Cryptography Final UPDATED Actual Exam Questions and CORRECT Answers

Cryptography Final UPDATED Actual
Exam Questions and CORRECT Answers
Cryptology - CORRECT ANSWER✔✔- is the study of cryptanalysis and cryptography



cryptanalysis is used - CORRECT ANSWER✔✔- to find some insecurity in a cryptography
scheme


CIA Triad - CORRECT ANSWER✔✔- Confidentiality, Integrity, Availability



According to x.800 the architecture of security is - CORRECT ANSWER✔✔- the three
aspects of information security
a) security attack
b) security mechanism (control)
c) security service


an intelligent threat is called - CORRECT ANSWER✔✔- an attack, a deliberate attempt to
evade security services and violate the security policy of a system.


the passive attack type is: - CORRECT ANSWER✔✔- Release of message contents


protection agains denial by one of the entities involved in a communication (origin,
destination)is called a: - CORRECT ANSWER✔✔- Non-Repudation



Conversion of cypher text to plaintext is - CORRECT ANSWER✔✔- decryption


the information known to a cryptanalyst is known plaintext attack is - CORRECT
ANSWER✔✔- encryption algorithm
cipher text
one or more plaintext-cyphertext pairs formed with secrete key.

,what is the difference between mono alphabetic and poly alphabetic cipher - CORRECT
ANSWER✔✔- The monoalphabetic cipher is a permutation of a finite set of elements S is an
ordered sequence of all the elements of S, with each element appearing exactly once. In
mono- the relationship between cipher text and plain text is one to one.
The polyalphabetic cipher improves on this by using different monoalphabetic substitutions
as one proceeds through the plaintext. The polyalphabetic cipher is more complex. In a poly-
one letter of plain text can be mapped to many letters of cipher text.


the method of Caesar cipher is - CORRECT ANSWER✔✔- substitution



what is the encryption algorithm for Vigenere cipher? - CORRECT ANSWER✔✔- Ci = (pi
+ ki) mod 26


what is the decryption algorithm for vernam cipher? - CORRECT ANSWER✔✔- ci = pi⊕ki
where pi = ith binary digit of plaintext ki = ith binary digit of key ci = ith binary digit of
ciphertext


what is the rail fence transposition technique? - CORRECT ANSWER✔✔- the message is
written in a rectangle, row by row, and read the message off, column by column, but permute
the order of the column, the order of the columns then becomes the key to the algorithm.


give an example for play fair cipher - CORRECT ANSWER✔✔- The keyword is
MONARCHY
Message = Move forward
Plaintext = mo ve fo rw ar dx
mo -> ON; ve -> UF; fo -> PH, etc
Ciphertext = ON UF PH NZ RM BZ


how many rounds does the AES-192 perform? - CORRECT ANSWER✔✔- 12



AES uses a _______ bit block size - CORRECT ANSWER✔✔- 128



the leftmost 4 bits in s-box represents the following value - CORRECT ANSWER✔✔- row

, the number of s-boxes in AES - CORRECT ANSWER✔✔- 1



the number of stages in each round of AES includes - CORRECT ANSWER✔✔- 4



the number of subways in key expansion is - CORRECT ANSWER✔✔- the number of
rounds +1


AES algorithm is derived by - CORRECT ANSWER✔✔- Rijndael



AES is faster then 3DES - CORRECT ANSWER✔✔- true



AES follows Fiestel structure - CORRECT ANSWER✔✔- false



the stages defined in AES encryption are - CORRECT ANSWER✔✔- substitution bytes
shift rows
mixed columns
and add round key


GCD(a,b) is the same as GCD(| a |, | b |) - CORRECT ANSWER✔✔- true


calculate the GCD of 1160718174 and 316258250 using Euclidean algorithm - CORRECT
ANSWER✔✔- 1160718174 = 3(316258250) + 211943424
316258250 = 211943424 + 104314826
211943424 =2(104314826) + 3313772
104314826 = 31(3313772) + 1587894
3313772 =2(1587894 )+ 137984
1587894 =11(137984 )+ 70,070
137984 = 70070 + 67914
70070 = 67914 + 2156