Today’s Math Monday begins a multi-part series on the columnar transposition cipher.

It’s Math Monday! In this third post in a series on columnar transposition ciphers, we look at a formula for the underlying permutation of a CTC and specialize it to the rail fence cipher.

To decrypt a double transposition, construct a block with the right number of rows under the keyword, blocking off the short columns. Write the cipher in by columns, and read it out by rows.

Provide students with definitions and examples of the two main cipher systems described below. Then have pairs write one transposition and one substitution cipher.

Explaining one of the simplest and historically well-known ciphers, the Caesar cipher, Holden establishes the key mathematical idea behind the cipher and discusses how to introduce flexibility and ...