like identity-based encryption, attribute-based encryption, functional encryption, two-party/multi-party computation, bitcoin and crypto-currency and postquantum cryptography. The cryptanalysis part will help us understanding challenges for cybersecurity that includes network security, data security, mobile security, cloud security and endpoint security.

### COURSE LAYOUT

• Week 1: Introduction to cryptography, Classical Cryptosystem, Block Cipher.
• Week 2: Data Encryption Standard (DES), Triple DES, Modes of Operation, Stream Cipher.
• Week 3: LFSR based Stream Cipher, Mathematical background, Abstract algebra, Number Theory.
• Week 4: Modular Inverse, Extended Euclid Algorithm, Fermat’s Little Theorem, Euler Phi-Function, Euler’s theorem.
• Week 5: Advanced Encryption Standard (AES), Introduction to Public Key Cryptosystem, Diffie-Hellman Key Exchange, Knapsack Cryptosystem, RSA Cryptosystem.
• Week 6: Primarily Testing, ElGamal Cryptosystem, Elliptic Curve over the Reals, Elliptic curve Modulo a Prime.
• Week 7: Generalized ElGamal Public Key Cryptosystem, Rabin Cryptosystem.
• Week 8 : Message Authentication, Digital Signature, Key Management, Key Exchange, Hash Function.
• Week 9 : Cryptographic Hash Function, Secure Hash Algorithm (SHA), Digital Signature Standard (DSS).
• Week 10: Cryptanalysis, Time-Memory Trade-off Attack, Differential and Linear Cryptanalysis.
• Week 11: Cryptanalysis on Stream Cipher, Modern Stream Ciphers, Shamir’s secret sharing and BE, Identity-based Encryption (IBE), Attribute-based Encryption (ABE).
• Week 12: Side-channel attack, The Secure Sockets Layer (SSL), Pretty Good Privacy (PGP), Introduction to Quantum Cryptography, Blockchain, Bitcoin and Cryptocurrency.

CRITERIA TO GET A CERTIFICATE

Average assignment score = 25% of average of best 8 assignments out of the total 12 assignments given in the course.
Exam score = 75% of the proctored certification exam score out of 100

Final score = Average assignment score + Exam score

YOU WILL BE ELIGIBLE FOR A CERTIFICATE ONLY IF AVERAGE ASSIGNMENT SCORE >=10/25 AND EXAM SCORE >= 30/75. If one of the 2 criteria is not met, you will not get the certificate even if the Final score >= 40/100.