# 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

Explanation:

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

Options

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

Explanation:

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?
or
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

Explanation:

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

Explanation:

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

Explanation:

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.

Explanation:

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

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