The Official Top Secret XDM Decoder Disk

XDMs often need to communicate privileged information(1). When this need arises (as it often does) these secret messages are encrypted using the ancient Official Top Secret XDM Decoder Disk(2)! This marvelous object, originally created by the mystical XDMs of Tibet in the third century, is used not only as a means of secure communication between XDMs but is also handy for cyphers used in XDM performance games as well.

What you will need:

1. In ancient times an XDM had to undergo an arduous spirit walk and cleansing before being able to receive their Decoder Disk at the hands of an XDM Master. But today you will only need to download either the color version or the black and white version of the decoder ring in PDF format.
2. A printer … for the PDF file, right?
3. A copy of the XDM: Xtreme Dungeon Mastery book.

Some assembly required:

1. Print the version you prefer on CARD STOCK thickness or better. Anything less ruins the karma and looks bad.
2. Cut out the larger base disk and the  smaller disk.
3. Carefully cut out the white rectangle on the smaller disk.
4. Position the small disk on top of the Base Disk and attached them in the middle so that the small disk can turn. Use might use a thumb tack with a piece of eraser on the back or you might use a brass brad for this. Go crazy with how to do this … so long as the key code figures on the base disk show through the rectangle you cut on the smaller disk and the smaller disk turns.

How to use your Official Top Secret Decoder Disk:

An XDM message consists of two parts: the key code cipher and the message cipher. A key code cipher looks like this:

115/19/3/3/4

You read this as follows: open to page 115 in your XDM: Xtreme Dungeon Mastery book, count down 19 paragraphs from the top left corner, including any partial paragraph at the beginning of the page and all heading as paragraphs then go to the third line down in that paragraph, find the third word in the line and the fourth letter in that work. THIS IS THE KEY CODE for the cipher. Turn the top disk until the key code printed on the base disk shows through the cutout window of the smaller disk.

Then the message itself might read:

With the Key Code showing in the window, simply transpose the symbols into the English letters and numbers, insert spaces where it makes sense and then proceed as directed.

Message Format:

All properly formatted XDM messages start with a single figure code signifying the type and usage of the message received:

• A: This represents a coded message where everything being communicated in in the body of the message itself.
• W: This means that the message is actually a password that will allow you access to a protected web page. This is often used when larger messages or graphic are needed to be conveyed securely.
• P: Like W, this is a secret webpage location designator. In this case, type in www.xtremedungeonmastery.com as your web location and then, after a ‘/’ mark, simply append the secret web page designator. This is most often used to get you to a link-through page to a secret page not located on our server.

IMPORTANT NOTE: The single figure code is NEVER part of the message itself. For example, if the code started with a W, indicating that the following message was a password then that first W would be dropped and all letters after it would be considered the password. If the password itself started with the letter W … then TWO ‘W’s would appear at the start of the message.

Special Case in this Symbol Set:

There is one special character on the disk designed to confound code breakers. If the Code Key were ‘V’ then it would be the symbol opposite the ‘A’ character that looks like a horizontal mark.

In practice, this mark actually appears OVER the previous character … for example in the following code…

… the figure that appears to be second to last with a horizontal line above it is actually two separate symbols — with the horizontal line being the second to last.

Security of your Official Top Secret XDM Decoder Disk:

It is important that you keep these materials secure at all times! Do not loan your disk to anyone outside of the game environment nor communicate any secret information you have gained from secure communications unless you are certain you are talking to a Certified XDM … but then, if they WERE certified, why do they not have the disk themselves, eh?

We may change new disks from time to time if security is breached. Be vigilant!

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(1) Usually because we just don’t want Grandmaster Frank to know.
(2) We wanted decoder rings for obvious reasons but are still working some manufacturing issues.