Skytale

Functionality and example

The scytale (Greek for „baton“) is the oldest known cryptographic technique. More than 2.55 years ago the Spartans were said to deliver encrypted messages. They used a rod with a predefined diameter, the scytale. It is the classical example for an transposition cipher. A transposition cipher does not subsitute any letters or words with other one but only shuffles the letters systematically.

Quelle: Wikipedia

n order to compose a message

the author had to wrap a parchment or a strip of leather around the scytale

and then to write the message on the parchment along the scytale.

Afterwards the parchment would be removed and the message brought to the recipient without the rod. (the letters of the first line are marked in red, those of the second one in yellow).

If the message would fall into the wrong hands it would be uncomprehensible since the letters would appear to be in arbitrary order. Yet the correct recipient would be able to decipher the message using a scytale (a rod with the same predifined diameter the author used). The diameter of the rod itself is the key for this encryption method.

Operation

Input

Input of the text to be de- or encrypted
Choice of the diameter as “secret key” (Letters per "round")
Choice of strip width; in most cases the single letters are written down the strip as in "T E S T 1 2 3". But sometimes the strip width is big enough for more letters as in "TE ST 12 3". But this is more unsecret because of the bigger continous readable text parts
Choice of de- or encryption

Output