Symmetric Ciphers MCQ

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• RC4 algorithm uses the concept of Block Cipher System.
  ক

  True

  খ

  False
• Till when was the RC4 algorithm kept a secret?
  ক

  1990

  খ

  1992

  গ

  1996

  ঘ

  1994
• Which one of the following RC4 algorithm not used in?
  ক

  SSL

  খ

  TLS

  গ

  FTP

  ঘ

  WEP
• Which of these is not a characteristic of block ciphers?
  ক

  Variable key length / block size / number of rounds

  খ

  Mixed operators, data/key dependent rotation

  গ

  Key independent S-boxes

  ঘ

  More complex key scheduling
• Which RC5 mode will have the ciphertext longer than the plaintext by at most the size of a single RC5 block?
  ক

  RC5 block cipher

  খ

  RC5-Cipher Block Chaining

  গ

  RC5-Cipher Block Chaining Pad

  ঘ

  RC5-CipherText Stealing
• Which one of the following is not a RC5 mode of operation?
  ক

  RC5 block cipher

  খ

  RC5-Cipher Block Chaining

  গ

  RC5-Cipher Padding

  ঘ

  RC5-CipherText Stealing
• “RC5 uses the Feistel Structure.”
  ক

  True

  খ

  False
• RC5 encryption uses Right shift and decryption uses Left shift.
  ক

  True

  খ

  False
• Calculate the number of subkeys required in RC5 for 18 rounds of computation.
  ক

  40

  খ

  38

  গ

  36

  ঘ

  34
• In RC5, the initialization operations makes use of magic constants defined as follows: P_w=Odd. Q_w=Odd. What is the hexadecimal value of Qw for word size of 32 bits?
  ক

  . Q_w=Odd. What is the hexadecimal value of Qw for word size of 32 bits? ] 9D3779B4

  খ

  (e-2) 2w

  গ

  (e-2) 2w

  ঘ

  (e-2) 2w
• In RC5, the initialization operations makes use of magic constants defined as follows: P_w=Odd. Q_w=Odd. What is the hexadecimal value of Pw for word size of 16 bits?
  ক

  . Q_w=Odd. What is the hexadecimal value of Pw for word size of 16 bits? ] B7DF

  খ

  (e-2) 2w

  গ

  (e-2) 2w

  ঘ

  (e-2) 2w
• The value of the golden ratio is
  ক

  ᶲ =2.618

  খ

  ᶲ =1.622

  গ

  ᶲ =1.743

  ঘ

  ᶲ =1.618
• The value of the base of natural logarithms is
  ক

  e= 2.7073

  খ

  e= 2.7183

  গ

  e= 3.7183

  ঘ

  e= 1.7273
• RC5 uses 2 magic constants to define their subkeys. These are
  ক

  Base of natural Logarithm and Golden ratio

  খ

  Base of natural Logarithm and Pi

  গ

  Golden Ratio and Pi

  ঘ

  Pi and Golden Ration
• The total number of subkeys t used in the RC5 algorithm is given by the formula (r corresponds to number of rounds)
  ক

  t=2r+4

  খ

  t=2r

  গ

  t=2r+2

  ঘ

  t=2r-2
• The standard/nominal version of the RC5-w/r/b has parameters w/r/b as
  ক

  32/18/16

  খ

  16/18/16

  গ

  32/12/16

  ঘ

  32/16/18
• The number of rounds in RC5 can range from 0 to _____________
  ক

  127

  খ

  63

  গ

  255

  ঘ

  31
• What are the allowable values of word size in bit for RC5 algorithm?
  ক

  16, 32

  খ

  16, 32, 64

  গ

  8, 16, 32

  ঘ

  16, 32, 48
• The 32bit output of s-box 1 is XORed with s-box 2.
  ক

  True

  খ

  False
• A single blowfish s-box converts 8-bits to _________ bits.
  ক

  32

  খ

  44

  গ

  56

  ঘ

  64
• What is the number of iterations required in total to generate all the sub-keys in blowfish?
  ক

  512

  খ

  521

  গ

  256

  ঘ

  128
• P15 gets XORed with
  ক

  K3

  খ

  K14

  গ

  K1

  ঘ

  K6
• P17 gets XORed with
  ক

  K3

  খ

  K12

  গ

  K17

  ঘ

  K6
• To generate the sub-key P1 to P18 we use the hexadecimal equivalent digits of ____________
  ক

  0.7864

  খ

  0.1415

  গ

  0.1542

  ঘ

  0.7535
• In blowfish, the keys are stored in the form of an array ranging from K1, K2 to Ki. What is the value of i?
  ক

  12

  খ

  16

  গ

  8

  ঘ

  14
• How many entries are present in each of the S-boxes present in the blowfish algorithm?
  ক

  256

  খ

  512

  গ

  1024

  ঘ

  64
• How many S-boxes are present in the blowfish algorithm?
  ক

  2

  খ

  4

  গ

  6

  ঘ

  8
• XOR and addition operations take place on bytes of size
  ক

  8 bits

  খ

  16 bits

  গ

  32 bits

  ঘ

  64 bits
• Blowfish algorithm uses the Feistel Structure.
  ক

  True

  খ

  False
• The blowfish algorithm’s key expansion converts a key of at most 448 bits into several subkey arrays totaling ___________ bytes.
  ক

  4096

  খ

  4608

  গ

  4168

  ঘ

  4864