Question

Which block cipher mode of operating requires that both the message sender and receiver access a counter that computes a new value whenever a ciphertext block is exchanged?

1) CD
2) CTR
3) CXL
4) CN

Answer 1

The CTR (Counter) mode is the block cipher mode that requires both the message sender and receiver to access a counter that computes a new value whenever a ciphertext block is exchanged.

Step-by-step explanation:

The block cipher mode of operating that requires both the message sender and receiver to access a counter that computes a new value whenever a ciphertext block is exchanged is the CTR (Counter) mode. The CTR (Counter) mode is the block cipher mode that requires both the message sender and receiver to access a counter that computes a new value whenever a ciphertext block is exchanged.

In CTR mode, a unique counter value is used for each block of ciphertext, and this counter is combined with the encryption key to generate a keystream that is XORed with the plaintext to produce the ciphertext.

CTR mode is commonly used in applications where parallel encryption and decryption is required, such as disk encryption and VPNs.