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In _____ substitution, a character in the plaintext is always changed to the same character in ciphertext, regardless of its position in the text.

  1. polyalphabetic
  2. monoalphabetic
  3. transpositional
  4. multialphabetic

2 Answers

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3 votes

Answer :mono-alphabetic

Mono-alphabetic Substitution Ciphers are probably the most common form of cipher. They work by replacing each letter of the plain-text with another letter (or possibly even a random symbol). 

A mono-alphabetic substitution cipher, also known as a simple substitution cipher, relies on a fixed replacement structure. That is, the substitution is fixed for each letter of the alphabet. Thus, if "a" is encrypted to "R", then every time we see the letter "a" in the plain-text, we replace it with the letter "R" in the cipher-text.

Reference : Example is here

1 votes
1 votes

ans is B

 rest options do not guarantee  that  a character in the plaintext is always changed to the same character in ciphertext  as 

polyalphabetic (or multialphabetic) cipher is any cipher based on substitution, using multiple substitution alphabets.

transposition cipher is a method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the ciphertextconstitutes a permutation of the plaintext.

as same alphabet may have different positions in a text hence its cipher text will be different

Answer:

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