Which of the following ciphers is a subset on which the Vigenere polyalphabetic cipher was based on?

A.
Caesar

B.
The Jefferson disks

C.
Enigma

D.
SIGABA

Explanation:
Julius Caesar (100–44 B.C.) developed a simple method of shifting letters of the alphabet. He simply shifted the
alphabet by three positions.
Today, this technique seems too simplistic to be effective, but in the time of Julius Caesar, not very many
people could read in the first place, so it provided a high level of protection. The Caesar cipher is an example of
a monoalphabetic cipher. Once more people could read and reverse-engineer this type of encryption process,
the cryptographers of that day increased the complexity by creating polyalphabetic ciphers.
In the 16th century in France, Blaise de Vigenere developed a polyalphabetic substitution cipher for Henry III.
This was based on the Caesar cipher, but it increased the difficulty of the encryption and decryption process
Incorrect Answers:
B: The Vigenere polyalphabetic cipher is based on the Caesar cipher, not the Jefferson disks.
C: The Vigenere polyalphabetic cipher is based on the Caesar cipher, not Enigma.
D: The Vigenere polyalphabetic cipher is based on the Caesar cipher, not SIGABA.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 761-762