Which of the following is not a DES mode of operation?

A.
Cipher block chaining

B.
Electronic code book

C.
Input feedback

D.
Cipher feedback

Explanation:
DES modes include the following:
Electronic Code Book (ECB)
Cipher Block Chaining (CBC)
Cipher Feedback (CFB)
Output Feedback (OFB)
Counter Mode (CTR)
Input feedback is not a DES mode.
Incorrect Answers:
A, B, & D: Cipher block chaining, Electronic code book, and Cipher feedback are modes of DES.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 802-807