Bach question carries $0\mathrm{.}5$ marks $-12$x$0\mathrm{.}5=6$ Marks

$1$ In the Vigenere cipher, judge the purpose of the keyword.

A$.$ To determine the number of shifts for each letter

B$.$ To create a random substitution alphabet

C$.$ To define the transposition pattern

D$.$ To determine the shifted alphabets for each letter

$2$ The attack is based on the cryptanalyst having temporary access to the encryption machine and encrypting a large number of suitably chosen plaintexts?

A$.$ Cipher text only

B$.$ Known plaintext

C$.$ Chosen plaintext

D$.$ Chosen cipher text

$3$ In the Bell$-$LaPadula Model, the $"-$property enforces the $"$no read up$"$ rule, allowing a subject to read information at a higher security level. $($True $/$ False$)$

$4$ The Biba Model's No Read Down principle restricts subjects from reading data at higher integrity levels than their own. $($True $/$ False$)$

$5$ The Enigma machine, used by the Germans during World War II$,$ was considered theoretically unbreakable due to its complex encryption algorithm. $($True$/$False$)$

$6$ In symmetric cryptography, the same key is used for both encryptio and decryption. $($True $/$ False$)$