Explore topic-wise MCQs in Cryptography and Network Security.

This section includes 20 Mcqs, each offering curated multiple-choice questions to sharpen your Cryptography and Network Security knowledge and support exam preparation. Choose a topic below to get started.

1.

The last two blocks of the XTS-AES mode are

A. padded as 10*
B. encrypted/ decrypted using ciphertext-stealing
C. padded as 10*1
D. padded and then swapped after encryption/ decryption
Answer» C. padded as 10*1
Discussion
2.

Which of the following statements are true with respect to the blowfish algorithm?i) Provided key is large enough, brute-force key search is not practical, especially given the high key schedule costii) Key dependent S-boxes and sub keys make analysis very difficultiii) Changing both halves in each round increases securityiv) Blowfish has improved avalanche effects

A. i) ii) and iv)
B. ii) and iii)
C. i)
D. All are trueView Answer
Answer» E.
Discussion
3.

The blowfish algorithm’s key expansion converts a key of at most 448 bits into several subkey arrays totaling ___ bytes.

A. 4096
B. 4608
C. 4168
D. 4864
Answer» D. 4864
Discussion
4.

Which of the following statements are true.i) In the CBC mode, the plaintext block is XORed with previous ciphertext block before encryption.ii) The CTR mode does not require an Initialization Vectoriii) The last block in the CBC mode uses an Initialization Vectoriv) In CBC mode repetitions in plaintext do not show up in ciphertext

A. iii)
B. ii) and iv)
C. All the Statements are true
D. i) ii) and iv)View Answer
Answer» E.
Discussion
5.

A total of seven messages are required in the Public-Key distribution scenario. However, the initial five messages need to be used only infrequently because both A and B can save the other’s public key for future – a technique known as ____________

A. time stamping
B. polling
C. caching
D. squeezing
Answer» D. squeezing
Discussion
6.

Suppose that A has obtained a certificate from certification authority X1 and B has obtained certificate authority from CA X2. A can use a chain of certificates to obtain B’s public key. In notation of X.509, the correct order of this chain is represented as –

A. X2 X1 X1 B
B. X1 X1 X2 A
C. X1 X2 X2 B
D. X1 X2 X2 A
Answer» D. X1 X2 X2 A
Discussion
7.

It is desirable to revoke a certificate before it expires because –

A. the user is no longer certified by this CA
B. the CA’s certificate is assumed to be compromised
C. the user’s private key is assumed to be compromised
D. all of the mentioned
Answer» E.
Discussion
8.

The multiplicative Inverse of 550 mod 1769 is –

A. 434
B. 224
C. 550
D. Does not exist
Answer» B. 224
Discussion
9.

III)?$

A. ii) and iv)
B. All the Statements are true
C. i) ii) and iv)
Answer» D.
Discussion
10.

The blowfish algorithm’s key expansion converts a key of at most 448 bits into several subkey arrays totaling ___ bytes.$#

A. 4096
B. 4608
C. 4168
D. 4864
Answer» E.
Discussion
11.

What_is_the_number_of_possible_3_x_3_affine_cipher_transformations_?$

A. 168
B. 840
C. 1024
D. 1344
Answer» E.
Discussion
12.

i) ii) and iv)

A. ii) and iii)
B. i)
C. All are true
Answer» C. All are true
Discussion
13.

Which of the following statements are true with respect to the blowfish algorithm?

A. Provided key is large enough, brute-force key search is not practical, especially given the high key schedule cost
B. Key dependent S-boxes and sub keys make analysis very difficult
C. Changing both halves in each round increases security
D. Blowfish has improved avalanche effects
Answer» E.
Discussion
14.

For the group Sn of all permutations of n distinct symbols, what is the number of elements in Sn?

A. n
B. n-1
C. 2n
D. n!
Answer» D. n!
Discussion
15.

Which of the following slows the cryptographic algorithm –$

A. Increase in Number of rounds
B. Decrease in Block size
C. Decrease in Key Size
D. Increase in Sub key Generation
Answer» C. Decrease in Key Size
Discussion
16.

A total of seven messages are required in the Public-Key distribution scenario. However, the initial five messages need to be used only infrequently because both A and B can save the other’s public key for future – a technique known as ____________$

A. time stamping
B. polling
C. caching
D. squeezing
Answer» D. squeezing
Discussion
17.

Certificate extensions fall into 3 categories. Which one of the following is not a Certificate extensions category?

A. Subject and Issuer attributes
B. Key and Policy information
C. Certification path constraints
D. All of the above are Certificate extensions categories
Answer» E.
Discussion
18.

Suppose that A has obtained a certificate from certification authority X1 and B has obtained certificate authority from CA X2. A can use a chain of certificates to obtain B’s public key. In notation of X.509, the correct order of this chain is represented as –$

A. X2 X1 X1 B
B. X1 X1 X2 A
C. X1 X2 X2 B
D. X1 X2 X2 A
Answer» D. X1 X2 X2 A
Discussion
19.

It is desirable to revoke a certificate before it expires because –$

A. the user is no longer certified by this CA
B. the CA’s certificate is assumed to be compromised
C. the user’s private key is assumed to be compromised
D. all of the mentioned
Answer» E.
Discussion
20.

The multiplicative Inverse of 550 mod 1769 is –

A. 434
B. 224
C. 550
D. Does not exist
Answer» B. 224
Discussion