Cryptography MCQ

Test your knowledge with important Cryptography MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30 + more Cryptography MCQs at Bissoy

• What is the role of Key Distribution Center?
  ক

  It is used to distribute keys to everyone in world

  খ

  It intended to reduce the risks inherent in exchanging keys

  গ

  All of the mentioned

  ঘ

  None of the mentioned
• Which two of the following are authentication algorithms?
  ক

  MAC

  খ

  AES

  গ

  DAS

  ঘ

  Digital-signature
• SHA-1 produces __________ bit of hash.
  ক

  128

  খ

  160

  গ

  150

  ঘ

  112
• MD5 produces __________ bits hash data.
  ক

  128

  খ

  150

  গ

  160

  ঘ

  112
• Which of the following is not a stream cipher?
  ক

  Two fish

  খ

  RC5

  গ

  RC4

  ঘ

  TBONE
• What is not an encryption standard?
  ক

  AES

  খ

  TES

  গ

  Triple DES

  ঘ

  DES
• What is cipher-block chaining?
  ক

  Data is logically ‘ANDed’ with previous block

  খ

  Data is logically ‘ORed’ with previous block

  গ

  Data is logically ‘XORed’ with previous block

  ঘ

  None of the mentioned
• What is not a role of encryption?
  ক

  It is used to protect data from unauthorized access during transmission

  খ

  It is used to ensure user authentication

  গ

  It is used to ensure data integrity

  ঘ

  It is used to ensure data corruption doesn’t happens
• What is the preferred way of encryption?
  ক

  pre shared secret key

  খ

  using key distribution center (KDC)

  গ

  public key-encryption

  ঘ

  symmetric key
• Reduce the following Big-O notation. O = . b) O. c) O. d) O.
  ক

  = ] O.

  খ

  ax7 + 3 x3 + sin(x)

  গ

  ax7 + 3 x3 + sin(x)

  ঘ

  ax7 + 3 x3 + sin(x)
• 12. For p = 11 and q = 17 and choose e=7. Apply RSA algorithm where Cipher message=11 and thus find the plain text.
  ক

  88

  খ

  122

  গ

  143

  ঘ

  111
• Using SDES, the Plaintext for the Ciphertext 00001111, given that the key is 1111111111 is,
  ক

  01100111

  খ

  00001010

  গ

  11111111

  ঘ

  01101101
• Using Differential Crypt-analysis, the minimum computations required to decipher the DES algorithm is-
  ক

  256

  খ

  243

  গ

  255

  ঘ

  247
• In the DES algorithm the Round Input is 32 bits, which is expanded to 48 bits via ______________
  ক

  Scaling of the existing bits

  খ

  Duplication of the existing bits

  গ

  Addition of zeros

  ঘ

  Addition of ones
• Which function can be used in AES multiplication –
  ক

  m(x)=x7+x4+x3

  খ

  m(x)=x8+x4+x3+x+1

  গ

  m(x)=x8+x3+x2+x+1

  ঘ

  m(x)=x8+x5+x3+x
• The inverse s-box permutation follows, b’i = b(i+2) XOR b(i+5) XOR b(i+7) XOR di Here di is –
  ক

  di is the ith bit of a byte ‘d’ whose hex value is 0x15

  খ

  di is the ith bit of a byte ‘d’ whose hex value is 0x05

  গ

  di is the ith bit of a byte ‘d’ whose hex value is 0x25

  ঘ

  di is the ith bit of a byte ‘d’ whose hex value is 0x51
• In AES, to make the s-box, we apply the transformation – b’i = bi XOR b(i+4) XOR b(i+5) XOR b(i+6) XOR b(i+7) XOR ci What is ci in this transformation?
  ক

  ci is the ith bit of byte c with value 0x63

  খ

  ci is the ith bit of byte c with value 0x25

  গ

  ci is the ith bit of byte c with value 0x8F

  ঘ

  ci is the ith bit of byte c with value 0x8A
• Division of (131B6C3) base 16 by (lA2F) base 16 yeilds
  ক

  1AD

  খ

  DAD

  গ

  BAD

  ঘ

  9AD
• The plain text for the cipher text RRLMWBKASPDH. Given the encryption key is –
  ক

  is – ] PAYMOREMONEY

  খ

  (17 17 5 | 21 18 21 | 2 2 19)

  গ

  (17 17 5 | 21 18 21 | 2 2 19)

  ঘ

  (17 17 5 | 21 18 21 | 2 2 19)
• On Encrypting “thepepsiisintherefrigerator” using Vignere Cipher System using the keyword “HUMOR” we get cipher text
  ক

  abqdnwewuwjphfvrrtrfznsdokvl

  খ

  abqdvmwuwjphfvvyyrfznydokvl

  গ

  tbqyrvmwuwjphfvvyyrfznydokvl

  ঘ

  baiuvmwuwjphfoeiyrfznydokvl
• Maurer’s Universal Statistical Test is
  ক

  a test to determine whether the number of runs of ones and zeros of various lengths is as expecte

  খ

  a test to detect if a sequence can be significantly compressed without loss of information

  গ

  a test to determine whether the number of ones and zeros in a sequence is approx the same as in a truely random o/p

  ঘ

  a test for the check of evenness in the 1s and 0s
• The GCD of x5+ x4+ x3– x2 – x + 1 and x3 + x2+ x + 1 over GF(3) is
  ক

  1

  খ

  x

  গ

  x + 1

  ঘ

  x2 + 1
• Multiply the polynomials P1 = (x5 + x2 + x) by P2 = (x7 + x4 + x3 + x2 + x) in GF(28) with irreducible polynomial (x8 + x4 + x3 + x + 1). The result is
  ক

  x4+ x3+ x+1

  খ

  x5+ x3+ x2+x+1

  গ

  x5+ x4+ x3+x+1

  ঘ

  x5+ x3+ x2+x
• The last two blocks of the XTS-AES mode are
  ক

  padded as 10*

  খ

  encrypted/ decrypted using ciphertext-stealing

  গ

  padded as 10*1

  ঘ

  padded and then swapped after encryption/ decryption
• 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
• A total of seven messages are required in the Public-Key distribution scenario. However, the initial five messages need to be used only infrequently because both A and B can save the other’s public key for future – a technique known as ____________
  ক

  time stamping

  খ

  polling

  গ

  caching

  ঘ

  squeezing
• Suppose that A has obtained a certificate from certification authority X1 and B has obtained certificate authority from CA X2. A can use a chain of certificates to obtain B’s public key. In notation of X.509, the correct order of this chain is represented as –
  ক

  X2 X1 X1 B

  খ

  X1 X1 X2 A

  গ

  X1 X2 X2 B

  ঘ

  X1 X2 X2 A
• It is desirable to revoke a certificate before it expires because –
  ক

  the user is no longer certified by this CA

  খ

  the CA’s certificate is assumed to be compromised

  গ

  the user’s private key is assumed to be compromised

  ঘ

  all of the mentioned
• The multiplicative Inverse of 550 mod 1769 is –
  ক

  434

  খ

  224

  গ

  550

  ঘ

  Does not exist
• 10.Find the solution of x2≡3 mod 23
  ক

  x≡±16 mod 23

  খ

  x≡±13 mod 23

  গ

  x≡±22 mod 23

  ঘ

  x≡±7 mod 23