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