Paper Enigma Machine by Mike Koss

Enigma PDF (also available in German) Download this one-page PDF file by clicking the link below: Paper Enigma (also available in German) Just print (I suggest using heavy card stock), cut out the strips, and follow the directions on the page to build your own fully functional Enigma machine. This machine is compatible with the original 3-rotor German Enigma used during World War II.  For simplicity it omits the "ring settings" and plug board, but the primary workings of the machine are captured in this model.  Great as an educational tool, or just for fun! I have two other Enigma Simulators you may be interested in: Enigma Machine Simulator (Web Page) - encode and decode Enigma messages directly from the web. Pocket Engima Machine (Android mobile phones) - a highly realistic simulation using images and sounds from an authentic Enigma machine ($2 in the Android Market). | View | Upload your own Presentation given at University of Washington, History of Computing, in December of 2006. Includes more details on how daily keys were used during WWII, and has pictures of the Enigma and other coding machines. | View | Upload your own Presentation given at The Overlake School, 6th grade class in January, 2002. It describes the importance of the Enigma machine in World War II, and how the Britsh organized to break the code on a daily basis. Download the Paper Enigma (Free) Paper Enigma.pdf 10-Pack and Detailed Instructions If you don't want to print the Paper Enigma yourself, I will print and send 10 copies for you printed on heavy card stock (mailed to US addresses only).  I will also includes detailed 5-page instruction manual.  $10. Online Detailed Instructions Please make a $2 donation to help support the distribution of this and other educational downloads.  With your donation, you will be directed to a downloadable version of the 5-page instruction manual. blog comments powered by Disqus   Cindy Caviani and Willie D. 2nd Grade Mind Fair - Eberwhite Elementary Ann Arbor, Michigan March 2008 Joseph Larson's 7th Grade Math Class Martin Luther King Jr. Early College Denver, Colorado December 2007 Security of Systems and Networks University of Amsterdam November 2007 Ken Parker's lecture - Codes and Codebreakers 5th and 6th graders at University of Kansas (Lawrence, KS, USA) Math Awareness Month April 2006 Rob Beezer's Class - University of Puget Sound - Tacoma, WA (USA) February 2006 The Paper Enigma is protected by copyright.  Permission is granted for personal educational uses.  If you wish to copy or redistribute, please contact for permission. If you don't have Adobe Acrobat reader you can download it for free.

April, 2005 - FAQ: Detailed Explanation of Rotor Motion

I've had many fine emails from people who have enjoyed the Paper Enigma.  Many have been confused about the subtlety of the motion of the rotors.  One of the benefits of building and using a model like this is that you can gain a deeper understanding of the details of the Enigma machine.

Note that the VERY FIRST STEP before encoding (or decoding) each character is to move the rotors.  That is why, even though the starting position of my sample is "MCK" - the rotors are moved to the "MCL" position while decoding the first letter.  Also note that any rotor motions should be done in one step (the actual Enigma machine uses a pawl to rotate 1, 2, or all 3 rotors all at once when a letter key is pressed - and before a lamp is lit with the encoded letter).  The right rotor always moves up by one space; the other rotors move up if the rotor to their right has the up-arrow symbol in the first row.  No rotor will move more than one position for each letter encoded.

Before encoding each letter, there are only three possibilities for rotor motion:

• Right only

• Right and Middle

• Right, Middle, and Left all move

Follow these rules to determine which rotors move:

• If your starting position has the middle rotor arrow (notch) in the top position -> all three rotors will move.

• If your starting position has the right rotor arrow in the top position (but not the middle rotor arrow) -> the Right and Middle rotors move.

• All other times, just the Right rotor moves.

Note that the notch on the left rotor position is irrelevant - it cannot effect the rotor motion at all. Perhaps this table sums it up best:

Middle Arrow	Right Arrow	Rotor Motion
no	no	Right only
no	yes	Right and Middle
yes	no	All Three Rotors
yes	yes	All Three Rotors

All rotors move at the same time based on the position of the notches BEFORE any of them are moved. You have to look at where the arrows are, use the rules above to determine which of the three conditions apply, and then move 1, 2, or all 3 rotors accordingly.

January, 2005 - User feedback

Special thanks to René Tajoburg (Vienna, Austria) for his innovation to cut slits in the background to more permanently hold the strips in place.  It's optional, but I really like how it holds all the pieces together.

January 21, 2003 - MIT Club Lecture

The Paper Enigma began as a lecture given to the MIT Club of Puget Sound.  In addition to showing the actual Enigma (and other coding machines in my collection), I wanted to provide a hands-on experience for this relatively technical audience.  So I created the Paper Enigma, and handed out scissors so that the club members could learn by doing (in the MIT tradition).

Photos courtesy John Malley