This was one of the most secure hand ciphers used in the Second World ... A T H E R S M E L T O F E L D E R B E R R I E S Now number the letters in the keyword in alphabetical order.

The first step in breaking any cipher is to try to find ... it is easy to see that the number of places it would fit are limited by the fact that no letter can be enciphered as itself.

A cipher is a code used to protect information ... Now you can encrypt messages with numbers instead of letters. You could start by making A = 1, B = 2 and C = 3, but once you've practised a ...

One person encrypts, and the other decrypts using the key." In a cipher system, for example, each letter is replaced with a number. To make it more complicated, each letter can be substituted with ...