Columnar Transposition Grid Reconstruction

Your alarm goes off and, after hitting “snooze” once or twice, you pry yourself out of bed. You make a cup of coffee to help you get going, and then you shower, get dressed, eat breakfast, and check your phone for messages. On your way to school, you stop to fill your car’s gas tank, almost making you late for the first day of chemistry class. As you find a seat in the classroom, you read the question projected on the screen: “Welcome to class! Why should we study chemistry”

Figures (10)

The Playfair cipher uses a 5×5 grid of letters, and encrypts a message by breaking the text into pairs of letters and swapping them according to their positions in a rectangle within that grid: "HI" becomes "BM".

Lord Playfair, who heavily promoted its use.

The Playfair system was invented by Charles Wheatstone, who first described it in 1854.

Marian Rejewski c. 1932, when he first broke Enigma

Key Points

In a columnar transposition, the message is written out in rows of a fixed length, and then read out again column by column, and the columns are chosen in some scrambled order.
With 600 possible bigrams rather than the 26 possible monograms (single symbols, usually letters in this context), a considerably larger cipher text is required in order to be useful.

Terms

Tap a term for a plain-language explanation.

Sources & licensing(4)

OpenStax — openstax.org/books/chemistry-2e/pages/1-introduction (Creative Commons Attribution 4.0)
Wikipedia contributors — en.wikipedia.org/wiki/Transposition_cipher (Creative Commons Attribution-ShareAlike 4.0)
Wikipedia contributors — en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma (Creative Commons Attribution-ShareAlike 4.0)
Wikipedia contributors — en.wikipedia.org/wiki/Playfair_cipher (Creative Commons Attribution-ShareAlike 4.0)