160+ Cryptography and Network Security (CNS) Solved MCQs

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Uncategorized topics .

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51.	If the key is 110100001, the output of the SP network for the plaintext: 101110001 is
A.	110100011
B.	110101110
C.	10110111
D.	11111010
Answer» B. 110101110

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52.	What is the number of possible 3 x 3 affine cipher transformations
A.	168
B.	840
C.	1024
D.	1344
Answer» D. 1344

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53.	What is the expanded key size of AES-192?
A.	44 words
B.	60 words
C.	52 words
D.	36 words
Answer» C. 52 words

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54.	In affine block cipher systems if f(m)=Am + t, what is f(m1+m2+m3) ?
A.	f(m1) + f(m2) + f(m3) + t
B.	f(m1) + f(m2) + f(m3) +2t
C.	f(m1) + f(m2) + f(m3)
D.	2(f(m1) + f(m2) + f(m3))
Answer» C. f(m1) + f(m2) + f(m3)

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55.	The 4×4 byte matrices in the AES algorithm are called
A.	states
B.	words
C.	transitions
D.	permutations
Answer» A. states

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56.	If the block size is ‘s’, how many affine transformations are possible ?
A.	2s (2s-1)(2s-1)(2s-12) ………(2s-1(s-1))
B.	2s (2s-1)(2s-2)(2s-22) ………(2s-2(s-2))
C.	2ss (2s-1)(2s-2)(2s-22) ………(2s-2(s-1))
D.	2s (2s-1)(2s-2)(2s-22) ………(2s-2(s-3))
Answer» C. 2ss (2s-1)(2s-2)(2s-22) ………(2s-2(s-1))

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57.	For the AES-128 algorithm there are similar rounds and round is different.
A.	2 pair of 5 similar rounds ; every alternate
B.	9 ; the last
C.	8 ; the first and last
D.	10 ; no
Answer» B. 9 ; the last

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58.	The DES Algorithm Cipher System consists of rounds (iterations) each with a round key
A.	9
B.	12
C.	18
D.	16
Answer» D. 16

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59.	DES follows
A.	hash algorithm
B.	caesars cipher
C.	feistel cipher structure
D.	sp networks
Answer» C. feistel cipher structure

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60.	Every cyclic group is .
A.	a group with finite order
B.	a group with prime order
C.	a non abelian group
D.	an abelian group
Answer» D. an abelian group

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61.	In the DES algorithm the round key is bit and the Round Input is bits
A.	48, 32
B.	64,32
C.	56, 24
D.	32, 32
Answer» A. 48, 32

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62.	is not a binary operation on the set of natural numbers.
A.	addition
B.	product
C.	difference
D.	none
Answer» C. difference

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63.	In the DES algorithm the Round Input is 32 bits, which is expanded to 48 bits via
A.	scaling of the existing bits
B.	duplication of the existing bits
C.	addition of zeros
D.	addition of ones
Answer» A. scaling of the existing bits

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64.	Which of the following is group under multiplication?
A.	q
B.	q-{0}
C.	q-{1}
D.	q-{0,1}
Answer» B. q-{0}

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65.	The Initial Permutation table/matrix is of size
A.	16×8
B.	4×8
C.	12×8
D.	8×8
Answer» D. 8×8

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66.	The number of unique substitution boxes in DES after the 48 bit XOR operation are
A.	8
B.	4
C.	6
D.	12
Answer» A. 8

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67.	The DES algorithm has a key length of
A.	128 bits
B.	32 bits
C.	64 bits
D.	16 bits
Answer» C. 64 bits

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68.	What is the size of the key in the SDES algorithm?
A.	24 bits
B.	16 bits
C.	20 bits
D.	10 bits
Answer» D. 10 bits

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69.	The Plaintext for the Ciphertext 10100101, given that the key is 0010010111 is
A.	1100111
B.	110110
C.	1001000
D.	1001100
Answer» B. 110110

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70.	Assume input 10-bit key, K: 1010000010 for the SDES algorithm. What is K1?
A.	10100100
B.	1011011
C.	1101000
D.	10100111
Answer» A. 10100100

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71.	Assume input 10-bit key, K: 0010010111 for the SDES algorithm. What is K2?
A.	11101010
B.	11011011
C.	1101000
D.	10101111
Answer» A. 11101010

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72.	Which of the following is a mode of operation for the Block ciphers in cryptography?
A.	a. electronic code book (ecb)
B.	cipher block chaining (cbc)
C.	counter (ctr) mode
D.	all of the above
Answer» D. all of the above

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73.	Which of the following modes of operations can be followed for both stream ciphers as well as block ciphers?
A.	a. cbc (cipher block chaining)
B.	ecb (electronic code book)
C.	a. cfb (cipher text feed back)
D.	all of the above
Answer» C. a. cfb (cipher text feed back)

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74.	The Plaintext for the Ciphertext 00001111, given that the key is 1111111111 is
A.	1100111
B.	1010
C.	11111111
D.	1101101
Answer» C. 11111111

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75.	Which one of the following RC4 algorithm not used in?
A.	ssl
B.	tls
C.	ftp
D.	wep
Answer» C. ftp

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76.	Till when was the RC4 algorithm kept a secret?
A.	1990
B.	1992
C.	1996
D.	1994
Answer» D. 1994

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77.	The Plaintext for the Ciphertext 00100010, given that the key is 1111111111 is
A.	1100111
B.	1010
C.	1001000
D.	1001100
Answer» D. 1001100

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78.	The man-in-the-middle attack can endanger the security of the Diffie-Hellman method if two parties are not
A.	authenticated
B.	joined
C.	submit
D.	separate
Answer» A. authenticated

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79.	RSA is also a stream cipher like Merkel-Hellman
A.	true
B.	false
Answer» A. true

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80.	Rabin Cryptosystem is a variant of the Elgamal Cryptosystem
A.	true
B.	false
Answer» B. false

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81.	In RSA, Ф(n) = in terms of p and q
A.	(p)/(q)
B.	(p)(q)
C.	(p-1)(q-1)
D.	(p+1)(q+1)
Answer» C. (p-1)(q-1)

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82.	In Asymmetric Key Cryptography, the two key, e and d, have a special relationship to
A.	others
B.	data
C.	keys
D.	each other
Answer» D. each other

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83.	Using Rabin cryptosystem with p=23 and q=7 ,Encrypt P=24 to find ciphertext. The Cipher text is
A.	42
B.	93
C.	74
D.	12
Answer» D. 12

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84.	For RSA to work, the value of P must be less than the value of
A.	p
B.	q
C.	n
D.	f
Answer» C. n

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85.	Session keys are transmitted after being encrypted by
A.	make-shift keys
B.	temporary keys
C.	master keys
D.	section
Answer» C. master keys

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86.	Which Cryptographic system uses C1 = (e1r) mod p and C1 = (e2r x P) mod p at the encryption side?
A.	elgamal
B.	rsa
C.	rabin
D.	whirlpool
Answer» A. elgamal

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87.	The certificate message is required for any agreed-on key exchange method except
A.	ephemeral diffie- hellman
B.	anonymous diffie- hellmanc
C.	fixed diffie- hellmand.
D.	rsa
Answer» B. anonymous diffie- hellmanc

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88.	Sender chooses p = 107, e1 = 2, d = 67, and the random integer is r=45. Find the plaintext to be transmitted if the ciphertext is (28,9)
A.	45
B.	76
C.	66
D.	13
Answer» C. 66

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89.	In Asymmetric key Cryptography, although RSA can be used to encrypt and decrypt actual messages, it is very slow if the message is
A.	short
B.	long
C.	flat
D.	thin
Answer» B. long

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90.	Which of the following is not a type of symmetric-key cryptography technique?
A.	caesar cipher
B.	data encryption standard (des)
C.	diffie hellman cipher
D.	playfair cipher
Answer» C. diffie hellman cipher

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91.	In Elgamal cryptosystem, given the prime p=31,Choose e1= first primitive root of p and d=10, calculate e2
A.	24
B.	36
C.	25
D.	62
Answer» C. 25

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92.	How many bytes of the secret key is generated using Diffie-Hellman encryption/decryption scheme?
A.	256
B.	871
C.	1024
D.	962
Answer» A. 256

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93.	Computation of the discrete logarithm is the basis of the cryptographic system
A.	symmetric cryptography
B.	asymmetric cryptography
C.	diffie-hellman key exchange
D.	secret key cryptography
Answer» C. diffie-hellman key exchange

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94.	In Elgamal cryptosystem, given the prime p=31,Encrypt the message “HELLO”; use 00 to 25 for encoding. The value of C2 for character ‘O’ is
A.	9
B.	7
C.	23
D.	27
Answer» A. 9

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95.	What is the block size of RC6 Feistel block cipher?
A.	5013 bits
B.	128 bits
C.	596 bits
D.	1768 bits
Answer» B. 128 bits

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96.	What is the general equation for elliptic curve systems
A.	y3+b_1 xy+b_2 y=x33+a_1 x2+a_2 x+a_3
B.	y3+b_1 x+b_2 y=x2+a_1 x2+a_2 x+a_3
C.	y2+b_1 xy+b_2 y=x3+a_1 x2+a_2
D.	y2+b_1 xy+b_2 y=x3+a_1 x2+a_2 x+a_3
Answer» D. y2+b_1 xy+b_2 y=x3+a_1 x2+a_2 x+a_3

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97.	USENET falls under which category of public key sharing?
A.	public announcement
B.	publicly available directory
C.	public-key authority
D.	public-key certificates
Answer» A. public announcement

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98.	In Singular elliptic curve, the equation x^3+ax+b=0 does roots
A.	does not have three distinct
B.	has three distinct
C.	has three unique
D.	has three distinct unique
Answer» A. does not have three distinct

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99.	The value of 52003 mod 7 is(use fermat's theorem)
A.	3
B.	4
C.	8
D.	9
Answer» A. 3

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100.	Elliptic curve cryptography follows the associative property
A.	true
B.	false
Answer» A. true

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160+ Cryptography and Network Security (CNS) Solved MCQs

If the key is 110100001, the output of the SP network for the plaintext: 101110001 is

What is the number of possible 3 x 3 affine cipher transformations

What is the expanded key size of AES-192?

In affine block cipher systems if f(m)=Am + t, what is f(m1+m2+m3) ?

The 4×4 byte matrices in the AES algorithm are called

If the block size is ‘s’, how many affine transformations are possible ?

For the AES-128 algorithm there are similar rounds and round is different.

The DES Algorithm Cipher System consists of rounds (iterations) each with a round key

DES follows

Every cyclic group is .

In the DES algorithm the round key is bit and the Round Input is bits

is not a binary operation on the set of natural numbers.

In the DES algorithm the Round Input is 32 bits, which is expanded to 48 bits via

Which of the following is group under multiplication?

The Initial Permutation table/matrix is of size

The number of unique substitution boxes in DES after the 48 bit XOR operation are

The DES algorithm has a key length of

What is the size of the key in the SDES algorithm?

The Plaintext for the Ciphertext 10100101, given that the key is 0010010111 is

Assume input 10-bit key, K: 1010000010 for the SDES algorithm. What is K1?

Assume input 10-bit key, K: 0010010111 for the SDES algorithm. What is K2?

Which of the following is a mode of operation for the Block ciphers in cryptography?

Which of the following modes of operations can be followed for both stream ciphers as well as block ciphers?

The Plaintext for the Ciphertext 00001111, given that the key is 1111111111 is

Which one of the following RC4 algorithm not used in?

Till when was the RC4 algorithm kept a secret?

The Plaintext for the Ciphertext 00100010, given that the key is 1111111111 is

The man-in-the-middle attack can endanger the security of the Diffie-Hellman method if two parties are not

RSA is also a stream cipher like Merkel-Hellman

Rabin Cryptosystem is a variant of the Elgamal Cryptosystem

In RSA, Ф(n) = in terms of p and q

In Asymmetric Key Cryptography, the two key, e and d, have a special relationship to

Using Rabin cryptosystem with p=23 and q=7 ,Encrypt P=24 to find ciphertext. The Cipher text is

For RSA to work, the value of P must be less than the value of

Session keys are transmitted after being encrypted by

Which Cryptographic system uses C1 = (e1r) mod p and C1 = (e2r x P) mod p at the encryption side?

The certificate message is required for any agreed-on key exchange method except

Sender chooses p = 107, e1 = 2, d = 67, and the random integer is r=45. Find the plaintext to be transmitted if the ciphertext is (28,9)

In Asymmetric key Cryptography, although RSA can be used to encrypt and decrypt actual messages, it is very slow if the message is

Which of the following is not a type of symmetric-key cryptography technique?

In Elgamal cryptosystem, given the prime p=31,Choose e1= first primitive root of p and d=10, calculate e2

How many bytes of the secret key is generated using Diffie-Hellman encryption/decryption scheme?

Computation of the discrete logarithm is the basis of the cryptographic system

In Elgamal cryptosystem, given the prime p=31,Encrypt the message “HELLO”; use 00 to 25 for encoding. The value of C2 for character ‘O’ is

What is the block size of RC6 Feistel block cipher?

What is the general equation for elliptic curve systems

USENET falls under which category of public key sharing?

In Singular elliptic curve, the equation x^3+ax+b=0 does roots

The value of 52003 mod 7 is(use fermat's theorem)

Elliptic curve cryptography follows the associative property