Question

What will be the plain text corresponding to cipher text “XKS” if the bifid cipher is used with key as “KEY” and period as 5?

(a) IND

(b) USA

(c) RSA

(d) AUS

This question was posed to me in an online quiz.

This question is from Cryptography topic in section Cryptography of Data Structures & Algorithms II

Answer 1

Right answer is (b) USA

Best explanation: The decryption in bifid cipher begins identically to encryption. Then we find the corresponding coordinates and then we get the plain text. So the plain text is “USA”.