Question

In which of the following cipher the plain text and the ciphered text does not have same number of letters?

(a) affine cipher

(b) autokey cipher

(c) columnar cipher

(d) additive cipher

I had been asked this question during an interview.

Origin of the question is Cryptography in division Cryptography of Data Structures & Algorithms II

Answer 1

The correct answer is (b) autokey cipher

Easy explanation - In transposition cipher and mono alphabetic cipher the number of letters remain same in ciphered and deciphered text. But in poly alphabetic cipher the number of letters are different. So here as autokey cipher is the only poly alphabetic cipher so it will be the answer.