Scytale Cipher
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Introduction
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Scytale was a simple transposition cipher that was used by the ancient
Greeks and Spartans to communicate during their military campaigns. It
was quite popular due to the easy and speed in which the message could
be deciphered by the other party. All that was required was a roll of
wood that was exactly the same size as the roll used by the sending
party.

What is a "Transposition Cipher"?
---------------------------------
A transposition cipher is used when a message is encrypted by changing
the position of the letters in the text into a different order/sequence. In
order to decipher the cipher text, all that is needed is for the text to
be reversed by the same method that was used in encrypting it. In other
words, if we took the word "test" and changed it by shifting all
characters one space to the right with text wrapping, we would get
"ttes". All that is needed to get the original word back is to shift it
by one character to the left.

How Does The Scytale Cipher Work?
---------------------------------
The Scytale cipher involves three pieces of equipment, namely a pen, a
long strip of paper (leather was used by the Greeks and Spartans), and a
cylinder of some sort. The long thin strip of paper is then wrapped
around the cylinder, going from one end to the other. The message is
then written on the paper, one letter for each wrap around, going from
left to right. The cylinder is rotated and the rest of the message is
written until the message is complete. Once its complete, the strip of
paper is taken off and the result is the cipher text.

To try and explain visually...

Here is our long thin strip of paper:
 __________________________________________________________
 |                                                                                                    |
 |                                                                                                    |
 |_________________________________________________________|

The paper is wrapped around the cylinder like so:
 
 .......______________________________________________.....
 |     /         /         /        /         /         /         /         /        /    |
 |    /         /         /        /         /         /         /         /        /     |
 |.../_____/_____/_____/_____/_____/_____/_____/_____/......|

Then, taking this wrapped cylinder, the message is written horizontally
across the paper like this:

 .......________________________________________________.....
 |     /     T    /    H   /    I    /    S   /   W  /      I    /    L   /   L   /    |
 |    /    B    /    E   /   M   /    Y   /    L   /     A   /    S   /   T   /     |
 |.../__M__/__E__/__S__/__S__/__A__/__G__/__E__/__!__/......|

Reading across, I have written the message "THIS WILL BE MY LAST
MESSAGE!". When that strip of paper is unrolled, this is what the
message will look like:
 __________________________________________________________
 |                                                                                                    |
 |      MBT     EEH     SMI     SYS     ALW     GAI     ESL     !TL       |
 |_________________________________________________________|

I have written it from bottom to top because thats the way the drawing
above depicts the roll of paper. With this new message, the only way to
read the original is to re-wrap it around a cylinder of equal width and
read the letters from left to right.

I hope this has been an interesting read.

...:: Peace, invas10n ::...

[Ask the Experienced, not the Learned]