Question

__________________ is also used to turn a block cipher into a stream cipher. This is much like OFB mode. CTR generates the next keystream block by encrypting successive values of a "counter." The counter can be any simple function that produces a sequence that is guaranteed not to repeat for a long time. A) ECB (Electronic Codebook)

B) CBC (Cipher Block Chaining)

C) CFB (Cipher Feedback)

D) CTR (Counter)

Answer 1

CTR (Counter) mode is used to convert a block cipher into a stream cipher by encrypting successive values of a counter, producing a unique keystream for each block without repetition.

Step-by-step explanation:

The mode of operation that is also used to turn a block cipher into a stream cipher and is similar to Output Feedback (OFB) mode is CTR (Counter) mode. Like OFB, CTR mode generates the next keystream block, but it does this by encrypting successive values of a counter. This counter is a number that increments with each block processed, thereby ensuring each block is encrypted with a unique keystream. It's critical that the counter value never repeats, as any repetition would compromise the security of the encryption.