Question 8931 – ISRO CS 2020
December 24, 2023Question 8953 – ISRO CS 2020
December 24, 2023Question 8935 – ISRO CS 2020
In a columnar transposition cipher, the plain text is “the tomato is a plant in the night shade family”, keyword is “TOMATO”. The ciphertext is
Correct Answer: A
encrypt the message “The tomato is a plant in the nightshade family” using the keyword tomato. We get the grid given below.
We have written the keyword above the grid of the plaintext, and also the numbers telling us which order to read the columns in. Notice that the first “O” is 3 and the second “O” is 4, and the same thing for the two “T”s.
The plaintext is written in a grid beneath the keyword. The numbers represent the alphabetical order of the keyword, and so the order in which the columns will be read.
Starting with the column headed by “A”, our ciphertext begins “TINESAX” from this column. We now move to the column headed by “M”, and so on through the letters of the keyword in alphabetical order to get the ciphertext “TINESAX / EOAHTFX / HTLTHEY / MAIIAIX / TAPNGDL / OSTNHMX” (where the / tells you where a new column starts). The final ciphertext is thus “TINESAX EOAHTFX HTLTHEY MAIIAIX TAPNGDL OSTNHMX”.