Question

What will be the plain text corresponding to cipher text “RSEADC” if with the number of columns are given to be 3 and route of reading is down the columns?

(a) SACRED

(b) DERSAC

(c) REDSAC

(d) SEDRAC

I have been asked this question during an interview.

My question is taken from Cryptography in chapter Cryptography of Data Structures & Algorithms II

Answer 1

The correct option is (c) REDSAC

The explanation is: For decryption we reverse the process used in encryption. So we arrange the letters of cipher text down the columns and then read the grid horizontally.

R

E

D

S

A

C

So the resulting plain text is “REDSAC”.