Thursday, October 30, 2014

APC Magazine example decoded

APC Magazine shows an enigma machine built with an Arduino, a two line LCD shield and a PS/2 keyboard.

http://apcmag.com/arduino-projects-enigma-cipher-machine.htm

An encrypted text is given as an exercise to the reader to decode.

I-II-III APC MAG DY AP CM
OLCRH ICCKD CWWMO ZQFNR ISPCI KREKM VMSLI BJZGM DXDEJ WXQZQ EI

Using the manual available at:
http://users.telenet.be/d.rijmenants/Enigma%20Sim%20Manual.pdf

Following the instructions on how messages were sent over the air, I was using a 3 wheel machine with a B reflector and rotors I,II,III, then trying to set the starting position to APC, and then typing MAG to obtain a message key of PWE. The rotors were moved to PWE and then OLCRH was typed, yielding gibberish.

Looking at LCD pictures of their machine, I finally realized that the first line matched the settings required in the order their program asks for them:



Thus, the rotors are I,II,III, APC is the rotor start setting, MAG is the ring setting, three plugs are used DY AP CM and then the message is simply typed starting at OLCRH.

I entered the same settings in my Enigma Engine and created the EnigmaSerialAPCMAG.ino sketch that decodes this text. To use it, upload to an Arduino UNO, open the Serial Monitor with 9600 baud and start typing OLCRH... a neat message about an early supercomputer will appear.

https://drive.google.com/folderview?id=0B0nObKKDtir6Wlk2dzh2NC1vTjg&usp=sharing#list

Enjoy

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