Which of the following provides additional encryption strength by repeating the encryption process with
additional keys?

A.
AES

B.
3DES

C.
TwoFish

D.
Blowfish

Explanation:
Triple-DES (3DES) is a technological upgrade of DES. 3DES is still used, even though AES is the preferred
choice for government applications. 3DES is considerably harder to break than many other systems, and
it’s more secure than DES. It increases the key length to 168 bits (using three 56-bit DES keys).
Incorrect Answers:
A: Advanced Encryption Standard (AES) has replaced DES as the current standard, and it uses the Rijndael
algorithm. It was developed by Joan Daemen and Vincent Rijmen. AES is the current product used by U.S.
governmental agencies.
It supports key sizes of 128, 192, and 256 bits, with 128 bits being the default.
C: Twofish is quite similar to Blowfish and works on 128-bit blocks.
D: Blowfish is an encryption system invented by a team led by Bruce Schneier that performs a 64-bit block
cipher at very fast speeds. It is a symmetric block cipher that can use variable-length keys (from 32 bits to
448 bits).
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis,
2014, pp. 250, 251, 255-256