Which of the following was NOT designed to be a proprietary encryption algorithm?

A.
RC2

B.
RC4

C.
Blowfish

D.
Skipjack

Explanation:
Blowfish is a block cipher that works on 64-bit blocks of data. The key length can be anywhere from 32 bits up
to 448 bits, and the data blocks go through 16 rounds of cryptographic functions. It was intended as a
replacement to the aging DES. While many of the other algorithms have been proprietary and thus encumbered
by patents or kept as government secrets, this wasn’t the case with Blowfish. Bruce Schneier, the creator of
Blowfish, has stated, “Blowfish is unpatented, and will remain so in all countries. The algorithm is hereby placed
in the public domain, and can be freely used by anyone.”
Incorrect Answers:
A: RC2 was designed to be a proprietary encryption algorithm.B: RC4 was designed to be a proprietary encryption algorithm.
D: Skipjack was designed to be a proprietary encryption algorithm.

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