Question

What is the rule for encryption in playfair cipher if the letters in a pair appear in same column?

(a) they are replaced by the letter appearing immediately below them respectively

(b) they are replaced by the letter appearing immediately right to them respectively

(c) they are replaced by the letters at the corner of the row

(d) that pair is neglected

I have been asked this question in an online interview.

The query is from Cryptography topic in division Cryptography of Data Structures & Algorithms II

Answer 1

Right option is (a) they are replaced by the letter appearing immediately below them respectively

The best I can explain: If the letters in a pair appear in the same column then they are replaced by the letters appearing immediately below them respectively. If the element to be replaced appears at the corner of the column then we wrap around to the top side of that column.