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MCQ | Cryptography Ciphers (Level: Easy)

Here, we have a set of multiple-choice questions and answers (quiz) on ciphers in Cryptography (basic concepts of Cryptography Techniques and different types of ciphers).
Submitted by Monika Sharma, on February 02, 2020

1) We are provided the plain text “SUN”. You need to convert the given plain text into ciphertext under the Ceasar cipher encryption technique. Which of the following options is the correct ciphertext for the given text if the key is 2?

  1. UWP
  2. NUS
  3. WUP
  4. QSL

Answer: a) UWP

Explanation:

In the Caesar cipher technique, the encryption is performed as follows,

    E ( P , K ) = ( P + K ) mod 26

    Therefore, 
    E ( S , 2 ) = ( 18 + 2 ) mod 26 = 20 = U
    E ( U , 2 ) = ( 20 + 2 ) mod 26 = 22 = W
    E ( N , 2 ) = ( 13 + 2 ) mod 26 = 15 = P
    Hence, the ciphertext is "UWP".

2) Which of the following cannot be chosen as a key in the Caesar cipher?

  1. An integer
  2. An alphabet (A-Z or a-z)
  3. A string
  4. None of the above

Answer: c) A string

Explanation:

In Caesar cipher, we can choose a number or a character which when performed addition modulo operation with the given letters of the plain text gives us ciphertext. However, a string cannot be chosen for encryption in this case.


3) Which of the following cipher techniques include the involvement of matrix operations in their algorithms of encryption and decryption?

  1. Hill Cipher
  2. Playfair cipher
  3. Both a and b
  4. None of the above

Answer: c) Both a and b

Explanation:

The hill cipher includes a square matrix as the key, and in Playfair cipher, we create a 5X5 matrix using the given key string. Hence, both these ciphers include the use of matrices.


4) Which of the following ciphers is a block cipher?

  1. Caesar cipher
  2. Vernam cipher
  3. Playfair cipher
  4. None of the above

Answer: c) Playfair cipher

Explanation:

The Playfair cipher uses a block of plain text, each block containing 2 characters.


5) Which of the following ciphers uses asymmetric key cryptography?

  1. Rail Fence Cipher
  2. Data Encryption Standard (DES)
  3. Diffie Hellman Cipher
  4. None of the above

Answer: c) Diffie Hellman Cipher

Explanation:

The Diffie Hellman cipher uses asymmetric key cryptography. It uses a pair of keys, one private and one public.







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