UNIT 2 DES,BLOCK CIPHER

Which of the following is a mode of operation for the Block ciphers in cryptography?

• Electronic Code Book (ECB)

• Cipher Block Chaining (CBC)

• Counter (CTR) mode

• All of the above

For which of the following should EBC (Electronic Code Book) process not be used for encryption?

• For large block sizes

• For fixed block sizes

• For small block sizes

• none of the above

Which of the following options is not correct according to the definition of the Cipher Block Chaining (CBC)?

• CBC is a mode of operation for stream ciphers.

• Initialization vector (IV) is used in CBC in the initial phase.

• It has better resistive nature towards cryptanalysis than ECB

• None of the above

Which of the following modes of operations can be followed for both stream ciphers as well as block ciphers?

• CBC

• ECB

• CFB

• ALL THE ABOVE

Data Encryption Standard (DES) is a __________.

• Stream Cipher

• Bit Cipher

• Block Cipher

• Substitution Cipher

The S-Box is used to provide confusion, as it is dependent on the unknown key.

• true

• false

This is an example of

• SP Networks

• Feistel Cipher

• Hash Algorithm

• Hill Cipher

Which of the following slows the cryptographic algorithm –

1) Increase in Number of rounds

2) Decrease in Block size

3) Decrease in Key Size

4) Increase in Sub key Generation

• 1 and 3

• 2 and 3

• 3 and 4

• 2 and 4

During decryption, we use the Inverse Initial Permutation (IP-1) before the IP.

• true

• false

A preferable cryptographic algorithm should have a good avalanche effect.

• true

• false