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

Her duress code was to use a double transposition key with precisely 18 letters, so we know this message was not sent under duress.

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.

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 ...