CompTIA Security Plus Mock Test Q1048

Which of the following symmetric key algorithms are examples of block ciphers? (Select THREE).

A. RC4
B. 3DES
C. AES
D. MD5
E. PGP
F. Blowfish


Correct Answer: B,C,F
Section: Cryptography

Explanation:
B: Triple DES (3DES) is the common name for the Triple Data Encryption Algorithm (TDEA or Triple DEA) symmetric-key block cipher, which applies the Data Encryption Standard
(DES) cipher algorithm three times to each data block.
C: Advanced Encryption Standard (AES) is a block cipher that 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.
F: Blowfish is an encryption system invented by a team led by Bruce Schneier that performs a 64-bit block cipher at very fast speeds.

Incorrect Answers:
A: RC4 is a stream cipher, not a block cipher. It is the most widely used software stream cipher and is used in popular Internet protocols such as Transport Layer Security (TLS).
D: MD5 is a hash function not a block cipher. It is a widely used cryptographic hash function producing a 128-bit (16-byte) hash value, typically expressed in text format as a 32 digit
hexadecimal number.
E: Pretty Good Privacy (PGP) is not a block cipher. It is a data encryption and decryption program that provides cryptographic privacy and authentication for data communication

References:
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis, 2014, pp. 250, 251, 255-256, 272-273