160+ Cryptography and Network Security (CNS) Solved MCQs

1.

In symmetric-key cryptography, the key locks and unlocks the box is

A. same
B. shared
C. private
D. public
Answer» A. same
2.

The keys used in cryptography are

A. secret key
B. private key
C. public key
D. all of them
Answer» D. all of them
3.

Cryptography, a word with Greek origins, means

A. corrupting data
B. secret writing
C. open writing
D. closed writing
Answer» B. secret writing
4.

A transposition cipher reorders (permutes) symbols in a

A. block of packets
B. block of slots
C. block of signals
D. block of symbols
Answer» D. block of symbols
5.

Network Security provides authentication and access control for resources.

A. true
B. false
Answer» A. true
6.

Which is not an objective of network security?

A. identification
B. authentication
C. access control
D. lock
Answer» D. lock
7.

The process of verifying the identity of a user.

A. authentication
B. identification
C. validation
D. verification
Answer» A. authentication
8.

Which of these is a part of network identification?

A. user id
B. password
C. otp
D. fingerprint
Answer» A. user id
9.

The process of transforming plain text into unreadable text.

A. decryption
B. encryption
C. network security
D. information hiding
Answer» B. encryption
10.

An algorithm used in encryption is referred to as cipher.

A. true
B. false
Answer» A. true
11.

A process of making the encrypted text readable again.

A. decryption
B. encryption
C. network security
D. information hiding
Answer» A. decryption
12.

A person who enjoys learning details about computers and how to enhance their capabilities.

A. cracker
B. hacker
C. app controller
D. site controller
Answer» B. hacker
13.

A small program that changes the way a computer operates.

A. worm
B. trojan
C. bomb
D. virus
Answer» D. virus
14.

An asymmetric-key (or public-key) cipher uses

A. 1 key
B. 2 key
C. 3 key
D. 4 key
Answer» B. 2 key
15.

We use cryptofraphy term to transform messages to make them secure and immune to

A. change
B. idle
C. attacks
D. defend
Answer» C. attacks
16.

In cryptography , the original message before being transformmed , is called

A. simple text
B. plain text
C. empty text
D. filled text
Answer» B. plain text
17.

A straight permutation cipher or a straight p-box has the same number of input as

A. cipher
B. frames
C. outputs
D. bits
Answer» C. outputs
18.

The man-in-the-middle attack can endanger the security of the diffie-hellman if two parties are not

A. authenticated
B. joined
C. submit
D. separate
Answer» A. authenticated
19.

Which of the following is not a transport layer vulnerability?

A. mishandling of undefined , poorly defined
B. the vulnerability that allows fingerprinting & other enumeration of host information
C. overloading of transporting layer mechanisms
D. unauthorized network access
Answer» D. unauthorized network access
20.

Transmission mechanisms can be subject to spoofing & attacks based on skilled modified packets.

A. true
B. false
Answer» A. true
21.

TCP/IP model does not have                layer but OSI model have this layer.

A. session layer
B. transport layer
C. application layer
D. network layer
Answer» A. session layer
22.

In cryptography, what is cipher?

A. algorithm for performing encrption and decryption
B. encrypted message
C. both algorith for performing encrption and decryption and encrypted message
D. decrypted message
Answer» A. algorithm for performing encrption and decryption
23.

In cryptography, the order of the letters in a message is rearranged by

A. transpositional ciphers
B. substitution ciphers
C. both
D. quadratic ciphers
Answer» A. transpositional ciphers
24.

What is data encryption standard (DES)?

A. block cipher
B. stream cipher
C. bit cipher
D. byte cipher
Answer» A. block cipher
25.

Cryptanalysis is used                         

A. to find some insecurity in a cryptographic scheme
B. to increase the speed
C. to encrypt the data
D. to make new ciphers
Answer» A. to find some insecurity in a cryptographic scheme
26.

Choose from among the following cipher systems, from best to the worst, with respect to ease of decryption using frequency analysis.

A. random polyalphabetic , plaintext , playfair
B. random polyalphabetic , playfair , vignere
C. random polyalphabetic , vignere , playfair , plaintext
D. random polyalphabetic , plaintext , beaufort , playfair
Answer» C. random polyalphabetic , vignere , playfair , plaintext
27.

On Encrypting “thepepsiisintherefrigerator” using Vignere Cipher System using the keyword “HUMOR” we get cipher text-

A. abqdnwewuwjphfvrrtrfzn sdokvl
B. abqdvmwuwjphfvvyyrf znydokvl
C. tbqyrvmwuwjphfvvyy rfznydokvl
D. baiuvmwuwjphfoeiyrf znydokvl
Answer» B. abqdvmwuwjphfvvyyrf znydokvl
28.

. Rail Fence Technique is an example of

A. substitution
B. transposition
C. product cipher
D. ceaser cipher
Answer» B. transposition
29.

Public key encryption is advantageous over Symmetric key Cryptography because of

A. speed
B. space
C. key exchange
D. key length
Answer» C. key exchange
30.

The sub key length at each round of DES is

A. 32
B. 56
C. 48
D. 64
Answer» B. 56
31.

Which one is the strong attack mechanism?

A. chosen plaintext attack
B. chosen cipher text
C. brute force attack
D. man in the middle attack
Answer» C. brute force attack
32.

Interception is an attack on

A. availability
B. confidentiality
C. integrity
D. authenticity
Answer» B. confidentiality
33.

Chosen cipher text attack is based on

A. cryptanalysis
B. cryptography
C. encryption
D. decryption
Answer» A. cryptanalysis
34.

The process of writing the text as rows and read it as columns is known as

A. vernam cipher
B. ceaser cipher
C. transposition columnar cipher
D. homophonic substitution cipher
Answer» C. transposition columnar cipher
35.

Biometric authentication works on the basis of

A. human characteristics
B. passwords
C. smart cards
D. pin
Answer» A. human characteristics
36.

Which layer filters the proxy firewall?

A. application
B. network
C. transport
D. none of the above
Answer» A. application
37.

Encryption Strength is based on

A. strength of algorithm
B. secrecy of key
C. length of key
D. all of the above
Answer» D. all of the above
38.

GCD(a,b) = GCD(b,a mod b)

A. true
B. false
C. cannot be determined
D. none
Answer» A. true
39.

All groups satisfy properties

A. g-i to g-v
B. g-i to g-iv
C. g-i to r-v
D. r-i to r-v
Answer» C. g-i to r-v
40.

An Abelian Group satisfies the properties

A. g-i to g-v
B. g-i to g-iv
C. g-i to r-v
D. r-i to r-v
Answer» A. g-i to g-v
41.

A Ring satisfies the properties

A. r-i to r-v
B. g-i to g-iv
C. g-i to r-v
D. g-i to r-iii
Answer» D. g-i to r-iii
42.

A Ring is said to be commutative if it also satisfies the property

A. r-vi
B. r-v
C. r-vii
D. r-iv
Answer» D. r-iv
43.

An ‘Integral Domain’ satisfies the properties

A. g-i to g-iii
B. g-i to r-v
C. g-i to r-vi
D. g-i to r-iii
Answer» C. g-i to r-vi
44.

Does the set of residue classes (mod 3) form a group with respect to modular addition?

A. yes
B. no
C. can\t say
D. insufficient data
Answer» A. yes
45.

For the group Sn of all permutations of n distinct symbols, what is the number of elements in Sn?

A. n
B. n-1
C. 2n
D. n!
Answer» D. n!
46.

a(b+c) = ac+bc is the representation for which property?

A. g-ii
B. g-iii
C. r-ii
D. r-iii
Answer» D. r-iii
47.

a.(b.c) = (a.b).c is the representation for which property?

A. g-ii
B. g-iii
C. r-ii
D. r-iii
Answer» A. g-ii
48.

AES uses a                             bit block size and a key size of                        bits.

A. 128; 128 or 256
B. 64; 128 or 192
C. 256; 128, 192, or 256
D. 128; 128, 192, or 256
Answer» D. 128; 128, 192, or 256
49.

Like DES, AES also uses Feistel Structure.

A. true
B. false
C. cannot be determined
D. none
Answer» B. false
50.

Which one of the following is not a cryptographic algorithm?

A. jupiter
B. blowfish
C. serpent
D. none
Answer» A. jupiter
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
52.

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

A. 168
B. 840
C. 1024
D. 1344
Answer» D. 1344
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
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)
55.

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

A. states
B. words
C. transitions
D. permutations
Answer» A. states
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))
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
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
59.

DES follows

A. hash algorithm
B. caesars cipher
C. feistel cipher structure
D. sp networks
Answer» C. feistel cipher structure
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
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
62.

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

A. addition
B. product
C. difference
D. none
Answer» C. difference
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
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}
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
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
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
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
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
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
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
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
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)
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
75.

Which one of the following RC4 algorithm not used in?

A. ssl
B. tls
C. ftp
D. wep
Answer» C. ftp
76.

Till when was the RC4 algorithm kept a secret?

A. 1990
B. 1992
C. 1996
D. 1994
Answer» D. 1994
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
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
79.

RSA is also a stream cipher like Merkel-Hellman

A. true
B. false
Answer» A. true
80.

Rabin Cryptosystem is a variant of the Elgamal Cryptosystem

A. true
B. false
Answer» B. false
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)
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
99.

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

A. 3
B. 4
C. 8
D. 9
Answer» A. 3
100.

Elliptic curve cryptography follows the associative property

A. true
B. false
Answer» A. true
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