Question

Which of the following statements are true

i) In the CBC mode, the plaintext block is XORed with previous ciphertext block before encryption

ii) The CTR mode does not require an Initialization Vector

iii) The last block in the CBC mode uses an Initialization Vector

iv) In CBC mode repetitions in plaintext do not show up in ciphertext

(a) iii)

(b) ii) and iv)

(c) All the Statements are true

(d) i) ii) and iv)

The question was posed to me in an interview for job.

My doubt is from DES Modes of Operation in division Advanced Encryption Algorithm and Block Cipher Operation of Cryptograph & Network Security

Answer 1

Correct choice is (d) i) ii) and iv)

The explanation is: The first block in CBC mode uses an IV.