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Question 11

Electromechanical rotor-based cipher used in World War II

A.ROT13 Cipher
B.Cipher Disk
C.Enigma Machine
D.Rail Fence Cipher

Correct Answer: C

Enigma Machine
https://en.wikipedia.org/wiki/Enigma_machine
The Enigma machine is an encryption device developed and used in the early- to mid-20th century to protect commercial, diplomatic and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the German military.
Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet.
Incorrect answers:
Rail Fence Cipher - a form of transposition cipher. In the rail fence cipher, the plain text is written downwards and diagonally on successive "rails" of an imaginary fence, then moving up when the bottom rail is reached. When the top rail is reached, the message is written downwards again until the whole plaintext is written out. The message is then read off in rows.
Cipher Disk - an enciphering and deciphering tool developed in 1470 by the Italian architect and author Leon Battista Alberti. He constructed a device, (eponymously called the Alberti cipher disk) consisting of two concentric circular plates mounted one on top of the other. The larger plate is called the "stationary" and the smaller one the "moveable" since the smaller one could move on top of the "stationary". The first incarnation of the disk had plates made of copper and featured the alphabet, in order, inscribed on the outer edge of each disk in cells split evenly along the circumference of the circle. This enabled the two alphabets to move relative to each other creating an easy to use key. Rather than using an impractical and complicated table indicating the encryption method, one could use the much simpler cipher disk. This made both encryption and decryption faster, simpler and less prone to error.
ROT13 Cipher - ("rotate by 13 places", sometimes hyphenated ROT-13) is a simple letter substitution cipher that replaces a letter with the 13th letter after it, in the alphabet. ROT13 is a special case of the Caesar cipher which was developed in ancient Rome.

Question 12

Which of the following algorithms uses three different keys to encrypt the plain text?

A.Skipjack
B.AES
C.Blowfish
D.3DES

Question 13

A _____ is a function that takes a variable-size input m and returns a fixed-size string.

A.Feistel
B.Asymmetric cipher
C.Symmetric cipher
D.Hash

Question 14

An authentication method that periodically re-authenticates the client by establishing a hash that is then resent from the client is called ______.

A.CHAP
B.SPAP
C.PAP
D.EAP

Question 15

A 160-bit hash algorithm developed by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel for which there are 128, 256 and 320-bit versions is called what?

A.SHA1
B.MD5
C.FORK
D.RIPEMD

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