Whetstone Cipher Machine


This is not really a paper and pencil cipher, it is one of the simplest cipher machines. It uses a watch-like setup: A long hand pointing towards the plain text alphabet and a short hand pointing towards the cipher text alphabet. The plaintext alphabet consists of the 26 letters A-Z in the normal alphabetic order preceded by a word separator. The cipher text alphabet consists of the 26 letters A-Z, unordered and without additional word separator. The long and the short hand are connected by a 27/26 gear, so that moving one pointer by one character moves the other by one character as well.

To encipher, the long hand is moved clockwise until it points to the character to be enciphered and it's cipher text substitution is obtained from the position of the short hand. At the end of a word, the long hand is moved clockwise to the word separator and the character at the position of the short hand is written down, too. Thus this cipher conserves the word spacing.

Note that the cipher can't encrypt double letters: They must either be omitted, separated a null or the second must replace by a null.

When using this cipher, you need to know the (mixed) cipher text alphabet and the initial positions of the pointers. Within CipherClerk's Applet's implementation, you specify the the cipher text alphabet by a key word and an algorithm how to generate the mixed alphabet (see how a substitution is generated), while the two hands point to the first letters of the alphabet.

To proceed, you may