How many rounds are used by DES?

A.
16

B.
32

C.
64

D.
48

Explanation:
DES uses a 64-bit key, of which 8 bits are used for parity, and 56 bits make up the true key. DES divides the
message into blocks, which are put through 16 rounds of transposition and substitution functions, and operates
on them one at a time.
Incorrect Answers:
B, C, & D: RC5 is a block cipher that has a selection of parameters that it can use for block size, key size, and
the number of rounds used. The number of rounds can go from 0 up to 255.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 809, 810