The Scytale Cipher

  • Scytale Cipher
    --------------
    
    Introduction
    ------------
    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]