In order for transposition to be effective, the rearrangement of letters needs to follow a straightforward system, one that has been previously agreed by the sender and receiver, but kept secret from the enemy. In this section we explore two types of transposition: the rail fence cipher and the Latin Square.

The rail fence cipher involves writing the message such that alternate letters are written on separate upper and lower lines. The sequence of letters on the upper line is then followed by the sequence on the lower line, to create the final encrypted message. You can see how the rail fence cipher works by going to the next page.