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.

Here's your chance to crack ciphers similar to those Bletchley Park's codebreakers faced during World War II. Below, we present three ciphers of different levels of difficulty, from easiest to ...

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.