Ethical Hacking week 6 NPTEL Assignment Solution

ABOUT THE COURSE :

Ethical hacking is a subject that has become very important in present-day context, and can help individuals and organizations to adopt safe practices and usage of their IT infrastructure. Starting from the basic topics like networking, network security and cryptography, the course will cover various attacks and vulnerabilities and ways to secure them. There will be hands-on demonstrations that will be helpful to the participants. The participants are encouraged to try and replicate the demonstration experiments that will be discussed as part of the course.

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.

Q1. Which of the following is not an example of active security attack?

a. Masquerade

b. Replay

c. Traffic analysis 

d. Modification

e. Denial of Service.

Q2. Consider the following statements:

(i) In symmetric key cryptography, single shared key is used by sender and receiver.
(ii) In Asymmetric key cryptography, separate keys are used by sender and receiver.
a. Only (i) is true

b. Only (ii) is true

c. Both (i) and (ii) are true.

d. Both (i) and (in) are false.

Explanation:-

Secret/Private key cryptography (symmetrical encryption): Both the sender and receiver must use the same key to encrypt and decrypt messages being sent.

Private or Symmetric Key Cryptography

    -A common secret value K (called key) is shared between sender

and receiver.

Asymmetrical encryption (Public key):-

   - Separate keys for sender and receiver.

Q3. 15 parties want to exchange messages securely using a symmetric key encryption algorithm. The number of distinct key values required will be______

Answer :- 105

Explanation:-

15 parties want to exchange messages securely using a symmetric

(Private) key encryption algorithm.

So, the number of distinct key values required will be

=

n(n−1)

2

=

15(15−1)

2

=

15∗14

2

= 105

Q4. Consider a mono-alphabetic cipher with the following key value:
(ABCDIJKLEFGH MNO PUV WXQRST Y Z)
What will be the encrypted form of the message “WIN DO W” ?

a. WENDHW

b. SKNGHS

C. SENDOS

d. None of these.

Q5. How many AES rounds are required for 192-bit key size?

a. 10
b. 11
c. 12
d. 14

Explanation:-

The number of rounds (AES) depends on the key length as follow:

* 128-bit key – 10 rounds

* 192-bit key – 12 rounds

* 256-bit key – 14 rounds

Q6. What is the key length in data encryption standard (DES)?

a. 56
b. 64
c. 128
d. 192

Q7. 100 parties want to exchange messages securely using some public key encryption technique like RSA. The number of distinct key values required will be _______________

Answer:- 200

Explanation:-

100 parties want to exchange messages securely using some public

key encryption technique like RSA. The number of distinct key values

required will be ___________

For public key encryption = 2n

=2*100

=200

Q8. In Digital signature sender signs a message with its:

a. Private key
b. Public key

In digital signature sender signs a message with its which key?

 This signals an issue with authentication. A person creates

a digital signature using a private key to encrypt the

signature. At the same time, hash data is created and

encrypted. The recipient uses the signer's public key to

decrypt the signature.

 Digital signatures rely on asymmetric cryptography, also

known as public key cryptography. An asymmetric key

consists of a public/private key pair. The private key is

used to create a signature, and the corresponding public

key is used to verify the signature.

Q9. On which difficult mathematical problem does the security of RSA algorithm depend on?

a. Discrete logarithm problem.
b. Testing whether a given number if prime or not.
c. Prime factorization problem.
d. The RSA threshold detection.
e. All of these.

Q10. Which of the following statements) is/are true for Diffie-Hellman Key Exchange algorithm?
a. It allows group of users to agree on secret key over insecure channel.
b. The security of the algorithm depends on prime factorization problem.
c. The algorithm is vulnerable to man-in-the-middle attack.
d. It does not require any prior communication between sender and receiver.
e. All of these.