Question

Which of the following is a difference between running key cipher and vigenere cipher?

(a) they use different tables for encryption

(b) vigenere cipher is poly alphabetic whereas running key cipher is mono alphabetic

(c) in vigenere cipher the key is repeated whereas in running key cipher key is not repeated

(d) vigenere cipher was used in ancient time whereas running key cipher is used in modern world

The question was asked in examination.

This intriguing question comes from Cryptography in chapter Cryptography of Data Structures & Algorithms II

Answer 1

Correct choice is (c) in vigenere cipher the key is repeated whereas in running key cipher key is not repeated

Easy explanation - In running key cipher key is not repeated unlike vigenere cipher. They both use the same table for encryption.