The Data Encryption Standard (DES) encryption algorithm has which of the following characteristics?

A.
64 bits of data input results in 56 bits of encrypted output

B.
128 bit key with 8 bits used for parity

C.
64 bit blocks with a 64 bit total key length

D.
56 bits of data input results in 56 bits of encrypted output

Explanation:
DES is a symmetric block encryption algorithm. When 64-bit blocks of plaintext go in, 64-bit blocks of ciphertext
come out. It is also a symmetric algorithm, meaning the same key is used for encryption and decryption. It uses
a 64-bit key: 56 bits make up the true key, and 8 bits are used for parity.
When the DES algorithm is applied to data, it divides the message into blocks and operates on them one at a
time. The blocks are put through 16 rounds of transposition and substitution functions. The order and type of
transposition and substitution functions depend on the value of the key used with the algorithm. The result is64-bit blocks of ciphertext
Incorrect Answers:
A: When 64-bit blocks of plaintext go in, 64-bit blocks of encrypted data come out.
B: DES uses a 64-bit key (not 128-bit): 56 bits make up the true key, and 8 bits are used for parity.
D: DES uses 64-bit blocks, not 56-bit.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 801