Paper Enigma Machine
by Mike Koss
 




 Paper Enigma Machine

Download this one-page PDF file by clicking the link above and print (I suggest using heavy card stock).  You can then 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!

For a great article on the history and operation of the Enigma, visit:

http://en.wikipedia.org/wiki/Enigma_machine

Teachers - please see contest below and get a $25 Amazon gift certificate!

For a very beautifully designed Enigma Simulator (that you can download to your computer), I highly recommend this program created by Dirk Rijmenants.  Using it is a great check that you're operating your paper Enigma correctly and will give you a better understanding of the operation of the original machine.

http://users.telenet.be/d.rijmenants/en/enigmasim.htm

10-Pack and Detailed Instructions

Order 10 copies of the Paper Enigma printed on heavy card stock (mailed to US addresses only).  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.

Teachers - Win a $25 Amazon Gift Certificate!

of your class using the Paper Enigma and I'll send you a $25 Amazon Gift Certificate (Please include your name, city, and country with your submission. By sending me your class picture, you give me permission to post the picture, your name, city and country on this web site.  I will not disclose your email address).

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:

Follow these rules to determine which rotors move:

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).

Thanks to John Malley, for posting his photographs of the event on his web site.