MCQ | Cryptography Techniques of Block Cipher

Here, we have a set of multiple-choice questions and answers (quiz) on Cryptography Techniques of Block Cipher.
Submitted by Monika Sharma, on March 22, 2020

1) What is the block size of plain text in SHA- 512 algorithm?

  1. 512 bits
  2. 1024 bits
  3. 2048 bits
  4. None of the above

Answer: b. 1024 bits


The SHA- 512 algorithm uses blocks of plain text one at a time to encrypt them into ciphertext. The size of each block in the SHA- 512 algorithm is 1024 bits.

2) All the below-stated processes are performed in the AES (Advanced Encryption Standard) Algorithm. Which of the following process(s) are not performed in the final round of the AES?

  1. Substitution bytes
  2. Shift rows
  3. Mix columns
  4. Add round key


  1. i.
  2. iii.
  3. All of the mentioned
  4. None of the mentioned

Answer: b. iii.


In the AES algorithm, the MIX COLUMN operation is performed in all the rounds except the final round of the algorithm.

3) What does IDEA stand for in the world of cryptography?
The IDEA word in the IDEA algorithm is the abbreviation for which of the following?

  1. Independent Decryption Environment Analysis
  2. International Defense Encryption Area
  3. International Data Encryption Algorithm
  4. None of the above

Answer: c. International Data Encryption Algorithm


The IDEA Algorithm stands for "International Data Encryption Algorithm".

4) How many sub-keys in the total are used by the IDEA for encrypting the plain text into ciphertext?

  1. 64 sub- keys
  2. 48 sub- keys
  3. 52 sub- keys
  4. Only one key and no subkeys

Answer: c. 52 sub- keys


There are a total of 8 rounds in the IDEA technique for encryption and each of them uses 6 keys. Apart from that, 4 extra keys are used in the final round that is the output transformation round. This gives us a total of 52 subkeys.
(8 x 6) + 4 = 52

5) "The number of rounds in the AES algorithm depends upon the key size being used."
Which among the following shows a correct relation between the size of the key used and the number of rounds performed in the AES algorithm?

  1. 128 key size: 10 rounds
  2. 192 key size: 12 rounds
  3. 256 key size: 14 rounds
  4. All of the above

Answer: d. All of the above


All the mentioned options display the correct relation between the number of rounds and the key size used in the AES algorithm.

6) Which of the following properties are the characteristic properties of a block cipher technique which differs from stream cipher?

  1. Avalanche effect
  2. Completeness
  3. Both a. and b.
  4. None of the above

Answer: c. Both a. and b.


Avalanche effect and Completeness are the two characteristic properties of Block ciphers which differ them from stream ciphers.

7) Encryption algorithms are divided into two categories based on the ______.

  1. Output type
  2. Input type
  3. Process type
  4. All of the mentioned above

Answer: b. Input type


Encryption algorithms are classified into two categories based on the type of input they receive: block cyphers and stream cyphers. Block cyphers are the most used type of encryption technique. This type of encryption technique takes as input a defined size of data, such as b bits, and outputs as output another block of data of the same size as the input.

8) Cipher block chaining or CBC is an advancement made on _____.

  1. Electronic Code Book
  2. Decrypted code
  3. System engineering
  4. All of the mentioned above

Answer: a. Electronic Code Book


Cipher block chaining, also known as CBC, is an improvement on the Electronic Code Book. The electronic code book is the most straightforward block cypher manner of operation. It is simpler since each block of input plaintext is directly encrypted, and the output is in the form of blocks of encrypted ciphertext.

9) A secure block cipher is suitable for the encryption,

  1. True
  2. False

Answer: a. True


A safe block cypher is a type of encryption that is ideal for encrypting only a single block of data at a time with a fixed key. As building blocks of various cryptographic protocols, block cyphers can be found in a variety of configurations, including universal hash functions and pseudorandom number generators.

10) Cipher Feedback Mode is given as feedback to the ____ of encryption with some new specifications.

  1. Next block
  2. Previous block
  3. Middle block
  4. All of the mentioned above

Answer: a. Next block


Cipher Feedback Mode is provided as feedback to the following block of encryption with some new specifications, and it is used as a feedback mechanism.

11) In cryptography, a product cipher combines two or more transformations,

  1. True
  2. False

Answer: a. True


As used in cryptography, the term "product cypher" refers to the combination of two or more transformations in such a way that the final cypher is more secure than the individual components and hence more resistant to cryptanalysis. Using the product cypher, we may combine a series of simple transformations such as substitution (S-box), permutation (P-box), and modular arithmetic into a more complex transformation.


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